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  1. #1
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    Fatbike braking -vs- skinny tire braking

    Can fatbikes have brakes that will really stop the bike quickly? I.e. like a skinny tire bike where many brands of brakes will basically stand the bike on it's nose.

    I ask because my brother bought a custom made fatbike, great bike, super fun, we went riding yesterday and just for fun I hopped on it (I've never ridden a fatbike) and I was like oh this is a blast, hopping logs, riding like it's a monster truck...until I tried to stop. I'm useto my skinny tire brakes (Shimano SLX) which even with my weight (235lb) I can really stop hard and fast, they really clamp down good. His brakes (brand new Hope, on 160mm rotors) were just not stopping. They were very smooth and progressively slowing down but nothing like the "omg hold on we're clamping down on the brakes hard now" feeling on my bike. This wasn't just my perception, it was his (~160lb) also, he loved my brakes and felt a bit wishy washy about his.

    I looked at his setup and it has 160mm rotors front and rear, which I was shocked by, even my XC bike has 180/160 and most people I know run 203/180 even for XC trails, just cause they like the extra stopping power of the larger rotors.

    So I was going to suggest he at least put on larger rotors on, but ofcourse the fatbike wheels/tires have *lots* more rolling momentum/inertia than skinny tire ones, so maybe the "feel like you're slowing a freight train" feel is normal and all we can expect from brakes on a fatbike? I've never ridden one so I know jack about that.

    Also the rotors currently on his bike are one of those styles where there is more air holes than actual material. I know they are supposed to dissipate heat better that way but it seems at some point the pad has to actually touch metal to stop the bike, so having more than 50% air holes limits how much pad-to-metal engagement you can have, so if he goes to larger rotors I was going to suggest some other brand that maybe looks less sexy but has more contact area.

    Ideas?
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  2. #2
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    I just replaced my fork. New fork had brakes that were set up for a 160mm rotor old one a 180mm. Old fork had the adapter that wouldn't work on new one, so I traded out for a 160mm, and it was night and day. 160mm wasn't even as good as some of my old cantilevers and I am lucky to get to 140 lbs. after dinner. Adapter for the 180mm should be here tomorrow and will be going back on tomorrow plus 10 minutes.
    Dash Pt. State Park (Tacoma), Big Sky Montana during Snowboard Season, Duluth Mn, a couple of times of year incl. Xmas.

  3. #3
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    For one, how long has he ridden it? Have the brakes bedded in yet?

    Number two, absolutely - bigger rotors, I think, are more important on fatbikes, because the bigger tires have a lot more momentum to slow down. I am running 180/180 on my Bucksaw with XTR Trail brakes. There's plenty of power for me to use, at 175lbs. I am in Indiana, however. I have taken the bike to some trails with some far longer downhills and while I didn't have any problems, I could see bumping rotor size at least to 203/180 would be a good idea if I did more long downhills.

    I think 160/160 rotors on a summer use fatbike ridden on trails is shortsighted component spec. If we're talking about a winter bike or a sand/beach bike, I think it's a different story. Speeds would be lower in those scenarios, so you don't need as much power from the brakes. But at the sorts of speeds you'll attain on dry summer trails, you definitely need bigger rotors on a fattie.

  4. #4
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    Yes, fatbikes (tires & wheels) need more power to stop.

    I've tried the "uber-lightweight" rotors (alligator, axim) , they just don't provide the bite that a normal one does.

    On my bucksaw I recently removed the axim rotors (180F+R), and installed Hope floating rotors, 203F, 183R. They are much much better! Also run a beefier caliper up front, the Hope M4, and an X2 in the rear.

    Pads make a difference too. Hope seem to be the best although $$. Tried the cheapo online ones (truckerco, discobrakes), they are OK, but not as good as the factory Hope pads and don't last as long.

  5. #5
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    I switched my front to a 203mm rotor from a 160, it made a huge difference. The rotor and bracket came to a whopping $22... Money well spent.
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  6. #6
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    I have a pretty strong preference for metallic pads, also. That one is a pretty longstanding preference, though. I have tried, and never liked, resin/organics.

  7. #7
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    Quote Originally Posted by Harold View Post
    Number two, absolutely - bigger rotors, I think, are more important on fatbikes, because the bigger tires have a lot more momentum to slow down.
    Not really. With your bike in a stand, turn the cranks to make the rear wheel spin really fast. Yank the brake lever. Stops really easy, doesn't it? The momentum caused by the wheel and tire weight is negligible compared to what it takes to stop a grown man.

    What does matter is the larger diameter of the wheel. A 26" fatbike wheel easily equals about a 30"-31" skinny wheel, which means it'll have a bigger mechanical advantage (it acts as a longer lever). To match this, you'll need a bigger brake disc to match the increased force it'll have to overcome. Not counting improved heat dissipation, a 180mm disc brake will give you 12.5% more stopping power than a 160mm disc (10/80*100) with equal force on the brake.

  8. #8
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    I originally installed 180F and 160R on my Pugs (Avid G2 clean sweep rotors, Avid BB7 mechanical pull levers and calipers), just going on general advice that I'd gleaned from various threads. I ride the beach, trails, and logging roads. This setup seems adequate, as it works for me and my riding. I went with 160 on the rear thinking that it wouldn't lock up so easily, but a 180R might have been a better choice. I don't really know.
    I think that a 160mm rotor up front would not be enough, though. I'm just an old dude cruising when riding on trails, not some young stunt rider. I like to keep within my personal limits.
    My gps told me that I had hit 27.4 mph before having to slow down a bit for a turn at the bottom while bombing down a rough gravel logging road, and I managed to feather my speed down just enough to maintain control, although I experienced some drift. I almost scared myself. I sure didn't want to brake too hard and go into a skid, lose control and wipe out, since I was riding solo a couple of miles back in the hills, and didn't have my first aid kit along.
    27.4 mph doesn't sound like much, but it seems like a million miles an hour to an old fart charging down a sketchy gravel road on a fat bike! I felt lucky as I came out of the turn. I was running just under 6 lbs F, and about 7.5lbs R pressures on my Fat B Nimbles/Marge Lites, so I had plenty of contact patch going for me.
    Total weight of bike, water bottles and rider was just a hair over 200 lbs.

  9. #9
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    Quote Originally Posted by mabrodis View Post
    Can fatbikes have brakes that will really stop the bike quickly? I.e. like a skinny tire bike where many brands of brakes will basically stand the bike on it's nose.
    Yes. Make sure the brakes are properly bedded in (https://www.sram.com/sites/default/f...n_update_0.pdf), the brakes are bled, and consider bigger discs.

  10. #10
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    Quote Originally Posted by Farbar View Post
    Not really. With your bike in a stand, turn the cranks to make the rear wheel spin really fast. Yank the brake lever. Stops really easy, doesn't it? The momentum caused by the wheel and tire weight is negligible compared to what it takes to stop a grown man.

    What does matter is the larger diameter of the wheel. A 26" fatbike wheel easily equals about a 30"-31" skinny wheel, which means it'll have a bigger mechanical advantage (it acts as a longer lever). To match this, you'll need a bigger brake disc to match the increased force it'll have to overcome. Not counting improved heat dissipation, a 180mm disc brake will give you 12.5% more stopping power than a 160mm disc (10/80*100) with equal force on the brake.
    A workstand is not the trail. For me, actually RIDING the bike, I notice heavier fatbike wheels spin up faster and take more effort to stop than lighter fatbike wheels/tires all other factors being equal (rim/tire width, bike, brake rotor sizes, trail, etc). The differences in total weight on these parts can easily be multiple pounds between the two wheels. All rotating mass, of course. It's noticeable. I also notice a difference between stopping force required on my 26er compared to my fatbike. Static weight of the wheels is very nearly the same, so weight is not the factor there. But diameter is very different, so yeah, you are correct that that's also a factor. But to say that weight ISN'T based on your workstand test doesn't tell the whole story.

    We don't know the exact wheels/tires being compared here. So yeah, it's hard to get too detailed with the analysis not knowing a lot of factors. We don't know if the OP is comparing a 26er with 2.0's to a fatbike with 100/5" setup, or a 50/4" setup. We don't know if any of the rims in question are super lightweight and $$$$ carbon, or anything else.

    And yeah, those ultralight wimpy rotors do suck for power.

    Combine all of these factors together, and you're going to wind up with a bike with $hitty braking performance.

  11. #11
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    It seems like the only times I've ever been riding faster than what my brakes could easily bring me to a quick stop (on the proverbial dime), have been while riding down hills on gravel logging roads, when I certainly don't want to try to stop on a dime, but just keep under control. I'm riding on roads closed to motor vehicles.
    I'd probably just have to hollar at a bear stepping out on the road in front of me, under such circumstances, and hope that its adequate warning, but we only have black bears around here (no Grizzlies, fortunately), and they usually flee the scene immediately.

  12. #12
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    Quote Originally Posted by PlutonicPlague View Post
    It seems like the only times I've ever been riding faster than what my brakes could easily bring me to a quick stop (on the proverbial dime), have been while riding down hills on gravel logging roads, when I certainly don't want to try to stop on a dime, but just keep under control. I'm riding on roads closed to motor vehicles.
    I've had situations like that (trying to stop on loose terrain) and I wouldn't call it necessarily a brake issue. For me, that's been more of a tire issue. Try to stop too quickly on a loose surface, and your tires lose traction. Brakes worked fine in that case, but they weren't the limitation.

    I ran into that scenario in Pisgah a few weeks ago. Riding down a fast downhill with a jumble of loose rocks all over. Brakes had enough power to stop me quickly, and my tires gripped the rocks just fine. But if I tried to brake too hard, the rocks moved too much underneath the bike. Try to stop too quickly on that stuff, and you're going down. I had a dirt/gravel road descent (that was open to motor vehicles) where stopping too quickly would have been a problem. Surface was mostly pretty firm and solid, but there was a layer of loose material on top, where excessive braking would cause the tires to break loose.

  13. #13
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    ^^ Yeah,
    I can easily lock up the front brake if I want to. I rode down a steep sand dune and tried locking the back up, and didn't have a problem doing so with strong grip pressure, but the R tire was skidding on the loose sand. I wonder if asphalt would provide the traction to keep the R tire rolling (overpowering the 160 rotor) when braking hard on a fast steep downhill paved road. I should go check that out.
    On trails, I usually don't ride so fast. I like to ride within control on the trails. I'm not a racer, and I never race.

  14. #14
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    Quote Originally Posted by Harold View Post
    A workstand is not the trail. (...) But to say that weight ISN'T based on your workstand test doesn't tell the whole story.
    The whole point of the "workstand test" is indeed that it is not the trail. It removes all those other factors, while the mass of the wheel remains constant and the speeds comparable. It shows that stopping a heavy wheel is in itself a piece of cake, compared to all other factors.

    Leaving that theoretical discussion aside, having effective brakes on a fat bike is very much achievable. I weigh in at 180lbs, run Avid Guide brakes on 180mm brake discs, and regularly do one finger stoppies while riding.
    Last edited by Farbar; 05-18-2015 at 01:51 PM.

  15. #15
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    Just came back from 4 days in the mountains, worked out that a freeride downhill course isnt really rigid fatty territory, but at no stage did l have braking issues.
    Full Shimano SLX on 160mm rotors

    you lot must be hell fast.........

    Having said that, l set my brakes very touchy, its how l like it, so maybe when they begin to fade l still have the ability to pull harder on them as l still have ~50% of my lever movement available, ie my lever is no where near my bars when lm braking.

    btw: my fatty weighs in at 12.5kgs, and lm down to ~91kgs, l dont see how 10kg lighter rider on a 10kg heavier bike will be any different.
    always mad and usually drunk......

  16. #16
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    Too many variables to try and compare the 2 types of bikes if you ask me. Kind of loaded question because of the variables between the 2 bikes...

    -Speed
    -Mass (Bike weight/rider weight)
    -Tire width
    -tire tread pattern
    -Tire compound
    -Tire pressure

  17. #17
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    Excellent info guys, I wasn't so much trying to compare brakes between my skinny bike and his fatbike (which are 26" wheels that look like 4.5" wide tires if that matters) cause there are way too many variables to get anything meaningful out of that...but basically just to ask if fat bikes can ever stop quick/aggressive.

    From the responses here it is very clear that they can (and should) be able to be setup to stop quick. That's good news cause I think he'd love to ride it a bit more aggressive than the gentle brakes are currently allowing...hahah...and whenever I buy/build a fat bike for myself I'll want kick ass brakes too.
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  18. #18
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    I'd bet something isn't set up right on the brakes. I'm on a Pug with 160's front and back with my weight at 210lbs. The brakes are Avid BB 7's, metallic pads, Jaguar cables and they will stop quick. Have a mechanic used to fatbikes check the system before switching rotors.

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    I tested my rear brake today going down a small hill. The surface was chip seal type of pavement. Rough asphalt. I got up to 16 mph and clamped down pretty hard on my R brake lever. R brake locked up immediately and I was skidding. The 160mm rotor feels plenty adequate. I didn't apply the front brake on this test (have 180mm rotor up front), just the R.
    I'm 160 lbs dressed to ride, and my Pugsley is about 40 lbs, so about 200 lbs or so total.
    I've also got the Jaguar cables, and metallic pads on my BB7s. My brakes work just fine.

  20. #20
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    Hope X2's with a proper alignment, bleed and bed in will do a bang up job. They must be set up properly, then and only then will they out perform anything else. They cost a premium up front, but they work. Heavier riders will certainly benefit from larger rotors.

    Get 'em set up, wet 'em and ride 'em. This will hasten the bed in process.

    I compare everything to the stopping and holding power required for observed trials because a brake flat doesn't work if it can't hold a bike in position. Slipping brakes there is the recipe for a hospital bill the size of a mortgage. My fatty's brakes enable me to get trialsy with it with confidence. X2's, 160mm rotors, 160# rider. 180's should serve you well.
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  21. #21
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    Quote Originally Posted by Harold View Post
    A workstand is not the trail. For me, actually RIDING the bike, I notice .
    This argument doesn't make a whole lot of sense.

    That's like saying, "I know the scale says my new bike is only 3 grams lighter, but RIDING it I can feel how much faster it makes me!"

  22. #22
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    The workstand test is great for showing that the momentum of a fat tire is easily stopped by a 160mm rotor with even the crappiest brake on the market. The fat tires add some mass, and rotating mass at that, but it is pretty insignificant compared to the mass or momentum of the rider. That's what really matters, speed and total mass.

    160mm is more than enough stopping power for rear brakes. Larger rotors on the rear of bikes are typically for heat dissipation rather than stopping power.

    With the front it is possible to use much more stopping power before skidding and people routinely run a 180mm rotor or even 200mm for riders with a lot of mass to stop.

    From the sound of it though, there was likely a problem with his brakes, regardless of rotor size. The pads could have been contaminated with something that makes them not grip or there could be air in the hydraulics.

  23. #23
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    On snow, at snow-speeds, I do fine with a 180 xtr M987 (essentially same as M9000) and the light ashima rotors. The inertia of summer riding is likely far more and going to take more brake, especially with some of the heavier setups out there. I'd think harder-stopping brakes like XTs and decent rotors would make a good bit of difference though before having to go 203 in the front, but it probably wouldn't hurt either. I agree that there's little point to a 203 rear rotor, for equal brake power and correct front-bias, you need a larger front usually.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  24. #24
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    Quote Originally Posted by Farbar View Post
    The whole point of the "workstand test" is indeed that it is not the trail. It removes all those other factors, while the mass of the wheel remains constant and the speeds comparable. It shows that stopping a heavy wheel is in itself a piece of cake, compared to all other factors.
    Yep
    The mechanical advantage you have with the disc brakes is such that the weight of the wheel between a fatty and a 29er is a non-factor. Especially when you consider that you can spin the rpm of the fat wheel on the stand up much higher than when you're actually riding, and stopping it is still no problem.

    That said, increased traction with a 4"+ tire might require higher braking forces before the tire skids, especially noticeable in the rear since you're not applying front brake to the point of a skid on any bike.

  25. #25
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    Quote Originally Posted by Gambit21 View Post
    Yep
    The mechanical advantage you have with the disc brakes is such that the weight of the wheel between a fatty and a 29er is a non-factor. Especially when you consider that you can spin the rpm of the fat wheel on the stand up much higher than when you're actually riding, and stopping it is still no problem.

    That said, increased traction with a 4"+ tire might require higher braking forces before the tire skids, especially noticeable in the rear since you're not applying front brake to the point of a skid on any bike.
    We are looking at a dynamic situation in braking. There are a lot more factors at play than just the spinning wheel. There is forward momentum, which is affected by rider weight. There's the trail surface and tire traction to consider. A lot of things, including brake setup, characteristics of the brake system itself, characteristics of the rotor, etc. Saying that the forces of wheel weight aren't a factor in that equation simply because if you eliminate all of the others from the equation with the workstand test, the brakes work fine, is kinda dumb. Because on the trail, ALL of the factors matter, ALL together.

    As has been hashed out in this thread, it sounds like a lot of factors went into the OP noticing poorer brake performance on his brother's fatbike compared to his own bike. On the original post, a few things are apparent. Wheel size is different between the two bikes, rotor size is different between the two bikes, and rotor construction is different between the two bikes. Those are absolutely all three factors in the equation.

    All of the factors (which probably include a few not mentioned by the OP) work together, some in an additive manner, and others probably multiplicative or some other nonlinear relationship. A given set of calipers and pads have a given capacity for braking power. A larger rotor adds to the capacity. A smaller one subtracts. Less material on the braking surface subtracts. More material on the braking surface adds. A larger wheel subtracts. A heavier wheel subtracts. Does adding a couple inches to the diameter or a couple hundred grams to the weight entirely overcome the capacity of the caliper to stop the wheel from rotating? Of course not. Nobody ever suggested that it was the only factor.

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    OK, but nothing you typed negates the fact that momentum from the rotating wheel can be isolated as a factor as correctly indicated above.

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    I use the sram guide rsc, with 200mm front and 180mm rear rotor, swapped from 180-160, i know i had enough stopping power, but i have rather a bit to much than a little less stopping power, modulation is super!!
    Scott Scale 710 plus, with guide rs, XX1

  28. #28
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    Quote Originally Posted by Harold View Post
    We are looking at a dynamic situation in braking. There are a lot more factors at play than just the spinning wheel. There is forward momentum, which is affected by rider weight. There's the trail surface and tire traction to consider. A lot of things, including brake setup, characteristics of the brake system itself, characteristics of the rotor, etc. Saying that the forces of wheel weight aren't a factor in that equation simply because if you eliminate all of the others from the equation with the workstand test, the brakes work fine, is kinda dumb. Because on the trail, ALL of the factors matter, ALL together.

    As has been hashed out in this thread, it sounds like a lot of factors went into the OP noticing poorer brake performance on his brother's fatbike compared to his own bike. On the original post, a few things are apparent. Wheel size is different between the two bikes, rotor size is different between the two bikes, and rotor construction is different between the two bikes. Those are absolutely all three factors in the equation.

    All of the factors (which probably include a few not mentioned by the OP) work together, some in an additive manner, and others probably multiplicative or some other nonlinear relationship. A given set of calipers and pads have a given capacity for braking power. A larger rotor adds to the capacity. A smaller one subtracts. Less material on the braking surface subtracts. More material on the braking surface adds. A larger wheel subtracts. A heavier wheel subtracts. Does adding a couple inches to the diameter or a couple hundred grams to the weight entirely overcome the capacity of the caliper to stop the wheel from rotating? Of course not. Nobody ever suggested that it was the only factor.
    This is missing the point about the workstand test. The only point there was that the difference in momentum of a spinning fat wheel vs a spinning skinny wheel is negligible. The significantly higher mass of the rider obscures that difference in tire weight.

    But really what we should be talking about is making sure the rotors and pads aren't contaminated. Also, make sure the brakes are properly bled, without air robbing some of the stopping power. If that doesn't resolve the situation, up-size to 180mm rotors or even 200mm for bigger riders.

  29. #29
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    Quote Originally Posted by dfiler View Post
    This is missing the point about the workstand test. The only point there was that the difference in momentum of a spinning fat wheel vs a spinning skinny wheel is negligible. The significantly higher mass of the rider obscures that difference in tire weight.
    But that's not the point in the discussion. I wouldn't call the difference in weight negligible. Put a fat bike and a skinny one in a stand. Spin the wheels up to the same (high) RPM and mash the brakes to force them to stop suddenly. Tell me you don't see/feel a difference. Sure, the wheels will both stop suddenly with no additional forces involved. But to say that the difference between them is negligible is disingenuous. They absolutely do differ, and that difference will result, in the workstand test, with more energy being transmitted throughout the whole apparatus, making it move more, with the heavier fatbike wheel. When we are closer to the limits of the caliper/rotor/tire/ground system by adding a rider who has forward momentum in addition to the rotational momentum of the wheel, that difference can very well be enough to affect stopping distance. That is why the workstand test has very little bearing on real world scenarios in this case.

    You're taking the forces in question FURTHER from the limits of the calipers. Seems to me that if you wanted to test the differences between wheels of different weights, you would want to perform your tests CLOSER to the limits of the brake calipers. So a workstand test would be data point number one. You need additional data points WITH rider weight added, and at different speeds to find a relationship between the two bikes.

    The point of the workstand test has nothing to do with the original question and the rest of the questions that have come from it. We're talking about the same rider comparing bikes with different brake setups and different wheel dimensions. He's asking if it's possible to get the same braking performance on a fatbike as he can on his current bike. The answer is yes - but bumping up rotor size a little might help depending on riding style. And also replacing the weight weenie rotors with something that offers more surface contact with the pads. And making sure they're properly bedded and not contaminated and blah blah that's the same for every disc brake out there.

  30. #30
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    Quote Originally Posted by Gambit21 View Post
    OK, but nothing you typed negates the fact that momentum from the rotating wheel can be isolated as a factor as correctly indicated above.
    It can be isolated, but why does that matter? As I mentioned, you reduce the overall forces involved so that the brake calipers are nowhere near their limits, so differences between the two can't be determined. To determine the extent of those differences, you need to be far closer to the limits of the brakes. By adding rider weight, you DO move closer to the limits of the brakes. It becomes easier to perceive more subtle differences in wheel weight as you approach the limits of the brakes.

    When the OP jumped from his own bike to his friend's bike, he absolutely could perceive differences in braking capability between the two bikes. We have no way of knowing if the fatbike's brakes were correctly bedded and not contaminated. We DO know that the fatbike wheels are bigger and probably weigh more. We DO know that the fatbike had smaller rotors, with less surface in contact with the pads. The sum of all the known and unknown factors resulted in crappy braking. Putting the bike in a workstand to check the braking doesn't do us any good, because the bike brakes like $hit with a rider on it.

  31. #31
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    Harold is correct in stating that heavier tires will require more force to stop/accelerate than ones weighing less. It is rotating mass, a lighter wheel will spin up w/ less effort. Farbar is basically disproving his own theory by stating that the weight isn't as big of a factor as the diameter.

    While both play a factor, tell me which one of the objects you would prefer to have hit you in the face: A 10lb brick on a 12" string being swung in a circular pattern, or a 1lb brick on a 18" string being swung in the same pattern? The 10lb brick will destroy your pretty little face real fast, and maybe even keep moving on for another shot....while the 1lb brick will more than likely not.

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    Jeebus nobody is saying a heavier object won't hurt more if it hits you in the face at a given velocity. Going way off the rails with that one. The discussion is the relative difference between the rotating mass and therefore braking effort required between 2 tire sizes. Again the mechanical advantage afforded by disc brakes negates this small factor. The points have already been made above, but this being the Internet we of course find ourselves dealing with and discussing bricks in the face.

    More traction equals better power transfer to ground, and it would stand to reason that higher braking forces would be possible before traction is lost. That's the difference.

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    Interesting argument. if you dig into the physics, rotating mass located at the edge of the wheel will take twice as much energy to stop as non rotating mass. Say you have a 12kg bike and a 70 kg rider with same brakes/rotors/etc and only vary the wheel weight and diameter.

    for the fatbike: 860g rim + 1800g tire + 460g tube
    for the skinny 26" bike: 500g rim + 650g tire + 100g tube

    so you end up with 6.2 kg rotational weight on the fatbike and just 2.5 kg rotational weight on the skinny bike. Assuming all this weight is right at the edge of the wheel (giving it twice the inertia), you end up with the fatbike being about 9% harder to stop. I used the approximate weight of my equipment as a starting point (and hopefully didn't make any huge weight errors) - obviously the difference will decrease with a heavier rider and a lighter fatbike setup.

    When you combine that with the ~12% increase due to the decreased leverage from the larger wheel, you're going to end up needing to pull the lever on the order of 20% harder on the fatbike to get the same deceleration (assuming no skidding) and of course you may want to pull even harder then that given that you may be able to apply more braking force before your tire loses traction.

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    McCarthy you reasoning stands up (taking you 20% as being roughly correct just for the sake of discussion) while the bike is on the stand. That's 20% of an already negligible force. Now add a 190lb rider. The additional force becomes even more negligible from a rotating mass perspective.

    From a braking force due to traction perspective, then maybe we're on to something.

    Anyhow, let's call it a discussion rather than argument.

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    Just install XTR's and call it a day. No need to over think this....

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    Quote Originally Posted by litespeedaddict View Post
    Just install XTR's and call it a day. No need to over think this....
    Make mine XT for 'bang for the buck' reasons - but yeah

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    icetech 203mm front and 180mm rear.. xt brakes... stock fatboy brakes sucks.. going fast on a downhill trail and halfway thru, stock brakes were already done..san diego btw.. some things you just don't skimp on your bikes.. brakes and lights among other things..

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    Quote Originally Posted by Gambit21 View Post
    That's 20% of an already negligible force. Now add a 190lb rider. The additional force becomes even more negligible from a rotating mass perspective.

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    Oh brother, can the op just get his bike into a shop with someone qualified to service brakes already???
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    Quote Originally Posted by BansheeRune View Post
    Oh brother, can the op just get his bike into a shop with someone qualified to service brakes already???
    The bike with crappy brakes isn't the OP's bike.

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    Quote Originally Posted by Harold View Post
    Unintentionally ironic post of the month?

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    Quote Originally Posted by Gambit21 View Post
    McCarthy you reasoning stands up (taking you 20% as being roughly correct just for the sake of discussion) while the bike is on the stand. That's 20% of an already negligible force. Now add a 190lb rider. The additional force becomes even more negligible from a rotating mass perspective.

    From a braking force due to traction perspective, then maybe we're on to something.

    Anyhow, let's call it a discussion rather than argument.
    Fair enough, we'll go with discussion haha.

    Anyway, my knee jerk reaction when first seeing this was that the difference in how hard you'd have to pull the levers would be negligible, but now I don't think so at least for my set up. Of course I agree that none of this makes a huge difference in my case since with properly set up cheap mechanical disc brakes, compressionless housing, and 160 mm rotors, I can easily lock up front or rear brakes with one finger on either bike.

    For what it's worth, if you modify the calculations I did before to have a 190 lb rider and set the fatbike up tubeless you're looking at a ~6% increase in braking force purely due to the increased linear+rotational mass of the heavier wheels.

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    This is ridiculous. You can get bogged down in minutia and scientific dick measuring. But the fact remains that in real life the braking power needed to stop fat tires is negligible compared to stopping the mass of the rider.

    Assuming the pads aren't contaminated and the bleed is good, upsize the rotor if more stopping power is needed.

  44. #44
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    There's no problem stopping a fatbike. Even the heaviest fatbike is only 10 to 15 lbs more than an equivalent 29er, which is much less than the weight range difference of most riders.

    When you have a tyre with the grip of a motorbike tyre, then it's obvious that you can use bigger brakes more effectively than on a narrow tyre which simply slides.

    Bigger brakes are worthwhile on a fatbike not because braking is deficient with standard size, but simply because the extra retardation is capable of being be used without losing the wheel grip.
    As little bike as possible, as silent as possible.
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    Quote Originally Posted by Velobike View Post
    Bigger brakes are worthwhile on a fatbike not because braking is deficient with standard size, but simply because the extra retardation is capable of being be used without losing the wheel grip.
    Bingo

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    Quote Originally Posted by Gambit21 View Post
    Make mine XT for 'bang for the buck' reasons - but yeah
    Make mine SLX for a bangier buck

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    True enough

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    Quote Originally Posted by mabrodis View Post
    ...but basically just to ask if fat bikes can ever stop quick/aggressive.
    The answer is yes. Very much yes.

    I have received way too many bikes back from way too many shops with careless brake setup. I now either do that work myself or take it to a shop that knows their butt from a hole in the ground.

    A fat tire is heavier than a skinny tire, but the most flyweight person in here is an ANCHOR compared to a fat tire.

    You don't have fat bike problems here, just mountain bike problems. Annoying, common, HOW DID THE BRAKES GET THAT DIRTY THAT QUICKLY AGAIN FFFFFFUUUUUUUUU******** kind of problems.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

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    Changed front rims and hubs lost 300 grams with the same tire and tube. Had to change (temporarily) to 160mm rotors from 180mm rotors due to direct mount and no adapter on hand. Same down hill, same dry conditions, same rider weight (me 138lbs.), and huge loss in braking power (I'm going to guess 30%). I did do a total readjustment on the brakes, so I'm discounting that as a factor.
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  50. #50
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    Ease or difficulty of braking in a fat bike or regular mtb depends only on the total amount of energy to be drained other than a little more rotational inertia.

    My fatboy came with low end shimano brakes with 180/160 rotors. When I wore out the first set of pads, I switched out the brakes to XTs and went to 203/180 ice tech rotors. I believe in big powerful brakes given the lack of level in Nor Cal.

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    Wow, do I dare comment on this?

    As I posted on another thread "The Dole in the (Semi) Wild"

    I never gave the stock brakes on the Dole a try. When I got it they didn't work so I pulled them off and installed Avid BB7s 160mm disks with HS-1 (heat shedding) rotors. There have been statements that fat bikes need bigger then 160mm for good stopping. In my opinion a good set of 160mm brakes properly setup work great. My total ride weight including the bike, me, motor, batteries rear rack and a bunch of modifications including new tires, tube, handle bars crank arms and a rear rack is about 280 lbs, My ride speed so far is around 20mph on the flats. And the brakes pull the bike to a stop very well.

    Bob

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    Quote Originally Posted by Go4itfatty View Post
    Wow, do I dare comment on this?

    As I posted on another thread "The Dole in the (Semi) Wild"

    I never gave the stock brakes on the Dole a try. When I got it they didn't work so I pulled them off and installed Avid BB7s 160mm disks with HS-1 (heat shedding) rotors. There have been statements that fat bikes need bigger then 160mm for good stopping. In my opinion a good set of 160mm brakes properly setup work great. My total ride weight including the bike, me, motor, batteries rear rack and a bunch of modifications including new tires, tube, handle bars crank arms and a rear rack is about 280 lbs, My ride speed so far is around 20mph on the flats. And the brakes pull the bike to a stop very well.

    Bob
    Maybe not using your opening line would be a good start

    I think the way you are trying yours out and the way I use mine are 2 completely different things. That being said I run bigger rotors on all my mtb bikes fat and skinny alike, there are other advantages in some terrain other than just stopping faster.

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    I notice a huge difference in rear brake performance on the fatbike. There's so much more traction that simply doesn't exist with a skinny tire.

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    you can never go overboard when it comes to brakes.. if you feel 180mm front and 160mm rear is good enough for you then am happy for you.. personally where i ride here steep downhill with boulder and rocks, loose sand on hardpack soil, i need all the braking i could get.. i run 203mm f and 180mm rear ice tech rotors with xt brakes on my fatboy.. wasn't happy with the tektro brakes with 180mm and 160mm orig equip with the bike.. if anything " it's better to have it and not need it, then need it and not have it"..

  55. #55
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    Quote Originally Posted by av8or View Post
    . if anything " it's better to have it and not need it, then need it and not have it"..
    How dare you add 75 grams of usable performance weight to your bike At least to me having good reliable braking system helps me to go faster.....if that makes any sense? Spot on dood!!

  56. #56
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    Guys, no question points are valid. Different uses have different requirements. But many comments in this thread are very general and simply stating that 160mm brakes on a fatboy aren't big enough. Following that general comment I am simply disagreeing. If your going to be specific as to some extreme usage then I would 100% agree with you. But the need for the bigger stopping power in not related to a fatbike. It's related to what your using it for. In that case you would be wise to have bigger brakes no matter what your riding. Wouldn't you agree?

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    bb7 fan here since 2003. all of my bikes get them. no complaints. 180 front 160 rear on my cooker maxi.

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    grimeca system 12's on 160's.

    so there!
    If steel is real then aluminium is supercallafragiliniun!

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    fatboy here with XT brakes and shitty Tektro rotors

    Im dieting, so currently about 245, but when I was 260 the bike would still lock up just like my CX bike. Never even considered it honestly, stops on a dime.

  60. #60
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    Outright power was never the problem with my BB7s, it's that extended heavy braking would heat up the rotor and it would glaze over, then the braking would significantly decrease. Also, the pads only lasted for about a month of regular riding, I got far more life out of my hydro disc sets. I think avid intentionally made very "grippy" pads, good for most riding, good if you don't have to do heavy extended braking.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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    just got a full year out of a set of bb7 pads. fresh set just went in. guess it depends on how hard you pull lever and how often. never had any issues with overheating or brake fade on extended steep descents as i have with shimano hydros (slx)

  62. #62
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    Wow, the DHers are using the wrong brakes!
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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    Ya they shouldnt be using em at all

  64. #64
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    Shimano XT, 203 front 160 rear. I wouldn't say i needed 180 at the back as i don't live on a mountain. But 203 on the front is where it's at.
    Carbon Fat Bike Rider

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    Sure 160mm works! Physics dictate that 180mm work even better with regard to both power and heat dissipation. If you don't need that, it's fine! There's no single correct answer here, which is why rotors are available in everything from 140mm to >200mm.

    With regards to ergonomics and control over rough conditions, I would highly recommend people finding a good 1-finger braking setup. This will give you a much stronger and comfortable grip than if you reserve 2 fingers for braking, and will reduce strain on the rest of your hand. Move the brake lever several cm towards the center of the bar in such a way that your index finger hooks up to the outermost part of the brake lever. Adjust reach. If you then have to struggle to pull your bike up on the front wheel when stopping, I'd argue you're not getting enough braking power.

    This appears to be a good guide: How-To: Mountain Bike Cockpit Set Up with Art's Cyclery - Mountain Biking Videos - Vital MTB

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    I've been riding my fatty for 3+ years on Hopes (X2) with 160 rotors (Ashimas - cheap, light and good). As someone mentioned, bedding in the pads PROPERLY is super important. Follow Hope's instructions. I like the sintered pads the best.

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    Quote Originally Posted by Slow_Thyroid_Bike View Post
    fatboy here with XT brakes and shitty Tektro rotors

    Im dieting, so currently about 245, but when I was 260 the bike would still lock up just like my CX bike. Never even considered it honestly, stops on a dime.
    OK, I'm honestly trying to learn something so please help me out. I was under the impression that in many cases the same pads are used with different size rotors. As in the BB7s pads and mountings can be used with larger rotors with the use of an adapter. Am I incorrect? I realize there would of course be a limit to this.

    I would agree over heating of smaller disks could be an issue depending on usage. That's why I bought the HS-1 heat sheading disks. I was hope they would help avoid the glazing problems.

    Bob

  68. #68
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    Now that all the techno science behind braking has been hashed out, good see what dudes are actually running and how they shake out on their bikes. I really think larger rotors are key for the fattys...along with proper setup that should include: rotor alignment, a tight bleed, pad contact, lever feel and reach, clean rotors. Clean rotors cant be understated... I had some greasy fingers and happen to touch up my rotors taking off the rear wheel and that grease on the rotor effected the stopping power, so clean em up with alchohol. Guide RS with 180 f/r has been the best all around and stop on a dime 1 - finger for what its worth. Still need to test em on the Redtail in NoCon though!
    Last edited by NH Mtbiker; 07-07-2015 at 05:56 PM.
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    Quote Originally Posted by NH Mtbiker View Post
    Now that all the techno science behind braking has been hashed out, good see what dudes are actually running and how they shake out on their bikes. I really think larger rotors are key for the fattys...along with proper setup that should include: rotor alignment, a tight bleed, pad contact, lever feel and reach, clean rotors. Clean rotors cant be understated... I had some greasy fingers and happen to touch up my rotors taking off the rear wheel and that grease on the rotor effected the stopping power, so clean em up with alchohol. Guide RS with 180 f/r has been the best all around and stop on a dime 1 - finger for what its worth. Still need to test em on the Red Trail in NoCon though!
    redtail trail is no match for bb7's dozens and dozens of descents on that trail

  70. #70
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    Loved bb7 on one wet and very muddy vt50...08? Able to flip the bike upside down and dial in the pads trail side without skipping a beat!
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  71. #71
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    Quote Originally Posted by NH Mtbiker View Post
    Clean rotors cant be understated.
    ...well they could be quite easily actually, definitely not overstated though.

  72. #72
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    I don't notice any difference in braking on my fat bike vs my other bikes. 180/160 rotors on all of them. XT on the fatty, slx on the 27.5, BB7 on the 29er.

    Sent from my SM-G900V using Tapatalk
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  73. #73
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    This thread is a little messed up. As stated, brakes should serve the application... which basically comes down to weight and speed. The fact that the bike is a fatbike is irrelevant.

    I read something about a guy who put super light aftermarket wheels on his turbo car. He said it ruined his wheel bearings on track day. Why? Heat management. The auto mfr. specified certain wheels for the car. When he went super light, there was no where to dissipate the heat from braking. If he was driving on the street, he never would have noticed a problem. Wrong application for the wheels.

    For heavy duty stopping, you probably need bigger, if not thicker, rotors (think off-road tandem). If you are just tooling along and don't weigh a lot, then it probably doesn't matter much.

    -F

    Quote Originally Posted by NH Mtbiker View Post
    Loved bb7 on one wet and very muddy vt50...08? Able to flip the bike upside down and dial in the pads trail side without skipping a beat!
    This happened to me once in TN. I was cranking out my barrel adjusters between corners just to maintain a little braking. It was aggravating and a little dangerous. By the time I reached the bottom the rotors were grinding on the calipers. If it'd been any longer of a hill, I'd have had to stop and turn the red dials. However, that is my only beef with BB7s. I have them on 2 bikes including the tandem.
    It's never easier - you just go faster.

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    I completely agree that body weight/terrain/ridding style and brake choice/setup can have a much bigger effect than tire size.

    That said, I think a good summary when comparing fat vs skinny with identical riders/terrain/brake set up is that a couple factors make it so you will build up more heat and also need to apply a bit more force to the brake lever on the fatbike:

    1) in some cases a fat wheel will have a larger diameter giving the rotor less leverage.
    26" to 29" is about a 10% increase similar to going from a 160 to a 180 rotor.

    2) increased inertia of the heavier wheel during deceleration (doesn't make a difference if applying brakes to maintain a constant speed). I crunched through the numbers in a previous post and for me, a relatively light weight rider on somewhat heavy bikes, the difference here was about 9%. Again, almost a full rotor size.

    3) increased traction on the fatbike means it is often possible to apply a larger braking force before skidding

    I get by just fine with one finger braking on 160mm rotors front and rear on both my fat and 26" bike, but that's probably just because I'm not pushing my equipment near the limit of what it can do. I'm guessing I could go down a rotor size on my skinny bike, but I'm not enough of a weight weenie to care.

    If a 160mm rotor is almost too small for you on a skinny bike, it isn't unreasonable to expect you might want to jump up a rotor size on a fatbike.

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    #3 FTW - the others are irrelevant by comparison.

  76. #76
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    Brake test for beach riding on the Kenai Peninsula Alaska, summer 2015.
    Fat bike; no brakes, no rotors, stopping power = stop peddling and putting foot down. Skinny bike; never started moving no need to for brakes. This test was done without the use of a mongoose or any other department store bike.
    ptarmigan hardcore

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    Yeah, I remember reading an article, I think it was in Bunyan Velo, of several guys who were riding/packrafting the coast of Alaska, and half skipped brakes. Scares me to think of it, but I guess if you are always going slow enough. Plus the one guy (I believe Eric of Revelate Designs) said that brake pads were gone in a day anyways.

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    This happens in every forum I've ever visited. Someone ask for advice and people start fighting about who is right about the required length of your fingernails during a full moon summer night dance.

    Quote Originally Posted by mabrodis View Post
    I know they are supposed to dissipate heat better that way but it seems at some point the pad has to actually touch metal to stop the bike, so having more than 50% air holes limits how much pad-to-metal engagement you can have.
    Ideas?
    If disc were not perforated, they would provide more braking surface, but they would also be heavier. And we all know how reducing half a pound from a bike boosts its sales.

    And interestingly too, those perforations create "hot spots" on the disc, where the heat remains isolated, thus keeping a lower overall temp.

    Also, the holes aid in removing water from the rotor surface, creating a gap where the water can go when they contact the brake pads.

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    Just because...

    So initially I decided to spend money on brakes, my bike had the simple but effective cable tektro with 160 mm front and rear. So I decided upgrade to XTR hydraulic brakes and 203 / 180 mm rotors. When order the components I forgot to order the 203 mm adapter so I went to The Home Depot and bought some stuff like longer bolts, loctite, washers, nylon spacers etc, so below is the result:
    Attached Thumbnails Attached Thumbnails Fatbike braking -vs- skinny tire braking-img_7201.jpg  

    Fatbike braking -vs- skinny tire braking-img_7200.jpg  

    Fatbike braking -vs- skinny tire braking-img_7199.jpg  

    Fatbike braking -vs- skinny tire braking-img_7196.jpg  

    Fatbike braking -vs- skinny tire braking-img_7195.jpg  


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    What you did with those hardware pieces is basically what the branded spacer does. However, I'd consider replacing your set up for a solid 1 piece spacer. Just for peace of mind while riding. Also, easier servicing
    Last edited by patico_cr; 04-25-2017 at 07:54 PM. Reason: Change 'piece' to 'peace'

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    What you are doing with the longer bolts is applying more force to the bolts themselves. Please go get the proper spacers before you do damage to your bike or yourself.

  82. #82
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    Geez, no kidding , I agree with the two posts above. Get the proper adapter and bolts from a bike shop, not home depot.
    You'll be spending a lot more on a trip to the hospital...

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    Quote Originally Posted by Shark View Post
    Geez, no kidding , I agree with the two posts above. Get the proper adapter and bolts from a bike shop, not home depot.
    You'll be spending a lot more on a trip to the hospital...
    Thanks every once for the advise, I just ordered both, should be here in a week jeje

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    By tilk in forum Brake Time
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    Last Post: 12-07-2011, 10:47 PM

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