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  1. #1
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    Is your bike "over-braked"?

    So, we're always trying to shed bike weight in this forum, and I thought I'd share something I've noticed about brake setup...

    Moved to an Epic last year (size L), and it came with 160mm rear, and 185mm up front. Braking was brisk, plenty - more than enough. I'm ~185 lbs geared up, BTW, and do XC.

    In a continued effort to lighten my bike, I noticed that the frame itself is setup for 140mm on the rear and 160mm up front if no adapters are used. Thought I'd take a chance and ditch the weight of the adapters, and rotors, by downsizing. (Also moved to XTR from Avid XX brakes if that's relevant.) Found the braking was great. I was a bit surprised actually.


    So, Phlegm, what's with the essay? Your post sucks. What's your point?


    Well, I guess I'm saying that you might consider downsizing one or both rotors if you are running out of ideas to kill weight. If you're lucky you might be able to drop some adapters too. I'm starting to wonder if some bikes are just "over-braked" from the factory. (?)

  2. #2
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    The new XTR brakes have plenty of power with 140/160 rotors and I'm 200 pounds. When I ran 160mm rear rotors the rear wheel locked all the time.
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  3. #3
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    Agreed. I ended up 140/160 for a while due to available parts and stumbled on a 170 front without adapters. Good control without lockup or funky rigging. Deore 525 Hydros. In fact, same principle applies to car brake design for the same reason.
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  4. #4
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    My brakes used to be a bit touchy, went tubeless and they grab like a beast now, on/off, not much in between. I started using one or the other, not both together, complete PITA. My guess is the decreased momentum of the lighter wheel is effectively making the brakes more powerful?

    Hayes Stroker Ryde, 160mm XT rotors.

  5. #5
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    Quote Originally Posted by shupack View Post
    My brakes used to be a bit touchy, went tubeless and they grab like a beast now, on/off, not much in between. I started using one or the other, not both together, complete PITA. My guess is the decreased momentum of the lighter wheel is effectively making the brakes more powerful?

    Hayes Stroker Ryde, 160mm XT rotors.
    The weight you saved is almost negligible when you consider the weight of the bike/rider combo that your brakes are trying to slow.

    I'd bleed your brakes and look at some different pads, because what you have isn't working properly.

    How many fingers do you have on your brake levers? Try just one.
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  6. #6
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    The weight you saved is almost negligible when you consider the weight of the bike/rider combo that your brakes are trying to slow.
    I agree, but going tubeless was the ONLY change from when the brakes were OK but grabby on my ride Wednesday to horribly grabby on Friday, the change in the brakes was immediate. It was only 1/2lb/wheel, which I agree, is a fraction of the whole package, but a significant amt of rotating mass reduction (which lead to my guess).

    I'd read several stories of people getting sealant on their disks, so I removed them before doing the conversion, wore surgeons gloves to keep them free of finger oils...

    I had the same wheels/rotors and Fox fork on my last bike with LX brakes and they worked beautifully.

    I use one finger on the lever, I experimented with moving the levers outward on the bar so my finger is closer to the lever pivot. Better, but still grabby.

    I flushed the fluid and bled them 3 weeks ago, made no difference then.

    I've already ordered new pads, will see how that goes when they get here.

  7. #7
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    I've only ridden the first gen Hayes brakes, and they were very on/off, as you describe.

    Maybe save your coins for something else? I've always been impressed with Shimano brakes, and the 2014 XTRs are very light.
    www.seanhannity.com <=not what you think it is.

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  8. #8
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    Maybe the increased braking performance is due to better brakingtraction in the tire now that it deforms better and grips better to the surface due to being setup tubeless?

  9. #9
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    Quote Originally Posted by juan_speeder View Post
    I've only ridden the first gen Hayes brakes, and they were very on/off, as you describe.

    Maybe save your coins for something else? I've always been impressed with Shimano brakes, and the 2014 XTRs are very light.
    Yeah, I've been searching for a deal on a close-out 2013 XTR set.

    Maybe the increased braking performance is due to better brakingtraction in the tire now that it deforms better and grips better to the surface due to being setup tubeless?
    possible, but I had them at 40psi last ride to make sure they were sealed/seated (a bit squirly, but still had great traction). I'll see if it's different at 30psi today or tomorrow on my next ride.

  10. #10
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    Yes, agree that with 180/160mm my braking is always enough or 'too much' - can lock even with 1 finger. Haven't noticed fade during long descents.

    My Front (2012 Rockshox Sid) can be changed down to 160mm, saving weight of adapter and some disc weight.

    Rear doesn't have adapter so looks like being stuck to 160mm. But because it is over braked it could be changed for a WW 160mm rotor that saves weight at the cost of some braking power.

    Many newer bikes with rear caliper post mounts may be limited to 160mm minimum diameter, although I 'think' Specialized can run down to 140mm (?).

    Some Random Calcs based on my current setup:
    Avid 180mm = 135g
    Avid 160mm = 93g
    Fr P-P adapt = 13g
    Existing Total = 241g

    Simply changing to a stock Avid 160mm on front saves 42g + 13g adapt = -55g.

    Going 'exotic' with 2x Ashima Ai2 160mm (@65g ea) saves 98g + 13g adapt = -111g.
    At <$60 a pair that's 54c/g of rotating mass
    (the Ashima Ai2 180mm adds 15g + 13g adapt, for an 83g saving over stock).
    Last edited by purdyboy; 11-05-2013 at 06:55 PM. Reason: Added weight calcs at bottom...
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  11. #11
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    Yep, that's some nice weight savings, for reasonable cash.

    Correct, my Epic frame runs a 140mm in the rear sans adapter, so that's what I've done. No complaints after several months running smaller-than-stock front and rear.

  12. #12
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    it's a good idea if you are running shimano brakes. With avid brakes i woldn't do it.

  13. #13
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    If you have brakes, your bike is definitely over-braked, as Casey Brown demonstrates

    https://www.youtube.com/watch?v=WXZugEbDzes
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  14. #14
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    Quote Originally Posted by rockyuphill View Post
    If you have brakes, your bike is definitely over-braked, as Casey Brown demonstrates

    https://www.youtube.com/watch?v=WXZugEbDzes
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  15. #15
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    Yep, gotta agree.
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  16. #16
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    Quote Originally Posted by shupack View Post
    My brakes used to be a bit touchy, went tubeless and they grab like a beast now, on/off, not much in between. I started using one or the other, not both together, complete PITA. My guess is the decreased momentum of the lighter wheel is effectively making the brakes more powerful?

    Hayes Stroker Ryde, 160mm XT rotors.
    Moving rotors used with one brand of brake pad to another doesn't always give good results.

    My experiences have shown that it is your used rotors that are the problem. The rotors you have were basically embedded with the LX brake pad material from your previous set up and they are likely to also be worn unevenly in their own unique way. They may not be excessively worn, but they are used. They may have previously had resin pads and now you have metallic pads. Maybe not. Either way, the bedding in process is more important on some brakes than others. But when you mix and match used rotors and put them on a brand new brake from a different manufacture, its a crap shoot. It might work perfect, it might not.

    I think you are merely being distracted by the fact that you went tubeless around the same time as installing new brakes. New brake calipers on used rotors that are unevenly worn or simply well used can in fact take longer to bed in. It may have taken more than one ride. A new pad and a new rotor will bed in rather quickly because of the matching surfaces that are almost perfectly flat with a lightly scuffed finish from the factory. A used rotor has peaks and valleys that run all the way around the rotor. Even if its not excessive, it is still factoring in to your problem overall.

    If your rotors aren't too unevenly worn, you can try to sand the rotors thoroughly with most any medium or fine sandpaper you have laying around and clean with a strong solvent of your choice. Wash off with very lightly soapy water.

    Fresh brake pads typically have (in one form or another) an outer surface/texture that is designed to aid in the bedding in process involved with their specific pad and rotor. Sanding your (now used hayes) brake pads will likely help regain a flat surface.

    New pads, and a fresh rotor from Hayes is your best bet. Its all about the bed in process. Its expensive, but true. Of course, you can simply try sanding down the rotor and pads that you have and give that a shot before spending the money.

  17. #17
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    Quote Originally Posted by SmilMick View Post
    Moving rotors used with one brand of brake pad to another doesn't always give good results.

    My experiences have shown that it is your used rotors that are the problem. .
    I agree, the first thing I did was sand the rotors/pads for a fresh surface then re-beded the brakes. Acted exactly the same. Just found a set of new XT brakes for $220, that (plus new rotors) should cure my issues

  18. #18
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    Quote Originally Posted by SmilMick View Post
    Moving rotors used with one brand of brake pad to another doesn't always give good results.

    My experiences have shown that it is your used rotors that are the problem. The rotors you have were basically embedded with the LX brake pad material from your previous set up and they are likely to also be worn unevenly in their own unique way. They may not be excessively worn, but they are used. They may have previously had resin pads and now you have metallic pads. Maybe not. Either way, the bedding in process is more important on some brakes than others. But when you mix and match used rotors and put them on a brand new brake from a different manufacture, its a crap shoot. It might work perfect, it might not.

    I think you are merely being distracted by the fact that you went tubeless around the same time as installing new brakes. New brake calipers on used rotors that are unevenly worn or simply well used can in fact take longer to bed in. It may have taken more than one ride. A new pad and a new rotor will bed in rather quickly because of the matching surfaces that are almost perfectly flat with a lightly scuffed finish from the factory. A used rotor has peaks and valleys that run all the way around the rotor. Even if its not excessive, it is still factoring in to your problem overall.

    If your rotors aren't too unevenly worn, you can try to sand the rotors thoroughly with most any medium or fine sandpaper you have laying around and clean with a strong solvent of your choice. Wash off with very lightly soapy water.

    Fresh brake pads typically have (in one form or another) an outer surface/texture that is designed to aid in the bedding in process involved with their specific pad and rotor. Sanding your (now used hayes) brake pads will likely help regain a flat surface.

    New pads, and a fresh rotor from Hayes is your best bet. Its all about the bed in process. Its expensive, but true. Of course, you can simply try sanding down the rotor and pads that you have and give that a shot before spending the money.
    Yeah, mix and match is a crap shoot. I'm running Ashima AiRotors (v1) 160/160 on my singlespeed bike with Hope Mono Minis and cheap ebay Kevlar pads, and that combo works nicely. On my hardtail, I got Ashima AiRotors (V2) with Shimano XTR brakes and Shimano semi-metallic pads, and it chatters like crazy at low speed. I'm tempted to get new rotors, it drives me so crazy. I have a couple of tight downhill steep switchbacks on my regular backyard ride, and that bike is a handful to get around those turns at very low speed.

    anybody have luck with sanding the rotors?

    But yeah, most of my friends' bikes are over-braked, IMO. I see a lot of 205 rotors on XC bikes. Now, I'm 210 pounds these days (and please, no hassle about weight weenie-ing... I know I gotta lose weight... working on that too) and most of my bikes run 160/160 rotors. I ride steeps and I can overheat my brakes if I try to, but I know how not to. My trail FS bike runs 180/160 rotors. That bike I can only smoke the brakes if I take it up to Downieville, or some other High Sierra riding spot, and hammer the hills. Other than that, no issues.

    I just have a hard time believing that my friends are smoking 205mm rotors and weigh 20-40 pounds less than I do.

  19. #19
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    anybody have luck with sanding the rotors?
    Yes and no, sanding my rotors and pads gave a nice fresh surface, bedded them in again and braking was more powerful, but still just as grabby. So cleaning them up improved things, but did not solve the issue I was after.

    I have a set of m758's with new rotors on the way. that should do it for me.

  20. #20
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    I recently did the swap to 160/140 using G3 Cleansweep rotors and M785 XT brakes. It worked well enough and I like that it prevented me from unintentionally locking up the rear, however after a few races and several hours I put the 160 back on the rear (160/160). Lever feel was never as good with the 140 and I missed being able to lock up the wheel in certain cases. Plus the weight savings was not too large, because even with a 140 I have to use a is-post adapter.

    29" Hardtail, 175#

  21. #21
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    Quote Originally Posted by zippinveedub View Post
    I recently did the swap to 160/140 using G3 Cleansweep rotors and M785 XT brakes. It worked well enough and I like that it prevented me from unintentionally locking up the rear, however after a few races and several hours I put the 160 back on the rear (160/160). Lever feel was never as good with the 140 and I missed being able to lock up the wheel in certain cases. Plus the weight savings was not too large, because even with a 140 I have to use a is-post adapter.

    29" Hardtail, 175#
    Thanks for sharing that bit. At the end of the day you have to find a setup that you like, so weight takes a back seat in that case. Also, as you mention, you had to add an adapter to drop down to 140mm in the rear, so the weight difference isn't as large.

    Also, appreciate the bike and weight details - good as a reference point. I'm running a 29er FS, and I'm 185 geared up.

  22. #22
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    I have gradually gone down to running 160 fr/rr over the last year and a half. Not going to say I was over braked but with each new build I've been gravitating to more powerful brakes that enable me to use a smaller rotor.

    My old standard would have been using Formula RX's with 180 fr/rr, I used those on a couple of bikes and really liked them, much better than the Avid's out a couple years ago and relatively light. I often used light rotors like ashima air, etc.

    Last year I started out with Magura MTs brakes, came on the Epic's last year, was running a 180/180 and then dropped to a 160 in the rear but the brakes were never great. Then the guys at my LBS said I had to try the new XT icetechs, I ran those on last fall's bike build and they were a game changer. But I bought them with 180/180 as I got them for the same price as the 160's. In retrospect I should have gotten 160/160 but the performance was alarming lol. Modulation was not as prevalent but the power was nuts.

    On my latest build with new X0 trails I'm running 160/160 HS1's and so far they have been great. At first they felt off compared to the XT's, running smaller rotors and different design with more gradual power delivery and modulation makes "finesse" feel like less power but I have adjusted my riding style a bit, back to the way I was riding before the XT's, and really like them now.

    I have no desire to run a larger rotor, and as someone else mentioned above, you get to drop the adaptor weight and extra hardware as well which not only drops some grams but also running a smaller rotor with fewer parts helps eliminate power loss through movement of the braking parts.
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