Soon to be 29r. I've got a question about brakes- Mtbr.com

# Thread: Soon to be 29r. I've got a question about brakes

1. ## Soon to be 29r. I've got a question about brakes

I am soon to recieve my new "Juice" frame and this is my 3rd bike but the first one that I am building up. I have a question for you guys. Thanks for any input in advance!
What is the best size disc brake to run? 160,180? I would think 180mm would be better having larger wheels but, does 160mm work good? I just don't know what to expect with the larger wheels/tires. Thanks again!

2. ## Doing the math...

Originally Posted by Konapdlr
I am soon to recieve my new "Juice" frame and this is my 3rd bike but the first one that I am building up. I have a question for you guys. Thanks for any input in advance!
What is the best size disc brake to run? 160,180? I would think 180mm would be better having larger wheels but, does 160mm work good? I just don't know what to expect with the larger wheels/tires. Thanks again!
160mm = 6.299 inches
180mm = 7.086 inches

Ratio of 6.299"/7.086" = ~.88
Ratio of 26"/29" = ~.89

So my guess is go with 180mm on a 29" for a similar feel to 160mm rotors on a 26".

I'm in the same position BTW - waiting on a Leviathan. I'd like to hear some anecdotal experiences with different rotor sizes.

3. OT, but what is that blue bike? It looks really nice.

4. ## Either are fine

Originally Posted by Konapdlr
I am soon to recieve my new "Juice" frame and this is my 3rd bike but the first one that I am building up. I have a question for you guys. Thanks for any input in advance!
What is the best size disc brake to run? 160,180? I would think 180mm would be better having larger wheels but, does 160mm work good? I just don't know what to expect with the larger wheels/tires. Thanks again!
I'm a big heavy guy and I stop just great with Avid BB7s and 160mm rotors on my SS 29r. I will admit I stop a slight bit better with the larger rotors and same BB7 brakes on my 26" FS bike. Get good brakes to start with, I'm very fond of Avid mechanicals and won't put anything else on my bikes. There are many here who are fond of their various hydraulic brakes (they are entitled to their opinion). If you do a lot of steeper technical descents, the bigger rotors can't hurt, just a small price and weight penalty for a bit more stopping power.

5. ## Looks like a Waltworks.

Originally Posted by Ojai Bicyclist
OT, but what is that blue bike? It looks really nice.
I have a yellow one. That is a cool pic!
Later, Doug

6. I'm running Avid mechanical disc brakes with a 185mm front and 160mm rear. Works pretty well in my opinion. I think it makes a lot of sense to run a larger brake in the front than the rear. (Just look at any motorcycle).

7. ## Thor's right on

185 front
160 Rear.

Avids, Magura, hayes whatever. I initially had the 160 front rotor, but swapped out for the 185 and it's felt much better. I try to stay off the brakes as much as possible, but when I need'em, I really need'em!

My 2 cents...

8. Originally Posted by NoCoasting
160mm = 6.299 inches
180mm = 7.086 inches

Ratio of 6.299"/7.086" = ~.88
Ratio of 26"/29" = ~.89

So my guess is go with 180mm on a 29" for a similar feel to 160mm rotors on a 26".

I'm in the same position BTW - waiting on a Leviathan. I'd like to hear some anecdotal experiences with different rotor sizes.

I suck at math!

9. Awesome, I am also in the process of building up my new Juice. Sure hope that Reba comes on the brown truck tomorrow, thats all I need.

Anyway, I was thinking about the same thing today. Right now what I have are my Hayes HFX9 hydros with the standard 6" rotors. I expect some loss of braking power, but given the fact that I have always had plenty of it, I don't think I am going to upsize to a 180 in the front. In my case, I think the Hayes brakes will work a little smoother on the 29er. A lot of people will comment on the on/off feel of Hayes brakes and I am one of them. I would think the extra rotational mass on the bigger wheels will help calm that down.

Post some pics when you get it built up. I will do the same.

10. ## Hydro's are the shizzle!

I recently converted to Magura Louise, and Louise FR in the front(big rotor) from an Avid set.

The diff. is amazing. I can modulate much better now, and I have tons more braking power. THe Avids are still a great choice, but if you have the \$\$, and the setup doesn't scare you off, hydro is the way to go.

I think you're spot-on about the Hayes brakes. The added mass of the big-wheels, will cancel out the modulation sensitivity. Should be a good setup.

JohnnyD

11. ## Rotor size, depends on where you ride, right?

Seems like rotor size would be dependent on where you ride, right? I have 160s both front and rear and would never even consider a need to get larger rotors. But my most ridden trail is named "Flatwoods" to give you an idea of my terrain :-)

12. ## I wanted big rotors

but started out with 6 inchers and found that after properly setup and bedded in, they work great...as for brake force...I use one finger and can lock up the rear if i get too anxious, and the front will toss me if i get into it too hard.

comming off v-brakes and going to 6 inch discs, i found discs to produce that "how did i ever live before these things" type of feeling. I suspect that larger rotors would be even more plush, but dont fear the 6.

Ken

13. The only two guys I know personally that ride 29ers run 6" rotors and have no complaints. That said, I don't know how a larger rotor could hurt, so I don't see any reason not to upsize. In fact, my 185mm Avid mechs are listed on UPS.com as 'out for delivery' as we speak. They're slated for my Niner. More parts! Yay!

Oh, and I weigh in at around 200 and am of the opinion that when you're riding the steeps, it's better to have more braking than less. Just my two cents.

14. ## The Big Blue Beast

Originally Posted by Ojai Bicyclist
OT, but what is that blue bike? It looks really nice.
That's my Waltworks SS 29r, it is a beauty. Walt built it to endure, and it rides great!

15. Rock Lobster has 185 front 160 rear. BB5's. Stops great.

Rig has 160 front and rear. BB7's. Stops great.

What I'm trying to say is that I don't think a 185 is needed out back. It adds a bit more stopping power up front, but I don't think it's something that is a complete necessity.

16. 6" juicy's on my monkey. THey were not large enough coming down the SE ridge of Mt Elbert. Probably would have liked larger rotors on some of the other longish descents like the Monarch Crest trail. I got through though. They squealed, howled, and burned up in half a season (no, i'm not a skidder either).

THinking about it, I'd go 185/160 or 185/185 if I had a geared or a full squishy for sure (assuming I'd ride more hills or faster - but perhaps that's a bad assumption)

I recently converted to Magura Louise, and Louise FR in the front(big rotor) from an Avid set.

The diff. is amazing. I can modulate much better now, and I have tons more braking power. THe Avids are still a great choice, but if you have the \$\$, and the setup doesn't scare you off, hydro is the way to go.

I think you're spot-on about the Hayes brakes. The added mass of the big-wheels, will cancel out the modulation sensitivity. Should be a good setup.

JohnnyD
And as I suspected, the on/off modulation is gone. I can still do a stoppie even with the 29er wheels. I am impressed so far.

18. Alot of great info. Looks like I can just put on whatever good deal I run across whether it be 6" or 8", mech or hydralic. I think I would like to go with hydralic though. Both of my other bikes have mechanical so it would be nice to try out hydralics.
It is good to hear that 6" is working fine. I found a deal for 6" Avid juicy 7's for \$299 (front and rear). Can't remember which shop though. Gonna have to do some searching again for it.
Thanks again for the two cents everyone put in. My frame wont be in til the end of March but the parts will be coming in all next week I will post pics as it gets assembled.

19. Originally Posted by Konapdlr
Alot of great info. Looks like I can just put on whatever good deal I run across whether it be 6" or 8", mech or hydralic. I think I would like to go with hydralic though. Both of my other bikes have mechanical so it would be nice to try out hydralics.
It is good to hear that 6" is working fine. I found a deal for 6" Avid juicy 7's for \$299 (front and rear). Can't remember which shop though. Gonna have to do some searching again for it.
Thanks again for the two cents everyone put in. My frame wont be in til the end of March but the parts will be coming in all next week I will post pics as it gets assembled.
Why so long of a wait? My supplier had them in stock, so I had it in 2 days. Are you holding out for the red one?

20. ## No difference...

....in the stopping force needed for a 26er or 29er.

Force = Mass * Acceleration

Assuming approx. same total weight (yeah I know, the 29er will be slightly heavier but neglectible IMHO compared tot the total mass of bike+rider) and same speed the total forward force will be the same, hence the force needed to stop this mass will be the same.

Like someone posted before it depends more on your total weight and riding conditions wether or not you might need extra braking force. Heavy or lots of long descends and you might appreciate a bigger rotor and/or more piston caliper.

21. 160 is fine for me....180 is not worse certainly but heck, for XC riding (unless a clyde of course) 160 is fine (note: DH racers did not always have disc brakes)

22. ## Correct

[QUOTE=Dave.]Seems like rotor size would be dependent on where you ride, right?

Just got back from Tampa, did some riding and 160's would be fine. But here in Cal most of our trails are long up hill and long down hills. 180mm hydros for me.

23. Originally Posted by TiBiker
....in the stopping force needed for a 26er or 29er.

Force = Mass * Acceleration

Assuming approx. same total weight (yeah I know, the 29er will be slightly heavier but neglectible IMHO compared tot the total mass of bike+rider) and same speed the total forward force will be the same, hence the force needed to stop this mass will be the same.

Like someone posted before it depends more on your total weight and riding conditions wether or not you might need extra braking force. Heavy or lots of long descends and you might appreciate a bigger rotor and/or more piston caliper.
I have to disagree. It works the same on a lifted truck or SUV. When you put bigger wheels and tires, braking performance decreases. I certainly noticed a difference when I put my 160s on the 29ers, though not much of one. It is still much better than v-brakes.

24. ## Great Discussion

What a brake does of course is convert the mechanical energy of vehicle and rider into heat, with ME being a total of the kinetic and rotational energies of the vehicle: ME = KE + RE.

If they weighed the same and were travelling at identical speeds, a 26" and 29" bike will have identical KE. The latter will have a little bit of extra rotational energy to dissipate from its larger wheels, about 10% by my calcs of RE (my assumptions were based upon the 29er tire, tube, and rim being 10% heavier than 26" equivalents because their circumferences are 10% greater- seems reasonable). For a bicycle with rider I think the KE term is predominant over RE so the '9er guy will just need to apply slightly more lever force to stop or slow down.

Other Stuff: the 29er doesn't have the "benefit" of a 26er's slightly greater rolling resistance under braking, so maybe toss another 3-4% stopping disadvantage to the 'niner. He might need another pound of lever force, who knows? If a 29er can take advantage of the added traction made possible by its longer contact patches then the rider will be tempted to brake later and harder, which would also increase the demands placed on its braking system.

I think The Bottom Line is the biggest reason 29ers would need larger rotors is if the rider's newfound confidence results in much higher speeds and resulting much higher KEs. If speeds have not gone up then it doesn't appear there's a real need to upsize based solely upon wheel size.

Anyway, interesting discussion and most thought provoking- but it's time to go ride now!

25. Bikerboy.....yes, I am holding out for the red one. Two weeks ago I was riding with a couple and they had a red juice. Absolutly a sweet color. I have been wanting a copper colored bike and this "red Spice" comes real close. But, to be honest. When I saw the "midnight grey" I think thats what they call it, I was torn. But, the red won out. The one thing I like about the grey one is that it is disc specific. I talked with Justin at Soma and he said the red isn't (why cant they just take the ones slotted to be painted in the grey and also paint some red?)
And I am getting ready to order my brakes tonight. From all the post I have read I have decided to get Hydros. 180 up front and 160 in the rear. Should work great.

26. Originally Posted by Konapdlr
Bikerboy.....yes, I am holding out for the red one. Two weeks ago I was riding with a couple and they had a red juice. Absolutly a sweet color. I have been wanting a copper colored bike and this "red Spice" comes real close. But, to be honest. When I saw the "midnight grey" I think thats what they call it, I was torn. But, the red won out. The one thing I like about the grey one is that it is disc specific. I talked with Justin at Soma and he said the red isn't (why cant they just take the ones slotted to be painted in the grey and also paint some red?)
And I am getting ready to order my brakes tonight. From all the post I have read I have decided to get Hydros. 180 up front and 160 in the rear. Should work great.
I think running a 180 up front isn't a bad idea. I was taking parts from an existing bike and putting them on the Juice, so I didn't have much choice unless I wanted to spend extra money on a larger rotor. I think 160 is fine, but it never hurts to have more braking power.

What brand/model of brakes are you getting?

27. 160mm rotors stop me like rim brakes stop small guys.

I can get away with 185mm up front and 160mm out back and have plenty of power...but with that set up the rear heats up much easier and squeels, etc.

I've settled on dual 185mm rotors on all my bikes except my Behemoth which gets dual 203mm...

p.s. i'm falling in love slowly with the Juicy 7's. I'd be head over heals if for some strange reason the front left caliper didn't surge inward today and cause some noise/rubbing 30 miles in to a ride.

every time i get back on mechanicals i begin to think..."wow, these just don't feel as good."
they stop well, but they usually only feel great for about 3 rides until the housing begins to muck up....at least IME.

28. Originally Posted by bikerboy
I think running a 180 up front isn't a bad idea. I was taking parts from an existing bike and putting them on the Juice, so I didn't have much choice unless I wanted to spend extra money on a larger rotor. I think 160 is fine, but it never hurts to have more braking power.

What brand/model of brakes are you getting?
I ended up buying Avid juicy 5's. Pricepoint has a great deal on them. Paid \$257.00 total for 185 front, 160 rear. I think they will be a good intro hydro set. They are already pre-bled, no dial in knob on the lever but thats ok. I also like their lever design/angle compared to Hayes. On the average, 1 set of juicy 7's run for the price I paid for the 5's.
Man! Christmas has come early! I have so many parts being shipped out. All I am missing is wheels, fork.....Oh, and the frame

29. Mattman,

I've got that same color Waltworks that should be bult up here within the week. I even have the same brakes. Having come off a brief stint with XTR discs, I'll be interested to see how they compare. Before that it was several years with XTR V-brakes. I moved from the South to the Northwest and it's just too wet and muddy for the rimmies to cut it.

Also, is that a Turner 5 Spot I see? That's the other bike I had and wish I had back! Tell me more about it. The mech discs are working well on it too?

30. I switched from 160 f+r to 185's f+r....I definetely get alot more braking power and modulation is also better in my opinion. I rarely had problems with my 160's, just the long South Mountain decents would give me some brake fade and I felt like I had a death grip on my levers...

31. I have a pair of BB7 160mm's. Can I simply buy a larger rotor (185mm) or is it an entirely different brake?

32. Originally Posted by cocheese
I have a pair of BB7 160mm's. Can I simply buy a larger rotor (185mm) or is it an entirely different brake?
All you need is the larger rotor and an adapter bracket to line up the caliper with the larger rotor. Its a fairly cheap conversion.

33. Originally Posted by singlespeedsycip
I switched from 160 f+r to 185's f+r....I definetely get alot more braking power and modulation is also better in my opinion. I rarely had problems with my 160's, just the long South Mountain decents would give me some brake fade and I felt like I had a death grip on my levers...
So did you hit Hawes today? I am heading out there in about an hour. I have never ridden Twisted sister so I think I am gonna hit it.

34. Thanks bb, I'll look into that.

35. ## I talked two the two owners of

the biggest 29er shop around here and they both are totally sold on vee-brakes for 29er. I find that interesting- one is a big guy (over 200) and the others is really little but they both say they prefer vees on twenty niner, saying that the slight loss in power just turns into more modulation using vees for 29 inch wheels. I'm using avid arch rivals, just because of the ease of taking off the back wheel/changing flats/changing gearing and they work well. It's mostly dry around here as well. Oh, and they weigh a lot less.

36. Wouldn't V-brakes be more powerful on a 29er than a 26er? Seems like the same principle as larger rotors.

37. ## that's what they said

Originally Posted by bikerboy
Wouldn't V-brakes be more powerful on a 29er than a 26er? Seems like the same principle as larger rotors.
that said, I'll likely go with discs anyway. I just can't quite convince myself to go back to Vs. I'm trying, just really can't.

38. Uh oh....the V-brakes vs disc argument. Run while there's still time....

On a slightly related subject, I got my set of 185mm BB7s on Friday. 160 for the pair, new in box. Good deals over at Greenfish if anybody is interested.

39. Originally Posted by Lucky 7
Uh oh....the V-brakes vs disc argument. Run while there's still time....

On a slightly related subject, I got my set of 185mm BB7s on Friday. 160 for the pair, new in box. Good deals over at Greenfish if anybody is interested.
Well I have recieved alot of responce to this topic so, Hijack if you must!

40. from my own experience.
larger rotors may help negate any caliper spoke lovin you may not want.
however i was able to solve my problem with 160 rotors.
may not be an issue with yer soma.

41. I was on a Juice today over at Slippery Pig (LBS). Had V brakes on it. Didn't really care for them but I also wasn't on a trail really testing them out. I think disc is the way to go (personal opinion). This will be my first hydralic disc brakes and I am looking forward to no cables anywhere (shifters, brake lines, derailers) and no cable stretch and wear. Not that it's that big of an issue. It's just a simple thing!

42. Originally Posted by Konapdlr
I was on a Juice today over at Slippery Pig (LBS). Had V brakes on it. Didn't really care for them but I also wasn't on a trail really testing them out. I think disc is the way to go (personal opinion). This will be my first hydralic disc brakes and I am looking forward to no cables anywhere (shifters, brake lines, derailers) and no cable stretch and wear. Not that it's that big of an issue. It's just a simple thing!
the pig? hell we prob. would recognize each other.
this was my first run at discs and i think it's one of those things - i'm hooked. even with the polarizing juicy 7s. 200+ miles on em and lovin it.

43. Originally Posted by YuriB
the pig? hell we prob. would recognize each other.
this was my first run at discs and i think it's one of those things - i'm hooked. even with the polarizing juicy 7s. 200+ miles on em and lovin it.
You go there alot Yuri? That was my first time in there. Since moving to AZ I have been trying to hit most of the bike shops. So far "the pig" is my favorite. Eric is a cool guy and they stock things that most bike shops here locally dont have. They are a 29'r friendly shop. They had pretty much everything I ordered online for this build. Wish I would have known I would have given them the business.
I get tired of going into bike shops and seeing nothing but Trek & Specialized. Nothing against those manufacturers, they make a good product. I am just more of a "off the beaten path" kind of buyer. I like the smaller builders.

44. Originally Posted by Konapdlr
So did you hit Hawes today? I am heading out there in about an hour. I have never ridden Twisted sister so I think I am gonna hit it.
Sorrry I'm a little late with my reply, I just saw your post. I did ride Hawes, the usual stuff cardiac hill, mine trail, and some of twisted....my juicy's started the dreaded shuddering that some have experienced...Its really bad, the whole fork flexes. I talked with Avid and they are sending me the clean sweep rotors which are supposed to fix the problem...time will tell...I just want to ride my damn bike with no problems for a while.
Did you ride twisted? Its a great trail, just real loose right now....

45. Originally Posted by singlespeedsycip
Sorrry I'm a little late with my reply, I just saw your post. I did ride Hawes, the usual stuff cardiac hill, mine trail, and some of twisted....my juicy's started the dreaded shuddering that some have experienced...Its really bad, the whole fork flexes. I talked with Avid and they are sending me the clean sweep rotors which are supposed to fix the problem...time will tell...I just want to ride my damn bike with no problems for a while.
Did you ride twisted? Its a great trail, just real loose right now....
That whole dang trail is loose! No, I didn't ride twisted. I went up towards Hawes Rd entrance off of Pig so I could cruise back down and hit a few jumps. Get this......there were NO tire tracks on that part of the trail towards Hawes. I couldn't believe it! Was wondering if it's built up at Hawes Rd now and there is no entrance? Anyways, I just zig-zagged around the loop. Tried to change it up a bit. Starting to get bored there. I ride Hawes to much and nowhere else. Gonna have to change that.

46. Originally Posted by Konapdlr
You go there alot Yuri? That was my first time in there. Since moving to AZ I have been trying to hit most of the bike shops. So far "the pig" is my favorite. Eric is a cool guy and they stock things that most bike shops here locally dont have. They are a 29'r friendly shop. They had pretty much everything I ordered online for this build. Wish I would have known I would have given them the business.
I get tired of going into bike shops and seeing nothing but Trek & Specialized. Nothing against those manufacturers, they make a good product. I am just more of a "off the beaten path" kind of buyer. I like the smaller builders.
eric sold me my 29er and a 26er kona so yea i spend some time and lots of money there. being a mile from my house and just off my commute path helps too.

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