Mountain Bike Reviews Forum banner

Is your bike "over-braked"?

3K views 21 replies 12 participants last post by  madsedan 
#1 ·
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. (?)
 
#3 ·
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.
 
#4 ·
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 ·
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.
 
#6 ·
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.
 
#9 ·
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 · (Edited)
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 :thumbsup:
(the Ashima Ai2 180mm adds 15g + 13g adapt, for an 83g saving over stock).
 
#19 ·
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 ·
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 ·
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 ·
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.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top