Brakes, carbon braking surfaces, and more power!

j-sworks

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#1
So I've got a wheel set from Tim, love them, but I want more stoping power and more predictable braking.

I'm left with two options, buy different wheels or upgrade my brakes in the hope of improved braking.

So I'm leaning towards Dura Ace 9000 or TRP.

Thoughts?
 

j-sworks

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#5
So what wheels did you get?


If I like them (and they are going for a steal to make way for new brakes), I'd say go for different wheels. :p
I had a set of Dura Ace 7900 hubs and built up a 38mm front and 52mm rear carbon clincher rim laced with Sipam Lazer spokes.

Might let them go, but not sure yet. They are bad ass wheels.
 

FarEast

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#6
first of all make sure that the brakes are set up as follows:

  • No slack in the cable pull
  • Brake blocks toe with the rotation of the wheel
  • Calipers are correctly aligned and that you get equal pressure from both left and right pads
  • Calipers are 2-3mm from the surface of the rim
  • You are using correct brake blocks/pads for the rims (I recommend the tNi carbon brake pads)
  • The surface of your braking track on the wheels are clean
Finally that your braking techniques are correct.
 
Sep 2, 2009
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#7
Whatever brakes you have at the moment, Dura Ace 9000 calipers, used with Dura Ace 9000 cables will be much, much stronger and smoother.

I use them on carbon rims and have no problem slowing down. I weigh more than you too, and go faster, so if they can stop me, they will definitely stop you. You do need a grip strong enough to be able to at least squeeze toothpaste out of the tube though, to get the most from them.
 

j-sworks

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#8
first of all make sure that the brakes are set up as follows:

  • No slack in the cable pull
  • Brake blocks toe with the rotation of the wheel
  • Calipers are correctly aligned and that you get equal pressure from both left and right pads
  • Calipers are 2-3mm from the surface of the rim
  • You are using correct brake blocks/pads for the rims (I recommend the tNi carbon brake pads)
  • The surface of your braking track on the wheels are clean
Finally that your braking techniques are correct.
All good information for sure.

Without having training on how to brake, I think I'm pretty much ok. I brake in a similar fashion to motor biking, as I've had a few of those, and I seem to brake more efficiently than your average Rider. Perhaps ;)
 

j-sworks

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#9
Whatever brakes you have at the moment, Dura Ace 9000 calipers, used with Dura Ace 9000 cables will be much, much stronger and smoother.

I use them on carbon rims and have no problem slowing down. I weigh more than you too, and go faster, so if they can stop me, they will definitely stop you. You do need a grip strong enough to be able to at least squeeze toothpaste out of the tube though, to get the most from them.
Wow that's nice Owen. I love the way you inform and demean at the same time.

Thanks for the tip about the DA cables, I didn't think about that party actually.
 

theDude

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#10
Without having training on how to brake, I think I'm pretty much ok. I brake in a similar fashion to motor biking, as I've had a few of those, and I seem to brake more efficiently than your average Rider. Perhaps ;)

I'd be interested to hear more about technique. I'm not sure how much of the motorcycle stuff applies.... Certainly the 'get braking done while going straight' does. But as there isn't really any suspension compression, that's all out the window in terms of however you deal with that (e.g. start light to compress forks before really grabbing them). Also not sure about trail braking / throttle out of the turn, etc.? We don't all have the power of Franz, er, I mean Owen, so that'll be a bit different I think.

More questions than answers from me, I'm afraid....

My braking is horrible. I keep forgetting which one is which. Even though I know it is EXACTLY backwards from my scooter, which I ride every day. Oh well.
 
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j-sworks

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#12
I'd be interested to hear more about technique. I'm not sure how much of the motorcycle stuff applies.... Certainly the 'get braking done while going straight' does. But as there isn't really any suspension compression, that's all out the window in terms of however you deal with that (e.g. start light to compress forks before really grabbing them). Also not sure about trail braking / throttle out of the turn, etc.? We don't all have the power of Franz, er, I mean Owen, so that'll be a bit different I think.

More questions than answers from me, I'm afraid....

My braking is horrible. I keep forgetting which one is which. Even though I know it is EXACTLY backwards from my scooter, which I ride every day. Oh well.
I use my body as the suspension which I can move around and unload/load, for instance when going through the apex I rotate my weight directly over and somewhat behind the BB so my weight is not resting on the front tire, and then in the straight between turns I go back to normal, and then again during heavy braking make sure my weight is directly centered over the BB.

With carbon I have found that it is helpful to feather the brakes, so no trail braking but sort of. I think of my body as what is being loaded/unloaded during braking.

I have not training here so don't take my comments as advice.
 

Yamabushi

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#13
I use my body as the suspension which I can move around and unload/load, for instance when going through the apex I rotate my weight directly over and somewhat behind the BB so my weight is not resting on the front tire, and then in the straight between turns I go back to normal, and then again during heavy braking make sure my weight is directly centered over the BB.

With carbon I have found that it is helpful to feather the brakes, so no trail braking but sort of. I think of my body as what is being loaded/unloaded during braking.

I have not training here so don't take my comments as advice.
Start jumping on my rides, you'll get plenty of descending practice, I promise! :D
 

saibot

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#14
I broke down a bought a couple of Reynolds Aero Carbon clinchers a few weeks back, with the intent of using them on the flatter rides, and as my main wheels once back home in sweden where we don't have any (paved) hills to speak of.
I did however take them on a shiraishi run, and descended on them too. I was super surprised about the breaking, I would say it was almost on par with my c24's (dry weather). But while the breaking power was more than sufficient, in the back of my head I was still worried about the heat build up.
That also turned out to be unfounded as as soon as I got down and touched the rim is was not hot at all, despite pretty constant breaking. Not very scientific I know but my c24s rims have been hotter after a descent. Will still use the c24 in the mountains because of the weight though.
While I have extremely limited experience with carbon clinchers, Reynolds seems to have done something right.
Breaks: DA9000
Pads: Reynolds Cryo Blue
(Wheels actually came with a sticker that warned not to use any other pads, especially cork based ones. No warranty with other pads than the Cryo Blue)
 

GSAstuto

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#16
I've been testing the new Swiss Stop 'Black Prince'. This pad debuted this year at the Giro (I believe) and is designed to be a high 'dusting' type of pad that offers good modulation and friction characteristics while decreasing heat transfer to the rims. Remember the old Swiss Stop Yellow pad is designed more towards old<er> carbon rims with smooth scrims. So - if you have newer rims with textured or basalt brake surface, the Yellow pads will destroy them due the increased friction. The Black Prince (and TNI's for that matter) are designed more towards the newer rims and will not melt into the rim causing excessive heat xfer and eventually rim failure. In fact, they won't melt at all - they simply deteriorate more rapidly into a fine powder.

Braking effort with these pads is lower than I expected - they feel almost like riding alloy wheels. Rain response is good, too. And high speed modulation is much better than both cork compounds or super hard pads. I'm pretty impressed.

I'll continue to test them - but I think they are on the right track here. We ship all our wheels with the OE version of the (black) pad and as long as riders used them correctly, they were good. However, as soon as the rider switched to other pad, we saw more rim failures due to excessive heat.

Almost every rim mfg recommends a particular pad. Pay attention to that! Even though rims look the same, the resins, layup materials, embedded particles and thickness are all different. Especially with carbon clinchers, its very difficult to have brakes that both stop effectively and don't fry the rims. Braking requires friction, friction generates heat, heat melts carbon. Period. It's a very fine line to cross.

What happens in a carbon rim is completely different than alloy. Alloy will absorb and dissipate heat through the metal. Aluminum, in particular, does a great job of this. During braking, the rim will eventually reach a fairly constant temperature throughout it's entire structure acting as a pretty good heat sink. When heat builds up too much, though, it will transfer to the tube, and under high enough temps, will cause the tube to become weak and fail. Latex tubes are very sensitive to heat - so , if you're running latex tubes in your clinchers - be very careful about how you brake!

In a carbon rim, the braking friction generates heat in a very localized manner. Carbon does not dissipate or spread heat very well. The heat that builds up may cause the surrounding matrix to reach its glass transition temp (Tg) where it turns suddenly from a solid to a mush. Combine that with the outward pressure of tire and tube and WHAMMM! Or at lesser levels a BUMMMMP! when the rim flares out.

Given that this is how it works - braking on a carbon rim should be firm and relatively short bursts. Control the speed, but don't over do it. Stay off the brakes when you don't need them. Dragging the brakes unnecessarily will just raise the rim temp and decrease the bandwidth you have to reach Tg. You want to start the braking process at lowest temp possible. This is also why the rims will be more sensitive to Tg issues as the environmental temperature goes up. The hotter it is outside, the less temperature envelope you have to play with. Bear in mind, as fast as carbon heats up , it cools down too! So - this is also why relatively shorter, firmer braking sessions are better with carbon. Alloy rims heat up slower and soak more heat, they also cool down slower. Back in the day it wasn't unusual to have a rim hot enough over a long descent to cook the glue on the tire and turn it to useless muck. That doesn't happen on a carbon rim as you could barely get enough heat to 'soak' through to the center section of the rim. However the brake / outer surface would get hot enough to see some seepage and / or Tg issues, but very rarely would you see any glue deterioration in the center - so risk of tire rolling is actually lower on a carbon rim when it's properly glued.
 

kiwisimon

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#17
Great post Tim, won't it be great when discs get light enough to be the default system. Now that I am not a racer type, they have become mine.
 
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Doug3

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#18
Great post Tim, won't it be great when discs get light enough to be the default system. Now that I am not a racer type, they have become mine.
I have been riding hydraulic discs on my city bike for the past 6 months and am amazed by the stopping power. I was somewhat anti-disc before, but will definitely look for them on my next road bike.

This is a sweet looking road bike with race geometry coming to the market in 2014.
http://cdn.media.cyclingnews.com/2013/06/12/1/bianchi_670.jpg

If the UCI approved discs for competition, I think that would really open up the market. Then we would not need to think as much about heat in the carbon rims.
 

Gunjira

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#19
I also love the disc brakes on my CX bike. Will built up a titanium bike around the new udi2 group with disc brakes coming out.
 

j-sworks

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#20
I broke down a bought a couple of Reynolds Aero Carbon clinchers a few weeks back, with the intent of using them on the flatter rides, and as my main wheels once back home in sweden where we don't have any (paved) hills to speak of.
I did however take them on a shiraishi run, and descended on them too. I was super surprised about the breaking, I would say it was almost on par with my c24's (dry weather). But while the breaking power was more than sufficient, in the back of my head I was still worried about the heat build up.
That also turned out to be unfounded as as soon as I got down and touched the rim is was not hot at all, despite pretty constant breaking. Not very scientific I know but my c24s rims have been hotter after a descent. Will still use the c24 in the mountains because of the weight though.
While I have extremely limited experience with carbon clinchers, Reynolds seems to have done something right.
Breaks: DA9000
Pads: Reynolds Cryo Blue
(Wheels actually came with a sticker that warned not to use any other pads, especially cork based ones. No warranty with other pads than the Cryo Blue)
I agree that a lot is just your brain holding you back, stupid brain always trying to keep me live...

Furthermore I can tell you that you should heed that warning from Reynolds about the wheel specific brake pads.