Hyrdaulic Disk Brakes

Discuss light weight issues concerning road bikes & parts.
fromtrektocolnago
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by fromtrektocolnago

PhilippCX wrote:
mpulsiv wrote:
fromtrektocolnago wrote:
mpulsiv wrote:
fromtrektocolnago wrote:I don't like the noise disc brakes make.


QR's is the root cause of noise due to marginal misalignment, right? I read that thru-axle remedy the noise issues.



My set-up is thru-axle


Noisy even in dry condition?


I also run discs with thru-axles and they are indeed noisy in wet conditions. Same story on my CX bike with QRs and mechanical disc brakes.

Misalignment does not cause the squealing. My understanding is that it is caused by the ratio of static and dynamic friction coefficients of brake pads and disc surfaces.
Sintered metal pads are the worst in this respect. Btw. it's the same issue with cars. I had sintered metal pads on my previous sports car and they were squealing like crays when cold.


Agree, and it occurs in wet conditions. I'll put up with it when it comes to winter riding. Plan to do some off-road riding this weekend however. It's nice for a change of pace.
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Nefarious86
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by Nefarious86

This compatability with zee calipers interests me :D
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MichaelB
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by MichaelB

tomee wrote:
interesting. I didnt know you could use mtb brakes with road. In the end i guess if you have the right line connection and mounts then it shouldnt matter.
Have you got any pics? im intrigued by this setup.


No pics, as nothing to see really.

What the brakes (claipers) were designed for doesn't matter. The initial thoughts were the grerater piston area of the calipers would make the lever feel softer, but that hasn't been the case. Over 4k km on this setup already and no issues at all. :thumbup:

MichaelB
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by MichaelB

Nefarious86 wrote:This compatability with zee calipers interests me :D


Been done many a time with MTB levers, so I thought "why wouldn't it work with road levers ?" :noidea:

And it does :thumbup:

Pluses are better hose alignment (for my bike), bigger pads (~ 33% bigger surface area), plenty of pad options out there (finned & non-finned), weight difference was 12g (I think from memory) at each end including pads (Zee vs RS785 calipers), and allows me to run 140mm rear disc.

Win all round :mrgreen:

Cheetahmk7
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by Cheetahmk7

If the RS885 has 22mm diameter pistons and the Zee has 16 & 18 mm pistons then the piston area is 20% more, so there would be 20% more clamping force. The brake lever travel will also increase by 20%.

MichaelB
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by MichaelB

Cheetahmk7 wrote:If the RS885 has 22mm diameter pistons and the Zee has 16 & 18 mm pistons then the piston area is 20% more, so there would be 20% more clamping force. The brake lever travel will also increase by 20%.


All the twin piston calipers (that I've managed to find out) have the same piston dia, as do the master cylinders (road & MTB), so they are all interchangeable.

The mechanics are not that simple as it also has variables like lever ratio, pad clamping force vs pad area etc, etc, etc.

That is the theory, but in practice, I still get a very solid lever and the travel is 99% the same as a mate who has the same levers but with the RS785 calipers.

The lever feel is not soft at all and does not have excessive travel (as you would think).

It was the multiple reports of success with the MTB levers that I gave it a go. Been done with the old M810 calipers, so had good confidence.

MichaelB
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by MichaelB

@ Brus - so what is the issue that doesn't work for you and hence going back to rim brakes ?

Cheetahmk7
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by Cheetahmk7

MichaelB wrote:
All the twin piston calipers (that I've managed to find out) have the same piston dia, as do the master cylinders (road & MTB), so they are all interchangeable.

The mechanics are not that simple as it also has variables like lever ratio, pad clamping force vs pad area etc, etc, etc.

That is the theory, but in practice, I still get a very solid lever and the travel is 99% the same as a mate who has the same levers but with the RS785 calipers.

The lever feel is not soft at all and does not have excessive travel (as you would think).

It was the multiple reports of success with the MTB levers that I gave it a go. Been done with the old M810 calipers, so had good confidence.


The images and text I have read show two different sized pistons in the Zee caliper. They do this to make pad wear more even.

If you are using the same shifter, then the stroke must increase for the same clamping force. Pad area doesn't change the brake torque capacity (but the coefficient of friction does). At your index finger you may see the lever travel increase from 30 to 36mm which may not be particularly noticeable. The lever won't feel soft unless there is gas in the hydraulics.

iamalex
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Location: London, UK

by iamalex

Any way to stop Shimano R785 levers levers rattling so much?
Right hand Di2 buttons especially noisy as they have more play than the left.

Braking and shifting are fantastic but over the lumpier country roads the noise is ridiculous.

Nefarious86
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by Nefarious86

Its probably the lever rattling on the stop. A Trick in here to fix it.
http://www.bikeradar.com/au/road/gear/a ... ere-41888/
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iamalex
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by iamalex

Thanks Nefarious86! That looks like it'll help, I'll have a go later today.

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mpulsiv
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by mpulsiv

Nefarious86 wrote:Its probably the lever rattling on the stop. A Trick in here to fix it.
http://www.bikeradar.com/au/road/gear/a ... ere-41888/


Interesting read. Perhaps 140mm rotors are inadequate and one should consider a bike with 160mm rotors? Weight penalty = better stopping power, less heat and less noise?

"Going to a bigger rotor (160mm) up front, and perhaps in the back as well, would likely eliminate the heat-induced squeal, Legan said."




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Stueys
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Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

I run sram 160mm up front and 140mm at the back, the only time i see brake squeal is when it's wet.

iamalex
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Location: London, UK

by iamalex

Hi mpulsiv.

My issue is that the brake lever/Di2 button assembly rattles, not the calipers or cables. There's enough free movement of the components for them to rattle against one another.

160mm discs front and back work well for me.

loudboxer
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by loudboxer

jeffy wrote:Descending fast, tight corners. One finger, gentle braking. Exceptional control.

I have heard said, from someone with rim brakes to someone with hydraulic discs "you start braking when i start praying"


This. Cruising around on the flats, discs are overkill and pretty much just extra weight. But on good steep and twisty descents - Mount Diablo's North Gate for example - they really earn their ride. Throw in some wet fog-rain and the discs are in a league of their own. Horses for courses...
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