r9170 disc brake calipers and heat

Discuss light weight issues concerning road bikes & parts.
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Delorre
Posts: 966
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Hi, for the users of those disc brake calipers : did you already encounter the issue that when coming to a complete stop after a hard braking downhill from f.ex 50km/h (red light, stop sign,...), one of the pistons don't retract and stay in contact with the disc rotor? I've had it twice yesterday (or, it's the first time I really spend attention to it) : when stoppend, the right piston didn't go back, and when braking again, pushed the disc rotor to the left. The brakes were hot, but not to a point over overheat! When cooled down, everything went back to normal, both pistons are perfectly spaced around the disc, and I have 0 rub when riding, even when out of the saddle. For info, the bike has around 1000km, bit of rain and grit, but nothing really bad. The brakes have already been cleaned with brake cleaner once...

Is that a trait of those calipers, or is there something wrong? I don't remember having that behaviour with my 785 calipers. As I'm also a motorbiker, I use the front brake as main brake, the rear only as a little help/ support for the front. The rear one had no issues, but was not that hot I suppose.

I will do some repeated ,intentionnally hard braking tomorrow, as you would do during 'breaking in' period, also with the rear also. Curious to see if the rear remains fine or not. During normal driving and after normal braking, I have the 'usual', but occasional and very light disc sounds you also read in reviews, but nothing really wrong, and only just, just after braking. One or 2 revolutions of the wheel and it is completely silent again.

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TonyM
Posts: 2620
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

I heard of that in some reviews.

But on my Dura Ace disc brake I did not have it (yet?).
I used Dura Ace rotors with Dura Ace Ice resin and now with the Dura Ace Ice metal.

by Weenie


dricked
Posts: 70
Joined: Tue Jan 09, 2018 1:57 pm

by dricked

Don’t use brake clean on the calipers as it will dry the seals out and cause premature issues.

Delorre
Posts: 966
Joined: Sat May 24, 2014 12:09 pm

by Delorre

TonyM wrote:
Wed Jan 10, 2018 6:57 pm
I heard of that in some reviews.

But on my Dura Ace disc brake I did not have it (yet?).
I used Dura Ace rotors with Dura Ace Ice resin and now with the Dura Ace Ice metal.
Lucky you! 8) Same stock setup, incl resin pads. I first though it was the rotor that 'moved' due to heat, but if so, the rotor would not be in the middle of the caliper anymore when hot, and at first sight, it still was. Will have a closer look at it tomorrow (it's raining outside for the moment)

Delorre
Posts: 966
Joined: Sat May 24, 2014 12:09 pm

by Delorre

dricked wrote:
Wed Jan 10, 2018 7:04 pm
Don’t use brake clean on the calipers as it will dry the seals out and cause premature issues.
:noidea: Why is it called brake cleaner then? :noidea: Been using this for some years on the motorbike (and previous disc brake bike also) without issues!

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TonyM
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Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

I use metal part cleaner (same than for motorcycles) on the rotors. You can really feel after the cleaning that the brakes are working much better (my current bike with DA 9170 is my winter/ rain bike so that it is mostly used when it is raining or when the roads are not dry like now in the winter).

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TonyM
Posts: 2620
Joined: Thu Jan 22, 2015 4:11 pm

by TonyM

Delorre wrote:
Wed Jan 10, 2018 7:06 pm
TonyM wrote:
Wed Jan 10, 2018 6:57 pm
I heard of that in some reviews.

But on my Dura Ace disc brake I did not have it (yet?).
I used Dura Ace rotors with Dura Ace Ice resin and now with the Dura Ace Ice metal.
Lucky you! 8) Same stock setup, incl resin pads. I first though it was the rotor that 'moved' due to heat, but if so, the rotor would not be in the middle of the caliper anymore when hot, and at first sight, it still was. Will have a closer look at it tomorrow (it's raining outside for the moment)

My other thought is that it may be related to the resin brake pads maybe.

I have the metal brake pads on my bike (winter/ rain bike) and don't experience that problem of the piston. I just had yesterday after a very sharp descent a little bit of rubbing after, between rotor and brake pad, but it disappeared after 100 m. And as I used the resin brake pads I did not have this problem but I was biking only when raining so that less heat is generated I suppose.

dricked
Posts: 70
Joined: Tue Jan 09, 2018 1:57 pm

by dricked

Delorre wrote:
Wed Jan 10, 2018 7:09 pm
dricked wrote:
Wed Jan 10, 2018 7:04 pm
Don’t use brake clean on the calipers as it will dry the seals out and cause premature issues.
:noidea: Why is it called brake cleaner then? :noidea: Been using this for some years on the motorbike (and previous disc brake bike also) without issues!
It’s meant to clean rotors/pads not rubber seals. Notice how quickly it dries and also dries out your skin, it does the same to the seals.

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wheelbuilder
Posts: 517
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

Seems like a pretty common, inherent problem with most of the flat mount systems that I have worked on. For one reason or another, repeated hard braking efforts slows down the return of the one or both pistons to the fully retracted position. They seem to eventually retract, but the speed at which they do so is diminished. I have found that removing the pads, lubing around the piston seals with the brake fluid that the system uses while working the action of the brake lever helps a bit. Stick a plastic tire lever between the pistons, squeeze the lever a few times, then pry the pistons back with the tire lever. Road systems have such tight pad/rotor clearances I think a small amount of noise is just the price of admission.

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corky
Posts: 1201
Joined: Thu Jul 06, 2006 5:53 pm
Location: The Surrey Hills

by corky

I suspect the pistons are expanding with the heat and causing them/it to stick....... it relies on capillary action to retract the pistons after the lever has been released I believe.......happy to be corrected.

Just confirms to me that disc brake technology for road bikes is still immature......

Delorre
Posts: 966
Joined: Sat May 24, 2014 12:09 pm

by Delorre

**UPDATE**

As it was already dark during my ride yesterday, I didn't test anything, but today (home work), I did 7 or 8 full stops in a row from 25 to 0 mph. Front disc was pretty hot and, it seems it's the disc that moves to one side. After a close look, it appears the disc was not centered anymore. The gap with the left brake pad was larger than when cold.

Pretty unacceptable being top of the range DA stuff, but good news, as it's easier to change to others rotors than the other calipers.

It has been discussed in other threads, but it looks like Sram Centerline X and the new H11 rotors are pretty good stuff. The H11 makes a little to much noice to my liking. Someone posted of video, and I think I could not use brakes that makes that noice (some will find it cool sounding for sure). Could the users of those 2 rotor type post their experience with them, as well as rotor thickness. DA is 1.8mm. Thx!

jlok
Posts: 674
Joined: Tue Jun 30, 2015 3:30 am

by jlok

Delorre wrote:
Fri Jan 12, 2018 2:05 pm
**UPDATE**

As it was already dark during my ride yesterday, I didn't test anything, but today (home work), I did 7 or 8 full stops in a row from 25 to 0 mph. Front disc was pretty hot and, it seems it's the disc that moves to one side. After a close look, it appears the disc was not centered anymore. The gap with the left brake pad was larger than when cold.

Pretty unacceptable being top of the range DA stuff, but good news, as it's easier to change to others rotors than the other calipers.

It has been discussed in other threads, but it looks like Sram Centerline X and the new H11 rotors are pretty good stuff. The H11 makes a little to much noice to my liking. Someone posted of video, and I think I could not use brakes that makes that noice (some will find it cool sounding for sure). Could the users of those 2 rotor type post their experience with them, as well as rotor thickness. DA is 1.8mm. Thx!
H11 is quiet at my rear eTap brake with sintered pads
Giant Propel Advanced SL Disc 1 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

by Weenie


ooo
Posts: 590
Joined: Sat May 21, 2016 12:59 pm

by ooo

What is diameter of dura-ace/ultegra caliper piston?
'

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