disc brake rub out of saddle

Discuss light weight issues concerning road bikes & parts.
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cshong88
Posts: 10
Joined: Fri Jan 16, 2009 4:49 am

by cshong88

I recently took my disc brake bike, only 6 months of riding use, to bike shop to trouble shoot front brake disc rub. While much better, it still rubs consistently when out of saddle although it is much quieter in the saddle and even in the rain. My rotor is true and the highly do not suspect the bike needs a rebleed given no brake lever fade at all. Pads still have half of life left according to the shop. Shop recommends rebleeding the bike...

Is mild disc rub normal for disc brake bikes or should I expect silence? This is a new high end di2 bike and I weigh 120 pounds... It consistently has a slight rub when out of the saddle - not sure if it is really costing me any speed but I sure can't shake the feeling that it is. It's really annoying. Any ideas?

dricked
Posts: 184
Joined: Tue Jan 09, 2018 1:57 pm

by dricked

Are the caliper pistons clean and retracting correctly? If you remove the pads and squeeze the lever just enough to move the pistons out 2mm or so there will probably be a ring of crud on the piston. A bit of dish soap and a toothbrush should scrub them up nicely. Dry them and then push them back into the caliper. It’s a quick and easy step to narrowing down your issue.

by Weenie


asiantrick
Posts: 221
Joined: Fri Dec 04, 2015 11:18 pm
Location: the OC, CA

by asiantrick

Road bike with Disc, time for you to get used to slight rub. I've came to term that it's impossible for no rub on my disc bike. Even if you fix it now, it will rub again at some point.
Last edited by asiantrick on Thu Apr 18, 2019 11:20 pm, edited 1 time in total.

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Lewn777
Posts: 725
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

I agree with dricked. It can be caused by dirt on the piston(s) causing them not to retract into their cores. Although some rub is common, it depends on how much.

Remove the pads and pump the brakes a few times to expose the pistons and clean the pistons. Be careful not to pump the brakes too many times or you'll eject them from their cores, then you'd need a rebleed. I often use diluted degreaser 50/50 with water. You can lube the pistons with mineral oil or silicone grease if you want when dry. When finished push the pistons back into their cores using something made from wood or plastic (I use a tire wrench) preferably pushing on the pads rather than directly on the piston.

Other things can be the thru-axle or centerlock isn't torqued up to tight enough.

TobinHatesYou
Posts: 3611
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Make sure the caliper isn’t cocked at all and look at pad clearance from the top down and bottom up...different edges of the brake pads. As Lewn777 mentioned, not torquing a TA to a consistent value can result in slight changes in wheel position.

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corky
Posts: 1288
Joined: Thu Jul 06, 2006 5:53 pm
Location: The Surrey Hills

by corky

Road bike disc callipers need a redesign, they rely on the deformation of square edged seals and capillary action of hydraulic pad to retract the pistons upon release....... this means there has to be a very small gap between pad and rotor...... rub is inevitable...... wet dirty conditions are where they are supposed to excel but these are also the conditions that will lead to rub and squeal.

I like a silent bike personally........

ChiZ01
Posts: 208
Joined: Wed Jan 01, 2014 6:20 pm

by ChiZ01

out of saddle rub is due to TA not tighten enough or TA flex, get a beefier TA, this is not a place to save weight

marioc
Posts: 32
Joined: Sat Mar 26, 2016 2:26 pm

by marioc

I had the same issue with the front brake, rotor rubbing when out of the saddle and after hard braking rotor did rub pads for a second or two until cooled. As dricked and Lewn777 suggested, after I properly cleaned pistons there is no rubbing at all.

bm0p700f
in the industry
Posts: 4775
Joined: Sat May 12, 2012 7:25 pm
Location: Glermsford, Suffolk U.K
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by bm0p700f

Rotors rub. They do on cars hey will on bikes. A bit more flex on the fork than the wheel or the way the other way around and you get rub.

My genesis equilibrium disc is generally quiet except when it wet then I get some noise. Light weight forks can be a problem as they flex more.

RedbullFiXX
Posts: 87
Joined: Sat Aug 05, 2017 6:13 am

by RedbullFiXX

Wheel build/design plays a role
Fork build design plays a role

No rub on my road bike, Cross bike does it with enough effort

Both are SRAM equipped, fyi

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MattMay
Posts: 63
Joined: Thu Apr 10, 2014 3:26 pm
Contact:

by MattMay

I get disc rub if my thru axle is overly tight. If I torque to spec, all good. Tighter is better to a point.

Dan112
Posts: 32
Joined: Sat Dec 22, 2018 7:14 am

by Dan112

This is pretty normal I'm affaird. I got disc rub on my old attain gtc with the 105 old style shifters. I ended up having rebleeds, upgraded the upset to ultegra R8020 still got disc rub same as you when out the saddle.

I can tell you slight rub after hard braking is totally normal due to the heat with the disc. If your not running a 160mm this may help as a 140mm rotor will ontained a lot more heat. Aswel as the finned cooling pads.

Only way I got rid of the rub out of saddle is I moved from my attain to a giant tcr frameset. With same capilors, same discs, same pads, same wheels, same through axles... the only change was the fork so I can only assume it was flex in the fork.

andreas
Posts: 129
Joined: Thu Jun 12, 2014 10:21 pm

by andreas

If all else fails, the mounting points on the frame could need a refacing, done with a dedicated tool by an experienced mechanic.

by Weenie


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