R9170 Dura Ace disc - constant readjustment required

Discuss light weight issues concerning road bikes & parts.
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hkgmatt
Posts: 2
Joined: Sun Apr 08, 2018 9:17 am

by hkgmatt

Hello everyone.

I have recently acquired my first disc brake equipped bike, after several decades of cycling with various types of rim brakes on road, mountain and touring bikes. I got a custom made Legend frameset with a Dura Ace R9170 groupset installed by my dealer.

The problem I have is this: After practically every outing involving hills, the disc starts rubbing and I need to readjust the front caliper to realign it with the rotor. Sometimes, but not always, the rotor is out of true in which case I straighten or replace it. But even if the rotor is not obviously out of true, the alignment seems to get messed up during each ride that has healthy descents. Sometimes I only notice the rubbing a while after the ride, when the rotor has cooled down.

I'm a heavy rider (90+ kg) and ride some steep descents (exceeding 12%) which require a lot of braking but I'm using decent braking techniques (avoid dragging the brake, alternate front and rear brake) and I'm really frustrated that the brakes are so fiddly. I wanted to take the bike to a Gran Fondo but do not want to experience the rubbing midway.

I have:
- tightened the caliper bolts to Shimano spec
- cleaned and regreased the pistons in the caliper to ensure they retract properly
- replaced the brake pads with new original Shimano sintered pads
- replaced the rotors with new original Shimano Freeza ones, then tried SRAM Centerline rotors on recommendation of a member in this forum - the SRAM have less of a tendency to go out of true but the rubbing problem still occurs
- had the brakes bled by the LBS

I don't have much of a problem with the rear disc but then it doesn't have to work that hard. I'm running 160mm rotors front and rear.

Since I'm new to disc brakes, user error is a likely possibility, so I was wondering whether you had any suggestions I could try, or whether I'm asking too much from disc brakes.

Many thanks

Matt

CallumRD1
Posts: 107
Joined: Mon Apr 03, 2017 2:54 pm

by CallumRD1

"I have:
- tightened the caliper bolts to Shimano spec"

It sounds like you're doing everything right. Are you using the caliper bolts that came from Shimano with blue locktite preinstalled? If so, you likely need to tighten them down significantly firmer than spec. I've long set my brakes up with bolts without loctite to fascilitate easy, quick asjustment. I built up a bike for a friend recently and used the included bolts with loctite preapplied. The loctite made them so stiff going in that at ~5 nm I could still move the caliper by hand with a firm shove. I don't know if this is the cause of your problem, but it's certainly somethign to look at. You should also check that the mounting points for the calipers are faced properly to be perpendicular to the plane of the rotor. If the angular alignment of the caliper to the rotor is imperfect then you'll have loads of issues.

Another question: when you say that you're getting rubbing, is it just a little pinging of the rotor off the pad that doesn't appreciably slow down the wheel or is it real rubbing that stops the wheel from spinning prematurely?

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wheelbuilder
Posts: 433
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

You are definitely not alone and unfortunately I think you are going to have to live with a little noise. The "ting ting ting" of the pads brushing the rotors after a panic stop, or a particularly long descent is kind of just how these things perform. The pistons become slow to retract due to heat and swelling of the seals. When they cool down they will usually return to their starting point. Sometimes they kind of "get stuck" further out and this becomes your new baseline if they are not manually lubed and pushed back in with a tire lever or cone wrench handle. I am not trolling here at all.........please believe me, but I think these brakes are "coming home to roost" in a sense. The shop I work at sold a boat load of disc Emonda's to usually Fred types or Rich fat guys who want to be cyclists, and they are not happy with the brakes. They expect silent perfection and the tolerances are just too close right now to get that. These brakes are not without their problems either. I have personally warrantied three Ultegra calipers for leaking piston seals, and two Dura Ace Calipers for pistons that fail to retract. Shimano has been great about granting warranties for just about any complaint you have. I said this before, and I will say it again...........I don't think road disc was quite ready for market when it was pushed...........for Freds that is. Experienced riders riders who know a bit about maintenance and expect a small amount of noise are loving the performance of disc brakes.

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