R9170 Dura Ace disc - constant readjustment required

Discuss light weight issues concerning road bikes & parts.
hkgmatt
Posts: 6
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

by Weenie


CallumRD1
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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
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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.

hkgmatt
Posts: 6
Joined: Sun Apr 08, 2018 9:17 am

by hkgmatt

Thanks a lot for your thoughtful comments and suggestions.

@CallumRD1

The bolts between the caliper and the 140mm>160mm adapter didn't have loctite on them when they came (the ones between the adapter and the frame do) so I don't think the tightening is a problem - I would not want to tighten them much more. As to the rubbing, it starts with a little pinging but often it is bad enough to slow down the wheel when not under load and after cooling down completely.

@wheelbuilder

Your observations kind of confirm what I was afraid of - that for the gradients I'm using the bike for and considering my weight, I'm pushing against the limits of a hassle free use of the technology (after reading all the glowing reviews by the bicycle press and buying Shimano's top of the range, you can definitely put me into the "expecting silent perfection" category!). It just seems to me that the rotors deform too easily under heat and don't go entirely back to their original shape, so that together with the tight tolerances at caliper level there is bound to be a problem. I'm wondering whether in the MTB world this has been solved given that disc brakes have been around for much longer or whether the inherently higher speeds on the road make the two systems not really comparable. I'm also wondering whether another system (especially Campagnolo H11) is better in this respect.

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

by RedbullFiXX

Seems odd, does this Legend have a thru axle setup ?

memikeyp
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Joined: Fri Jul 14, 2017 12:54 am

by memikeyp

Like you Matt, I've had the same problems. I have tried every solution posted on very forum to no avail over the past 6 months. Seems to be something we have to live with. The rubbing noise drives me nuts, I've actually recently gone back to rim brakes. Sure they don't stop quite as well, but to me the less maintenance, is WELL worth it.

ODC
Posts: 120
Joined: Mon Aug 14, 2017 9:40 am

by ODC

If I read it like this, then I think you have a faulty front brake.
I had (almost) the same issue with my rear brake on my new Tarmac SL6. Not always, but sometimes after breaking I could have a ping noise for a minute of longer. Sometimes it helped to brake again and then the ping noise was away.
After some trail and error first the shop installed a new brake and didn't have the ping noise again.
Shimano has said there are some faulty brakes + they also said a lot of shops are installing the brakes with to much oil what causes much faster the ping noise.

jeanjacques
Posts: 124
Joined: Thu Apr 14, 2016 11:01 am
Location: France

by jeanjacques

Did you align the caliper with a light ? Try to put it perfectly on the center of pads.

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Conza
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Location: Melbourne, Victoria, Australia
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by Conza

I avoided DA disc rotors because of this... read a lot of issues with noise from those testing the new BMC Team Machine SLR01.

Ultegra 8000, nope, far less so. I got those as stock, but see little need to go to DA - when I keep hearing folks have issues.
It's all about the adventure :o .

CallumRD1
Posts: 129
Joined: Mon Apr 03, 2017 2:54 pm

by CallumRD1

I will add that I've never had warping issues like this on my 160mm RT-99 or RT-81 centerlock rotors or RT-86 6 bolt rotors. I'll true them up maybe once a year, mostly just for the piece of mind, not because it really needs done.

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ms6073
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by ms6073

hkgmatt wrote:
Thu Jun 21, 2018 11:04 pm
It just seems to me that the rotors deform too easily under heat and don't go entirely back to their original shape, so that together with the tight tolerances at caliper level there is bound to be a problem.
Sorry, 1 + 1 or not adding up to 2 here. While I am by no means a disc brake expert, I have had none of these issues with a 9170 equipped Scott Solace disc. My take is that if the rotor were to small such that is was unable to dissipate heat to the point of warping the rotor, then I would think the brake fluid would start to boil as well resulting in significant brake fade. Regardless of whether the bike has post mount or flat mount brakes, if the mounting surfaces are properly faced (they were not on my Solace) and you have done due diligence to ensure the caliper is centered and pistons are not dragging, the only other thing I can see causing a rotor to get deformation under braking would be because the fork blades or rear stay are flexing under the load.
Michael - The Anaerobic Threshold is neither...

ODC
Posts: 120
Joined: Mon Aug 14, 2017 9:40 am

by ODC

Conza wrote:
Fri Jun 22, 2018 2:24 pm
I avoided DA disc rotors because of this... read a lot of issues with noise from those testing the new BMC Team Machine SLR01.

Ultegra 8000, nope, far less so. I got those as stock, but see little need to go to DA - when I keep hearing folks have issues.
The ultra 8000 are the same as the Dura ace 9100. Just the DA gets more black plastics for the esthetics.

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Miller
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Location: Reading, UK

by Miller

hkgmatt wrote:
Thu Jun 21, 2018 11:04 pm
I'm also wondering whether another system (especially Campagnolo H11) is better in this respect.
Well... I took my new Potenza disc-equipped bike to France a couple of weeks ago and gave the brakes some very thorough testing on big descents. What I found is that the brake performance was absolutely outstanding in terms of sheer braking power and control available, almost a revelation in that regard. However - not always silent. After hard braking the front rotor would complain for about 30s, perhaps due to the factors outlined above, I don't know. Although I have wondered whether the disc mounts are properly faced. But who do you get to do that task?

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Calnago
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by Calnago

In my opinion, any dealer installing disc brakes should have the proper tools to face the mounting points, period. It should be standard procedure. It's no different than facing steel or alloy threaded bottom brackets. It was just part of normal frame prep. It's usually done at the factory, often before paint, and the paint can make a difference, especially if it's uneven as could be the case simply from settling as it dries. It's a quick job, but really important where perfect alignment is necessary for perfect performance. No different for disc brake mounting points. The tools are available, dealers should have them. And use them.
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darnellrm
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Location: NC, USA

by darnellrm

How do you face both caliper mounting points AND assure that they are coplanar or at leat parallel with each other?

by Weenie


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