R9170 Dura Ace disc - constant readjustment required

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

Well, you have to assume that the mounting holes are perfectly placed and drilled from the factory, because you can't change that. Facing simply removes excess paint etc from the surfaces, and the facing tools should ensure that they are faced square etc. For instance, even though the example below is of direct mount brakes vs discs the principle is the same... I'd want the surfaces of these mounting holes faced before mounting brakes, but I doubt it would actually get done in most shops. Would it make a difference, not sure... but I certainly know that a little extra paint can make the difference in how smoothly a bottom bracket will run if it isn't faced before installing some Campy ultratorque cups for example.
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hkgmatt
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Joined: Sun Apr 08, 2018 9:17 am

by hkgmatt

Thank you for all your insightful comments.

Yes the Legend has thru-axles.

The calipers are aligned as well as they can be with the rotors, using a flashlight and a Hayes feeler gauge for best adjustment.

The pinging after prolonged braking does not bother me as it goes away after 30s or a minute or so; it's more that when the entire system cools down it seems seriously out of whack.

I have not experienced brake fading.

I have the ParkTool disc facing tool but have not dared using it yet - would unevenly faced mounts not make initial installation / adjustment equally difficult?

by Weenie


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ms6073
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Location: Houston, Texas

by ms6073

darnellrm wrote:
Fri Jun 22, 2018 5:00 pm
How do you face both caliper mounting points AND assure that they are coplanar or at leat parallel with each other?
[YouTube]How to Use the DT-5.2 Disc Brake Mount Facing Set[/YouTube]

When I could not easily align BR-R9170 brake calipers on my Scott Solace disc road frame, I dropped some coin and got a Park Tool DT-5.2, read the directions, and watched a few videos, then read the directions again. Next, I first tried tool out by carefully facing the front and rear post mounts on my CX bike before messing.. I mean proceeding to the road bikes. While there was a bit of a learning curve, going slow and following the directions kept me on track and now the mounts on the Scott frames are properly faced as I can simply loosen the caliper, squeeze the brake lever, then torque the mounting bolts and the calipers are centered on both road and CX bikes.
Michael - The Anaerobic Threshold is neither...

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

by Lewn777

This issue is exactly what angered me about the rush to 'superior' disk brakes on road bikes. The issue you describe I've had again and again with my ten years on mountain bike disk brakes, but with mountain bikes I never really minded, becuase it was a different application. A brake on a road bike has essentially two jobs; stop you safely and not rub and steal watts. The latter is something that I can never trust any disk brake system to do reliably on any of the car, motorcycle or mountain bike disk brake system I've ever encountered. Going out of alignment is a symptom of the small size of a bicycle caliper and rotor. Go out to your car jack it up and spin the wheel, you won't see the wheel spin freely, it will spin half a turn and then stop accompanied by a light sssccccrrr sound, this is the pads lightly dragging on the disk. Practically guaranteed with single piston designs, likely with two.

Which is why I think dumping such a simple brake as the road rim brake which still has improvements including dual pivot, ceramic rim coatings and further improvements in pads etc is madness, unless you are on some bikepacking tandem rainy day commute over gravel.

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wheelbuilder
Posts: 477
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

ms6073 wrote:
Fri Jun 22, 2018 11:25 pm
darnellrm wrote:
Fri Jun 22, 2018 5:00 pm
How do you face both caliper mounting points AND assure that they are coplanar or at leat parallel with each other?
[YouTube]How to Use the DT-5.2 Disc Brake Mount Facing Set[/YouTube]

When I could not easily align BR-R9170 brake calipers on my Scott Solace disc road frame, I dropped some coin and got a Park Tool DT-5.2, read the directions, and watched a few videos, then read the directions again. Next, I first tried tool out by carefully facing the front and rear post mounts on my CX bike before messing.. I mean proceeding to the road bikes. While there was a bit of a learning curve, going slow and following the directions kept me on track and now the mounts on the Scott frames are properly faced as I can simply loosen the caliper, squeeze the brake lever, then torque the mounting bolts and the calipers are centered on both road and CX bikes.
Good job man! That tool is a pain in the ass. We got it at our shop 2-3 years ago, and I only unpack it in the worst possible case of uneven mounts...........calipers that simply won't sit on a correct plane. Every time I use it I have to watch the video again. One of the only tools in the arsenal that I can't get to become second nature. It definitely works well though.

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

by Delorre

hkgmatt wrote:
Fri Jun 22, 2018 10:30 pm
Thank you for all your insightful comments.

Yes the Legend has thru-axles.

The calipers are aligned as well as they can be with the rotors, using a flashlight and a Hayes feeler gauge for best adjustment.

The pinging after prolonged braking does not bother me as it goes away after 30s or a minute or so; it's more that when the entire system cools down it seems seriously out of whack.

I have not experienced brake fading.

I have the ParkTool disc facing tool but have not dared using it yet - would unevenly faced mounts not make initial installation / adjustment equally difficult?
I've been through this for 6 month's on my 9170 front brake. The rear has been perfect from day 1. I kept making adjustments because I didn't understand what was going on and what went out of true. I finaly went step for step:

-Bleeding of the system with the bleed blocks in place
-Make sure the pistons are fully pushed back
-Allign the caliper with the disc before applying any braking on the lever. (Ideally do this step with new brake pads) Use whatever you want and work. On lightly worn brake pads, a old crdit card works very well
-Apply the brakes (10, 20 times) and see if both pistons go in and out in perfect synchro.
-If all good, go out and ride. You may have some rub after hard braking, but when cooled down, everything sould return to its initial position.
-If after some rides, you have rub again, try to identify what has moved or not working as it should : Are both pistons equally retracted or not. If not, your problem is there. If yes, push both pistons fully back and check caliper alignement. Calipers don't move when torqued down properly, but check it anyway. A rotor can go out of true in some places, but not on the complete diameter. Make sure the discs are secure (are you using centrelock or 6 bolt)

In my case, the caliper was defective : the left piston didn't retract as well as the right one. No cleaning, resetting, bleeding cured it. I replaced the caliper, and after a very good bleed (2x), things seem OK for now. Good luck with yours!!

NickJHP
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Joined: Wed Feb 14, 2018 2:22 am

by NickJHP

darnellrm wrote:
Fri Jun 22, 2018 5:00 pm
How do you face both caliper mounting points AND assure that they are coplanar or at leat parallel with each other?
For flat mount calipers, I reckon the diamond hones that came with my Lansky knife sharpening kit would do it. The grinding surface is 0.5" x 4", and the hones are dead flat according to my big Starrett straightedge. You'd need to lay a small straightedge across the mount and parallel to the axle to check that their surface is parallel with the axle in that plane, and correct if needed.

https://lansky.com/index.php/products/c ... mond-hone/

sethjs
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Joined: Fri Feb 04, 2011 4:02 pm
Location: San Francisco, CA

by sethjs

I've noticed that in a lot of photos of pro bikes racing discs this yr, they're not on the 9170 discs, but rather something that looks like the RT99.

I weight 165. On my Diverge I have the R785 with RT99 setup that came standard. I go down long, technical 10-20% descents using the brakes extremely hard. Haven't had any issues whatsoever, other than the 30 second post descent pinging that everyone seems to get.

So...I do wonder if the pro teams found the 9170 discs more likely to warp and that's why they've been on the RT99s.

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Conza
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Location: Melbourne, Victoria, Australia
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by Conza

ODC wrote:
Fri Jun 22, 2018 4:17 pm
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.
I was pretty sure; DA was 30% more heat dispersing? Ice-Tech? Also slightly lighter?
It's all about the adventure :o .

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corky
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Location: The Surrey Hills

by corky

With current disc brake design( insufficient pad rotor gap) rub is inevitable at some point......

jeanjacques
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Location: France

by jeanjacques

Direct mount isn't more difficult to adjust very well ? Seem to see less problem with post mount but maybe just because there is less and less PM road bike.

darnellrm
Posts: 226
Joined: Thu Sep 10, 2009 1:06 pm
Location: NC, USA

by darnellrm

Nice tool! That would address my concerns, but $400 is a big investment

ms6073 wrote:
Fri Jun 22, 2018 11:25 pm
darnellrm wrote:
Fri Jun 22, 2018 5:00 pm
How do you face both caliper mounting points AND assure that they are coplanar or at leat parallel with each other?


When I could not easily align BR-R9170 brake calipers on my Scott Solace disc road frame, I dropped some coin and got a Park Tool DT-5.2, read the directions, and watched a few videos, then read the directions again. Next, I first tried tool out by carefully facing the front and rear post mounts on my CX bike before messing.. I mean proceeding to the road bikes. While there was a bit of a learning curve, going slow and following the directions kept me on track and now the mounts on the Scott frames are properly faced as I can simply loosen the caliper, squeeze the brake lever, then torque the mounting bolts and the calipers are centered on both road and CX bikes.

robo
Posts: 16
Joined: Sun Jan 01, 2012 8:01 pm

by robo

I think I'd be trying alternate rotors and a different brand of pads based on the comments in this post, together with very careful bedding-in of both.

My experience of road disc so far has been chequered, so in keeping with other folks comments. I've had poor experiences with Shimano calipers but very good experiences mating Hope RX4 calipers to Shimano levers. I've also found that extreme attention to bleeding has a significant impact on brake performance as has the choice of brake pad..

Good luck, unfortunately it feels like there's still some maturing to do with the technology as others have pointed out.

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ms6073
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Location: Houston, Texas

by ms6073

darnellrm wrote:
Tue Jun 26, 2018 1:45 pm
Nice tool! That would address my concerns, but $400 is a big investment
I agree, but when I called around town to find a LBS that might be able to face the mounts, none had the tool. So since all of our bikes are disc brake, and our cycling friends tell me my workshop is better equipped than the majority of the LBS in town, I decided it was worth the investment. :smartass:
Michael - The Anaerobic Threshold is neither...

darnellrm
Posts: 226
Joined: Thu Sep 10, 2009 1:06 pm
Location: NC, USA

by darnellrm

This thread is definitely firming up my previous opinion on disc brakes. Way too much hassle for negligible benefit where I ride.

by Weenie


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