Dura Ace 9170/9150 front brake losing power

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Milese
Posts: 224
Joined: Wed Mar 17, 2010 12:04 am

by Milese

Hi,

I've got the 9170 shifter with 9150 caliper set up on my Noah Fast which has been great for the first ~3000 miles over the last year.

I took the bike to Mallorca about 3 weeks ago and managed to get the bike into a bike box allen, but with the internal hoses it was a bit fiddly to move the bars enough, so its possible (probable) that the hoses have been stretched.

Brakes were great in Mallorca, but brake lever became increasingly close to the bar on my return. About 200 miles after I got back the lever went all the way to the bar and only worked a bit with a lot of pumping (scary). I loosened and tightened the nuts where the hose joins the lever and the caliper but neither seemed loose. Bled them and all was good.....for another approx 200 miles and the lever is now touching the bar again.

No signs of any leaks anywhere. I'm thinking that it would be sensible to take the bar tape off and remove and check the hose from both ends incase the nipple has been pulled down - but any other thoughts or advice greatly appreciated!

Lucily fault developed following return and not arrival in Mallorca, could have ruined a great trip!

:beerchug:

by Weenie


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aeroisnteverything
Posts: 893
Joined: Fri Aug 24, 2018 4:43 pm

by aeroisnteverything

Could be a kink in the hose - so you might need to replace the hose. Could be stubborn air bubbles trapped in the caliper or some other part of the system. I sometimes pump the fluid though back and forth though the whole system while tilting the caliper every which way to flush the stubborn air out.

Not an uncommon problem in any case, and solveable as per above. Probably start with another good bleed, and then if that does not help, go to an LBS to replace the hose.

The unfortunate reality of disc brakes: they are definitely more faff than rim brakes.

tommyboyo
Posts: 350
Joined: Sun Jun 21, 2020 12:49 am

by tommyboyo

Check for no leakage at the seal.

Bleed at the caliper end with the basic drain and then lever squeeze method.

Milese
Posts: 224
Joined: Wed Mar 17, 2010 12:04 am

by Milese

tommyboyo wrote:
Mon Jun 27, 2022 4:29 pm
Check for no leakage at the seal.
Thanks for reply - which seal?

Milese
Posts: 224
Joined: Wed Mar 17, 2010 12:04 am

by Milese

aeroisnteverything wrote:
Mon Jun 27, 2022 4:16 pm
Could be a kink in the hose - so you might need to replace the hose.
Thanks - A kink in the hose that prevents proper bleeding or is leaking? Either way worth checking out. There is a chance that the bars were twisted when off the bike I suppose.

tommyboyo
Posts: 350
Joined: Sun Jun 21, 2020 12:49 am

by tommyboyo

Milese wrote:
Mon Jun 27, 2022 5:45 pm
tommyboyo wrote:
Mon Jun 27, 2022 4:29 pm
Check for no leakage at the seal.
Thanks for reply - which seal?
The piston seals.

Check the back of the break pads for a fluid circle, which is the give away sign.

Sometimes you can hear when squeezing with the bleed spacer in as well.

pmprego
Posts: 2513
Joined: Mon Jan 21, 2019 3:16 pm

by pmprego

Milese wrote:
Mon Jun 27, 2022 3:10 pm
Hi,

I've got the 9170 shifter with 9150 caliper set up on my Noah Fast which has been great for the first ~3000 miles over the last year.

I took the bike to Mallorca about 3 weeks ago and managed to get the bike into a bike box allen, but with the internal hoses it was a bit fiddly to move the bars enough, so its possible (probable) that the hoses have been stretched.

Brakes were great in Mallorca, but brake lever became increasingly close to the bar on my return. About 200 miles after I got back the lever went all the way to the bar and only worked a bit with a lot of pumping (scary). I loosened and tightened the nuts where the hose joins the lever and the caliper but neither seemed loose. Bled them and all was good.....for another approx 200 miles and the lever is now touching the bar again.

No signs of any leaks anywhere. I'm thinking that it would be sensible to take the bar tape off and remove and check the hose from both ends incase the nipple has been pulled down - but any other thoughts or advice greatly appreciated!

Lucily fault developed following return and not arrival in Mallorca, could have ruined a great trip!

:beerchug:
I had this exactly but with sram red etap 11spd. According to the bike shop the problem is on my shifter (which they say I need a new one - waiting to find stock). :noidea: :noidea:

Please report back when you find your solution.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Milese
Posts: 224
Joined: Wed Mar 17, 2010 12:04 am

by Milese

Thanks for replies.

I've stripped the bar tape to allow removal of the hose from the shifter to make sure its seated properly.

Then given it the bleed of its life, with the lever tilted every which way from the bottom, then the lever open dribble down method. All from the Park tools video.

This was much better than any bleed I've done before so hopefully this solves it, but time will tell!!

No sign of fluid on pads.

Sent from my SM-G960F using Tapatalk


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