Shimano Hydraulic Brake Issue

Discuss light weight issues concerning road bikes & parts.
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Posts: 129
Joined: Mon Apr 03, 2017 2:54 pm

by CallumRD1

I've been running Shimano 685 levers on 785 calipers on my Felt F3x for about a year now and they've been great. I've only bled them once over that period because they just haven't needed it. Last weekend I did a bunch of work to my bike including disconnecting and reconnecting all the hydraulic hose and then doing a full bleed of the system. Here's the order of events leading up to my issue:

I first watched the bike thoroughly with the pads and rotors still installed. After that I removed the pads and disconnected the brake hoses. I rerouted the hoses and gear cables, then did a full bottom up bleed which resulted in the lever feeling really good. I wiped down any surfaces that got mineral oil on them with 99% isopropyl alcohol. I also cleaned the rotors with the same alcohol and a paper towel.

On my first ride Monday the lever feel was excellent, nice and firm, but I had no brake power. I was pulling extremely hard just to get the bike to slow on a 1% downhill. I tried dragging the brakes down a 600' 7-8% descent and by the bottom they felt much better, but after 10 minutes of easy riding they were back to having no power. This lack of power is accompanied with an extremely loud, horrible squeal, loud enough to have people in cars giving me very odd looks. This is true for both the front and back brakes.

Does anyone have any clue why I don't have any breaking power? Any ideas on what I can try to fix it?

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Joined: Wed Oct 29, 2008 7:55 pm

by TurboKoo

You have managed to contaminate brake pads. Change them to new and you'll have power without noise.
Scott Foil
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by Weenie

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Location: The Grim North.

by mattr

Take the old pads out then scrub, burn, chemically clean the discs. THEN put the new pads in.

Or you'll contaminate the new pads.

Also, some shimano calipers leak round the piston seals. Eventually.

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Joined: Sun Sep 29, 2013 4:34 pm

by androidavies

As Matt says, new pads and properly clean those discs.

Assuming they were fine before your work, then you probably don't have leaking piston seals, yet……

Having got extremely fed up with leaking Deore calipers, it now seems that the road calipers are proving just as unreliable.

Hope now make a Shimano road lever compatible caliper, which should be reliable. The Hope mtb brakes are well proven here in the UK.

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

by CallumRD1

It did indeed appear to be a contamination issue. I cleaned the rotors with acetone then cooked them a bit over a gas stove to try to get rid of any remaining residue. I took the pads out and cooked them as well until they stopped smoking. I quenched them in water and then sanded them until they looked nice and new. One more rinse and I put everything back on the bike and took it for a spin around the block. After a few bedding in stops they feel like new again! I was lucky that I was able to avoid having to trash the pads, but I'll probably order up a replacement pair just in case.

Thanks for the advice everyone!

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