Weird rear brake binding issue

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ToGGoT
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Weird rear brake binding issue

Post by ToGGoT »

Hi all, mobile posting so apologies for formatting.

2005 R1150R non-abs - riding a couple of weeks ago and the bike started to feel like I was towing a caravan.

Limped it home and after it cooled I could only spin the rear wheel around 1/4 a turn with a good shove. Pulled off the caliper which was admittedly quite dirty, and the wheel spins much more freely.

Pads out, cleaned everything, pad retainer pin was quite corroded so cleaned that back as well. Both pistons push back easily individually and together, but cleaned anyway, and reassembled it all with some copper grease on the slide pins, retainer pin and back of the pads. The hoses are overbraided and I don't think are that old.

Flushed all the brake fluid through with clean, and bled.

It's exactly the same - if I apply the rear brake and stop the rear wheel, the rotation is really stiff afterwards.

What am I missing?
Tigcraft
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Re: Weird rear brake binding issue

Post by Tigcraft »

Not sure. I’d take calliper off and put a flat bar same thickness as disc in between the pads to fool it thinking it’s got a disc in it and squeeze the brake a few times to see what it does or doesn’t in this case.
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Photoguy
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Re: Weird rear brake binding issue

Post by Photoguy »

Total wild guess here especially since it seems you've covered all of the initial things...caliper seals not retracting?
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riceburner
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Re: Weird rear brake binding issue

Post by riceburner »

Photoguy wrote:Total wild guess here especially since it seems you've covered all of the initial things...caliper seals not retracting?
That would be my thought too.
You may need to push the pistons out completely and clean out the seal beds.
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ToGGoT
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Re: Weird rear brake binding issue

Post by ToGGoT »

I think thats the next job tbh. Will have the caliper off completely and disassemble. I see there is a repair kit available which is nice.

Has anyone had the delaminating hose issue with the braided hoses that came standard on the 'R' models?

Thanks
AZBMWRIDER
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Re: Weird rear brake binding issue

Post by AZBMWRIDER »

Just a thought, I've heard of this on older airhead bikes . There usually is a small port at the bottom of the fluid reservoir not the hole that supplies fluid to the master cylinder piston . If that port is clogged, brake pressure gets trapped in the line and caliper, the brake stays applied .
With the reservoir cap removed, you get a small jet of fluid out of this port, when the brake is released .
'02 R1150R, Atlanta Blue
Been riding since 1979, BMW's since 1981 .
4 R65's, '87 Guzzi V65 Lario .
ToGGoT
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Re: Weird rear brake binding issue

Post by ToGGoT »

So, stripped it all down this afternoon, and pulled the caliper to bits. The pistons are fine - one of them has a small amount of corrosion on the side, which I'll need to keep an eye on, but it's not bad enough to warrant replacement. The seals look fine, and there is no muck anywhere behind them.

I took the thrust spring off and cleaned behind that in case it is pushing against the end of the pads. However, the top retaining clip thing (not sure quite what it is called - clips into the top of the caliper and sits atop the pads) is manky as hell. To a point where if it isn't causing a problem I'd be surprised. I took that out, and reassembled and it seems a LOT better.

What does that little clip do? I can't see any change in the way the pads sit, and I'm wondering if I will get away without it...
AZBMWRIDER
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Re: Weird rear brake binding issue

Post by AZBMWRIDER »

I think it's anti-rattle spring, keeps the pads from moving around .
'02 R1150R, Atlanta Blue
Been riding since 1979, BMW's since 1981 .
4 R65's, '87 Guzzi V65 Lario .
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