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Hi All
I'm really not sure how this has happened and am convinced I am the problem and not the brake. I'll try and explain. This relates to my Shimano Tiagra Rear Brake on my road bike, so naturally a rim brake. Like this one:
http://www.wiggle.co.uk/shimano-tiagra-br4700-rear-brake-caliper/
Cleaning my bike today I removed the entire caliper from the bike to give it a clean and inspection. Not really sure what I have now done but if I re-install the entire caliper on the bike and tighten the bolt that attaches it to the frame, the spring sticks and the calipers won't re-open once pushed together.
However, if I loosen the bolt that attaches the calipers to the frame, the spring works again and is "springy" when I push the calipers together with my fingers. To achieve this though, the bolt attaching the entire caliper unit has to be loosened way, way too much- to the point where the caliper unit isn't attached to the frame properly. As soon as I tighten to an appropriate force, the spring sticks again and won't return 😕
I was out riding yesterday and the brake was working fine.
The cable is completely un-tensioned so it's not a cable issue.
This has got to be me missing something obvious, right?
I thought there may be a spring tension adjustment bolt maybe but it seems there isn't. Also even if there was, I wouldn't have touched it anyway.
Does any of that make sense?!
Have you missed a washer out between the brake and the frame?
I'm pretty sure I haven't- there was one washer between the brake and the frame when I removed it and I put it back on
Yep, sounds like you've lost the serrated washer that goes between calliper and frame.
Serrated washer?
There was one "normal" washer that I saw tumble out when I removed the caliper (I retrieved it) but do you think maybe there was another washer that fell out that I missed?
Just a quick bump to see if anybody else has any ideas?
I had a look for any spilt/lost washers or bolts and can't see one anywhere.
I guess I may just have to buy another caliper and assume that something must have been lost or dropped and rolled into a crack in the garage floor or something.
Missing serrated washer *shouldn't* make the caliper spring stick. I've got several brakes fitted without the serrated washer. None of them move, or stick. All work exactly as they should.
FWIW the shimano exploded view doesn't even show a serrated washer on BR4700
http://si.shimano.com/#seriesList/19
I reckon either the lock nut (item 4) or the grub screw in the arm bolt unit (item 1) is the culprit.
this one ?
might be wrong one, i would find out the model, then search that model with the word PDF, you get all the shimano docs to go with it
Think that one might be slightly different- the sticker on my caliper says Shimano br-r561 if that makes any sense?
Ghostly- yes, that's the right caliper.
I think what happened is that I actually thought one of the caliper arms was a bit looses and so tightened the arm bolt unit (number 1 on the exploded diagram) and now I'm having problems. The thing is though I've now tried installing the caliper with the arm bolt unit both tight and loose and it doesn't seem to have made a difference either way.
You may have killed it, lots of springs, bushes and widgets relying on minimal clearances and (relative) cleanliness. And a randomly tightened bolt.
Might be time for either someone who knows what they are looking at, or a new caliper.
Cheers Ghostly, I think I might be looking at buying a new one then, I think they're like £25 or something so not much point in paying for it to be fixed I don't think