help need - can't bolt rear caliper back on!

[jcbadger]

Hi All

I need help please. I've changed discs and pads before no probs so this shouldn't have been a problem.

I'm putting on new rear brakes disc and pads. The job has gone ok until this. I've bolted on the new disc, I've bolt on the carrier frame that hold the pads, new pads installed, the piston has been pushed back in, the caliper fits over the pads no problem - the problem is that the guide pin bolts that pass through the black rubber bushes in the caliper body - I know it's supposed to be tight, snug fit but I can't get the bolts to completely pass through through the bushes - you can see the end of the bolt appearing the other end but they won't go any further no matter how much you screw them they just dont go any further and therefore don't quite engage into the female thread on the carrier frame so therefore the caliper can't be bolted on and I can't complete the job. This is the last (major) hurdle. I've taken out the two bolt s to check the inside of the rubber bushes - they're not smooth and consistent diameter straight through - should they be? There is a slight 'shoulder' in both of them and I guess this contriction if the rubber has swollen is making it difficult for the bolts to pass through to the other end. If the rubber bushes do need replacing are they available separately? The bolts themselves are perfecctly smmoth and clean - no rust.

Many thanks

JC

[jcbadger]

I've looked on realOem.com and there is a guide bush repair kit available. Down to BMW I think - but any comments welcome if anyone else has had the same problem. ta

[GCA3N]

Right I think I know what you mean I changed over the pads and discs on my 2002 coop and remember them being really tight and having the exactly the same issue as you. The way I done it was to put copper grease (or similar) on the bolts/pins so they slid through the bushes more easily. And then loads of elbow grease it can be tricky but that's all that i can think off just now.

[jcbadger]

Thanks for that - at least I know it's a pain to do and it's not just me. I tried copper grease as well but no joy. Apparently it's supposed to be a dry fit - ie. no lubricants should be used but I can't see how it can be possible without some sort of lube. I'll buy new BMW rubber bushes just in case the ones I've got have swollen up. when I removed the bolts they were covered in a blue fluid (not threadlock) this could have done something to the rubber.

[GCA3N]

Thanks for that - at least I know it's a pain to do and it's not just me. I tried copper grease as well but no joy. Apparently it's supposed to be a dry fit - ie. no lubricants should be used but I can't see how it can be possible without some sort of lube. I'll buy new BMW rubber bushes just in case the ones I've got have swollen up. when I removed the bolts they were covered in a blue fluid (not threadlock) this could have done something to the rubber.


might have. tbh like you i was stuck it was the only thing that allowed the bolt to start on the female.

[Crombers]

Phone the garage :rolleyes:

[jcbadger]

oh there is something else I'm curious about - why is there a thin wire 'spring' on the back of the pad that's next to the piston? What's the purpose of it? I've installed both pads into the carrier frame and pushed the caliper back on over them - I don't need to do anything differently to the pad closest to the piston that has the spring on it do I?

Thanks all

[GCA3N]

oh there is something else I'm curious about - why is there a thin wire 'spring' on the back of the pad that's next to the piston? What's the purpose of it? I've installed both pads into the carrier frame and pushed the caliper back on over them - I don't need to do anything differently to the pad closest to the piston that has the spring on it do I?

Thanks all

No you don't. I think the back spring assists in keeping the pad in place and located on the piston. I remember thinking the same thing.

[jcbadger]

Bingo - all done. I went to BMW and got new rubber bushes for £16.00 ish for two rubber sleeves!!! However I now know what was causing the tightness beyond normal and stopping the guide pin from going all the way in. I could have saved myself £16.00 if I'd thought about it first. When I pushed out the old bushes the holes in which they sit were no longer round - they were 'corroded' - not the normal brown stuff but white chalky build up (like calcium build up). The build up was so severe it was deforming the rubber bushes so they were no longer round and smooth straight through. The build up was also reducing the diameter of the hole thus causing a constriction in the rubber bushes. As the build up continued building up it gradually makes the diameter of the hole in the rubber sleeve smaller. This is why the brake failed it's MOT as the caliper was not sliding properly and binding. I used a round file and a drill mouted wire brush to get rid of the chalky build up in both holes and inserted the new bushes - although the old bushes would still have worked but now I've spent the money I might as well use them. Guide pins then slid in smoothly with no hinderance or brute force required. If anyone has the same probs then before splashing out money at BMW for extortionately priced pieces of rubber bushes - push them out first and check the holes.

[GCA3N]

Bingo - all done. I went to BMW and got new rubber bushes for £16.00 ish for two rubber sleeves!!! However I now know what was causing the tightness beyond normal and stopping the guide pin from going all the way in. I could have saved myself £16.00 if I'd thought about it first. When I pushed out the old bushes the holes in which they sit were no longer round - they were 'corroded' - not the normal brown stuff but white chalky build up (like calcium build up). The build up was so severe it was deforming the rubber bushes so they were no longer round and smooth straight through. The build up was also reducing the diameter of the hole thus causing a constriction in the rubber bushes. As the build up continued building up it gradually makes the diameter of the hole in the rubber sleeve smaller. This is why the brake failed it's MOT as the caliper was not sliding properly and binding. I used a round file and a drill mouted wire brush to get rid of the chalky build up in both holes and inserted the new bushes - although the old bushes would still have worked but now I've spent the money I might as well use them. Guide pins then slid in smoothly with no hinderance or brute force required. If anyone has the same probs then before splashing out money at BMW for extortionately priced pieces of rubber bushes - push them out first and check the holes.

Glad you sorted it mate, :thumbs up: