Rear brake shims - which way up?

Mark.T · Post by **Mark.T** » Mon Mar 15, 2010 11:25 pm

I recently obtained a second-hand rear brake caliper which had these half-shims between the pistons and the pads. I did not fit them to the car as they are not in the caliper on the other side and I had not seen these before. Also, they fell out without me noticing which way up they went. Are these shims common? I guessed that they are to prevent brake squeal in a similar way to how you angle bicycle brake blocks to stop squeal. Also, if I do get another set for the other side, which way up do they go? They are not shown in either the Haynes or in a couple of French manuals I have.

kiwi · Post by **kiwi** » Tue Mar 16, 2010 5:32 am

News to me as well I have never seen shims fitted on a BX before

citronut · Post by **citronut** » Tue Mar 16, 2010 8:11 am

i have seen them before but cant remember which way up they go,

if you know which one came from which side, you should be able to work out how they were by the make the piston left on one side of each of them,

even though i dont think it would matter either way up as they are anti squeele shims,

i had a look on service citroen and it dose not show them at all,

regards malcolm

kiwi · Post by **kiwi** » Tue Mar 16, 2010 9:01 am

citronut wrote:i have seen them before but cant remember which way up they go,

Probably on some other citroen but not on a BX that much I am sure of, and if you can not find it in a manual then thats probably a very good indicator they never were fitted.

I do note that the OP is in Australia and from experiance of cross referance of parts for Rear Brakes on a BX I did have a problem! This was due to an error in the parts numbers records in Australia.

Can not remember where I wrote about this but I had a problem where I ordered Rear BX parts and got sent the wrong size. Turned out to be a parts mismatch error. My guess is that this is the same problem the OP has with incorrect part numbers.

prm · Post by **prm** » Tue Mar 16, 2010 7:49 pm

Never seen them on a BX before. Possibly?? from an earlier Citroen model or, available to the damp Asian market? for a BX.

Are there two shims, one for each pad?
Looking at the shim, it appears to have the half-moon markings from the piston. I should imagine the shims are secured in place by the main pad nut and bolt, and positioned to give the pad forward edge a toe-in.

With any shims, a coating of copper grease helps.

Regards

Mark.T · Post by **Mark.T** » Tue Mar 16, 2010 8:06 pm

Thanks for the suggestions. Yes there were two shims in the caliper, one for each pad. As some people said, you can see the half-circle mark from the piston on this one, and yes the pad-retaining bolt does go through the hole in the shim. If I can find another pair of shims I might try fitting them to both sides on my next rear pad change.

ken newbold · Post by **ken newbold** » Tue Mar 16, 2010 8:23 pm

I've only ever seen these once before, some years ago on a Mk1 but as there were 2 in each caliper, one for each pad, I think one fits one way and the other fits the opposite way.

or just sling em

scarecrow · Post by **scarecrow** » Fri Mar 19, 2010 6:11 pm

I can remember having shims on my first BX - in similar circumstances, i.e they fell out so I left them out. The trouble was the brakes bound quite a lot afterwards - but probably unrelated as I replaced the callipers and that cured the problem.

scarecrow · Post by **scarecrow** » Fri Mar 19, 2010 6:21 pm

Another thought is that the brake pads might be stock items for other vehicles which do require the shims - and those bx's discovered with the shims already fitted may have got them because a previous owner did their own brakes and thought, "They're in the box, so they must fit somewhere."