Rear disc too deep & touches shoe backing plate - help!

[koala58]

On 7/2/2024 at 1:03 PM, flash22 said:

wire brush the backing plate and give it a tweak with a hammer and a lump of wood, its just warped with age and a bit of rust jacking, the previous discs have just self clearanced over time

Bob, thanks for your feedback.

The backing plate is undamaged, it's not warped and there's no significant rust. I'm very grateful for your input, but a spinning cast iron disc doesn't self clearance against a thin metal backplate, it's going to just wear away the backplate - and the backplate showed no marks indicating contact (until I put the new discs on!).

But I may use your suggestion as a last resort (as opposed to the shimming idea I suggested above) if I can't find discs that fit.

I would need to be careful though - the place where the new discs touch is very close to where the brake shoes are mounted/located. I don't want to bend the plate and screw up the shoe alignment - then I'm into another set of problems.

Cheers

[flash22]

the shoes are floating and will self-centre in the drum so no issues there, it could just be the discs are machined just within a tolerance, only way to tell is to measure them with a Vernia gauge another solution is to have 0.25mm machined off the lip

[koala58]

I thought I'd give an update to this thread for the benefit of the forum.

The new discs are now fitted and working OK!

I bought a pair of genuine Toyota branded discs and ... they had the same problem as all the others!

So as a last resort I followed Bob's suggestion and I took a hammer and drift to the backing plate - despite my concerns it solved the problem.

In the end I used a pair of Bosch discs - they seemed to fit marginally better than the others (ie I had to hammer the back plate a bit less). Once this was done all was OK - brakes working, handbrake working, all good. Annoyingly this would have been a very straighforward job had I not encountered the backplate issues.

My thanks to all who contributed to the thread and in particular to Bob.

Cheers

T

[flash22]

Thanks for the update, older cars sometimes require a bit of percussive maintenance rust/corrosion and heat cycling can do strange things 0.5mm at the centre can make the outer edge 2-3mm out

or

If in doubt, give it a clout