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Strengthening the Disk Brake backing plates

Strengthening the Disk Brake backing plates

Feb 18 2015

The tin plates that protect the disk brakes and ABS gear from inside the wheel have a bad reputation for cracking over corrugations.

The problem is that the plate is fixed by 3 bolts only on one edge, and the top part of the guard flexes and eventually fractures the bolt tabs. Over corrugations, the front edge of the plate flexes enough to hit the disk caliper, and causes a terrible metallic noise. One person I know has even had the plates fall off completely, and there is a chance that it will take out the ABS wiring and damage the brake lines if this happens.

The first plan I had was to cut down the backing plate so I could remove it on the road-side (when we reach roads that are badly corrugated), without having to remove the tyres, and then put them back on again when the road becomes bitumen again. So I took off the drivers side plate and attacked it with my plasma cutter.

Half way through doing this, I had a different thought!  Why not make a bracket to minimise the vibrations, and to give the 3 factory bolts more support so they don't fracture.  

It was too late to go back on the one I'd cut, so I just tidied it up with the linisher and put it back on the wheel. It is about 80% complete still so that should in theory still give me 80% protection.

So plan #2 was to fix another bracket at the far end of the plate to greatly reduce the oscillations and therefore the chance or cracking the plates. I had a few goes at prototyping a bracket, as the edge of the plate and the fixing point are in 2 different planes, which makes it tricky to work out how the bracket needed to be fabricated.

 

I drilled and welded a bolt onto the leading edge of the cover, for the bracket to attach to.

 


And this is how the strengthening ended up, with a brace back to the axle from the top of the plate.  It is 10 times firmer than the original setup, so hopefully this will stop the plates cracking.  The rear disk brakes have a similar setup and a similar problem. Unfortunately there is no convenient bolt hole to fix a bracket to, so that will require further thinking as to how I'm going to solve that issue.

 

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