Oversized drums, worn shoes and blowing wheel cylinders

[Jean-Sebastien Stoezel]

Hi:

Is it physically possible that either or both oversized drums or/and worn shoes can lead to blowing front wheel cylinders?

I have had front brake failures recently, on the same wheel. I have replaced the wheel cylinder with a brand new one and I seem to blow the piston out. The issue seems to be inconsistent, it comes and goes during a session.

Thanks,
JS

[BLS]

Jean,

For a wheel cylinder piston to come completely out requires more travel than is normal. I would check the brake shoes and make sure the height of the wheel cylinder contact flange, with respect to the brake shoe surface, is correct. Compare it with other shoes. They have been known to get ground, possibly to change from straight to angle shoes (or the opposite). A turned drum with standard shoes would make this even worse.

The other possibility, a shoe that gets pushed out of the wheel cyl mating groove. Even then I'm not sure there is enough room for the piston itself to come completely out.

[provamo]

another case for disc brakes?

[Jean-Sebastien Stoezel]

Hi Barry:

Thanks for the reply. By blowing off, I didn't mean the cylinders came out completely. I meant blowing fluid out of the cylinder. The issue seems to be happening with shoes I have been using for 4 seasons, and so I would think that the flange and cylinder surfaces are ok.


JS

Jean,

For a wheel cylinder piston to come completely out requires more travel than is normal. I would check the brake shoes and make sure the height of the wheel cylinder contact flange, with respect to the brake shoe surface, is correct. Compare it with other shoes. They have been known to get ground, possibly to change from straight to angle shoes (or the opposite). A turned drum with standard shoes would make this even worse.

The other possibility, a shoe that gets pushed out of the wheel cyl mating groove. Even then I'm not sure there is enough room for the piston itself to come completely out.

[BLS]

"...and I seem to blow the piston out"

Jean, sorry I misunderstood.

Still, you might want to check how much travel is required with the wheel cyl pistons. If they have to go way out it might lead to the seals getting out near the end and lead to some leakage. I had a problem once last year on the rear - a brake shoe came out of the groove somehow and hung up which let the seal get too far out and some fluid got out. I would at least check the shoe height. Since you have turned drums, unless you start with oversize linings they are already going to be further out. It's the only reason I can think of, short of a bad cylinder. Since you say you put in a new one and still had the problem... Of course, it's also possible you have a bad new cylinder, but it seems unlikely. Also, seems unlikely, but make sure the seals are properly oriented in the WC.