What is the maximum inside diameter from the brakedrums? I have a deep scratch in the brake drum now had to have turned out for this I need to know the maximum allowable inner diameter
Hopefully one of the experts will find a specific reference for the brake drums on your Chevy. I could not find that data in the shop manual or the specifications.
The normal limitation is that a brake drum cannot be turned to an inside diameter that is greater than .060” (1.5 mm) above the nominal or new size of the drum.
On your car the nominal or new size of the drum is 11” (280 mm).
My brake drum is pretty much still 11". The groove is 0.25mm (0.0098") deep, so turning it out should not be a problem. At the moment I leave it so, because the groove is already very old. I suspect there once a rivet of the brake pad has worked in. But it was not this lining, so already much older. Also do not think that makes a difference to the braking performance.
Hello Rusty, I hope so too. It's been almost exactly 6 years since the start of the restoration, so it's about time to experience this car. But at the moment most of the work is done, just bleeding the brakes and some cosmetics in the interior. Last but not least, I still have to clear the German TÜV hurdle, but that shouldn't be a problem.
Until the shoes "work in" there will be the lose of contact where the groove is until the shoes have sufficiently worn down and contact the bottom of the groove. The difference in braking will not be significant enough for you to be able to tell the difference.
I recall Porche didn't advise turning the rotors/drums until a certain depth of grooves was reached. I don't remember what that depth was.
By the way, I still have a tip for all those who also want to change the wheel brake cylinder. Disassemble in any case the new and lubricate the components with brake fluid. One of mine had been assembled completely dry
Now I have a new problem. I wanted to bleed the brakes. A procedure that I have already done successfully on many of my cars. I followed the manual exactly and no more air comes out of the cylinders. Unfortunately, I can't get a stable pressure point. It always feels soft. Is there a trick to this? We have bled with two people.
Sometimes I have had similar results if I did not adjust the brakes properly before I bled the system.
The other problem I have had is what the Chevy shop manual calls “toe clearance” for the brake pedal. You make this adjustment to make sure that the piston in the master cylinder returns completely to the home position when the brake pedal is released. In that position the small port between the piston chamber and the reservoir is open.
Hopefully you can get the brakes working properly.
