Hi all,

Does anyone know what the inner diameter of a wheel cylinder is on a drum brake system?

Thanks

 

THey vary; on these cars, seems like it's somewhere between 7/8" and 1".

 

If I got new ones (rather than rebuilding them), wouldn't it really matter what the size is so long as they bolted into place OK? Do you know why they differ in size so much?

 

The relative size of the MC bore and the WC bore acts like a lever; if you increase the bore size of the WC, then you'll have the same psi in the system acting on a larger area, which will give you more lbs of force, but you'll have to feed it correspondingly more fluid to make it move the same distance, since volume = the piston area x how far it moves, and it'll have to move the same distance that it does now.

They pick the sizes of all the brake parts to work properly together.

The right ones are $8 apiece at AutoZone for the whole cyl. Oddly enough, rebuild kits are $10 apiece. Still, incredibly cheeep. Brakes are not something worth half-a$$ing or experimenting with, when the right parts only cost pennies like that. Just do it right and move on.

 

Noted.

The reason I asked about the diameters is because I live in the southern hemisphere so parts for these cars aren't as plentiful as you'll be used to. By knowing what the inner diameter of the WC in my car is I can match the correct part with what we do have in the shops without taking my brake system apart. You'd have a hernia if I told you how much I've been quoted for WC's from some shops here.