Jump to content
  • When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Brake caliper question


Guest Anonymous

Recommended Posts

Guest Anonymous

What makes a caliper piston return into its bore??

Is it the design of the seal that pushes it back?

I know oil is sucked back when we release the brake pedal, but as the inards of the mc is made of reverse cups, very few or none sucking is present, so is should be something else?

It is because i am wondering about my Subaru calipers (with internal hand brake mecanism, screw type), wich dont seem to return back properly, they offer some kind of a constant friction onto the disk, as if i was pressing on the brake pedal always, and then makes the disc overheating. I did try to "adjust" them, but as soon as i press on the pedal, drag reapears. Every components are top notch quality, new, new hoses everywhere.

Could it be the fact that i am using the stock mc, wich shares the rear hose port with the front? (3 ports on the second piston of the mc, 2 for front dual hose system and one for the rear, where i am connected to for my rar calipers)?? so the mc sucks the oil that is into the front calipers, because they dont offer much resistance compared to the rear ones?

I have to fix it, it is not that much of a big problem, just that it drags and may remove too some performance out of the car... :)

Pat Allen

Link to comment
Share on other sites

Guest Anonymous

What makes a brake caliper piston retract is just what you guessed in your post:

The piston seal is a square cross-section rubber ring that stretches as the brakes are applied and the piston moves out. The seal is strong enough to pull the piston back when the brake pressure is released. This is how disc brake calipers can be self-adjusting for wear.

For rear drum brakes cars, there is another trick needed to keep the wheel cylinder's cup seals from relaxing and allowing air to be drawn in.

These systems may use "residual pressure" valves for the rear circuit that keeps a small pressure on the wheel cylinder cup seals, not enough to overcome the return springs.

Not all drum brake systems use residual pressure valves in the master cylinder or inline down stream, but if they are there and you switch to rear calipers, it would act like you describe.

Link to comment
Share on other sites

Guest Anonymous

Could it be the small aluminum part bolted under the mc, where the rear hose start? i tough it was a "presure reducer"...

Anyway, your description sounds logical, i will simply remove it to see what will happen.

Thanks!

Pat Allen

Link to comment
Share on other sites

Guest Anonymous

80's gl type...or at least, any suby of the 80's, they have the handbrake on the front wheels.

No special needs, only to have decent ofseted wheels as they will rub inside, an adapter and original banjo hoses.

Hand brake is fully working.

Pat Allen

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Upcoming Events

  • Supporting Vendors

×
×
  • Create New...