Front Calipers on C3 -- how much drag is normal?

[Craig J.]

I just installed rebuilt front calipers, brake hoses (with new copper washers), and Delco 17D8 pads on my '77. The calipers are rebuilt units from Precision Engineering and use o-ringed pistons. I noticed that the pistons were very difficult to press back into the caliper when the pads were installed. Got everything installed, flushed the brake fluid using the gravity method (works pretty well), and buttoned her up and went for a drive in my neighborhood.

Here's the problem: When I raised the front-end after my initial drive, the front wheels were very difficult to rotate. This was not the case prior to replacing the calipers. I understand that there should be a little drag from the brake pads, but this seems way to be an excessive amount of drag.

Is this typical of o-ring piston calipers? Should the wheel be able to rotate fairly easily but then stop fairly quicky due to a proper amount of brake drag? I have to put effort into turning the front wheels, and the wheel stops as soon as I stop rotating the wheel.

My concern is that driving on the highway would probably overheat the front rotors. The rotors may be original (still rivited and look like they are 37 years old), so I'd hate to damage them.

Part of me says to work with the vendor and get new calipers and send back the rebuilt units. Thanks in advance.

[Joe L.]

Re: Front Calipers on C3 -- how much drag is normal?

I just installed rebuilt front calipers, brake hoses (with new copper washers), and Delco 17D8 pads on my '77. The calipers are rebuilt units from Precision Engineering and use o-ringed pistons. I noticed that the pistons were very difficult to press back into the caliper when the pads were installed. Got everything installed, flushed the brake fluid using the gravity method (works pretty well), and buttoned her up and went for a drive in my neighborhood.

Here's the problem: When I raised the front-end after my initial drive, the front wheels were very difficult to rotate. This was not the case prior to replacing the calipers. I understand that there should be a little drag from the brake pads, but this seems way to be an excessive amount of drag.

Is this typical of o-ring piston calipers? Should the wheel be able to rotate fairly easily but then stop fairly quicky due to a proper amount of brake drag? I have to put effort into turning the front wheels, and the wheel stops as soon as I stop rotating the wheel.

My concern is that driving on the highway would probably overheat the front rotors. The rotors may be original (still rivited and look like they are 37 years old), so I'd hate to damage them.

Part of me says to work with the vendor and get new calipers and send back the rebuilt units. Thanks in advance.

Craig------


I would think that the o-ring calipers would have less drag than the stock type. That's because the o-ring calipers do not use springs behind the pistons whereas the stock type do. I can't figure out why you'd be experiencing such drag with the o-ring calipers. I can't even imagine any failure mode that would cause this.

[Craig J.]

Re: Front Calipers on C3 -- how much drag is normal?

Hi Joe, I'm baffled...Plan B will be to work with the vendor to return these and buy new calipers. In hindsight, I should have bought new to begin with. Thank you for your thoughts.

[Bill M.]

Re: Front Calipers on C3 -- how much drag is normal?

Check to see how much drag you have when they are dead cold. It may be the master cylinder holding pressure if they only drag when hot.

[Craig J.]

Re: Front Calipers on C3 -- how much drag is normal?

Check to see how much drag you have when they are dead cold. It may be the master cylinder holding pressure if they only drag when hot.

Hi Bill. I checked again yesterday (didn't drive it Sunday) and same thing. It feels as if the pistons are not free to travel in their bore...very odd.

[Terry M.]

Re: Front Calipers on C3 -- how much drag is normal?

Hi Bill. I checked again yesterday (didn't drive it Sunday) and same thing. It feels as if the pistons are not free to travel in their bore...very odd.

I am thinking there is a small bleed hole in the master cylinder for the fluid to bleed back into the MC when the brakes are released. That hole has to be clear when the MC piston is fully retracted -- that is all the way toward the rear of the car. If the piston is hanging up or not retracting fully and thus not exposing that bleed hole the fluid will remain in the front brake system and keep a slight pressure on the wheel pistons. If the MC piston is hanging up far enough forward it will also block the hole for the rear brakes.

Was work done to the master cylinder at the same time as the work on the front brakes?

[Jeff S.]

Re: Front Calipers on C3 -- how much drag is normal?

Craig

Not that this helps, but as a point of interest -- I have experienced the exact same thing with o-ring calipers from your source. Currently I have lip seals from Muskegon Brake at rear & o-rings from PE at front; there's most assuredly higher rolling resistance with the o-rings. ('66 model year).

Jeff

[Terry M.]

Re: Front Calipers on C3 -- how much drag is normal?

In thinking more about your situation it occurred to me that a quick way to test if the bleed port being covered is your issue would be with the front-end raised rotate the front wheel(s). Then open one of the front bleeder screws to see if any fluid comes out under pressure. After closing the bleeder again rotate the wheel(s) and note if there is any difference in wheel resistance to rotation.

If fluid comes out aggressively and/or the wheel(s) rotate more freely after releasing the pressure in the front brake system, your problem is the MC bleed port being covered or clogged with debris. If this bleed test does no good, I too am puzzled.

[Lawrence M.]

Re: Front Calipers on C3 -- how much drag is normal?

Hi Craig, As Terry said you may have a problem with the master cylinder, however what you describe is exactly the way O Ring pistons act. It's the nature of the beast. They should not over heat your rotors . You will get some pad knock back as you drive which will reduce drag a little but the o ring pistons will always have more drag than the lip seal pistons. It is usually suggested that the piston springs are omitted to help reduce the drag with o ring pistons. I rebuilt my brake system with o ring pistons and silicone brake fluid in 1997 and all is still fine.

[Edward J.]

Re: Front Calipers on C3 -- how much drag is normal?

Craig, If you feel there is to much drag, try backing off the master cylinder retainer nuts and see if the wheels free-up. it s a easy test to see if the booster push rod maybe adjusted improperly or a booster problem.

[Domenic T.]

Re: Front Calipers on C3 -- how much drag is normal?

Craig,
I am with Terry on his test. I had this happen after brake jobs & especially master cylinder replacements.

The compensater valve Terry is talking about also has to have the MC piston in the correct position to release the pressure or it will act as a hydraulic jack. Any change in the MC controll rod can do this if it doesn't return to it's normal position which allows the fluid to return to the MC.

DOM

[Craig J.]

Re: Front Calipers on C3 -- how much drag is normal?

In thinking more about your situation it occurred to me that a quick way to test if the bleed port being covered is your issue would be with the front-end raised rotate the front wheel(s). Then open one of the front bleeder screws to see if any fluid comes out under pressure. After closing the bleeder again rotate the wheel(s) and note if there is any difference in wheel resistance to rotation.

If fluid comes out aggressively and/or the wheel(s) rotate more freely after releasing the pressure in the front brake system, your problem is the MC bleed port being covered or clogged with debris. If this bleed test does no good, I too am puzzled.

Hi Terry. Great test! I'll run that tomorrow and see what happens. Thank you!

[Craig J.]

Re: Front Calipers on C3 -- how much drag is normal?

Hi Craig, As Terry said you may have a problem with the master cylinder, however what you describe is exactly the way O Ring pistons act. It's the nature of the beast. They should not over heat your rotors . You will get some pad knock back as you drive which will reduce drag a little but the o ring pistons will always have more drag than the lip seal pistons. It is usually suggested that the piston springs are omitted to help reduce the drag with o ring pistons. I rebuilt my brake system with o ring pistons and silicone brake fluid in 1997 and all is still fine.

Hi Larry. That's interesting...I would have thought the o-ring calipers would have less drag since there are no springs behind the pistons. If you had your front end raised, and then rotated the front wheels, would you have to exert much effort (hard to quantify effort) in order to rotate a front wheel? Thanks.

[Craig J.]

Re: Front Calipers on C3 -- how much drag is normal?

Craig, If you feel there is to much drag, try backing off the master cylinder retainer nuts and see if the wheels free-up. it s a easy test to see if the booster push rod maybe adjusted improperly or a booster problem.

Hi Ed, that's another great test I'll try. There wasn't a problem prior to the new calipers, but that doesn't mean something could have gotten clogged in the meanwhile. Thank you.

[Lawrence M.]

Re: Front Calipers on C3 -- how much drag is normal?

Hi Craig, Yes with the front wheels off the ground it is harder than you would think is normal to spin the front wheels. When I put the '69 on jack stands to do the winter chassis cleaning and chip touch up I squeeze the brake pads with channel locks to push the pistons in a little. The wheels spin freely until I push the brake pedal again. There is a you tube video out there about this oring verses lip seal debate. It was done by Werner Meier possibly at a Michigan chapter event. Try searching for it. He does not like orings because of the drag problem. The down side of the lip seals are they seem to leak after a few years no matter what you do.
My calipers have not leaked since I did them '97. It is a trade off I can live with.