Caliper Rub on Rear Rotors

[cv2065]

Getting ready to put my wheels on and getting some drag when I turn the rears. I realize I'm turning gears in the IRS but how much drag is 'acceptable' and do the pads clearance themselves once you get rolling?

[David Williamson]

The pads will rub lightly, that is normal. Can you turn it easily by hand?
David W

[cv2065]

The pads will rub lightly, that is normal. Can you turn it easily by hand?
David W

I can turn it by hand and you can hear the pads rubbing with each turn. Not sure I would call it easy. If I grab the rotor with one hand on the side I can rotate it, but again, I wouldn’t call it easy. Here's a short video:

https://youtu.be/EcBnXDxCsak

Now that I'm looking at my own video, doesn't look right. I know that it rotates freely without the caliper installed, so I'm wondering if the pistons were not rotated all the way into the bore. Would that be something to look at?

[initiator]

Check to make sure the caliper is spaced so that its opening is centered over the disc. Adjust your spacers if not.

Check to make sure the locating pins/nubs on the back of the brake pads are aligned with the piston reliefs.

Once I'd done both these things, the resistance went way down and I would just hear a light scraping from each caliper (normal) along with the differential gear noise.

It's possible your pistons need to be rotated back into the bore, but check the above first.

These points are relevant to 3-link standard brakes, I see you have the Wilwoods.

[cv2065]

Check to make sure the caliper is spaced so that its opening is centered over the disc. Adjust your spacers if not.

Check to make sure the locating pins/nubs on the back of the brake pads are aligned with the piston reliefs.

Once I'd done both these things, the resistance went way down and I would just hear a light scraping from each caliper (normal) along with the differential gear noise.

It's possible your pistons need to be rotated back into the bore, but check the above first.

These points are relevant to 3-link standard brakes, I see you have the Wilwoods.

Pins are definitely aligned from pad to caliper. Not sure about the spacers, as I didn't get any with the calipers. If you look from behind in my pics, they don't look completely centered, but should the pads "self adjust" as they are used?

Can't recall if the pistons were all the way back into the caliper, but I do know that the caliper installed easily over the bracket with pads. I can rent a tool from Oreillys if that will solve the issue.

[rich grsc]

ALL disc brakes rub, if you can turn it be hand, IT'S normal.

[cv2065]

ALL disc brakes rub, if you can turn it be hand, IT'S normal.

Thanks Rich. I posted a video. Does that amount of effort look correct?

[BadAsp427]

Watched your video.... I have the 2015 IRS, I dont think I can do what you did... not until I had the tires mounted could I turn the rear wheels... IMO The sound of your brake pads scraping is normal and if it were too tight, you could not have turned that rotor.

[Fixit]

Same here... My setup is a bit looser (less drag), but it's from a 1000 mile "take-out", and I'm reusing the pads - so the stuff has had a few applications and the newness worn off.

My gut says "run with it". After a few miles those parts will bed-in and get to know eachother. If you can rotate them by hand (granted with a bit of effort), you've got E-brake and Service brakes yer good to go.

[GFX2043mtu]

When installing calipers they should easily clear the pads to the point where you have to pump them to get the pedal to firm up. If yours where tight when assembled remove them turn and push the pistons in till they easily clear the pads. The other potential is if you adjusted the parking brake and over did it or possibly have it a couple clicks engaged and don’t realize it. This is given the caliper mounts fit correctly as well as tge hardware and the pads.

[cv2065]

Same here... My setup is a bit looser (less drag), but it's from a 1000 mile "take-out", and I'm reusing the pads - so the stuff has had a few applications and the newness worn off.

My gut says "run with it". After a few miles those parts will bed-in and get to know eachother. If you can rotate them by hand (granted with a bit of effort), you've got E-brake and Service brakes yer good to go.

Thanks guys. I’ll run with it and see how the pads settle. Still have to get my e brake sorted out.

[cv2065]

When installing calipers they should easily clear the pads to the point where you have to pump them to get the pedal to firm up. If yours where tight when assembled remove them turn and push the pistons in till they easily clear the pads.

The drivers side went in easily. The passenger side seated but it was a little tight. Just for my own edification, if the caliper fits over the pads and can be secured, why does it matter if the piston is tight or not? Doesn’t the piston travel back against the pad anyway no matter where it is positioned, tight or loose? Again, just curious as I was thinking about this earlier after reading a few posts from other threads stating the same thing. Thanks!

[Dthquazi]

My driver's side is super tight and hard to turn after applying the brakes and releasing them. After a bit it will loosen up to a point where I can turn it by hand. Are you noticing any difference after you apply and release the brake?

[cv2065]

My driver's side is super tight and hard to turn after applying the brakes and releasing them. After a bit it will loosen up to a point where I can turn it by hand. Are you noticing any difference after you apply and release the brake?

I don’t have any issues there. Just when I apply the e brake. I’ll be getting a spring in there to help return the arm as suggested by some other members.

[GFX2043mtu]

Yes and no. Yes, Calipers pistons are designed to have spring back so that they release. The issue comes from screw in calipers that need to be with in range. If they are not screwed in enough they can’t spring back enough causing excessive drag. This drag continues until the pad is worn. The issue is this causes a lot of heat and wear. The perk to these calipers is that the parking brake is incorporated in the caliper and is one nice easy package that doesn’t require a lot of other parts like drum in rotor parking brake systems. Also are you using calipers with the metal pistons or not? Some of the non-metal pistons can swell and stick? Light dragging is normal but if you have to yank to get a rotor to turn with the caliper on then something is wrong.

[cv2065]

Yes and no. Yes, Calipers pistons are designed to have spring back so that they release. The issue comes from screw in calipers that need to be with in range. If they are not screwed in enough they can’t spring back enough causing excessive drag. This drag continues until the pad is worn. The issue is this causes a lot of heat and wear. The perk to these calipers is that the parking brake is incorporated in the caliper and is one nice easy package that doesn’t require a lot of other parts like drum in rotor parking brake systems. Also are you using calipers with the metal pistons or not? Some of the non-metal pistons can swell and stick? Light dragging is normal but if you have to yank to get a rotor to turn with the caliper on then something is wrong.

Ok got it. Thanks for the explanation. Yes, I have metal pistons. I’m having an issue with my e brake lever sticking as well. If the pistons are not screwed in all the way and cannot spring back as intended, can that affect the way the e brake assembly works at the caliper since they are all inter connected?

[Dthquazi]

Did you fix this? I am having issues with one. This adjust brake think is new to me and for some reason it is hard to understand. I drove the car a little today and the drivers was smoking when I stopped.

[cv2065]

Did you fix this? I am having issues with one. This adjust brake think is new to me and for some reason it is hard to understand. I drove the car a little today and the drivers was smoking when I stopped.

Yes, it was the e brake dragging. Couple of forum members recommended a fix with a piano spring. I included it in my build thread with part numbers. Hope that helps!