I finished the calipers and bleeding on Friday. Bleeding was a bear, but after a couple of tries, I was able to get a decent pedal. I took it out for a couple mile drive to ensure the brakes were working well. When I returned I noted that the front drivers side wheel was very warm. I realized that though I spun the rotor when it was apart, I never spun the wheel after it was together. I jacked up the front and there was some drag when spinning the wheel. Not a whole lot, but enough to make the wheel warm.

Yesterday I took everything apart again. I confirmed that both the inner and outer pistons were moving. It did take a bit more effort to compress the inners, but I would not say it was unusual. What I noted was that the inside pad was fully back in the caliper and was dragging when I pushed the rotor to the correct position with the lug nuts. Both sides were more compressed like this, but the drivers side was the only one pushing the pad into the rotor. I checked for any damage to the brackets, but these look fine and worked well with the OEM calipers.

It looks like I may already be wearing the pads to a point where this is less an issue, but I do not want to drive further and risk damage due to the heat buildup. I will be on the phone with Wilwood tomorrow, but I was wondering if anyone else had this issue. This would seem to be an issue built into the casting and would be consistent. Is there any downside to the rotor not being centered in the caliper housing? I would not think so.

 

Is the rotor centered in the caliper? That is important with a fixed mount caliper. How thick are the rotors? Willwood calls for a 1.250" thick rotor. Let us know what Wilwwod says. My set should be here this week.

 

Shim it with steel washers. I just installed a Willwood disc brake conversion on a 71' Dodge Demon with 4 piston calipers........it came with gold iridite washers and said right in the instructions to shim if necessary. You will not need much judging from the picture......maybe .060 or so.

Jebby

 

Adding shims will move the caliper outboard making the clearance less. Rear calipers are the opposite, shims move the caliper inboard.

 

Bent caliper brackets. Check to see that both caliper mounting holes in the brackets are parallel. If not get a big hammer and pound em straight. I did. Perfect result but make sure it is the bracket first.

 

Copied this from another recent thread. This tells you where the mounting surface is relative to the rotor's center

 

Thank you for clearing that up....it has been a while since I removed one.

Jebby

 

only reason why I know this is my car is on stands waiting for these calipers to show up, hopefully this week.

 

Thank you for this! I missed that thread in my search. I will get out the calipers this weekend and see if I can determine if my bracket is giving me the correct offset to the disc. I did not purchase these rotors so it is possible that the machined offset is not perfect there too. The rotors do have CHINA stamped on the circumference. At least I will be able to determine where Wilwood thinks the bracket should be relative to the rotor.

Thanks again.

 

Well, it looks like it was everyone's fault (except mine of course) . There are no specifications that I could find from GM (at least published), so I need to chalk this up to tolerance stack. There were a few issues:

1. The rotors measured 1.265" thickness. Strange, but true. This pushed the inboard side in about 0.0075". Not a lot, but it added up.
2. My brackets were 1.028" from my disc near the bottom mounting hole and 1.048" at the top hole. With my disc thickness they theoretically should have been 1.0675" according to Wilwood.
3. It was harder to measure, but the Wilwood calipers seemed to be machined shallow on the ears by about 0.015", pushing the centerline out a bit. This is not a slam on Wilwood as I did not take the time to absolutely confirm this and with castings, it would be difficult to determine centerline exactly without measuring near the bores with a CMM. This could be the machining of the disc as well if the mounting surface was off relative to the rotor centerline.

Although it would be difficult to measure with my equipment, I was concerned about bending the ears back too far and creating an issue with the parallelism of the bracket to the disc. I bent the bracket so it was 1.050" from the disc at both mounting holes. This was enough to provide for no drag.

I would suggest that anyone who mounts these calipers reviews their distance from bracket to disc before mounting and adjusts prior as required. The Wilwoods and provided pads seem to be more sensitive to the tolerance stack than the OEM castings. It would be interesting to note if this was consistent in other installations. I have a feeling that the Wilwoods always are biased toward the inside slightly, but this only causes issues in rare cases.

69ttop502,
Just to let you know, you were correct if Wilwood specifications are correct.

ignatz,
Thank you again for the invaluable drawing.