# calipers



## Topkat (Sep 9, 2010)

I finally got my new 4 piston rotors, put new bearings in and started to install my rebulit calipers. When putting the bolts in finger tight I noticed the the bottom of the rotor rubbing on the new rotor.
(the rotor sits almost a 1/4 farther from the back plate, but I could shim that.)
I'd have to do so major grinding to the calipers.............(not me)
While snugging the bolts down the rotor wouldnt turn at all.
Looking at the old caliper i see the cut away.........:shutme:shutme
what do I do now?
:willy::willy::willy:
thanks


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## Topkat (Sep 9, 2010)

The "after market" 4 piston rotors that OPGI sold me are one piece,they do not have the "tapered centers" that allow the caliper to clear the rotors, as the factory ones do.
Starting to see "after market" as a bad word............
When I pulled the "AM" rotors off, now both inner bearings and the seals are tightly wedged on the spindles.
What causes this?
Was it just the "wrong rotors"?
The old ones fit 1/4' farther back on the spindles and dont hang up.
Just to be safe I ordered new inner bearings.
thanks as always


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## pontiac (Mar 6, 2011)

"noticed the the bottom of the rotor (_assume you meant caliper_) rubbing on the new rotor." the caliper mounting is in a fixed position, relative to the backing plate and the center of the spindle, so no amount of rotor adjusting will make up for the lack of taper on the new rotor which hits the caliper. the bearing wedged on the spindle is another problem, in regard to the new bearing either being located on a different position on the spindle, the race seated in a different position inside new rotor or the wrong inner bearing id. it might be fixed with a another bearing, or move the race to a position so the bearing does not wedge on the spindle. this is all trial and error, and not likely to work properly unless you fix the rubbing of the rotor on the caliper. machine shop could properly turn rotor to get clearance, but that would void any warranty on that rotor if there was one. IMO, your old rotors if not warped, don't look too thin to me. don't turn them, if grooved, so what, some people pay big money for grooved rotors, your new pads will quickly match those grooves, and pads are cheaper than any of the other parts or machine work. pads don't have rivets these days, so no more grooves anyway. you will actually have more contact surface.


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## Squidtone (Nov 26, 2010)

Topkat,
Well it does seem that either the rotor or caliper is wrong. I have a 67 with original disc brakes, and I replaced the original 2 piece rotors with 1 piece rotors 11 years ago from AMES performance. They were a perfect direct replacement. And they were sooooo much nicer (smooooth braking) compared to the 2 piece jobs. They now happen to be 2 feet from me (my car is in a million pieces right now) so I can measure the rotor and you can compare to the new units you have.

The hub diameter (with the studs) does NOT have a taper and the diameter is just a shave under 6 inches. 
I also measured the distance between the back surface of the rotor to the flange the inside bearing goes into, and that flange is about a quarter inch below flush. It's an 11 inch rotor by the way.

If your rotor is the same, I would also check that you have the correct calipers. Some calipers of that vintage had bigger pistons I think, and were for corvettes and/or big cars. You may have gotten a "big bore" caliper. I don't know how big the A body caliper bores were, but I can tell you the calipers I have (that do fit) say Delco Moraine with #5455946

If you want any other dimensions, lemme know


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## 66tempestGT (Nov 28, 2009)

sounds like you nailed the problem with the bearing.


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## 05GTO (Oct 6, 2004)

Topkat,

Check the bracket part numbers, I believe those calipers require a 3913797-L and a 3913798-R mounting braket, 

Here is a picture, Good luck


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## 66tempestGT (Nov 28, 2009)

that bracket looks a little custom.


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