Disc brake swap: Inner pad touching rotor

How much space should there be between new pads and a new rotor?

I mocked up my disc brake swap and my inner pad touches the rotor. Rotor does not spin freely, takes a good effort to spin it. There doesn't seem to be much room otherwise: there is only 1/16" between the outer pad and the rotor. I'm wondering if I installed something wrong (like the anti-rattle clip) or if both my caliper brackets are misshapen.

Look how there is a small gap on the outer edge, but somewhere closer to the center it touches, like the inner edge is being pushed in and the pad is at an angle. This happened with the other bracket (but I didn't try the other caliper).


I'm using early style hubs with stock bearings and races, 1-1/8" rotors, '78 K-10 calipers, organic pads, Chevy 1/2 ton/Dana 44 brackets. It's a combo that should bolt on.



From what I've read, the early style hubs don't need to be machined. This gap is 1/16", which, if eliminated, would then cause the rotor to rub the outer pad.

 

You shouldn't have any measureable clearance, the pads should both be right on the rotor. It sounds like the caliper may be a bit off center. They should center themsevles the first time you apply the brakes. If they don't, you may want to lube the pins the hold the caliper.

 

Are these new rotors? Do you have a way to accurately measure the rotor thickness? I've run into new
Rotors that were manufactured too thick. Another option would be to sand the pad a little bit for the clearance you need. Are you getting free movement of the caliper or is something keeping it from sliding back and forth freely?

 

They are new rotors. I don't have digital calipers, but with analogue ones I got spot on at 1-3/16" for the rotor and 1" for the center section.

The caliper has free movement (without the pads and rotor installed, the caliper can slide back until the tip of the head of the bolt reaches the rubber ring inside the caliper's "eyes"). Also, the piston is fully retracted and there is no fluid in the cylinder.

In order to get the pads on I have to leave the spindle nut about 1/2 to 1 turn loose, install the caliper, and then tighten the spindle nut. This seems dangerous as a future installer could be torquing down the spindle nut on the inner pad, not the hub's bearing.

I just tried pushing the caliper inward and testing for clearance as I tightened the spindle nut. I was definitely moving the caliper inward enough to get the inner pad as flush as possible to the caliper bracket. Same results: I spun the rotor as I tightened the spindle nut, slowly the inner pad was squeezed between the rotor and bracket, braking the rotor.

 

Its also possible the hubs are slightly thicker on the back side moving the rotor over slightly causing the clearance issue. You could have the excess removed from the back of the hub as well

 

I was initially thinking the same thing but he said he only has 1/16" between the rotor and the outer pad which would kill the idea of the thicker race. Good thinking though...

 

I thought that the thicker bearing race is only for the late style hubs, or is there a thicker race for the early style hubs as well? I'm using an early style hub with the stock bearing/race combination.

I did some more measurements and it looks like moving the rotor outboard, or caliper inboard, 1/16" is the sweet spot.

I was trying to think of a formula to give future disc swappers to know if they need to machine their hubs, but wow, it'd involve about 20-bajillion measurements...

 

Howdy, I was told by (Parts Mike) that the hubs should be .400 thick, when I asked about maching the back-side. nickmil, do you know if this is true.

 

Unfortunately I don't have that measurement on the early hubs. Next time I get up to the shop I can measure a new hub but that will be a couple days.

 

I sanded off 1/16". Thanks! It's sure is great having braking power again. And boy does she stop well. Once I know all the kinks are worked out I'll post a pictorial thread.

The other day I noticed reduced driving power, that is to say that I had to downshift on a hill where I typically don't have to. How would I test for dragging brakes? (heat on the rotor? spinning the wheel jacked up?)

 

I ran into the same thing when I modified my Dodge 2500 4x4 dana 60 to lock-free hubs. My set up was a kit that included new hubs, spindles, rotors, etc...basically everything on the outters changed. When I tried to install the calipers + pads...no go, too tight.

My solution; I took a micrometer to the Auto shop with me and mic'ed all the pad options they had for the truck. There was a considerable difference in pad thickness. The higher $$$ the pad, the thicker they were. I purchased the thinest set they had and they fit like a champ. That was 50,000 miles back. I have had to replace a couple of times and I always buy the thin sets. (I saved the pad box for future reference).

Not saying this will solve your problem, but NOT all pads for your application will have the same thickness.

Good luck