what's wrong here ??? help !!!

[mikkelstuff]

Am doing the Mustang GT rear disc brake conversion on my 2002 Ford Ranger XLT 4WD and am alarmed. When centering the calipers to the discs I find that the discs are not running true when rotating the axles.

I have bolted the discs to the axle hubs with all five lug bolts to be sure the disc is secured evenly to the axle hub.

When rotating the axle, the disc nearly scrubs the caliper ears (pad mounting section) from inner to outer extremes.

These discs came with the Ford Performance M-2300-M brake kit.

So ....., are the discs likely bad or can both of my axles be bent?

 

[cstarbard]

I'm not familiar with the brake swap you're doing but have a few thoughts. I'm assuming this axle has been in your truck a while and isn't an axle you swapped in? If so, I would think that if your axles were bent you would have known previously; I can't imagine a solid axle could really function right or feel normal with bent axles.

I don't 100% know this is possible but I would think if your rear wheel bearings were worn bad enough the axle might rotate out of true

Are these new discs you're using?

I'm assuming you had to add caliper mounting brackets, are they damaged or mounted out of line with the rotor somehow?

Is there heavy corrosion on the hub part of the axle shafts? I always clean these with a wire wheel prior to putting a drum or rotor on to be sure that the drum or rotor seats well. Even if they were rusty I can't imagine that could throw the rotors off that much

Are you sure your calipers aren't crooked somehow (severely bad guidepins or some other mounting issue)

 

[Curious Hound]

Calipers or brackets will not make your rotor run out of true. Anything mounted stationary just gives you a point of reference so that you see something is wrong. I wouldn't expect bearings to cause that either.

Take the rotors back off and rotate the axle and see if it spins true or not. If it's fine, then the rotors are the problem. If the axle flange still had run-out, then it is the problem. Also, make sure everything is clean. Cleanliness is almost always a good thing.

This message composed solely of recycled electrons. Go green!

 

[mikkelstuff]

This is the disc brake swap detailed on this website.

This is the original axle - no changes.

The calipers (that part that holds the pads) is fixed to the axle housing so really has no part in the disc wobble with axle rotation.

I'm thinking this has to be bad rotors because I would have known that 1/4" to 1/2" out of true with the original drum brakes.

I'm going to pickup another set of rotors just to see -- but one more frustrating thing to an otherwise neat drum to disc brake conversion.

 

[pjtoledo]

the rotors are not fitting over the small "brake register",,, that's the small enlarged ring where the flange transitions to the wheel mounting extension. or the rotor can't fit against the wheel mounting hub due to a round transition.
put the rotor on backwards to see where it hits.

the brake register is there to correctly locate the rotor.
if the rotor fits snug on the hub extension, but not over then registration you may have to cut a bevel edge on the inside of the rotor. only cut the inside edge, you must leave the outer edge to correctly center the rotor.

oh yeah, is the inside diameter of the rotor hat big enough to fit over the entire axle flange???? long shot, but gotta ask.


as usual, since this advice is on the internet,,, it must be true!!!

 

[mikkelstuff]

Ah ha, I will check that - the brake register that is. Very likely the problem.

I had a similar unexpected problem with the caliper brackets. I had to bevel the inside edge of the main center hole to fit over the weld bead on the axle mounting brackets.

 

[Ranger850]

Check your rotors for warp. Even brand new rotors can be warped right off the shelf. Put a small screwdriver near the edge of the rotor while it is on the truck. Setting the screwdriver on the caliper to keep it stationary. Give the rotor a spin and see if the edge of the rotor " wobbles " to and from the screwdriver. Make sure the hubs are good and clean where the rotors sit. Or take them to a local brake shop and ask the to turn the rotors, bout 15-20 bucks, and they can tell you if the rotors are warped. Warped isn't necessarily bad, it can be fixed with a few turns on the lathe.

 

[Curious Hound]

the rotors are not fitting over the small "brake register",,, that's the small enlarged ring where the flange transitions to the wheel mounting extension. or the rotor can't fit against the wheel mounting hub due to a round transition.
put the rotor on backwards to see where it hits.

That sounds very reasonable.

 

[mikkelstuff]

PJToledo was correct. There was a fine layer of rust/corrosion over the axle hub faces AND the brake register.

So a good hour of sanding, phosphoric acid rust remover, and wire brush on my 4" cutter/grinder with special attention to the brake register fixed the problem.

It remains a very tight fit of these rotors over the brake register and I did pull them up tight with all five lug nuts (50 ft-lbf torque) but, wheee whooo, they now run true.

I did not realize how critical it is to have those axle hubs clean and free of all corrosion.

 

[Ranger850]

So a good hour of sanding, phosphoric acid rust remover, and wire brush on my 4" cutter/grinder with special attention to the brake register fixed the problem.

Really bad rust or OVERKILL?
I think the wire brush would have done the job

 

[mikkelstuff]

Maybe overkill but the project was killing me with frustration. Soooooo - I took the time to be sure all was clean and free of rust/corrosion.