Ideas on excessive bearing endplay

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Stormy69

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I have a 71 Duster that has had a 74 or so disc brake swap. this was all done before i bought the car. i was doing some measuring for some new wheels and found the rotors to be lose. i tried to adjust them with no luck, with the nut bottomed out there is still 1/32 end-play. pulled the rotor to check the bearings and all looked good and it was obvious the bearings were replaced when the swap was done. i thought it must have the wrong bearings installed but a check of the part numbers on the inners matched 74 dart part numbers. i havent checked the outer p/n yet... anyone have any thoughts why this could be going on?
 
What do you mean the nut bottomed out? You should be able to tighten that nut until it completely locks the rotor down. Those are tapered roller bearings. They are designed to run with preload. In other words, you need to crank down on the nut. There's a torque spec for it, but after thirty years, I know what feels about right. BUt you are supposed tighten it past where all the slack is taken out. The tightness of the nut should have an influence on how that rotor spins.
 
1.Tighten wheel bearing adjusting nut to 240-300 inch/pounds while spinning rotor and hub.

2.Back off nut to release all preload on hub.

3. Re-tighten nut finger-tight.

4. Install lock nut on adjusting nut ans insert cotter pin.

If that does not fix the problem, replace the bearings AND races.
 
Dave, the spec is in the book. You don't just leave them finger tight. Tapered rollers are designed to have preload, or their bearing surfaces are not supporting the load correcrtly.
 
i am well aware of what is supposed to happen, the point is it does not... i havent spent any more effort on it since checking that the rear bearing was correct as i have other projects ahead i am working on and the car is more race car than street so i dont drive it but a couple of times a year. my initial thoughts were the wrong bearings were purchased for the rotors....
 
Well, probably a silly question, but is the outer washer there that rests on the outer bearing race?
 
yes sir, all required parts (inner seal, inner bearing and race, outer bearing, washer, nut, cap, cotter pin) both sides have the same issue, though i have only pulled one apart...
 
I would remove the rotors and inspect the spindles VERY closely for burrs that may be keeping the small front bearing from being tightened completely. That's about the only thing I could see that would cause it. If you find something, you should be able to polish it out with 320 grit emery cloth and mineral spirits.
 
Take a deep well socket the same diameter as the outer bearing and slip it over the spindle. Use the palm of your hand to push on the socket thus holding the bearing in tightly. Does the rotor feel tight? Does it spin o.k.?
 
StrokerScamp said:
What do you mean the nut bottomed out? You should be able to tighten that nut until it completely locks the rotor down. Those are tapered roller bearings. They are designed to run with preload. In other words, you need to crank down on the nut. There's a torque spec for it, but after thirty years, I know what feels about right. BUt you are supposed tighten it past where all the slack is taken out. The tightness of the nut should have an influence on how that rotor spins.
Click to expand...


is there a washer under the nut?
 
This should NOT be difficult to figure out, it is SIMPLE

You have a shoulder in the back of the spindle, the rear bearing "bears" against.

You SHOULD have enough threads on the spindle., along with the washer and nut, to tighten the bearing up until it won't turn.

So either you have a mis-match of wrong hub/ wrong spindle, or you have import / wrongly manufactured hubs, or wrong bearings or wrong races.

If it turns out to be something like hubs made wrong, can you add a SECOND washer?


How about RADIAL play? Do the races seat tightly in the hub? I've found hubs that had worn a sort of "pocket" so that after the inner races was installed, it actually had an INCREASED diameter that caused the inner race to fit loosely.
 
These rotors were brand new from a Diplomat in the wrecking yard, so before I put all this stuff on I ordered new inner & outer bearings and races, and new dust seals. Spindles were a nice used set. I've been mesing with mopars for almost thirty years and have owned my Demon for over 25 and never ran into an issue like this where the whole mess wobbles. I yanked the rotors off and knew I probably damaged the spindles. The back of the rotors also were rubbing the caliper adaptors.

Anyway, luckily I had a whole other front end setup from a Dart and swapped over the spindles and the rotors on this setup was new also, repacked the outer bearing and everything is good now. Either something was wrong with the new inner bearings / races, or the hub on the rotor..At this point I'm just not sure.

Here's a couple of pics of one spindle. You can see the base of the shaft is chewed up and marring where the spindle starts to taper towards the threaded end. Notice in the second picture the metal sliver about 11'oclock as the base of the spindle now has a deep groove in it. Inner bearing cage was also pretty much chewed up.

Thanks everyone for your input / help!!
 

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i havent had a chance to take a look again, other projects. i have alo had an abody since i joined the AF in 1987... as i already stated the washer is there and all bottoms out and the is still lateral play in the rotor. i owned this duster about 8 years ago, traded it off to a friend who did the swap and then traded back last year. it is mostly a race car at this point but can be driven when i can live without a/c or a heater. i am busy on 3 other cars right now and school so not sure when i'll pull this apart again. may enlist the kids help to get it done.
 
I've heard of this problem a few times on cars and trailers. Each time, the problem turned out to be that the wrong parts were installed. Sounds like your rotors and spindles may have come from different cars. Hope you have double-checked that those cars used identical rotors and spindles, thus the same bearing parts. If the rotors are rubbing the caliper adapters, it makes me wonder...
 
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