Is it common for the rotors to have some play in them?

[Michael L.]

Guys,

I'm restoring my 69 and I just noticed while I was setting the front wheel alignment preliminarily before I can get it to an alignment shop that rotors have some play in them. It's not much but there is a little bit of wobble there. The hubs are factory originals. It's been some time since I set the bearings and races on the wheel hubs, probably 8-10 years, (this resto is going on 20 years) and I believe I followed the aim by torquing it down to 12 ft/lbs to seat the bearings then loosening and then lightly snugging the bolt down again then installed the cotter pin. Is it common to have this play in the bearings? I can get a dial gauge and measure it but how much is acceptable?

Mike

[Joe L.]

[Michael L.]

Re: Is it common for the rotors to have some play in them?

Thanks Joe. My endplay feels like a bit more than .001 so I'll get my dial gauge and see if I can tighten it up a bit.

Mike

[Joe L.]

[Richard G.]

Re: Is it common for the rotors to have some play in them?

Joe;
Is that because of the grease makes it difficult to measure such a low amount of clearance?

[Joe L.]

Re: Is it common for the rotors to have some play in them?

Joe;
Is that because of the grease makes it difficult to measure such a low amount of clearance?

Richard------


Actually, the best way to set bearing end play is to do it before the bearings are packed with grease. But, that may be a bit of "overkill" for most people and will likely not result in much difference for the final product.

The main reason that it is not possible to select and hold a desired and exact end play is the limitations imposed by the nut locking feature. The nut can only be locked (i.e. the cotter pin inserted) in a limited number of positions. The movement of the nut by one flat (which is the minimum between cotter pin insertion positions) equals 0.008" of end play. So, let's say that the cotter pin hole aligns at zero end play (which is below spec). Then, backing off the nut by one flat will produce 0.008" of end play, the maximum acceptable end play.

Unless one gets lucky, the only way to set it at a particular end play (say, 0.001" which is ideal) is to adjust the thickness of the nut or washer or use shims. This can be tedious and somewhat "trial-and-error". GM NEVER recommended this and I don't, either.

[Tim G.]

Re: Is it common for the rotors to have some play in them?

That is interesting, thank you, Joe.

[Duke W.]

Re: Is it common for the rotors to have some play in them?

I recall the thread is 24 per inch and you can move the nut in twelfth turn increments - 6 positions in the castle nut and two perpendicular holes in the spindle for the cotter key.

So 1/12 turn of the nut is about .0035" axial movement. It's my experience that the closer clearance is to minimum clearance spec, the more precise the steering, so I shoot for about .001-.002". (If the thread is 20 per inch then the axial movement per 1/12th turn is about .004".

After you torque the nut to 25 lb-ft to "seat" the bearings, rotate the wheel through several revolutions. The back the nut off and tighen it as far as it will go with your fingers and insert the cotter key in the nearest hole, but don't spread it.

Rotate the tire a few more times. Grab the top and bottom of the tire and wiggle it. You should feel slight play.

Now remove the cotter pin, and rotate the nut, using a spanner if necessary, 1/12 turn to the next cotter pin location.

Repeat the above test and check for play. If so go to another 1/12" turn on the thread and repeat the test. When you reach the point that you cannot feel any play, back off 1/12 turn and test for play. If so you are in the OE spec range.

If you want to get as snug as possible shave a couple of thou off the washer with some 220-400 paper wetted with mineral spirits on a flat surface, and then go another 1/12 turn tighter. If no play shave off another thou or two and repeat until you can just barely feel clearance by grasping the top and bottom of the tire and aggressively wiggling it.

Duke

[Michael L.]