How much movement is still normal for a good front wheel bearing?

[berniedd]

RWD car. I'm trying to evaluate the health of my front wheel bearings. There's no abnormal sounds at the left front as far as I can discern, no grinding or grating noise as I rotate the tire but there is a very very slight movement of the left wheel and disc brake hat vs the brake backing plate as the tire is rocked back and forth by hands at the 3 and 9 o'clock position. It is not due to the tie rods. Is this still normal ?

 

[eljefino]

Usually 0.010" is good.

You tighten the big nut until it bottoms then back off 1/4-1/3 turn. With the thread pitch being what it is, you get your magic number.

This assumes the "classic" style.

 

[mattd]

This is what I have done on Tapered bearing adjustments in cars all the way to semis for years. Tighten the adjustment until you cannot turn it any more. rotate the wheel after each adjustment and make sure nut is still tight. Back off nut 1/2 turn. Then “snug” for the final setting. Don’t back off the nut to line up the cotter pin.

Obviously big trucks will be more than snug. About 60ish ft lbs for them. I have done it so long I do it by feel. I stopped using a torque wrench after checking my by feel adjustments, they’re were always correct. (There are exceptions with axle and hub design, some straight torque to 350 ft lbs because of a bearing spacer)).

Smaller trucks and cars can get away with less preload. You definitely don’t want any axial movement. A correct setting should give you no perceivable play shaking the wheel. But still rotate freely.

For reference F350 rear axle bearing final preload is 18 ft lbs

 

[berniedd]

Ah, so one can remove the slight play by slight tightening of the big nut in a slightly worn bearing.

The right front wheel does occasionally have a soft noise when the car is at speed, and makes a small movement that is discernible to the eye when I jack up the front and rock the tire. Can I cheat on the wear by tightening the nut, or I might as well replace the bearing since it's on its way out already?

 

[mattd]

Ah, so one can remove the slight play by slight tightening of the big nut in a slightly worn bearing.

The right front wheel has a soft noise when the car is at speed, and makes a small movement that is discernible to the eye when I jack up the front and rock the tire. Can I cheat on the wear by tightening the nut, or I might as well replace the bearing since it's on its way out already?

If there is any type of bearing noise I’d remove the hub and check the rollers and races.

 

[D60]

Ah, so one can remove the slight play by slight tightening of the big nut in a slightly worn bearing.

The right front wheel does occasionally have a soft noise when the car is at speed, and makes a small movement that is discernible to the eye when I jack up the front and rock the tire. Can I cheat on the wear by tightening the nut, or I might as well replace the bearing since it's on its way out already?

Depends on the resolution of the indexing. Sometimes you're left with a little loose or way too tight

 

[Joba27n]

I also want to point out that typically for automotive non drive axles, they spec a little bit of play in taper wheel bearings so that as the assembly heats up from driving and braking, the play will be taken up by thermal expansion.

That said if i have to give a number in absence of the service manual, after you seat the bearings via over tightening the nut while spinning the wheel, I would aim for 0.004"-0.001" play at the edge of the brake rotor. Use a screwdriver or other tool to move the rotor with the wheel off.

Also yes, any noise you should inspect if not just replace and repack the bearings along with a new seal.

 

[barryh]

Taper roller bearings have the longest life with a small amount of pre-load. I suspect most automotive manufacturers specify a very small amount of free play because it's relatively easy to measure rather than it's the optimum setting. Pre-load is very difficult to measure other than to infer it by a specified torque setting on the axle nut. I've never come across a car that specified pre-load but my BMW motor cycle specifies pre-load on the wheel bearings based on the the torque require to rotate the bearing once assembled and degreased which is a load of faff to do.

 

[Joba27n]

Thats interesting and I believe you because I figured that with me primarily driving on the highway in the winter, there wouldn't be the same thermal expansion as a taxi in NYC. On my personal vehicles I used to tighten the nut just until I had no movement. I thought that was improper though why I don't suggest it to people.

I've never honestly checked rotational torque but I remember my old ranger or f150, I forget, had bearings set with 17" lbs of nut torque vs a free play spec. I believe 2500 and larger gm products had a 20-30 ft-lbs(i forget) rear axle nut torque for the bearings and the front axle of old land cruisers with taper bearings also had a notable ft-lbs torque spec. Maybe they wanted preload instead

 

[D60]

Taper roller bearings have the longest life with a small amount of pre-load. I suspect most automotive manufacturers specify a very small amount of free play because it's relatively easy to measure rather than it's the optimum setting. Pre-load is very difficult to measure other than to infer it by a specified torque setting on the axle nut. I've never come across a car that specified pre-load but my BMW motor cycle specifies pre-load on the wheel bearings based on the the torque require to rotate the bearing once assembled and degreased which is a load of faff to do.

On my trailers -- which I realize are different than steer or drive axles -- I go just finger tight after seating the bearings.

By my crude calcs of simply feeling the hubs at each fuel stop, this is how they run the coolest. I've not personally had issues with bearing life, either.

IOW, near-zero preload on the nut. Everyone has their method and that's cool -- this is what works for me (on trailers)