slight vertical front wheel play when locking collars adjusted according to clarks/haynes procedure

[johan]

car: 944 1985.5

I have a slight play on the front wheels when I adjust the locking collars according to Clarks SUSP-08 procedure, which is similar to the procedure described in the Haynes 944 manual. The play is with the car jacked up and only vertical (when I pull on the tire with my hands top and bottom), not left-right. The play is approx 1mm. I did the adjustment procedure several times over with the same result.
When I tighten the locking collar somewhat more than Clarks/Haynes describe (hand tight, the washer cannot be moved anymore with a screwdriver) the play is gone. Or almost gone if I tighten it slightly less but still a tad too much, when the washer only can be moved with some more force.
I replaced the wheel bearings some time ago since the play was already there, thinking that it might solve the play, but it didn't make a difference. NB: control arms, tie rods, front shocks and top bearings were also replaced recently.
I did a test drive with the slightly over tightened locking collars and it seemed to drive more precisely but that might also be my imagination.

The play was also noticed by the garage during the Dutch equivalent of the MOT, a mandatory two-yearly check of the condition of the car. However it was still within the limits so no failure.

So it seems that I have the choice of a bit of vertical wheel play when following the correct adjustment procedure or no wheel play when I tighten the locking collars slightly more.
Can anybody tell me if a bit of vertical front wheel play with the car jacked up when the locking collars tightened according to Clarks/Haynes is normal and acceptable?

[danmartinic]

Old-school tapered spindle type bearings will *always* have some play. As the MOT suggests, it's fine

PS: This is something never mentioned in the manuals or procedures. Older mechanics just knew.. and it's how I eventually learned from one such mechanic

[dr bob]

Thoughts...

Old-skuul tapered spindle bearings --NEED- to have a small amount of clearance/play, to allow the formation and maintenance of a film of grease between the rollers and the races. Too tight, no clearance, no lubrication, and you have overheating, negative clearance from thermal expansion, and failure follows quickly.

Suggestion: The normal wear on the spindle is on the bottom, where most folks don't see it. The finish on the spindle itself leaves what looks like coarse grooves that the bearing races slide over. Inspect the bottom of the spindle where the inner bearing sits, looking for a polished (read: worn) section. You can use a micrometer to verify that the spindle is worn out of round, but the visual tells you plenty. You can manually fit the inner race thee and see if it can be rocked at all on its own; it should sit square with no rocking available at all. There's no easy recovery short of replacing the spindle, unfortunately. If the spindle is discolored from heat, another reason for replacement. Use care buying used replacements as they too are subject to the same wear and lack of inspection while on the car.

Meanwhile, the actual adjustment of the tapered bearings is usually defined in the WSM. I don't know the exact procedure for your 944, unfortunately, but from your description it sounds very similar to the 928 procedure. For the later 928 cars like my 1989, the procedure has you first snug the adjusting collar with freshly inspected and packed bearings. The actual description is "tighten clamping nut slightly" which is hardly definitive. The goal of this tightening is mostly to make sure all the rolling elements are squarely seated. From another car, there's a torque spec for this step in the 25 inch/lb range, so for the 928 I have the clamp bolt loose and use a flat-blade screwdriver in the slot to tighten the adjusting collar on the spindle while rotating the wheel. I'm pretty sure I can't overtighten in this step using just the screwdriver and my radio-announcer's hands. The 928 instruction continues to "slacken clamping nut until the thrust washer can be can just be moved with a screwdriver under finger pressure. Do not use hub as a lever for screwdriver. Tighten cap bolt of clamping nut to 11 lbs/ft. Recheck setting by moving thrust washer, readjust if necessary." The 928 uses a split adjusting collar with a socket-head pinch bolt to clamp and lock the adjustment; the 11 lbs/ft spec is for that pinch bolt that clamps the collar, not the tension for the collar on the spindle and bearings.

This very specific procedure leaves sufficient clearance in the bearing to maintain lubrication. There's also a consideration for relative growth of the hub in use, particularly from brake heat transfer from the disk.

The classic "rock the wheels looking for play" is a broad-brushed look for worn pieces like ball joints and tie rods, as well as a handy way to identify bearings that might have worn or failed. And for a worn spindle. Once the worn pieces are replaced with new, there's no rock-the-wheels test for adjusting the bearings. The procedure for checking for spindle thrust-washer movement is the only bearing clearance adjustment. Got more 'rock' clearance than you think is right after adjusting the inspected and packed bearings? Especially if there's a difference between 6/12 and 3/9 o'clock positions, it's not the bearing itself.

More fun thoughts -- Too Tight on the bearing clearance contributes to the inner races walking around the spindle, causing more wear on the weight-loaded face of the spindle where the bearing sits.


So take a hard look at the bottom of the spindle for evidence of wear and discoloring. My nickel says you'll find your cause there. If I'm wrong, send a SASE to me and I'll drop the nickel in there for you.

[johan]

I think you are right, no nickel for me The wear pattern on the bottom side of the spindle is quite different from the top side, much more matte on the bottom side and I could also feel a small edge with my nail. I've attached a not-so-good picture.

I've found a set of supposedly good used spindles so hopefully that solves the play. Will let you know after I've received and installed them.

[danmartinic]

so hopefully that solves the play

You have nothing to solve; the play you describe is normal and necessary

[johan]

Ok, (estimated) 1mm of play seemed a bit excessive to me even though it's in MOT limits but then I'll leave it alone for now. When the new used spindles arrive I'll probably do a bit of testing. Thanks!