Wheel shake-Bearings

[strep]

I have noticed a recent shake in my front steering wheel. While I was pulling all my wheels of to take to Al Reed. The front wheels don't spin freely. Also one is harder to spin than the other. Are these the bearings. Do I need to replace them. Please speak freely. Let me know.

[chrisp]

It could just be pad drag that makes them feel different when you are hand spinning them. Either retract the pads or remove the calipers to ge a better sense.

The vibrations could be an out of balance wheel. Try another set if you have access to one.

You can pull the dust caps and check condition of grease, check for proper adjustment, possibly see metal shavings, and listen to the sound the bearing makes.

[strep]

Ok I pulled off the caliper and it spins more freely. But still has some ressitance is this normal.

[chrisp]

It's never going to spin freely like a bicycle wheel. I think mine will spin perhaps 5-6 revolutions without the brakes attached. It's the inherent nature of the design. Plus although the rotor is heavy it's only 10-12" in diameter and there's not a lot of rotational mass to keep it spinning. If you made it to roll seemingly forever it would either be really expensive (i.e. Formula 1 level technology) or would not hold up to the weight/abuse (i.e. a bicycle wheel). Once you get 2500 lbs behind it this resistance isn't a factor.

Whatever you do, make sure the bearings are adjusted bearings properly. Use the Bently manual or Wayne's 101 Projects book (if it's in there).

[strep]

Hey I dont even get but a 1/4 turn out of them ?????

[89turbocabmike]

A crude way to check is to grab the wheel at the 12 and 6 position(difficult if the wheels are at Al's) and alternately push in at 12 and pull at 6 and feel for play. I had quite a bit of movement in mine and temporarily tightened up my bearings while awaiting the parts from pelican. After installing the new parts, my car is much more sure-footed at 100+.

[Don Z.]

So, my silly question is:
The "book" says to tighten the nut until the washer moves under "slight pressure". Is there a way to quantify this? The reason I ask is that I just replaced the front rotors, and I did the best I could, but I do have a slight wheel shake on the freeway, so I'm wondering if I didn't tighten the hub quite enough...

[chrisp]

Ya know this is weird because the 911 is the only car I have worked on (about 10 in total) that the washer needs to move under slight pressure. Usually you want them so the washer barely moves under pretty high effort. I set mine up with "slight pressure" and I felt they were loose. I couldn't eliminate play at the wheel (like described above) without setting them tighter. When I got to the point that I had little to no play at the wheel I checked and the washer was almost to the point of moving under pretty high effort....like every other car I've known. Maybe there is an error in Bentley and they meant "heavy pressure".

[89turbocabmike]

Chrisp, I agree. I set mine so the washer moves under higher effort than Bentley describes. There are quite a few mistakes in the Bentley, so it wouldn't surprise me. I was concerned about this and did some relatively careful temp readings with my IR gun and I don't think that running them tighter is going to be any problem. Bearings are pretty cheap and easy to replace.