How to work out if stub axle is bent?
 

There's a vibration in the steering wheel which is annoying. I've had all the wheels balanced by a professional.

When I jack the car up and spin the front wheels and put a straight edge against it I can see the tyre on the drivers side going up and down vertically. I've tried different tyres on the same hub with the same result. And yet the same tyres don't move up and down on the passenger side.

The car has high quality dunlops, no wheel spacers. It's driven once every two weeks so there should be flat spotting.

Any thoughts?

Try tightening the wheel bearing, if that doesnt take up the slack you may have to replace them. have a buddy move the wheel and look underneath for movement in the ball joints or tie rods.

Thanks - everything is new and bearing is adjusted correctly. Car has had a full Resto. Is there some way of checking if the spindle is bent etc.

Bent Hub
 

Pull the wheel off and put a dial indicator on the perimiter of the hub and spin it. You can use a magnetic base and mount it to the shock or some other local metalic part.
Bob B

Thanks for the replies. Sorry - feel like a dill asking but how do i spin the dial indicator around the spindle (as its fixed). Is there one that mounts to the spindle?

Also, where do I buy a new spindle from? Couldn't see one on Pelicans.

I guess one of the bearings is not seated squarely. Not sure what can be done about it however. Sometimes bearings can wear unevenly causing your problem, but you said new bearings?

Even without a dial indicator, spinning the hub with the wheel off will show if it is out.

Thanks. Re-reading this thread - it would be more likely the spindle is bent versus the hub being out of round wouldn't it? How do i check the spindle?

I don't think the spindles bend. They can break - I had one break where it thins down and gets threaded. Then can bend upward, putting a crimp in the strut tube (which makes removing he shock difficult at best). But this leaves the spindle straight, just aiming more up than it should and giving you a whole lot of negative camber. I forget the stock angle, but you can see the damage to the tube if it has been pushed up.

My guess is on a cocked bearing, but that's a guess.

If you have a rim without a tire mounted you could use a dial indicator on the lip of the rim to check things. If you have a fat spacer, you could hold that on with a couple of lug nuts (open end kind) and put the indictor on that.

No- if the spindle is bent, it will not cause any wobble or unusual movement to the wheel or tyre. It will only point the spindle in a different direction, and cause alignment issues.
If there is no play in the wheel bearings, then it sounds like the hub might be the issue.

Depending on what year your car is, there are factory tools for checking the front spindles.

http://forums.pelicanparts.com/uploa...1498716885.jpg

http://forums.pelicanparts.com/uploa...1498716918.jpg

http://forums.pelicanparts.com/uploa...1498716961.jpg

Walt, the spindles certainly can and do get bent. They're forged, so they do not break easily. They can also wear down.
The strut tube is more likely to be bent first, but I've seen some odd things that are not easy to explain.

The spindle may or may not be bent. But that is not the issue that is causing the wheel to move vertically while spinning. Think about. The spindle is fixed. The bearings, if tightened properly, are not the problem either. Even if loose they aren't likely the problem.

That leaves the hub or the studs......

Yes Scott, you are completely correct. Now that I think about it, it must be either the seating of the bearing or the hub itself is damaged. Just had a look on pelicans - $800! Wow. ��

double check all of this. wouldn't be the first time that something is not "wrong" just because its new.

and: before wildly spending money, maybe comparing measurements of left and right spindle may give you an idea if you find an offset of some sort.

a bent spindle will not cause this problem.

if nothing else is effected and the spindle is bent straight up, that would just add negative camber.

not much that can really do this.
I thought as someone said a race is not seated properly.
issue with the hub.
rotor disk not seated properly.

my bet is the disk is not seated.

I don't see how the disc brake rotor could cause this. The rotor is bolted to the hub. It could be way off and the hub would still spin true. The wheel is held in place by studs on the hub. Again, nothing the rotor would affect.

Switch front wheels and check again.

Switch the front hubs and bearings and check it. It's either the hub or the bearings. If you didn't have this problem before the rebuild I'd bet that it's the bearings then.


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because the wheel site on or against the hub.
put a washer on one stud, then slide the rotor on. your front wheel will look like a cartoon car or a car form the 3 stooges going down the road.
same with the back of the wheel. light sand paper on it.

I cleaned all those surfaces when I had the 930 apart just to make sure everything was flush.

Have you looked at a Porsche 911 front hub lately?? It appears not.

The rotor bolts to the backside of the hub. The wheel slides onto studs on the front side of the hub. The rotor has zero to do with the wheel/hub interface. The rotor has zero to do with the hub/spindle interface. In other words, the rotor has nothing to do with this.

Winders has the better of this side discussion, I think. T7's point might be well taken if the issue were a rear wheel, because the rotors are held on by the wheel and wheel studs. There is a small screw or two to keep them from rattling when the wheel is removed (the brake rotor prevents just pulling the rotor off), but those are not meant to deal with braking torque. However, a lateral misalignment of things doesn't seem like it would effect an up and down motion of the tire as opposed to a wobble.

But in front the rims don't touch the rotor, and the studs do not protrude through the rotor. A misaligned rotor would only act like a warped rotor - you'd feel a pulsation in your brake pedal.

944s have had strength/durability issues with front hubs, but I've not heard of this being an issue with 911s.

An out of round rim, or tire, or perhaps a mismounted tire (though I can't think of how this might be) might explain this, but the owner says he has just swapped the same tire (and I believe he means the tire and rim as a unit) from side to side, and the problem only exists on the one side. This pretty much rules out tire/rim issues.

Someone suggested the studs might be the problem. However, in all the rims I have used the tolerances are such that if a stud is at all bent, it is really hard to get the rim on at all. Plus as the rim approaches the seating surface of the hub, the effect of a bent stud goes away.

So the suggestion that the owner swap hubs side to side is the best I've seen here - if the problem follows the hub, something is wrong with the hub. Which means either figure it out, or get a used hub and use that. Odds are very good that a used hub will be good, except perhaps for the bearings. He could have an experienced Porsche shop do the bearing replacement if they looked worn to rule out operator error there.

My personal opinion is that we tend to replace bearings more than we need to in front. I've had a rear bearing wear out, and years later the replacement went bad. Never had the experience with the fronts. More of an issue is the spindle seating surfaces wearing, so the inner race of the outer bearing can spin on the spindle instead of staying put (but this wear is never enough to cause an up and down motion). And the seating surface in the hub for the grease seal can wear larger, so the grease seal can spin, lowering its life expectancy. Again, no relation to the issue.

The rule of "post hoc, propter hoc," so despised in scientific logic, is more useful in automotive diagnosis - if things were fine, and you did something, what did you do and could that somehow cause the problem. Here it is bearing replacement, which requires press fitting bearings. I haven't seen a more likely suggestion here. Most of us do fine with a punch and hammer (I've switched to a brass punch), not an actual press.