How To Eliminate Steel Wheel Wobble?

[david.g.chapman]

I thought that title might get your attention!

Yes, it sounds too good to be true (so it probable is). Let me explain.

I have been experimenting with glueing shims to the inside of the wheel where it bears against the hub. I jacked up the car (a +2), spun one of the front wheels, and marked where the wheel wobble of 1.5 mm brings the rim closest to the inside of the car. I took the wheel off, then glued a small 10mm square of steel shimming plate (10 thou thick) to the corresponding point on the "bearing ring" surface.

I then refitted the wheel.. and it runs true with no runout at all!
I then tried the other front wheel with a 2.5mm run out, and used a 20 thou shim. Same result!

Now for the down side. The wheel nut is only bearing on one side of the centre hole, and there are now gaps between the "bearing ring" of the wheel and the hub. The question is.. is this a problem or not?

I intend to refine the design of the shims to turn them into an arc shape with at least one hole in to go over one of the five hub dogs. I realise that the "bearing ring" of the wheel is kept bright by movement of the wheel against the hub. The hole idea should retain the shim even if the glue joint fails ( I will probable use high temp epoxy resin).

What do you think?

Dave Chapman.

[alaric]

Personally I don't think that sounds safe.

There's a chance that the wheel nut will come loose, that the thread will be damaged as the nuts are a loose thread - usually quite worn, and also, could you not damage the wheel bearings as the hub shaft will be pulled off centre.

Surely a better solution would be to mill the wheel rim so that it's 'true' and fit a spacer ring to compensate what's been milled off.

This is a safety critical fit. If I'm wrong or have misunderstood what you're doing, then I'm happy to be corrected, but I personally think it's not worth messing around with.

Sean.

[alan_elan_s2]

Wouldn't buying a set of Panasports solve the problem and be safer? If you want original, then keep the wobble!

Good luck,
Alan

[cliveyboy]

Dave
I had a similar problem with wheel run out but mine actually turned out to be a bent half shaft.
Have you checked the run out of the hub first as that way if it runs true it is definately a wheel problem

I talked to one of my engineer mates about shimming the wheels as you suggested but he told me it would cause other problems.
I think the words he used were dynamic instability.
You shim the wheel to get it running true but when you spin the wheel the centre line of the wheel is constantly changing and the wheel is not running parallel to your shaft so you get instability and side thrust etc.
(I think thats what he meant).
Either way its not a good idea.

Clive

[garyeanderson]

Hi Dave
Scarry dude, glad your in England. Seriousdly, buy some new wheels, steel or alloy.

Gary Anderson

[david.g.chapman]

Hmmm... I know what you all mean.

I went through the same thought processes some months ago and rejected the idea at the time.

Then I had a re-think. If the wheel rim runs true, then the axis though the centre hole will be pointing at a small angle to normal. The interior of the wheel will then "wobble" as a result.

However, if the wheel is rebalanced with the shim attached, does it matter? There should then be no other forces on the hub or the bearing?

If you do nothing, the run-out present on many steel wheels causes vibrations that affect the hub and the bearing anyway.

I am concerned about the fit of the wheel to the hub, and would consider adding material (like steel epoxy) to create a complete bedding surface for the hub and the wheel nut. This is easy to do, as you just apply a release agent to the surface you want to come apart, apply the epoxy to the other surface, and fit the wheel.

Dave.

[garyeanderson]

The center nut will be bearing only on one side with the shim under it (either .010 or .020 inch) and that will create a stress. If its does bear all the way around it will still stress the wheel. Really go buy some used wheels, much safer than being sorry later. I think you would be safer with just the 2.5 mm runout at the tire than to shim or epoxy or any other method. Like I said, glad I'm over here...

Gary Anderson

[CBUEB1771]

I have to agree with Gary that shimming the wheel against the hub is a frightening notion. Years ago I found that I had a small amount of runout in both hubs and wheels at all four corners on my +2S. I went through a somewhat laborious exercise of swapping wheels on hubs and "clocking" the wheels from peg to peg and indicating the net runout. I was able to cancel much of the net runout in this manner. I marked the best combinations with a punch so I can always recover the best orientations.

[david.g.chapman]

Thanks to everyone for their responses - I really appreciate them.

I will be waving the white flag for this idea for the reason that Gary pointed out. Even with the supporting epoxy resin, there will still be a differential stress on either side of the centre hole of the wheel, instead of the radial stress pattern of a normal wheel.

When the rolling stress wave of the weight of the car is added, plus any cornering forces, there is an increased risk of fatigue cracks developing in the wheel.

As I cannot quantify this risk, I find it unacceptable and will not proceed.

Dave.