C3 trailing arms question

[Phil D.]

Re: C3 trailing arms question

Well, after a long, long wait for parts, I used a BrakeAlign shim and a new rotor. Got the tir as measured on the hub face of the rotor down to right at .001. Still some wheel wobble so I took the wheel to a local tire shop and put on their balance machine and it wobbles on the balancer too. Can a steel wheel be straightened?

[Gary R.]

Re: C3 trailing arms question

Just to follow up on this, in case it helps others.

In an effort to get near perfect runout,without riveting the rotors on, I have tried several methods. I have used new USA,Imports,NOS rotors on good original spindles, new USA spindles, imported spindles, HD spindles, & HD 31 spline spindles, ALL had runout.

One test I ran was to face spindles in a lathe to under 001 runout and face another set with the rotors bolted on.

The faced spindles were setup with NOS rotors and still had over 003 runout(my max spec). The matched set were pretty much dead on until I broke the rotor off the spindle. I bolted it back on, the runout was still good but went from 000-002".

I prefer to bolt them on in case PB access is needed in the future. I have detailed this on many forums so for those interested you can find it or just PM me for the link.

The last set I did were the 31 spline spindles and new VB&P rotors. One was out 006 and the other 015. I got them down to 002 with ss shims and bolting on the rotors with flat heads. I checked them several times by removing the rotors and re-installing them. They stayed right on 002"

Most times turning the spindle face is not needed and I rather not remove material if not needed. I've seen and heard many times where people were told they had bent spindles, when the cars had no sign of impact or other reason that could damage a spindle and other parts in the area including the arms. Proper bearing setup, with either on the car rotor facing or correct shimming, will resolve any brake or bearing issue related to the rotor/caliper air pumping.

good luck and enjoy the car, Remember to bled the brakes if you store the car several months.

[Jack H.]

Re: C3 trailing arms question

"Can a steel wheel be straightened?"

YES! The process is called 'truing'.

If a wheel has been damaged ('curbed') and is no longer 'true' (in round), all the balancing in the world isn't going to fix it. AND, if you've run a tire on a wheel that's not true, it's quite possible you've damaged it.

Tire guys call the process 'taking a set'. That's when the wheel rotates unevenly causing the tread to wear unevenly and 'de-form' in a manner that compensates for the wheel's uneven profile. There are 'hoppers' (tread has misc high and low points) and 'squirmers' (tread is deformed side to side).

Short of having a tire 'shaved' to bring it back to its original trueness, the only 'fix' is to (1) get the wheel re-worked to make it true again AND (2) discard the mounted tire and replace it. If this IS the problem, doing one without the other won't provide relief...

Basically, few wheel shops offer to work on steel wheels because the going rate to 'true' a wheel runs $80-200 (depends on how much work is required, the specific wheel shop's labor rate, and the skill of the tech). The shops tend to 'blow off' doing work on steel wheels because they PRESUME the owner will 'freak' at the cost since replacement steel wheels are pretty cheap. This is the approach to true a wheel.

Remove wheel from car, demount the tire. Mount the wheel on a shop fixure (typically a matching stub axle that's been cut). Now, slowly spin the wheel with two dial micrometers attached. One monitors the concentricity profile of the wheel's outside diameter, the other measures concentricity of the rim.

So, they're looking for both the wheel's radial and axial profile to be in-round or 'true'. If not (there are mfgr specs), then the 'high' points are marked, the wheel is dismounted, laid down and HIT with tool (typically these shops have a large selection of hammers) to deform it in the correct direction.

The process is iterative, time consuming and VERY boring! But, good wheel shops can/do re-true wheels this way...

[Terry M.]

Re: C3 trailing arms question

In the 1950's I had a steel wheel ""trued," but the shop had a machine with rollers that set against the rotating wheel and pushed the edges of the wheel into alignment. They had a book that listed settings for the various wheels, and the roller adjustment had scribed marks that the rollers were set to as called out in the book.

I have never seen such a machine since. And this one was not new at that time. It was a fascinating operation to watch, and was not far from the process of making steel wheels -- which I observed some 30 years later.

There is a series on both the Discovery Channel and the Science Chanel called "How it's Made." A recent episode showed steel wheels being made. Other episodes have shown the making of gas tanks and radiators.