How true do AZ rims really have to be?

[Greg L.]

This might seem like a funny question but in an effort to distract myself from my piston search dilemma I deceided to check out my rims to see if they needed to be straightened.

I clamped my spindle and rotor assy in my vise and bolted each rim to this and checked for run-out. Three are dead on, one is dead on on the back side with a very slight ding on the front side where it looks like someone used a prybar to remove the tire at some point(no it wasn't me )

The one that I question seems to be bent in the hub area about 90 degrees from the valve stem hole because as the rim turns, one end goes up and 180 degrees opposite it goes down on both the front and back side. Total deviation is about .080 so it would take .040 movement to true it.

Question is, would this rim still balance out okay or should I get it straightened first? I'm useing bias plys if that matters.

Thanks

Greg Linton
#45455

[Jack H.]

Re: How true do AZ rims really have to be?

Hum, can't find a spec when you want to! Well, the straight answer is NO. Adding balancing weights to wheel that's not true won't compensate for the concentricity distortion.

You'll wind up with either a 'hopper' or a 'squirmer' in terms of rotation AND the tread will take a 'set' trying to compensate for the distortion. Bottom line, pitch a tire that's seen any appreciable driven distance on an out of round wheel.

Now, as to specs, I already mentioned trying to find the Chevy specification on wheel concentricity but failed. From memory, one who specializes in truing wheels here in town aims at getting wheels evenly round from both a radial and axial perspective within 12 mils and likes to come closer to 5-mils.

Your measured distortion of 80 and 40 mils wouldn't cut it. That's one of the problems we see with reasonable frequency on these classic Corvettes. Because wheels are coded and dated, we try to maintain them on the car instead of effecting repair by substitution. But, you can easily develop all kinds of objectionable vibration from an out of round wheel that appears to defy diagnosis and repair (remember once the tire takes a 'set', she's a goner no matter how new or how few miles it has)....

The last time I trued a set of AZ wheels, the job ran about $125 per wheel. The process is VERY labor intensive (mount, measure, mark, demount, WACK, and repeat until you get there).

The problem (wheel distortion) is probably more prevalant on Shark cars because there's an owner learning curve in getting to know where your front end starts and stops. So, the wheels tend to see curb damage....

[john daly]

[Greg L.]

Re: How true do AZ rims really have to be?

Thanks guys...never even thought to check the service manual! Now that I have, it shows 1/16" as a max runout which is .0625" so I'm about .020" out of spec as per the 69 manual.

I'll check around tomorrow to see if I can find someone to knock it back into spec but if I can't, do you think one could feel this .080" runout? Even if it can't be felt do you think it would be enough to wreck the tire? I know that the specs are there for a reason but sometimes you can get away with a little more...

[Steven S.]

Re: How true do AZ rims really have to be?

I just had a steel wheel straightened by Stockton wheel service for $45.00 plus shipping. Might be an option for you.