C3 wheel/tire balancing procedure at factory?

[E S.]

Does anyone know the procedure that the factory used to balance the wheel/tire assemblies?
Thanks-E.J.

[Terry M.]

Re: C3 wheel/tire balancing procedure at factory?

I believe John Hinckley described the process in one of his presentations, most of which are on the St Louis Chapter web site. I remember him talking about using a "high-low" (as he called it) a fork lift to most of the rest of us, to pull the frozen tires out of the box car in the winter. The AIM describes heating the tires, and John's presentation explained why.

There is a lot of information on the side wall of original tires. Numbered stickers for the overall diameter. Matched sets were to be installed on the car. Again reference to that is in the AIM. Colored wax dots for the location and size of weights.

At one of the Regionals there was an assembly Plant tour (They were building SUVs). New Jersey comes to mind, but I will need help with that. We got to watch them assembling and balancing wheels and tires. We were told the process was not a lot different in St Louis.

[E S.]

Re: C3 wheel/tire balancing procedure at factory?

Did not see much in the TIMJG about this- Did the wheel/ tire balance procedure include the center cap and beauty ring installed? Spare wheel and tire also?

[Terry M.]

Re: C3 wheel/tire balancing procedure at factory?

Did not see much in the TIMJG about this- Did the wheel/ tire balance procedure include the center cap and beauty ring installed? Spare wheel and tire also?

Lets be clear here. I am talking about chrome bumper C3s. Some or none of this may apply to later C3s, but the appropriate page(s) in the AIM will offer clues.

Balancing included all 5 wheels and tires. Trim rings and wheel covers were put inside the car in packaging that made a single package of four of each product (packaged by the item supplier). They were installed on the car by the dealer as part of new-car preparation. The All 5 tires were supposed to be the same overall diameter using the small numbers stuck on the sidewall by the tire manufacturer. The tire manufacturer placed a colored dot on the sidewall at the high point (or maybe it is the low point. It doesn't matter) of the tire. This was matched with a dot placed on the wheel by the wheel manufacturer. There is a description of all this in the TIM&JG that is better than my late-night memory. There is also a less clear description in the AIM. Then the wheel and tire was balanced by a machine that squirted colored wax drops onto the sidewall of the tire. The color determined the amount of weight and the location of the weight. There was a maximum amount of weight -- see the AIM for more. That's my story and I'm sticking to it. Read the TIM&JG (This information IS there. If you need a page reference let me know and I'll find it for you.) and there are more details are in the AIM.

One more thing. If your car is blessed with full wheel covers (PO1 or PO2 as appropriate): Those things weigh a lot. There is evidence that these covers were balanced by the manufacturer. We don't judge the backside of them, so official evidence is scant but look at the back of them in the swap meet, and most of us have the attitude that we have to draw the line someplace and such investigation is beyond the line. And one could make the argument that all this is too.

I just noticed in reference to the Mid-Ohio virtual tech sessions that there was one mentioned, in another nearby thread, about C3 wheels and tires. It might have some more information for you if you are inclined to do some further research on your own. There is a lot of information available, all one has to do is look. I gave you some direction in my first response and more lurks in another thread here. Go for it.

[James G.]

Re: C3 wheel/tire balancing procedure at factory?

This came up a few days ago on another forum - 1968 - 1969 -1971 -1973 AIM all state - if the balance weight exceeds 5 oz the wheel or tire is excessively out of balance and should be rejected.

[John D.]

Re: C3 wheel/tire balancing procedure at factory?

When I went to work at a GM plant in the 80's I caught the tail end of the static tire balance process. On the conveyor the tires and rims were sequenced manually per a paper schedule. The tires were placed at an angle across the rims and later jaws spread them open and onto the rims very quickly.
That assembly went down the roller conveyor to a static balance station where it sat atop a precision spindle with linear transducers which determined the imbalance and rotated it to the point where the weight will go and a wax marker on the end of an air cylinder made a mark on the tire. Further down it came to a station where an operator looked up at a panel with a light indicating what size weight to hammer on. That assembly then went on to an additional balance station known as an audit balancer which validated the assembly.

It was all high speed and relatively trouble free. The old timers said that process was the same for decades. We had a precision master wheel with perfect balance we kept in a mahogany box for calibrating the equipment.

Now its all dynamic spin balancing with lasers marking weight location. I believe weight placement now may be automated as well.

[Duke W.]

Re: C3 wheel/tire balancing procedure at factory?

Through the C2 era the wheel-tire assemblies were just static balanced with weights on the inside. I recall an article from Corvette News that described a new system of "match marking" the high and low spots of the wheel and tire to yield the least out of round of the assembly. More than about 30 thou out of round can cause a vibration like out of static balance, but no amount of balancing effort will correct it.

This may have started with the introduction of radial tires in the '73 model year.

Most modern tires have a red dot and wheels have a white dot. Both are about a quarter in in diameter and they should be lined up to yield the least out of round.

Duke

[Terry M.]

Re: C3 wheel/tire balancing procedure at factory?

Through the C2 era the wheel-tire assemblies were just static balanced with weights on the inside. I recall an article from Corvette News that described a new system of "match marking" the high and low spots of the wheel and tire to yield the least out of round of the assembly. More than about 30 thou out of round can cause a vibration like out of static balance, but no amount of balancing effort will correct it.

This may have started with the introduction of radial tires in the '73 model year.

Most modern tires have a red dot and wheels have a white dot. Both are about a quarter in in diameter and they should be lined up to yield the least out of round.

Duke

Duke
The match marking for out of round you refer to is called out in the 1968 to 1972 AIMS, so it was used during that period for nylon cord tires.

FWIW: My 2008 C6 had the wheels and tires mounted by a vendor, not in the Bowling Green plant. They arrived at BG in sequence order and the driver's front and passenger rear had the car's sequence number stenciled on the tire. I was told that vendor was Firestone although the tires are Goodyear, and I still think that is odd.