Rally Wheel Weights/Tire "Dot"

[Kenn S.]

Searching prior posts didn't turn anything up on this, so time to ask.

My '70 is missing the spare, completely. I happened across an AZ rim with a date one day earlier than my other (original) Rally rims. On the "new" spare rim, I happened to notice the "small B-B on the wheel" (pp. 50 in the TIM).

So I re-examined the TIM, and I began to wonder what is mean by "the low point" on the tire, which is the part that would "align" with the rim's B-B weld spot.

It sounds like they didn't want to spin-balance the tires/rims, so they somehow determined where the tire and rim were out of balance and put marks there. Then someone ran the machine to punch the tire onto the rim.

So my questions are:

1) Would I expect to find one of the "MICRO" balance weights at or near the same location as the weld? If they spin balance, the weight could be anywhere. If not, how would they know what weight to use?

2) What color orange is the dot? (There are millions of shades.) What kind of paint, keeping in mind it would have to adhere to rubber?

3) How far from the rim/tire juncture is the dot? Half inch? Inch? (It's a half inch in diameter according to the TIM.)

4) What do they mean by "low point" of the tire? If it's not perfectly round, you can't use it. So they can't mean the tire is out of round. Must be balance...

5) I read somewhere that it's OK if the spare's date code doesn't match the rest of the rims. In fact, in one place the TIM says only the spare is examined. But what about tire date codes? I think I found a good source of OEM tires, but tire date codes are (or will be) a question.

If anyone is interested, the tire source I found is:

http://www.kelseytire.com/pages/preformancetires.html

[Joe L.]

Re: Rally Wheel Weights/Tire "Dot"

Searching prior posts didn't turn anything up on this, so time to ask.

My '70 is missing the spare, completely. I appened across an AZ rim with a date one day earlier than my other (original) Rally rims. On the "new" spare rim, I happened to notice the "small B-B on the wheel" (pp. 50 in the TIM).

So I re-examined the TIM, and I began to wonder what is mean by "the low point" on the tire, which is the part that would "align" with the rim's B-B weld spot.

It sounds like they didn't want to spin-balance the tires/rims, so they somehow determined where the tire and rim were out of balance and put marks there. Then someone ran the machine to punch the tire onto the rim.

So my questions are:

1) Would I expect to find one of the "MICRO" balance weights at or near the same location as the weld? If they spin balance, the weight could be anywhere. If not, how would they know what weight to use?

2) What color orange is the dot? (There are millions of shades.) What kind of paint, keeping in mind it would have to adhere to rubber?

3) How far from the rim/tire juncture is the dot? Half inch? Inch? (It's a half inch in diameter according to the TIM.)

4) What do they mean by "low point" of the tire? If it's not perfectly round, you can't use it. So they can't mean the tire is out of round. Must be balance...

5) I read somewhere that it's OK if the spare's date code doesn't match the rest of the rims. In fact, in one place the TIM says only the spare is examined. But what about tire date codes? I think I found a good source of OEM tires, but tire date codes are (or will be) a question.

If anyone is interested, the tire source I found is:

http://www.kelseytire.com/pages/preformancetires.html

Ken-----


The purpose of the "bb" on the wheel and the colored mark on the tire was to help ensure that the lowest amount of wheel weights would be required to balance the wheel and tire assembly. The need for excessive balance weights can create problems of its own.

Originally, the wheel and tire assemblies were not spin (i.e. dynamic) balanced. They were simply static balanced.

I really wish the same system that was used "back then" was still in use today. One can simulate part of it, though. Using a static balancer, one can determine the "heavy point" of the wheel. The problem is that there is no practical way to determine the "light point" of the tire. I have been told that only one tire manufacturer currently marks its tires for this purpose. I'm told that manufacturer is Yokohama.

[Kenn S.]

Re: Rally Wheel Weights/Tire "Dot"

Fasinating, truly. Makes sense. They'd want to save time and money...less time to add weights, less weights to add.

Sounds like today we should just dynamic balance. We could pop the bead and spin the tire to get close to the point where few/less weights are required, but you'd need a friendly tire guy. Can't imagine what it would do the to paint on the rims, too, but that's part of it (none of them were perfect).

Anyone for orange paint color and manufacturer? Spare date code OK if not same as other four? (I imagine the paint question is a toughie...)

Thanks for the insight.

[Joe L.]

Re: Rally Wheel Weights/Tire "Dot"

Fasinating, truly. Makes sense. They'd want to save time and money...less time to add weights, less weights to add.

Sounds like today we should just dynamic balance. We could pop the bead and spin the tire to get close to the point where few/less weights are required, but you'd need a friendly tire guy. Can't imagine what it would do the to paint on the rims, too, but that's part of it (none of them were perfect).

Anyone for orange paint color and manufacturer? Spare date code OK if not same as other four? (I imagine the paint question is a toughie...)

Thanks for the insight.

Kenn-----

It wasn't just about the cost of weights and time to install. GM PRODUCTION specs required that no more than 5 oz TOTAL of weights was to be used. If more was required, then the wheel or tire was not to be used. I strongly suspect that if they didn't start off with the advantage of having the heavy point of the wheel matched with the light point of the tire, they'd end up with a LOT of assemblies requiring more than 5 ounces of weight and, therefore, a lot of wheels or tires being rejected.

Personally, I am in TOTAL agreement with GM regarding wheel weights. In my opinion, any wheel and tire assembly that requires more than about 5 ounces of weights indicates a problem with the tire or the wheel.

Have a tire installer move the tire around on the wheel to determine the point at which the least amount of weight is required for balance? Yeah, sure. If the installer were your brother I don't think you'd get this kind of service. To get this kind of service you'll need to buy the tire shop. Then, you can tell the installer to do this and, providing he doesn't quit, you might get it done.

[Terry M.]

Re: Rally Wheel Weights/Tire "Dot"

Ken,

One can read all about the details of C2 & C3 Corvette wheel/tire mounting and balancing in the AIM. Of course it is in "engineer speak," but that's OK we know some people who can translate that into language we all can understand.

Note the requirement to heat the tires before mounting and use a set of matched size (as in circumference). Good luck getting those two now days.


Not all wheel weights were Micro brand. There were AT LEAST seven wheel weight suppliers to the Corvette plant according to an article ont he subject in The Restorer.

If you have your wheels and tires balanced using a Hunter GSP9700 Road Force machine (and by an operator who knows how to use it) it can tell the operator to rotate the tire on the wheel to achieve minimum weight to balance. It can also detect tire manufacturing defects in the underlying tire structure. C6 Corvette wheels/tires are balanced using this kind of equipment, and I guarantee you they can achieve velocities that far exceeds anything your 1970 Corvette will ever see.

To find a location near you with the Hunter GSP9700:

http://www.gsp9700.com/search/findgsp9700.cfm

[Kenn S.]

Re: Rally Wheel Weights/Tire "Dot"

Thank you, Terry. I'll check it out...

[Terry M.]

Re: Rally Wheel Weights/Tire "Dot"

I just downloaded this image from last weekend. I had to clean the camera out. From a 1969 built February 1, 1969. The original Firestonel spare.

[Kenn S.]

Re: Rally Wheel Weights/Tire "Dot"

Nice. Great seeing originals like that.

[Kenn S.]

Re: Rally Wheel Weights/Tire "Dot"

Have a tire installer move the tire around on the wheel to determine the point at which the least amount of weight is required for balance? Yeah, sure. If the installer were your brother I don't think you'd get this kind of service. To get this kind of service you'll need to buy the tire shop. Then, you can tell the installer to do this and, providing he doesn't quit, you might get it done.

Well, yes, actually. In the small town I live in, I know for sure the owner of the local Tuffy would do that in a heartbeat once I told him why. This town is restoration crazy (near Auburn, Indiana, where they restore anything and everything that ever moved). My experience here has been car guys help car guys just because. I certainly would. And I'd pay him for his time. He'd love nothing more than to see the car drive up, too.

This is my dream car. I'll do whatever it takes...well, not stealing parts at Carlisle, obviously (string that guy up by his 'nads). The car deserves no less than my very best effort.

So if that's the only way I could get it done as nearly as it was originally, using the tools I have available to me, then that's what I'd do. Honestly, I believe you could get it pretty close with one spin. I also very much doubt it's the craziest thing ever done to try to restore/repro something on some Corvette somewhere.

But Terry's idea is the one to go with. Much better.

My original question was why this was done, not how I'd mimic it. Thanks for providing some insight. You are right on about the number of weights.

[Terry M.]

Re: Rally Wheel Weights/Tire "Dot"

Ken, you are in a good location -- join the Indiana Chapter of NCRS (see the contacts page -- click the radio button above).

Three weeks ago was the Illinois Chapter meet in Galena Illinois. A 1970 Bowtie Corvette was on display there. LT1 though.

Two weeks ago we had the Fall Indiana Chapter Meet in Valparaiso. Your back door, so to speak. There was four Bowtie Corvettes on display there. One a 1972 that might have provided some interesting moments for you.

The spare tire and the car it came from (18K miles) was at the North Central Chapter Meet last weekend in Minneapolis. A little traveling, but getting out and about is the best way to see original Corvettes. They are not always there, but the chances of original Corvettes go up as you go to Regionals and Nationals provide more original Corvettes than one can absorb in three or four days.

[Duke W.]

Re: Rally Wheel Weights/Tire "Dot"

"Matchmounting" provides the roundest final tire/wheel assembly. The red dot on the tires is the high point of the tire and the mark on the wheel is the low point on the wheel, but I may have the above reveresed. In any event, matching the red dot on the tire to the wheel mark results in the least out of round of the assembly.

As little as 1/32" out of round can cause vibration similar to slight static unbalance even if the tire is perfectly balanced, both statically and dynamically.

The 1970 Corvette may be the first car to use this system, and most modern cars do, but time can sometimes take away the small paint dot or other mark on the wheel.

Tires may also have a yellow dot. If the wheel is not marked to match the red dot on the tire, the tire should be mounted with the yellow dot adjacent to the valve stem, which should yield the least balance weight.

Duke

[John H.]

Re: Rally Wheel Weights/Tire "Dot"

"Matchmounting" provides the roundest final tire/wheel assembly. The red dot on the tires is the high point of the tire and the mark on the wheel is the low point on the wheel, but I may have the above reveresed. In any event, matching the red dot on the tire to the wheel mark results in the least out of round of the assembly.

That's correct - it was spawned by Chevrolet's analysis of what they called "smooth-road shake", which was unrelated to wheel balance - it was the result of radial runout, which will cause vibration even with a perfectly-balanced wheel and tire (which is what the Hunter GSP-9700 identifies through its road-force load drum).

OEM production-line wheels and tires are marked separately for the point of low and high radial runout, and those two marks are aligned when the tire is mounted on the rim; if you happen to see new cars still on the haulaway truck before the prep guy has worked on them, you'll see various colors of little arrows and stickers adjacent to each other on the tire and rim. Those marks have nothing to do with balance - only radial runout; you can perfectly balance a square wheel and tire, but it won't run smoothly down the road.

I remember very clearly when this requirement entered production, as we had to add manpower in the wheel room to manually orient the tire to the wheel after the tire was automatically loaded (randomly) onto the wheel on the mounting/balancing conveyor (which ran at 550 wheels per hour).

[Pat M.]

Re: Rally Wheel Weights/Tire "Dot"

I just downloaded this image from last weekend. I had to clean the camera out. From a 1969 built February 1, 1969. The original Firestonel spare.

Nice shot in the left picture of the spotty silver overspray on the back of the wheel. Is that more overspray than is typcially seen?

[Kenn S.]

Re: Rally Wheel Weights/Tire "Dot"

Wow...I had no idea it was so involved. Good stuff, thanks.

And for Terry. I'm a member of the Indiana chapter...just couldn't get to Valpo this year. Still workin' for a living, and apparently to support my car habit.

[Terry M.]

Re: Rally Wheel Weights/Tire "Dot"

Nice shot in the left picture of the spotty silver overspray on the back of the wheel. Is that more overspray than is typcially seen?

Pat, that looks like silver over spray, but it isn't. It is just the sun reflecting off the black paint. I wish I had one of the back from farther away, but I do not.

I did find this on my second look at the pictures full-size. I don't know if you can see the orange dot in the crook of the first "S" in SUPER SPORT -- closest to the rim BB. The thumbnail photo may be too small to see it. Someone cleaned this tire rather aggressively and most of the orange dot is gone, and I didn't see any of the colored wax that indicates where the wheel weight is to go.

You may also see the run in the silver paint at the top of the image.