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Old 10-22-2008, 10:49 AM
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Default Balancing big tires

There's always been a problem with getting a big heavy tire "balanced" and and not creating vibrations. But, off road tires always have that "bounce" to them.
BB's and dynamically moving weights help - sometimes.

Here's what happened to me:

I punctured a sidewall with cactus. A sidewall flexes too much for repairs to last very long. I took it to the dealer where I bought the 35x12.50 MTR. They gave me a new one under their road hazard warranty.
When they tried to balance it the readings kept changing. The balancer would tell them 1 oz inside, 6 outside. When they put that weight on and re-spin it, it'd get worse, like 7 inside and 24 outside. Readings were different each time they spun it.
No, the balancer was working fine on other tires, just mine seemed to affect it.
Finally they put it on another machine - along with their "expert" that had tried with the first machine. This one was far more sophisticated.

First step it spins it up to speed and recommends the weights to use.

Then it pushes a big roller up against the tire, pushing hard, simulating the pressure the tire would "see" on the vehicle. That detects soft spots in the tire.
Next it measures any runout from the rim and tire, both laterally and radially.
Then spins it up to speed and measures the "actual" balance with the weights the standard machine would recommend.
I may have gotten the procedure backwards here, but you can see what it measures.

That tire and rim combination was exerting 107 lbs of sideways force when spinning, even when balanced with weights!
That's probably why the other standard balancer was having so much difficulty. The sideways force was probably throwing it way off.

The machine recommended the tire be rotated on the rim! It told where to place a mark on the rim, and where to put a mark on the tire. Then you break the tire down off the rim, line both marks up and re-inflate.

That's sort of an old trick we used to do when excessive weight was needed, sometime we'd rotate the tire's position on the rim 180 degrees and hope. Now it told us exactly how much to rotate it. At best it was a guess before.

These calculations were not only based on the runouts, but included the soft spot in the tires.

Retesting it showed it was now 26 lbs! From 107 to 26! The machine indicated that was well within acceptable limits.
He balanced it with weights and put it on the front of my Jeep.
SMOOTH AS GLASS! At least on that corner, all the way up to 90 MPH. It was immediately obvious that the other wheels needed it too.
I didn't have time then, but It'll get done next week.

So - if you have that "bouncy bouncy" even after the tires have been balanced, you may want to try this.

Here's a link to the maker - Hunter Engineering - of that ROAD FORCE balancer, the site also has a locator where you can find one.

I'm sure they are expensive machines, and not everyone will have them. Those without them will probably poo poo them.

The place that took great care of me was America's Tire in Palm Desert, CA.

I wonder if this might help with DW problems too?


GSP9700 Road Force Measurement System
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Old 10-22-2008, 11:52 AM
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very interesting. I've never seen or even heard of such a machine to balance tires. I'm gonna look to see where the nearest place that has one.

Is it alot more expensive to have it balanced on this machine?
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Old 10-22-2008, 11:56 AM
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wow, there are 14 shops within 50 miles of me that has one. I didn't look yet, how big of a tire can they do on this?

edit: 40 inch max tire diameter
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Last edited by RickB; 10-22-2008 at 12:01 PM.
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Old 10-22-2008, 12:08 PM
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40" max.. mmmm... i'd love to give them one of my beadlocked 38's and see what they can do with it..
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Old 10-22-2008, 12:15 PM
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This is nothing new. Aligning the tire with the wheel is standard practice in auto plants. The wheel has a dot on the rim and the tire has a dot on the sidewall. When I first went to work at GM Leeds plant, there was a guy whose job was to sit there and align those marks. All day long, he aligned those marks. 60 jobs per hour, 4 tires per car, 5 with the optional full size spare, all day long he aligned those marks. Later they got a machine to do it but it didnít work so he kept on aligning those marks. The machines work now and it aligns those marks.

The mark will soon be gone on the wheel but you should find an arrow in the center of the hub in the bolt circle and new tires have the mark.

Anything that took over 5 ounces was a reject at the auto plant.

I had to check and calibrate those machines every night when I worked at GM Leeds. My job at GM Fairfax was to sit in the tire mount area and respond to equipment problems as long as there was production running. Luckily, I worked the 10 PM shift so production usually went down before 2 AM. It was a boring job. I still checked and calibrated everything every night after production.
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Old 10-22-2008, 07:32 PM
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TAZ - I wonder - that must be only on newer GM OEM rims? I just went out and looked, no markings, no dots, on any of mine. But almost all the rims I have are aftermarket. My 95 & 98 Astro vans with OEM rims did not have them. No arrows either. I have a set of aluminum OEM rims from a Cherokee - with the Jeep emblem on them, no markings.

The tires - Most are MTR's, no arrow. And a few BFG muds and AT's - none there either.

Maybe my fleet is too old? The '02 Rubi has rock crawler rims on it, no markings. The total in my fleet today is 12 vehicles. I need to change my sig line to insurance poor.

Sure would be nice if they did have those markings!

The place I went said they charge $30 to do it. I'm sure the machine is very expensive, so it's not something everybody has.

But it sure worked on mine. I'll let you know after I do the rest of mine (4) - probably next week.
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Old 10-22-2008, 10:54 PM
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This is unbelievable there are 102 shops within a 50 mile radius of my zip. I think I might just have to check one out soon. By the way great info. Thank you very much.
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Old 10-23-2008, 03:11 AM
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The guy at the store I went to said it takes quite a bit of training on the machine, there were only 2 guys there that knew the machine, out of about 15 - 18.

Just having it doesn't mean they really know how to use it - talk to them about it - you should be able to tell if they can explain it to you. There is a "dumb mode" where it just acts like a run of the mill balancer.

TAZ - how big is the arrow on the side of the tire? - Thinking I may be looking for the wrong thing? Was it put there by GM or by the tire mfgr, Goodyear, BFG, Firerock etc? How 'bout small truck tires - like Jeep size?

It sure would be nice to be able to do it once with the machine, mark the rim clearly, then the next new tire can go on the same way without bothering with the machine.
Was the mark/arrow at the soft spot or the hard spot? It wouldn't be so good if the machine marked the rim one way, but the tire was marked the other - it would end up backwards!

And, it may be calculated ideal spots, not just the soft spot, but runout and weights may also be incorporated in the calculation of the "ideal" marks. Dunno.


It's understandable aftermarket rims would not have the marks or numbers, it could show how bad they are.

I would think with beadlocks it would be doubly important with having so much weight added to the rim. Just think - beadlocks and a smooth ride? Nice!
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Old 10-23-2008, 11:16 AM
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Quote:
Originally Posted by RRich View Post
TAZ - how big is the arrow on the side of the tire? - Thinking I may be looking for the wrong thing?
The arrow I was speaking of is stamped into the wheel. It will be in the center of the hub between two of the bolt holes.

The tires have a dot on them. This is one of the set I put on my Buick a couple of months ago.




When you go back to get the wheels balanced, take a look at the new tires on the shelves. You should see the dots on them but maybe not in the large off-road styles.


After thinking more about this, it seems I misspoke some. When I was working at Leeds and Fairfax the wheels were painted in the plant so they would not, could not have had a dot on the rim back then. The dot on the tire was aligned with the valve stem. The dot and the valve cap had UV die marks for the machine to see. I also don’t remember the arrow in the center of the wheel back then.

I get real bad tunnel vision in these plants. I can see the equipment very clearly but the product is just a blurred shape. Unless something about the product catches my attention or I need to know it for my job, I just don’t see it.

I’ve been in several Ford and GM plants and only a couple of times had to deal with any tire conveyors so I can’t remember where I saw what.

I’ve never been in a Jeep plant and have only been in one Chrysler plant back in ’84 on an e-coat dip project so I don’t have any basis for how they do much of anything.




Did you know most plants dip car and truck bodies and use an electrical current to e-coat them for rust protection? The new Fairfax plant was being built when they came out with the “galvanized” body panels. They thought they didn’t need to e-coat any more. My former boss at one of the conveyor companies was an engineer for GM Fairfax at the time and he was telling me how the phosphate/E-coat line was an afterthought. They found out that “galvanized” is only on the outside and is so thin that it wipes right off. Unfortunately, the plant was already laid out and he had to tuck the phosphate/e-coat line in a corner to make room for it.

Some salesman may tell you how the body is “galvanized” for rust protection but it’s e-coat that does the job. That “galvanized” is only to protect the parts in shipping and storage. Ask that salesman about how the body is galvanized. If he tells you about all the body panels being galvanized prior to assembly, ask him how they keep it from burning off when the panels are welded together.
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Old 10-23-2008, 12:10 PM
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I see what looks like 2 dots on the tire in your picture. One's red, the other looks grey? But the dot on the rim - can't see it.
I just looked again, still none of my rims have a dot or arrow or any other marking like that. But then, very few are OEMs (11 vehicles and several spare wheels and tires in the garage.)

All my off-road tires have a paint mark next to the stem (put there by me, for me) to see if, and how much the tires slip on the rims. That's another big problem. Slippery rims let the tires slide around on the rim.
With the marks I can see if it slipped, and put it back without rebalancing.

Hmmm, since finding a new position for the tire on the rim can help considerably, then obviously the rims are out of balance or out of round as well as the tire. Else repositioning would do nothing. But each rim will be different by position and amount where it's "heavy" spot is.

So, how can a tire mfgr know that their heavy or soft spot needs to always line up with the stem since the rims will vary so much?

I'd think each individual tire/rim combination has to be evaluated on it's own. Plus after using a rim awhile, especially like we do, it's not going to be the same as it was new. That's where that machine comes in - that tire to that rim.

GM must have either analyzed the rims and tires, and marked them, before they got to you, or the suppliers did.
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