Wheel Balancing - When first try doesn't work

butch11

Several years ago I had a set of Michelin tires put on a Honda Accord by a large discount mass merchandiser. I watched them put the tires on the balancing machine. I was really surprised at how quickly they stopped the spinning of the tire and then applied weights. I asked about this and they said it only needs to turn a little bit.

Well my tires were out of balance-rather than fight with those people, I went to a large tire dealer and told him what happened. I asked if they would check the balance of the tires with the weights on-they did and were they out of balance.

Now when replacing tires at a new location, I watch them work on other peoples tires and try to make certain they let the balancer at least spin the tire up for a couple of minutes.

gus

A couple of minutes may be overkill. The tire balancer we have at work seems to balance tires okay, and does it in about 25-30 seconds.

vivona

Here are some answers to the balancing questions posed recently:

Even though the runout of the rims were within .004, reindexing the tire can remove that .004 from the runout of the tire. The tire radial runout was .035 for one and .050 for the other before the indexing. I haven't measured it since the balancing.

Though the rim may have been well within runout specs, I don't know if they were in perfect balance, but I suspect they were. If not, indexing the tire can offset the heavy spot of the rim with the light spot of the tire.

I haven't crawled under to see what weights are on the insides of each rim, but on the outside there is only one weight on each wheel (one has none) and they are in the range of .5 to 1.5 oz. One of the original tires taken off had a total of 3.5 oz, and that is too much.

I was not able to actually watch the balancing job being done, though I would have liked to. The machine wasn't in an area I could see from outside the shop and they restrict customers from the actual work area. The tech mentioned he was able to reduce the road force variance. Since he obviously could not reduce the actual sidewall flex variances, I suspect he measured the force variance on the roller before rebalancing the tire and runout/balance error contributed to the force variance reading. Once the balancing was done, the remaining force variance was due to the sidewall flex variance. The last set of tires at their best were only able to be balanced to around 16 lbs of variance. These were balanced down to 2 and 5 lbs.

I guess the real question will come several years down the road when the Goodyears need replacement. Stay with the Eagles or try Michelins? I did ask the car dealer which tires gave them the least problems and they said Michelins. And the Goodyear dealer admitted that it wasn't unusual for a set of their tires to have "ride disturbance" problems.

spokane

Thanks for the recap, Vivona. The substantial reduction in force variance and the elimination of need for 1.5+ oz weights do seem to confirm the good performance results you have experienced.

"Force Variance" is a new entity for those of us not familiar with the GPS9700, but it's importance is obvious based on the results you have obtained. I presume the tire-load roller (unique to this machine)is preloaded against the tire to a standard force level, the processor records the force pattern for a few revolutions, and a statistical variance is then computed.

Has the shop indicated any standards or limits for force variance on this equipment?

vivona

You can read a lot of information about the GSP9700 at: http://www.hunter.com/pub/product/balancer/4159T/4159t.htm I recommend you visit this site and read the information. More information is available at http://www.hunter.com/pub/product/balancer/4127t.htm

The roller is preloaded against the tire with a force of 700 lbs, which approximates the weight of one wheel of a medium weight car. The shop said anything under 15 lbs of variance is usually okay, though some cars can have up to 24 lbs of variance before it is felt.

quadrunner500

Thank you Vivona.

Obviously the GPS9700 worked well.

What I'm skeptical about, is not your results, but rather the potential for poor quality spin balance jobs in general.

Can it be that many spin balancers are out of calibration? Would not surprise me. With the beating they endure from tire installers, how good can they be?

If one assumes a state of the art balancer like the GPS9700 can identify an infinite number of imbalance locations, there are still only a finite number of locations where a weight can actually be placed. In your case, if there are not any weights you can't see, the placement of a single weight, in a single location was sufficient. Seems to me if balance alone was a problem, a conventional spin balancer in good calibration, or even a good "bubba" balancer should have been capable of giving satisfactory results where a weight was required for only one location on the rim.

Having said that, my last real balance problem was in the '70's on a Datsun 240Z. I tried every balancer I could find, but could never completely eliminate the problem. The tires I used were the Bridgestones that came on it, followed by Michelins, then more Bridgestones, and more Michelins. It never really made much difference.

But no other car, wheel, or tire has given me balance problems. My current vehicle, a '99 Chevrolet Silverado 1/2 ton truck has what I thought were probably the cheapest Firestone OEM tires I could imagine, humungous P265/75/R16 Wilderness A/T's on factory aluminum rims. I have 11,500 miles on them, and not a hint of vibration at any speed. They are as smooth and vibration free as any tire or vehicle I have owned. The largest wheel weight used from the factory balance was 1 ounce, others are 3/4 ounce.

My '94 Camaro with Goodyear Eagle GSC P245/50/ZR16 are just as good, with 34,000 miles on them.

It's irritating, with shops charging $9 dollars a wheel, to think that after thousands of tires, the balance machine is too busy for down-time to do periodic maintenance, or calibrations.

vivona

Traditional balancing machines cost around $1,500 to $2,000 (according to Goodyear dealer) and IF CALIBRATED can balance down to .25 oz, provided that the tech properly mounted the wheel on the machine. That used to enough for most cars, particularly rear wheel drive.

The following paragraph is a quote from this link:

http://www.dsm.org/how-tos/wheelvibrations.htm

"Most dynamic wheel balancers that shops use are accurate to 0.25 oz. (or about what a quarter weighs) -- this would generate a
force of about half a pound at 65mph for a 24inch diameter tire. This accuracy used to be enough and the forces generated were not
noticed in the days of rear wheel drive cars with long arm suspensions and parallelogram power-assisted steering. But on our cars, it
would be totally unacceptable. There is a new "European" accuracy standard which call for an accuracy rate of plus or minus one
gram ( that's 0.035 oz.!) Granted that this level of accuracy may be obsessive for the family van or the SUV, but for me, give me
only perfection!"

The GSP9700 can balance down to .5 grams, which is .01 oz. That is much better for today's cars with light wheels and light suspension parts with short arms and rack and pinion steering. Of course, the measurement of sidewall variance is only possible on a GSP. Only problem is that the GSP costs over $10,000, so few shops will pay the price to have one.

BTW, I did read about a "poor man's" variance tester which sounded like a roller you put under the tire while it was on the car. You then turned the roller with the weight of the car on it and monitored the center of the wheel to see if it moved as the wheel was turned. I forget where I read about it and I haven't run across anything like it in my web research. Sounds like something that a tire shop should have in lieu of a GSP.

quadrunner500

0.010 ounces is impressive, but what good if weights don't come in all increments. You put on the smallest 1/2 oz weight, and with the rounding error, you're nowhere. Not saying it hasn't worked for you, but must admit I have some doubts that a wheel balanced to 0.010 ounces is going to stay balanced that way for more than a few scuffs of the tarmac, or a few miles. Hope I'm wrong.

vivona

The GSP does come with smaller increment weights. The idea of balancing down to such a small weight is to allow a lot of latitude for changes brought about by scuffs, mud, etc. If you balance down to .25 oz and it happens to be at the end of the range, then any changes may cause an imbalance. But if you are balanced right down to the .01 oz, you have a long way to go either way before you are even at the level you would be if you had balanced down to "only" .25 oz.

quadrunner500

Well, the proof will be in the pudding. Let us know. Good luck.

quadrunner500

Now supposedly, indexing the tire on the rim can be used to offset the runout of the rim, to cancel the runout of the tire, by putting the two offsets 180 degrees apart.

Now in the Vivona case, we are told this technique was used to cancel a tire runout of 0.035 with a wheel runout of 0.004 inches. Since the wheel run-out becomes -0.008 when put 180 dg out of phase, added together a tire run-out of 0.027 remains. Thoughts?

Then we are told that the superior balance accuracy of the GPS9700, down to 0.010 ounces is relevant, since special weights in small increments are available.

It was stated that in the Vivona case, other more traditional balance methods were unsuccessful, and that the Mitsubishi is more sensitive to vibration due to various suspension and design factors. Not disputing that, but the question remains, how was the benefit of the GPS9700 balance machine germane to Vivona's case when the wheel weight increments applied were stated to be in the range of 0.5 to 1.5 ounces? Are we to believe the coincidence that the imbalance condition was exactly offset by 1/2 ounce wheel weight increments, with no rounding error? Or were these weights a non-integer decimal for some size in between?

All in all, I'm still a bit doubtful that beyond identifying some out-of-round tires to be discarded, the more conventional spin balancers should be able to adequately do the job, if in good working order. Since I suspect quite a few aren't, I might continue to state the case that a simple bubble balance, used on a good wheel, with a modern tire of good balance distribution and roundness in general, is also capable of doing a good job with its inherent simplicity.

vivona

The main advantage of the GSP9700 is in its ability to detect variations in sidewall flex. No amount of bubble balance or traditional spin balance will identify a vibration caused by a variation in the sidewall. The tire can be in perfect balance, and be perfectly round, and still have variations in sidewall flex due to manufacturing variances.

The second advantage is the ability to balance down to a smaller weight increment. On a FWD car with an independent suspension, the rear wheels often have little in the way of unsprung weight. According to the article at http://www.dsm.org/how-tos/wheelvibrations.htm accuracy to .25 oz could leave you with an imbalance of 1/2 lb in force at 65 mph. When the unsprung weight was much higher on cars of yesterday, that amount of imbalance usually wasn't detectable, but with multilink suspensions, aluminum suspension parts and alloy wheels, a modern car can feel such a small imbalance.

The proof is in the actual experience. Three attempts at traditional balancing, and two tire replacements didn't cut it. The GSP9700 did the trick.

spokane

Quadrunner points out that other than identifying tires that must be discarded, the pre-GSP9700 balancing technology can do a very good job. I agree.

Viviona's case demonstrates there are occasional tires that are dimensionally good and are properly balanced but do not operate smoothly on the road because of irregularities in flexural rigidity. While it is sometimes possible to play off the rigidity problem against balance or runout, this problem often requires replacement of the tire.

When using properly-calibrated conventional balance equipment on a tire with a "rigidity" defect, we can use the process of elimination to set this tire aside and try a replacement. One problem I see in this process is that the alternate tires of this brand, style, and size in the dealer's stock my be infected to some degree with this same problem. With its "force variance" determination, the GSP9700 allows measurement of all three driving-uniformity criteria (dimensions, balance, and rigidity) which can effect ride quality.

Looking to the future, suppose I have a problem with a new tire purchased at Joe's. Joe tries unsuccessfully to correct it using his conventional balancer so I then go across town to Sam who has a GSP9700. Sam finds the force variance to be out of limits. Now, Joe is a good tire guy but he's never heard of force variance so I imagine it could be awkward to ask him to replace the tire. Hopefully, other balance equipment makers will soon join Hunter in having force measurement machines and will acquaint all of the tire shops with this technology even if they don't sell the new machines right away.

vivona

In time I think the force variance method will gain popularity. I asked the Goodyear dealer if they had heard of them and they said, Yes, but at $10,000 apiece, we just can't justify buying them. However, the Goodyear dealer didn't have a problem at all replacing tires that were shown to be defective by my Mitsubishi dealer's force variance machine. I did have a vibration problem Goodyear couldn't solve, so having someone else come up with a definitive solution was to their advantage.

Hopefully, as other balancing manufacturers come out with similar machines the price will come down to a level that more tire stores will consider reasonable.

quadrunner500

Vivona, that's where I have a problem, "the proof is in the experience" as a blanket to write off other explanations.

Your case keeps raising more questions. And I realize you went to extraordinary length to be thorough, including measuring runouts.

Here's one problem. Please correct me if I'm wrong, but you said that Goodyear admitted to some bad tires, and gave you a second replacement set, your third set overall, balanced by them, that left you with a vibration that remained. Then you took that set to a business operating the GSP9700, and Mitsubishi paid for it. So the third set was both cause for a vibration when balanced by Goodyear, and was removed as a cause for vibration when balanced by the GSP9700. Same set of tires. Beyond indexing it on the rim to correct for 4 thousands of wheel runout, all it can do is balance correctly if it's not telling you to replace a tire for sidewall variance.

Now think about it. If the GSP9700 said put 1/2 ounce at 12:00 o'clock, and you put a 0.500 oz weight at the proper location, you would zero out the error. Great! But if the GSP9700 said put 1/4 oz at 12:00, and all you had was a 0.500 oz weight, then your wheel would be off by 1/4 oz whether you added the weight, or not. My point is that a standard balancer can balance to that accuracy. And I'm not missing your point that the GSP9700 can additionally identify sidewall variance, and index the tire to offset this against wheel runout. But with your negligible wheel runout of 0.004, you were left with 0.027 for the tire(s) you accepted.

Spokane, I agree. Well said.

vivona

If the GSP9700 said put 1/4 oz at 12:00, you would put 1/4 oz at 12:00. It is pointless to ask what would happen if "all you had was a 1/2 oz weight" since putting the wrong weight on is not an acceptable practice. Actually, if this situation really happened, the tech would take a 1/2 oz weight and cut it to half size.

It is a better argument to say what if the GSP9700 indicated that the weight should be .37 oz. With the GSP9700 you must stock many more weights in small increments, so you would have the .37 oz weight and install it. But a regular balancer couldn't measure to this accuracy and would either indicate .25 oz or .5 oz, depending on where the machine rounded to. In that case you would be .13 or .12 oz off, depending on the round off. That is enough to cause vibration on some suspensions.

The GSP9700 does have other advantages. It has an automatic mounting mandrel tightener to assure that the wheel is mounted tight enough and sensors to detect if the wheel is not mounted correctly. When balance problems are noted, the machine has a display screen that tells the tech exactly what to do. On a standard balancer the wheel or tire could be way out of round and the tech wouldn't even know if unless he actually looked under the balancer cover and estimated the wobble. They don't even have a runout gauge, they just do it by eye. I have watched many standard balancing jobs and never saw the tech watch the tire for runout except in the one case where I had a specific complaint about balancing that didn't work. And they did it by eye. And they mounted the wheel incorrectly, giving a false indication that the wheel was out of round. And they improperly indexed. And the tire still vibrated. And the GSP9700 found all the errors and corrected the vibration.

Works for me!

quadrunner500

Okay, fair enough, but one more question, still unanswered.

Were the ACTUAL weights used on your wheels, that you stated earlier to be 1/2 to 1 1/2 ounces, were they in between those amounts, or were they exactly 0.5, 1.0, 1.5 ounce weights? Because if you tell me they were trimmed, or one was 0.66 ounces, etc., I can let this rest. But I would have to remain skeptical of the likelihood that all 4 wheels actually zeroed out if standard wheel weights in 1/2 ounce increments were used.