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Out of balance feeling

Va Maddog

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My new tire adventure continues. Yesterday they tried for a third time to properly balance the tires and found one that was 2oz off, which is a lot. (Their admitted screw-up)

So today I had a 125 mile round trip and it was better, but not all better. The out-of-balance feel was still quite noticable at 40-45 mph. Go faster and it got much better. So I went back again. Today they found that three of the four tires were right on but one of the rears was off by about 1/2oz and it hopped a little while on the balancer like it might have had a flat spot. They changed that new tire out for another new tire. Again it seems better, but not all better.

I wish that I had another 95 SLS/STS to jump in and compare. I still think that there is something wrong. Perhaps I chose the wrong tires - I did intentionally go with a tire that would be less harsh then the Michelin X-ones that were on it, but perhaps I went too far away from a performance tire. I did not notice any of this out-of-balance feeling with the Michelins but I had to switch them out due to a tear in a front sidewall and normal wear on the rear tires.

It could also be that the RSS adjustment is off. I read the post on the home page that Jim put up over a year ago and thought that I might have the same issue, a bent RSS bracket. The right side of the car does sit about 3/16 of an inch higher than the left side when measuring from the garage floor to the unibody frame but the RSS brackets look fine to my eye. I don't have my service manuals yet (they are coming) so I do not have the detailed step by step regarding trim height and adjusting same via the RSS sensors.

The car just feels like it is hopping or wiggling a bit (great technical terms huh?), like a tire was out of round or out of balance. It will do this on apparently smooth (not rough) roads, although there could be some pavement unevenness that I can't see easily. I can feel it at slower speeds 25-30 and at 40-45. It is more pronounced at the slower speeds but with a slower frequency then at say 45, which seems to fit with it being a tire issue.

The car was initially out of allignment, but they did a full four wheel alignment so that should not be an issue.

They have offered to swap out the tires for something else if I remain dissatisfied which I might just do. Who has any suggestions on what to check regarding the suspension or for a decent performance tire, but one that is not so harsh, meaning I really don't want to feel every tar strip. I also dislike noisy tires. Any thoughts would be appreciated. This has gotten very frustrating. Thanks for your help.

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Make sure that there is no rust, dirt or debris on where the wheels contact the flanges, it is possible that you are experiencing run out. You can used a dial indicator to test for run out. Also just because the tire is new do not assume that the tire is good, it can be out of round causing an up and down vibration, I believe its called wheel tramp... The X-One by the way is an excellent tire in my experience. Stick with it, you will find the problem. If you can find a shop to balance the wheel 'in place' you may turn up a problem. Make sure that your wheel nut hole tapers are not worn so that the nut does not contact it fully, I have seen that happen. Good Luck, and let us know what you find. Mike

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I'm just shooting from the hip here but your comments about a "wiggle" brings to mind a story that might be pertinent. Several years ago after I purchased my previous car ('92 Deville) I noticed that the left rear wheel was canted inboard so I brought it back for a wheel alignment. Turns out the dealer had just gotten a brand new machine and they had to find someone who "knew how to use it". I left fat dumb and happy in March thinking it was properly aligned. Along comes winter and I would be driving along at 55-60 on bare pavement and hit a patch of hard packed snow and the car would get really squirrley (it actually scared me). I was worried that it might veer into oncomming traffic. After a while I realized that it was not me and that something was really wrong. Took it back and when they got it on the lift they called me back and said "here's your problem" pointing to a well worn left rear tire (meaning my alignment was out). After I told them that THEY had done the alignment 10 months ago and they wiped the egg off their face, a realignment solved the problem. My point of this long winded story is, don't assume that just because it was aligned, it is correct. Admittedly, that does not sound like your problem but food for thought.

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Ask your tire guys to check for wheel runout. It took me longer than I care to admit to diagnose two (2) bent wheels.


Drive your car.

Use your cell phone.


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What kind of balancer are they useing? My "tire guy" balanced my new Coopers twice and couldnt get the vibration out. They need to be "road force" balanced. Find someone with a machine and it will make all the difference.

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I have been reading posts about "out of balance wheels" for a little over a year now and have a few suggestions. Keep in mind that I have pretty much solved the wheel balance problems on my STS, but have come to the conclusion that they are NEVER going to be perfect.

First of all, ANY low (that's low) speed variations are due to tire construction problems or bent wheels. This means the tires or wheels are out of round, in your case, WAY out of round. I have had tires that you could feel "squirming" at as low as 25 MPH on some cars. This variation can typically be felt at or below 45 mph.

Second, the typical vibration caused by OUT OF BALANCE tires is felt at around 60 - 62 mph. This can be cured by rebalance and 2 oz. is way too much to be out of balance. 1/4 oz is OK on these cars.

Third, the vibration that plagues most Seville owners is felt at 68 - 72 mph. It is less apparent below or above that speed and can change while driving. It also changes due to the operating temperatures of the tires themselves. This type of vibration is caused by road force variation, or the tendancy of the tires sidewall or belt to flex or not flex while the tire is moving down the road. This type of variation tends to set up sympathetic vibrations in the suspension of the Seville due to its design and bushing materials. This is one reason that Caddy has gone back to rear wheel drive, though they won't admit it.

In your case, go for the tire swap and look for a bent wheel.

My "action plan" would go something like this. Have some QUALITY tires mounted and have the tires AND rims checked for straightness when they are mounted. This can be done with a dial indicator, but I can't tell you what tolerances to look for. If the tires and rims pass this preliminary test, THEN have them balanced. Next, take them for a test ride. Preferably a LONG test ride, enough to check them at all of the aforementioned speeds. After about 30 miles or more of driving during warm weather, they should be warm enough to be round. IF they are OK at this point, take them BACK to the seller, which you should have previously determined..has a Hunter GSP 9700 road force balancer...and BEFORE THEY COOL DOWN, get the tires road force balanced. This last process matches the reluctance of the sidewalls to give, to the low spots on the rim, theoreticaly resulting in a rotating tire that strikes the road evenly at all points during its rotation. Shoot for a road force number of 5 pounds or less. This is difficult or near impossible to get, but get them as low as you can and test drive them again.

This may sound like a LOT of work....it is. If you find the right shop with the right equipment, and they don't mind trying to satisfy you, then you will be fine. It will not be the cheapest process you have ever gone through either, but the results are worth it.

Never underestimate the amount of a persons greed.

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How sure are you that the remaining vibration is being caused by the tires?

Did the vibration start only after you had the tires replaced? If so, I'd focus on the tires and keep taking it back until you get it right. Take the service tech for a ride with you so they know for sure what you are talking about.

If the vibration was present before you got the new tires, it may be something else. Actually could be alot of things. Do you have a set of service manuals for your car? The GM manuals for my 99 STS had a very long and detailed section on isolating vibrations

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Hunter GSP 7900. Fixed my vibration.

2001 STS Mettalic Otter Grey, Black Leather, 213,000 kilometers - miles - ? Still running strong!

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This might at this point just be the belts feeling stiff, setting the suspension system to tighten up, if you think you will hold on to tires, wait 2000 miles and see what happens, the belts will come into there own, and calm the rss down, good luck

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  • 3 weeks later...

Its almost always the tires.

Take 100 new 'z' brand tires. No two will be identical. Its just the way tires are made. Its a very complex assembly process. Its technically impossible. Its a bit like baking bread. No 2 loves are the same.

Add to that the tire guys are making what? $7-8 per hour?

I actually like the Michelin X One. It rides a bit hard but they last 80K with minimal effort and fuss.

Internet tire stores. It seems I get 2nd class tires from these guys. Maybe they know something I dont....great prices but at what cost?

Finding a actual tire shop...that calibrates the machine daily, is rare. That and, I personally will not accept a new tire that requires more then 1 oz.

The Hunter 9700 unit is a great unit. But its not a cure all..

Possible other causes...

Bent wheels.

Rusted brake rotor surface area.

Lightly dragging caliper.

Aftermarket China rotors.

Warped front or rear rotors.

Tire pressure. Max is typically 35 psi. Run with 35 psi you will feel every bump in the road. I personally run about 30psi.

Engine mounts.

Road surface. Some roads cause vibration from their very nature. I think we are spoiled as to ride feel. Some roads can cause the perception of chuggle and vibration. In many cases its just road conditions.

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Larry's comment about the belts loosening up might be happening. It does seem like things are smoothing out and less noticable. I have a road trip to DC today - so that will be another 300 mile "test". I have not had time to go back to the tire dealer again but I need to do that soon if I'm going to press for a trade to different tires. I'll have to see what I think after todays trip. I appreciate everyones thoughts and comments.

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You havent said what type of balance your tire guys are doing.

Is it with the Hunter "road force" machine? If not, your probably not going to get it right.

You can go to the Hunter web site and find out who has their machine in your area. It may not be a cureall but it will eliminate the tires from the equation.

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