Tire vibe has me stumped! Help, please.

Deep6

Registered User
Ok folks I'm basically at my wits end. As some of you know, I've gotten new rims and tires. Since the swap over from the stockers, life has had much more vibe to it.

To give everyone the readers digest version, I've got a vibe all throughout the car at higher speeds and it gets worse the faster you go. I also feel the vibe through the steering wheel.

Now for me to address the obvious solutions.

The tires are 255-50ZR-17's on 17x9, 36mm offset Cobra Rims. I'm running the stock bolt pattern.

At anyrate, all of the tires and rims have been "road Force" balanced. When I had them done, they were balanced "very well" according to the tech who balanced them. The road force that each tire/rim assy produced was 5,6,7 and 9 lbs of road force respectively. I've been told that getting the road force below 10lbs is golden.

Now, just to be on the safe side, I've had a proper set of hubcentric rings to put on as well. They seem to work well and do their job.

And just to be sure that I'm not totally crazy, I went to sears and paid $100 for a 250Ft/lb torque wrench.

I installed the hubcentrics and torqued the lugs down properly yesterday. I used the proper "criss-cross, or star" pattern and torqued them down to 105ft/lbs each.

When I drove the car, I noticed that I still had the vibe and if anything it seemed worse at 75mph than it did before....

I'm really stumped. Some possibilities that have been floating around in my head:

Maybe a balancing weight fell off?

Maybe the tires got out of balance really fast due to me driving around without hubcentrics for a few hundred miles?

Maybe this isn't a tire balance issue, but maybe due to me having crappy engine mounts or a driveshaft out of whack?

Maybe this is some kind of suspension or wheel bearing issue?

In addition to all of this, I've noticed that the car now has a penchant to really follow ruts in the road and seems to require alot of correction for every minor thing. Could this be due to alingment specs or is it the punishment that I pay for the lower profile, Z rated tire?

Thanks any and all for your help, hopefully you guys can give me some direction to go in, cause I'm stumped!
 
Here are a couple of ideas,

Are you sure it's the new tires / wheels? You did not have this vibration bfore the tire and wheel change correct? Can you throw the old set back on to be sure?

Also A coworker was just talking yesterday about a set of new tires he bought last year that were manufactured out of round by about 1/8 inch. This was not caught when he had the tires balanced, and he had a hard time convincing the tire store to replace the tires. Finally they put the tires on the balancing machine, and moved a trash can very close to the tire as a point of reference. With the tire spinning you could clearly see the tire moving closer and further with respect to the can.

You could probaby do the same with the tires mounted on your car. Jack it up, and spin the tires, set something close to the road surface and see if the tire is moving in and out as it spins.
 
Wouldn't a road force variation balance...

...take care of that? I mean it's meant to catch out of roundness and match it with the rim?

I cannot put the old tires back on since I threw them out and the original SC rims are sitting in my dad's garage...

I did in fact rotate one of my tires and on the car and it seemed to do that, I'll check it again. but this is really got me stumped.
 
I would start looking at steering and suspension components-if they were worn before the new rim/tire combo, then the problem would have been aggravated by the wider combo.

Once you are sure that your steering and suspension are good, next is a good four-wheel alignment. I know that Sears Auto Center did a really good job on mine-the back end showed 1.4 and 1.3 camber, with the wheel showing a noticeable slant. The alignment has done wonders for the ride and feel of my car-I used to hit a nice little vibe/shudder starting at 65 and going up through 90-it's gone now.
 
Joe, I am not sure what road force balancing really means....

But I really doubt it is something that could compensate for a out of round condition. What I am talking about is that the opening of the tire is not centered on the same point as the road surface.....too much material on one side compared with the other. It is not only a problem with the mass of the tire being off centered (balancing weights could compensate for this) but one side of the tire is taller. It is like running over a bump everytime the tire rotates. Even worse it MIGHT be possible that the hub circle is not centered on the same point as the wheel lip. Doubtful if it is a name brand wheel, sounds like you have some kind of centering rings to help too.

Another possibility is a broken belt type of defect, where the tire stretches out of shape more in one place as cetrifugal force increases with speed.

Know anyone nearby with an MN12 that would let you borrow tires and wheels for a test drive? It would really be nice to narrow it down to tires / wheels or vehicle.
 
Andy, I can understand what you are saying...

If you don't know what "road force variation" is, let me try and explain it and sum it up. Our normal tire balance is a dynamic and static balancing. But with the road force variation it actually spins the tire up on a roller. This simulates a load applied to the tire and the tire traveling at high speed. As you know, a tire will perform different when load is applied to it and normal Dynamic/static balancing doesn't do this. R.F.V. balancing goes a step further by assuming that NO tire is perfectly round and NO rim is perfectly round either. The tire and rim are measured using a special side roller. When the computer get's a "picture" of what kind of "oval" the tire and rim are, it will make a recommendation to mark that section of tire and another section of rim. The tire operator then dismounts the tire and lines the marks up before remounting it. This way the computer recommends mounting the high spot of the tire with the low spot of the rim. This results in a much more concentric rolling assy. Every tire, no matter how well it is balanced will vibrate a little bit. The load roller will measure how much vibration there is in "pounds of road force". As I've been told by experienced tire balancers, most passenger car tires will balance out well if there are less than 20lbs of road force per tire. But on a sports car that has a sensitive suspension along with low profile tires getting the road force less than 10lbs per rotating assembly means very good news.

When I first got my 17" tires and rims, I was able to get 3 of the 4 tires under 20lbs. However, the 4th rim/tire was definatly out of round and no amount of R.F. balancing would be able to totally solve it. I would still feel a vibe. I sent that rim back, along with the other 3 good rims. I decided to get the 17x9" rims since those would mount the 255 series tires better. The tires mounted easier and all balanced under 10lbs like I had hoped. At first the ride seemed to improve, but I did notice a little nibble at highway speed. I requested hubcentric rings just for peace of mind and decided to properly torque the lugs, hoping that would solve any remaining vibe.

However, the vibe seems to have become worse. i don't know if drivng it while having the small vibe made the tires wear worse? Or what....

The rims I have are Dante Designs 2003 Cobra Knock offs in the T-bird bolt pattern. I swapped tires and rims with a guy who lived near me back when I had the earlier 17"s. The vibe was still there. But when I put my original 17"s back on and properly torqued them, the Vibe was like 95% gone! So that is where I came up with the assumption of properly torqeing things.

One other interesting note, the valve stem on my cobra's do not line up with one of the lug holes. There fore I cannot reference it with the painted wheel stud on my front hubs. I've located it as close as I can, but unless I had the rim redrilled to relocate the valve stem in-line with one of the lug holes it can't line up. So I'm wondering how serious it is to get the valve stem referenced to the painted wheel stud?
 
Vibration

Hi, I had a severe vibration problem at higher speeds 2 years ago. First thing I did was have the tires balanced and get a 4-wheel alignment. No help. Had the alignment re-checked, and then re-checked again at a speed shop. I decided to buy new tires and balance them. Still had vibration at higher speeds. Checked rims for out-of-round condition, had wheel bearings checked and packed. Had the tire dealer install a "softer ride" Yokohama tire. Still had vibration. Replaced Rack-and-Pinion gear box, ball-joints, swaybar endlinks, tie-rods. No Help! Had the tires balanced at a local speed shop that balances tires on the car at high speed. Solved the problem. I don't know what happened, but something from the axle on out to the tire (shifted, wore, went out-of-round,) changed. In San Diego at Clarence Brown Alignment, High speed balancing costs $15 per wheel (plus weights). I was next getting ready to replace U-joints and have the Drive-Shaft Balanced while it was out. Good Luck!
 
Sandiego Scott....

This "high speed balance" that you speak of, is it anything like the "Road Force Variation" balance that I described?

As far as I knew, "Road Force Variation" balancing with a Hunter 9700 computerized tire balancing machine was literally "the best private consumers could get commercially".

The R.F.V. balancing act cost me $25.00 per tire/rim at a specialty shop. The guy who runs the shop, may not have the prettiest shop but he definatly services the "tunerz crowd" and he advertizes that he specializes in "high performance wheel and tire combos"...
 
They call that road force thing "true balancing" here... I am assuming.

My tires are suspect of being flatspotted, due to sitting a few years ago for about a year with little use.

This was a local tire shop, this guy attached this deal to the wheel and then this roller thing spun it up to about 100MPH per tire, and "shaved off" part of the tire. This was done on the car by the way.
After that, it rode good for a few days, but I got the vibration back soon.
It is still acting that way, and is worse wheen it is cold.

I have been wanting to get new tires, but the ones on it are still less than 50% worn... I will porbably get some new ones soon; but now I am concerned about a what san diego scott says about replacing all that front end stuff... I do have new ball joints and another bushing or two that seemd worn, but the steering parts??? AGHHHH

My steering wheel does wobble slightly at certain speeds when braking or not and at really slow speeds usually lower speeds.

To be honesst it does feel like my car is limping along sometimes at really low speeds...

I am hoping that the new tires will correct that.

I have a lifetime alignment on the car at Firestone, and I've carried it back, and it has been in great alignment the 2 times I have carried it back.

It that what you guys are talking about with the high speed balancing???

Is there a particular machine I can look around for to get the best version of this "high speed" balancing?
 
High Speed Balancing

The computer method will balance the tire perfectly... but what if your hub (or something else on the car) is not balanced.

"High Speed Balancing" at Clarence Brown is done while the tires are on the car. The guy jacks the car up so the wheel will spin free, then uses a power roller to spin the tire at high speeds, then uses his HAND to grab onto the tie-rod and FEEL for vibration. He does trial and error approach to finding the correct amount of weight at the correct degree of rotataion on the wheel until ALL VIBRATION IS GONE. This method compensates for the sum of ALL rotational error for every rotating part that the wheel bolts to. He has been doing this for many years, and it takes him about 4 or 5 minutes per wheel.
 
That is about what this guy did, but at some point they actually shaved the tire itself.

He spun them up with the roller deal, and then took the tire off and put it on another machine, which shaved the tire.

He said it was balanced all the way to 100MPH...

Like I said it was smooth riding for a few days, and then the vibe came back...

I assume, and hope, the tires were just too flatpotted...

I hope this next set of tires fixes it, all that vibration can't be good for the car anyways... It isn't all that violent, just very annoying!
 
Hmmm...

SanDiegoScott: I wonder if that service is offered here in NY? I've never heard of it, but it does seem to make sense. It not only balances the tire/rim combo but also takes into account the wheel bearings and any other rotational drivetrain parts.
 
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