Tire Balancing

[wanab5150]

As far as the ball joints go I just installed a Poly windshield from Cobra Valley and I talked to him about the issue. He stated the ball joints cure the last little bit of turning ease and slight shimmy.......very slight. I asked specifically if I should swap out mine for his and he said NOT YET. Get the balance or whatever issue you have going on fixed then if you want the best FEEL, change them out. He said they're not a cure all...just an improvement. Also the fact that for 30K miles it was flawless then the next day with new tires it went to crap...that's not ball joints.

More on the Poly windshield from Cobra Valley in a post this week. I do have to say that I did not think I would be this happy with the clarity as I assumed it would be different than glass. I WAS WRONG! It's amazing!

OK.... So far today I removed the shocks and manipulated the A-arm up and down without a load feeling for any grit or stiffness. NADA! Smooth as glass. I also put the wheels and shocks back on and checked the ball joints for smoothness the old fashioned way with a long steel bar under the tire lifting up. No play on the joint and no gritty feel or stiction. None of that grabby sensation you read about some people having.

With my dial indicator I checked runout on 4 different places on every hub..... The brake caliper hub, outer stud flange edge, outer stud flange end, and the outside edge of the studs while rotating the assembly. One stud was out .015 from the others. I re-torqued it (and maybe hit it with a hammer in the process) but it's within .005 now. All four wheel stud flanges were within .008 at the worst. I am surprised they would be that close. Additionally, I put the dial on the tire bead and spun the tire and it was absolutely perfect on all four tires. I couldn't measure it because the dial would hit bumps on the bead but visually on the pointer I couldn't see ANY movement. So the wheels and tires are spinning round and true at least on the sidewall and the only out of round seems to be in the middle of the tire. But at this point no one seems to have a "to much" out of round spec. Not my dealer...America's Tire... or even Nitto when I called them.


Tomorrow I'm going to spin up fronts and rear on the car and see if I get a vibration.....I'm running out of ideas.

[Cobra #3170]

Originally Posted by wanab5150

As far as the ball joints go I just installed a Poly windshield from Cobra Valley and I talked to him about the issue. He stated the ball joints cure the last little bit of turning ease and slight shimmy.......very slight. I asked specifically if I should swap out mine for his and he said NOT YET. Get the balance or whatever issue you have going on fixed then if you want the best FEEL, change them out. He said they're not a cure all...just an improvement. Also the fact that for 30K miles it was flawless then the next day with new tires it went to crap...that's not ball joints.

More on the Poly windshield from Cobra Valley in a post this week. I do have to say that I did not think I would be this happy with the clarity as I assumed it would be different than glass. I WAS WRONG! It's amazing!

OK.... So far today I removed the shocks and manipulated the A-arm up and down without a load feeling for any grit or stiffness. NADA! Smooth as glass. I also put the wheels and shocks back on and checked the ball joints for smoothness the old fashioned way with a long steel bar under the tire lifting up. No play on the joint and no gritty feel or stiction. None of that grabby sensation you read about some people having.

With my dial indicator I checked runout on 4 different places on every hub..... The brake caliper hub, outer stud flange edge, outer stud flange end, and the outside edge of the studs while rotating the assembly. One stud was out .015 from the others. I re-torqued it (and maybe hit it with a hammer in the process) but it's within .005 now. All four wheel stud flanges were within .008 at the worst. I am surprised they would be that close. Additionally, I put the dial on the tire bead and spun the tire and it was absolutely perfect on all four tires. I couldn't measure it because the dial would hit bumps on the bead but visually on the pointer I couldn't see ANY movement. So the wheels and tires are spinning round and true at least on the sidewall and the only out of round seems to be in the middle of the tire. But at this point no one seems to have a "to much" out of round spec. Not my dealer...America's Tire... or even Nitto when I called them.


Tomorrow I'm going to spin up fronts and rear on the car and see if I get a vibration.....I'm running out of ideas.

I was the Tire and Wheel Manager for Ford Motor Passenger cars many years ago. One of our biggest issues was force variation because of sloppy production processes at the tire manufacturer. Michelin was the only manufacturer at that time that could meet our specification for maximum force variation. We found that coincidentally Michelin had the lowest warranty for tire balance on our new vehicles. The physics of the problem are related to overlapping splices in a tire that are either too thick or are aligned with other splices so that they are in the same sector of the tire. This causes a change in spring rate of the tire which causes a vibration under load. You can have 0 run out and perfect balance and have a tire that shakes like hell. A "bad set of tires" in NASCAR is sometime related to this problem although race tires are more closely controlled than street tires.
We offset bored our aluminum wheels a few thousandths and then matched those offsets using the valve stem hole and the manufactures mark for highest force area (yellow dot) to help cancel this variation. If a tire is truly bad the only fix is to replace it. All tires have force variation it is the magnitude that can get to you lighter cars are more susceptible than heavier cars. All this is just to suggest you might have a tire quality problem.

[jhv48]

If there was no vibration/shimmy in your car until you swapped tires, then the new tires are the problem.
I would return to your retailer and have them fit a new pair.

[wanab5150]

JHV48 maybe you have more swag than I do but so far they're not willing to cough up a set of new rubber without some visible or invisible defect which other than my word I can not prove other than the car vibrating.
Now if I'd had the foresight to take him for a ride before I bought the tires maybe I'd have a better chance. Then again, I've never in 55 years of driving had this issue.

[Tom Howland]

Another idea is to shave the tires. I had a shop in Watsonville do that years ago (now out of business.) That fixed the steering wheel shimmy. The tires were BFG's. May not get the same result with more expensive tires. I think the real problem is in what Cobra#3170 is talking about.

[wanab5150]

Yeah, what 3170 said is true but i had them road force balanced twice and it didn't work.

[wanab5150]

Sometimes the answer is hard for the blind to see which maybe is my case.

JHV48 I owe you an apology for your statement going right over my head. Sometimes the answer is so obvious I cant see it. The seller/dealer should (and is)required to send out a product that is road worthy. I will ask him to balance them again and if they don't balance I'll make the demand to replace them.....And of course have him ride in the car on video...ya think? Sorry again!

[jhv48]

Tom, here's another thought. The Nitto 555 G2's are harder ( treadwear 320 as opposed to 240) than your previous F1's. Try lowering the tire pressure to around 18 lbs. and see if that helps. I always try to stay with tires that have a 200 treadwear (soft) and keep my pressures down to 21-22 lbs.
Also, are you sure it's the fronts vibrating and not the rears?
I went through everything you've done. I replaced the wheels, tires, ball joints, tightened up the steering, replaced the shocks, and balanced and aligned the front end many times.
I finally found a pro who had the hunter road force GSP 9700 balancing machine. He spent some time and after rotating the tire to match the wheel, my problems were solved. If your guy isn't using that machine, find one that does.
It's the tires/balance. Our cars are so light, they need the wheel and tire to be a perfect match.

[lnfletcher]

Originally Posted by jhv48

Tom, here's another thought. The Nitto 555 G2's are harder ( treadwear 320 as opposed to 240) than your previous F1's. Try lowering the tire pressure to around 18 lbs. and see if that helps. I always try to stay with tires that have a 200 treadwear (soft) and keep my pressures down to 21-22 lbs.
Also, are you sure it's the fronts vibrating and not the rears?
I went through everything you've done. I replaced the wheels, tires, ball joints, tightened up the steering, replaced the shocks, and balanced and aligned the front end many times.
I finally found a pro who had the hunter road force GSP 9700 balancing machine. He spent some time and after rotating the tire to match the wheel, my problems were solved. If your guy isn't using that machine, find one that does.
It's the tires/balance. Our cars are so light, they need the wheel and tire to be a perfect match.

The key word is "pro"! I agree with jhv, it took the right tech (in my case the manager) to work the machine (road force) and figure out that it was causing a problem. I had to leave it with him for a day and I think he spent most of it working on my car but he found it. He did the same with mine as was suggested above, rotating the tire to offset the wheel. He charged me the same as a normal balance, but did get to drive a cobra a number of times to test it!

[Cobra #3170]

Originally Posted by wanab5150

Yeah, what 3170 said is true but i had them road force balanced twice and it didn't work.

Road force balancing requires the correct off set in the wheel then moving the tire radially on the rim to reduce the forces. Probably not going to happen in a tire shop. It cannot be done with weight because it is a tire spring rate problem.

[wanab5150]

I just walken in the door after doing multiple pressure settings. I always ran 26# in the 10 years I had the Goodyears without issue. Just for the heck of it I went out tonight and started at 30# and went down 2# (hot) to a final of 22# (hot) F&R. At 24# I could feel a significant difference in the front but still some in both the front shimmy and rear chatter. I hate to say 50% better but maybe. I also did the chalk mark across the tread and rolled it out of the garage and at both 26# and 22# the chalk mark faded consistently across the tread at both pressures......I'm surprised.

I just checked pressure after I rolled into the garage and F&R are 22# so I imagine they will be 20# or less in the morning when they cool. I am going to do 18# rear and 20# front and test. These pressures just scare the crap out of me because a few years ago our group of 25 Cobras from the SF area were on Highway 1 near Ft. Bragg....(a town ...not a military base). Highway 1 is twisty and rough. We, being a group of lunatics were hitting it pretty hard on these twisties and my car peeled the L.rear right off the bead of the wheel and Booooom...flat. Six hours later and two different tow trucks (car to low) I got it to a tire shop and they attempted to blow the tire back on the bead with one of those high pressure bottles. It went verrrrry close but not perfect on the bead. Good enough to get home though..That's why the thought of these low pressures scare me.......... But, I'll try anything at this point.

[wanab5150]

Hey #3170,

When I had the rears road force balanced one of them exceeded the 26# maximum which is for (I guess) any tire. The good one came out at 11# of force and the fronts were 6# and 8#.

The replacement for the rear came out high enough that they had to rotate it 180 degrees on the rim and it still came out at 17# of road force which satisfies the computer. I do wonder however if 25# of force is OK for my nearly 4000# tahoe or some 5000# truck, maybe 17# is way to much for my little 2400# Cobra......I would think that if 26# is max on anything, then half that (13) should be max for a car half the weight????

[Cobra #3170]

Originally Posted by wanab5150

Hey #3170,

When I had the rears road force balanced one of them exceeded the 26# maximum which is for (I guess) any tire. The good one came out at 11# of force and the fronts were 6# and 8#.

The replacement for the rear came out high enough that they had to rotate it 180 degrees on the rim and it still came out at 17# of road force which satisfies the computer. I do wonder however if 25# of force is OK for my nearly 4000# tahoe or some 5000# truck, maybe 17# is way to much for my little 2400# Cobra......I would think that if 26# is max on anything, then half that (13) should be max for a car half the weight????

Way too high you are correct lighter cars can tolerate less force variation looks like replacing high force variation tires is your best option.

[wanab5150]

Took the car to the shop and kidnapped the owner and made him go with me on a drive. he felt the whole mess front and rear issues and offered to swap them for either new Nitto's or something else......suggestions on different brand with good reputation.....or new set of Nitto's.

[spdbrake]

I installed M/T Street Comps 245/45R-17 & 315/35R-17 last year after removing the the 13 yr old F1s. I like em a lot.
Street Comp – Mickey Thompson Tires & Wheels

[PeteH]

Tom,
I'm having the same issues with Nitto's, and had them rebalanced, and, shimmy still exists, but different, at 70-75mph, however, on an F150 truck. I only have about 40K miles on them, and can't wait to get them off!

[wanab5150]

No shimmy....no shake?

[jhv48]

I seem to recall that your balancer should shoot for .012 or smaller for your combined wheel/tire runout. Anything bigger can cause problems for our cars.
Mine ended up with one at .012 and the other couldn't get any better than .015. Got rid of that damned vibration, so I'm happy.
And don't worry about running 20 lbs.of pressure in your front tires. The SPF manual recommends 18 lbs. for regular driving and 20-22 lbs. for sustained hiway driving.

[Bartruff1]

Originally Posted by spdbrake

I installed M/T Street Comps 245/45R-17 & 315/35R-17 last year after removing the the 13 yr old F1s. I like em a lot.
Street Comp – Mickey Thompson Tires & Wheels

When I was fighting the shimmy shakes on my SPF....

the tire guy emailed everyone he knew about the problem and THAT was the consensus....

get the micky t's ......I got rid of the car instead....

but the only thing that really helped was the 18 psi tire pressures ...

[vector1]

Good tires should easily be in the single digits on the road force machine. If not rotate them. I put some michelins on a rv and they were in the single digits, those big heavy wheels can make a mess if they don't balance out, vibrations in a rv can tear things up.

On my JBL which is sprung pretty soft, I had a vibration start around 80+mph, when I did some brake rotor work I had the rotors balanced, problem fixed.

I have a new Toyota truck with Bridgestone tires, they must be made with soft material, when it is cold they can flatspot easily, and the tread seems to squirm and will cause a shake until they warm up and round out.

Lower pressure might hide the problem but it is still there.


Food for thought.