I'm searching for information about what is an "unbalanceable"
tire, before I contact the company I bought my tires
from.

Just last Thursday 12-9, I had the Hunter 9700 GSP
Wheel Force Vibration System done on my '98 coupe. It
has just 30,000 miles on it. I installed a new set of
Firsestone R-Fs on new repro 2000-look chrome wheels
about 3 months ago. The company I bought the tires
from did the work. Anyway, after 3 months of an
annoying vibration - that I tried to have fixed at
another shop that did not have a Hunter system - I
took it last week to a frame & alignment shop here in
Indy that most sports car clubs in the area consider
the "Mayo Clinic" of chassis and wheel problems - the
Ferrari & Porsche clubs included. The shop owner - he
did the work, too - said ALL FOUR of my tires were out
of "spec", and none of them would ever balance on my
wheels. He said having more than two tires that could
not be balanced was very unusual, and he said "spec"
is a max of 16 pounds of force variation for ANY TIRE.
Ideally it should be at 10 or 12 pounds. He also also
checked each wheel and did not find one that was out
of round in any way. His shop is the only shop in the
area that can fix bent or out-of-round wheels without
sending them out, so I think he knows. Oh... they
don't sell tires so I doubt if there's an ulterior
motive.
They gave me the following pound variation for each
tire, before and after balancing:


before after
LF - 18 lb 18 lb
LR - 21 lb 21 lb
RF - 22 lb 22 lb
LR - 26 lb 20 lb

He started with the LR and when he could not get it
below 20 pounds, he told me it would be futile to try
the others because I would still feel a vibration with
just one that far above 16 spec. According to him,
about the most you can knock one down is about
six-pounds max.

My question is, what were the "pounds of force
variation" for the tires other members and were they able to be balanced?

The original stock wheels and Goodyears I replaced
NEVER had a vibration, of any sort... There's more to
this story and I will gladly tell it off-line, but
first I'm curious how other pound-variation numbers
looked. Anything anyone can tell me about their problems
will help clarify things for me.

Thanks!


'98 black / black coupe
(and it still looks as good as the day it left the
showroom floor - great car!)

 

Since they are runflats, I assume stock sized wheels/tires?

If so, (PITA I know but...) can the tires be mounted on your OE wheels to test?

Did they static (bubble) balance the tires alone and orient them correctly opposite the static balance of the wheel? This would have been the first thing to try. (mark heavy spot on tire and heavy spot on wheel and mount tires with the marks off 180 degrees).

Problem I see here, is the tire mfr is gonna blame the repro wheels, and in a case like this, I too would suspect the wheels first.
The wheels are supposedly fine, but doing both at once, you really don't know that for sure. Balance and out of round are 2 different things. Did they throw the wheels on the balancer alone and/or check for an axial runout too?

Lastly, did you remove the retaining clips off the 2 lug studs of each rotor? Most aftermarket wheels are not counterbored on the mountig surface to accomodate these clips like the oe wheels have. If you just bolt the wheels up w/o removing the clips, the wheels will not seat flat to the rotor hub, and could cause a vibration. Removing these clips is a must in any aftermarket wheel installation.

 

So have you gone to Firestone to see if they will stand by their warranty. This is not acceptable.

 

I feel for ya', man. I just struggled through a similar problem. Luckily the Hunter machine allowed the tech to fix a vibration problem I've had ever since putting the Kumhos on in August.

It is a PITA but if you still have the stock wheels I'd give them a try with the tires. Had to do this with my DD driver Maxima recently too; it helped isolate tires versus wheels quickly. You gotta hate it when you have problems with new tires on new wheels. Next time I'm ordering both from the same vendor..

Good luck!

 

Please go to http://www.hunterengineering.com
and research the h*ll out of balancing wheels and tires on their GSP 7000
mrgil
Great information there.
Go to the section "Under Car" There you will find special mounting, demounting the EMT Tires for Corvettes C4/C5
Regards and good luck
mrgil

 

They should be able to un-mount the tires and tell you if the new rims are true and balanced. If they are, then it's the tires. Most quality control measures would detect if a tire is out of round or balance, so I guess I'd agree that it's highly unusual for all 4 to have a problem - but...

Anyway, what's the name of the tire place? Would like it for reference in case I need something. I just live down the road from you..

Good luck...

JCR_Indy

 

they are called Tinnerman nuts.
mrgil

 

That machine (we have one ) also has the capabilities to "index" the tires.This is a procedure that will indicate where to mark the tire and remount it on the wheel to bring the "road force" down to an acceptible amount of lbs runout They may or may not have attempted that.18 lbs is out of limit and the machine can give you a printout stating so.Armend with this,you may have some recourse with the store you bought the tires from.You would be amazed at how many brand new tires fail a road force.

 

Had the wheels balanced today with the hunter machine. That thing is leps and bounds ahead of anything. Most places just throw weights on, the guys let me check out the machine and it was almost like ging to a clinic to learn how to use it. I am bringing in my daily driver this weekend because I was so impressed.

 

They indeed are impressive machines. I've used them twice on other vehicles where "standard" balancing would not solve a vibration issue. The first time they were able to remount the tire to get rid of the vibration. The second time they told me that they would not be able to get the assembly balanced. I took the tires back to the place I bought them and got a fairly sizeable discount on new tires.

I'm sure they are pricey machines but this ought to be the industry standard for any tire shop.

 

Does anyone know why Discount Tire doesn't use Hunter? Or is it just the Discount by me?

 

The people who did the balance should be able to give you a printout of the balance. Besides giving you the numbers on the tires it also gives you a number for the wheels and you should be able to use that information to get your money back. From the the numbers that you posted the first dealer actually balanced the tires the best they could. What I mean by that is, there is little variation between what the original numbers were and what they could be corrected to. I've had no problems with returning tires to the TireRack based upon printouts from the Hunter Machine. Good Luck!

 

I dont buy everything that your tire guy is telling you.The 16 lb limit for bad tires is an arbitrary number.Whether or not a higher number will be real life significant will depend on the particular vehicle,and how sensitive you are.I purchased a set of kumho runflats a few mos ago and the best tire is the same as your worst. The rest are significantly worse.I experience a slight vibration through the drivers seat and no steering wheel shake.I dont have another vette to compare mine to and I cant remember how the oem goodyears were since I was fixated on the godawful noise from them.BTW,I got areading from one or the rear oem goodyears and it was 22lbs.I have used the hunter machine on other vehicles and have never had a tire test as low as 16 lbs.If you are getting noticeable vibration with your readings you either have another source of the problem or you are extremely sensitive to vibrations.

 

BTW,the tech working with my tires said he contacted the hunter rep and they had no specific guidelines for what is acceptable with runflats.

 

John,

What you have encountered is excessive RADIAL FIRST HARMONIC FORCE VARIATION in your Firestone tires.

R1H cannot be corrected by balancing, no matter which machine you use.

If your tire store has a Hunter machine that can measure R1H, then they should do the following:

1) Remove the tires from the wheels

2) Using a 0.001 accuracy dial indicator, measure the individual bead seat runouts. Mark the low runout location on both beadseats.

3) Mount and inflate the tires.

4) Run them on the force variation mode of the Hunter. Record the amount and location of the R1H. If the level is below 8 lbs. you should be okay.

5) If the R1H is higher, deflate the tire and rotate it 90 degrees. Reinflate.

6) Run the Force Variation measurement again on the Hunter. Record the amount and location of the R1H. If the R1H value has changed, note the location and amount in relationship to the bead seat low runout locations.

What you are trying to do is to get the R1H high point of the tires to line up on the bead seat low runout locations. R1H can be lowered or eliminated by doing this MATCH MOUNTING exercise.

If, after MATCH MOUNTING you still have excessive R1H in the tire-wheel assembly, take the tires and the readings back to the tire store and tell them you want new tires with lower levels of R1H .

Merry Christmas everyone

 

John, Also do an Internet search for Hunter Balance to get to Hunter's Website. Once there you can see how the machine works and you'll see that it checks for runout on both the rims and tires and high points and makes recomendations for match mounting the tire to the rim.

 

What sorts of places would one expect to find a Hunter Machine? Discount Tire, likley nationwide, has just about taken over in the tire biz.

I'd like to know just for reference? DFW area.

 

Try this link and punch in your zip code:

http://128.242.141.111/pub/search/findgsp9700.cfm

 

Now THAT was impressive! They are all over the place. Must be 20 w/in 10 miles of me!

 

I had a set of 215-60-16 Falkens "match mounted" on a set of aftermarket rims for my wife's Lincoln LS, using the Hunter balancer. All four tires read under 10lbs. of road force. IIRC, the highest was 7 lbs.