Hunter Wheel Force System

[jseni]

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

Just last Thursday 12-9, I had the Hunter 9700 GSP
Wheel Force Vibration System performed 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 "pounds of force variation" numbers have others seen, and were the tires 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 anyone elses pound-variation numbers
look. Anything 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!)

 

[jwilliams]

jseni, I have a few questions for you. I am a tire dealer, happen to handle firestone as one of my lines. Anyway, did the shop w/ the hunter say how much weight each tire itself needed? (not the road force variance) Has anyone checked your rotors for those little push on speed nuts on the wheel studs? (keeps rotor on hub during assembly) These can cause runout on wheel when mounted to hub on aftermarket wheels. Saw it happen on an '03 Z06. To answer your question, none of the tire manufacturers recognize the hunter dsp balancer as a means to itself to deem a tire "bad" or subject to warranty adjustment. There are no guidelines that I am aware of from Bridgestone/Firestone, Michelin, or Goodyear for the type of measurement you ask about. It does not sound as though you went back to the shop that sold the tires and wheels to you? This shop will be asked by Firestone to diagnose your problem and that means letting them work with the tires and wheels, etc. I can tell you that it will take A LOT of lobbying by the selling dealer to convince firestone that all four tire are bad. If they mention "road force variance" as the cause I doubt you'll get the tires warrantied. Sadly tire shops usually won't warranty tires they did not sell. Why you ask? Because the manufacturers do not treat us well on warranty. Long story. It sounds like it's gonna take a fair bit of time to diagnose your problem(s). Unfortunately if you can't get the selling dealer to work with you, you may have to pay another dealer to diagnose. Firestone will not reimburse dealers for time or labor to diagnose, dismount, mount, balance tires under warranty, thus the reluctance of other dealers to get involved. I would also suggest a call to Firestone customer service and/or visit a corporate owned firestone store. Whatever you do you'll have to be persistant cuz it's gonna be hard to get 4 tires warrantied. Feel free to PM or email me if you like.

Jay

 

[froggy47]

I had a bad Kumho on that machine was about 18 lbs. My (Discount tire) guy said he sends any tire back that is more than 12 to 14 lbs out.


Tire Rack had no problem taking the Kumho back. A new one balanced perfect with a couple of ounces max.

The load force machine detects the problem of stiff/soft sidewall - especially in high performance tires. A tire can be the proper "weight" all around but have a problem in stiff/soft sidewall that cannot be "balanced out"

Don't have much use for Firestone in any event, although some guys swear by the Firehawk.

Good luck

 

[c4c5specialist]

Hi there,
Your road force variation psi are NOT out of characteristic for standard passenger car tires.
Every major tire manufacturer will tell you that about 25 lbs is acceptable. And I have never had a tire create a vibration with less than 25 lbs of road force variation.
We use the updated GSP 9700 in our dealership and this machine is the best there is for detecting problems.
Might I suggest a few things.
First, your rims or tires could have lateral runout, meaning NOT up and down away from the spindle center, but left to right.
I would suggest that the lateral runout of the rims, tires and the spindles themselves be inspected.
Make sure that your brakes are NOT pulsing when you push on the brake pedal.
Are any of your shocks leaking, or do you have a broken sway bar end link???
My theory is you will find your problem there.
All these things can create your condition.
Allthebest, c4c5