Gsp 9700

[RS84Syr]

I recently started getting some
vibration, and since I hadn't had the car
out for a few weeks (rainy season here
in CNY), thought it was flat spots.

Even after a 50 mile drive, it still
had some vibration. Read on this site
a few months back about the GSP 9700
wheel balancing, went to their site,
and turns out that my local shop has one.

Spun all 4 with new weights, and man
it is smooth again!!

Note from the shop was:
"Front tires are high on road force".
Guy in the shop could really explain what that
meant, but he did know it as a tire problem.
Tires are Goodyear Eagle GT - 255/50-VR16,
with about 10K miles.

Anyone knowwhat this means?

RS

 

[LarryBible]

Road force variation, if you stop and think about it, is the stiffness at different spots around the tire. As the stiffness varies it is measured and its position recorded. Thus the road force (stiffness) varies around the tire.

The GSP9700 is the only machine I know that can measure the road force, direct the operator exactly where to orient the tire on the wheel and use weights to offset some of the road force variation (stiff spot.)

This is not rocket science and ANYONE that is trained on the 9700 can understand it. I would be very suspect of a 9700 operator that does not understand it.

If a tire has more than about 16 pounds of road force variation, it will vibrate. This can be lowered, however, by breaking the tire bead and rotating the tire so that the stiff spot is at the lowest point (smallest radius) area of the rim. If he did not put the tire on the tire machine, break the bead and rotate the tire, he didn't do anything that could not have been on any decent computer balancer.

Most likely if the tires had been mounted and balanced correctly to begin with, you would not have had a problem. The correct way to mount a new tire is to orient the painted or stamped marking on the sidewall of the new tire with the valve stem of the wheel. The painted mark is the stiff spot of the tire, and the valve stem is put at the low spot of the rim. If you match these when mounting (which very few tire store yahoos bother with) and then dynamically balance the wheel with weights on an inboard and outboard plane, you will RARELY have any vibration at all.

The 9700 is a fabulous piece of technology, but as with many other items in the tire shop, there are too many people there that make minimum wage and they only have two concerns, quitting time and pay day. They couldn't care less about these simplest of steps that they could take to double or triple their number of satisfied customers.

There is more than you want to know about RFV on the GSP9700 website. This is at: www.gsp9700.com There is a technical section there with some .pdf's that go into great detail and explanation about this phenomenon.

Hope this helps,

 

[RS84Syr]

Thanks Larry.
Yeah the site has some info there.

The guy at the front desk really doesn't have a clue,
but the tech does. He should be in tomorrow.
He was gone when I picked up he car.

I basically am happy with the balance. It drives
a hundred time better. But, what caused it to
start acting up? What is the consequence of
high road force? On second drive, there is still
"some" vibration at cerain speeds, but not bad.

Was the problem caused by the initial installation
5 years ago? When will I need new tires? Is there
any danger with the current setup?

He said that sometimes tires come up with high
road force and they get replacements. Goodyear
don't play ball, but Cooper does.

Tires have about 10K.

RS

 

[LarryBible]

There is another factor in your case. You probably don't drive it everyday. Some tires are worse about flat spotting while parked. That could be what is causing you trouble.

Again, the 9700 is a great machine, but the operator has to be willing to do what the machine tells them to do, which in some cases means breaking the bead and rotating the tire.

If you put a Steinway Concert Grand in front of me I could make what, with a stretch of the term could be called music. If you put a true pianist at my old upright, you could have what anyone would call music.

It takes more than the right instrument to get good results.

Have a great day,

 

[RS84Syr]

Talked to one of the techs today.
He certainly knew his stuff, and agreed that
flat spots could definitely flag a road force problem.

Before I put it away for the long winter, I hope
to get it out and get the tires warmed up
to verify. I am confident in this shop based
on past history with other vehicles. Just gotta
get past the guy at the front desk.

Thanks Larry. You have you're own machine right?
Tech says that Goodyear bought these when they
first came out. Flagged so many tires as bad, they
say it's gotta be the machine. Sold them all.

Next set of tires for me in 10K????

That's all.

RS

 

[LarryBible]

Yes, I do have my own computer balancer, but not a 9700. They cost around $10,000, this is too rich for my home shop. I have a used Coats 1001 in great shape. This is a great machine for $800, but it does not measure road force or any of the other great things the 9700 does. For over 95% of tires, any properly working computer balancer, such as mine, is capable of doing a silk smooth balance. It is the tough cases like yours that requires it.

The tire companies were skeptical of the 9700 at first, thinking that it would point out bad tires. They have now learned that the 9700 helps them to reduce the number of rejected tires because the machine shows the operator how to reorient the tire to reduce the vibration. This was told to me by a regional manager with Hunter. I believe it.

In the case of Goodyear, their specialty tires such as the ones designed for our Vettes over the last 18 years are very good, but most of the Goodyear tires in their line are crap. They are finally starting to move toward radially sectioned molding methods, but they still make many tires in the ancient clam shell molds. These molds do not allow consistent placement of the belts.

Michelin pioneered the radially sectioned molds right after WWII. This makes for much more consistent belt placement in a radial tire, which drastically reduces the number of vibration prone tires. Because of the uniformity, a Michelin almost always requires very minimal added balancing weight. There are a few other brands that are moving very fast to radially sectioned mold construction. Continental is one of them, but they don't make Vette sizes.

Although Yokohama is not the best tire made, most of their tires are made with a radially sectioned mold and as a result usually balance with little added weight and run smoothly.

I'm glad your shop is paying the deserved attention to this much overlooked operation. IMHO the vast majority of tire stores give tire balance and proper mounting orientation very low attention.

I believe you can take most any brand tire, mount it on the rim with the paint mark oriented next to the valve stem and dynamically balance it with weights inboard AND outboard and have a smooth running tire. There will be exceptions, but if you follow this procedure, they will be rare.

This all gets to attitude and care on the part of the operator. It is not rocket science.

Good luck,