I have some vibration at a specific speed (most around 65 mph, some above ) in spite of my tires have been balanced several times. Last night I looked up the specs of some tire balancers, and the few that had their working RPM listed were quite low like 280 rpm, which would translate to about 24 - 25 mph with my tires. Since I can't feel anything up to 55 mph or so, it 's very possible that a relatively low RPM balancer won't find find anything wrong with my tires either.

Is there a balancer that can be set to do balancing at a specific RPM (754 - 755 in my case); or even better, do a sweep over a certain range like 700 to 800 RPM to find out if something is wrong with a tire? Note, I've sent an email to Hunter asking about the RPM range of their balancers, but I have yet to receive a reply from them.

TIA

 

Big truck suspension shops usualy have a balancer that balances the tire & wheel on the truck & they will work on pickups. Try a local shop/dealer.

 

It took them almost a week, but eventually I did get a reply from Hunter engineering:

With regards to our GSP9712 Road Force Measurement System:

(1) The balance cycle is between 300-330 rpm depending on the software.

(2) The runout and force measurement is 90 rpm.

(3) We can rotate the wheel at virtually any speed, direction or torque.
The drive is programmable.

 

I had the same problem with another truck. The tire shop spun them up on their machine, balanced dead on, but I still got a high speed vibration. Checked all the front end components, dead on. Took it to a race shop, balanced them on the vehicle, took care of the problem. It could be a bad rotor, axle, drum out of balance, etc.
Good Luck!

 

what size tires are we talking about?

 

Hmmm, never thought about a race shop. I called a few places around here, and none of them do on-vehicle balancing. The tires are only LT235/75R15, so they aren't that big.

 

The only balancers that would require rotating the tire at highway speed would be the old fashion on car balancers. Those balancers will only give you a static balance because they only add weights on the outside of the wheel. A clever and experienced operator might experiment with weights inside and outside, but that would be VERY time consuming and involve LOTS of guesswork.

Any computer spin balancer in good operating condition is capable of giving a proper balance with only moderate operator skill. The key is operator ATTITUDE. I could teach a 12 year old how to do a proper balance on a computer balancer in 30 minutes. After that it is a matter of that 12 year old WANTING to do a proper balance.

The balance speed of one of these machines is low so that the computer can resolve the imbalance. If the balance is done correctly, you will NOT have an imbalance at ANY speed that is due to wheel imbalance. If you then have a vibration, harmonic or otherwise, it will either be due to excessive Road Force Variation(RFV) or loose wheel bearings or steering/suspension components.

You can easily and quickly find the GSP97XX machine nearest you by going to: www.gsp9700.com There is also lots of educational data on that site for your study. The GSP Hunter machine not only checks balance but also uses a pressure wheel to analyze RFV to see if there are stiff spots in the tire. It also takes into account tire vs. wheel relationship.

With a competent operator, if the GSP says that your wheel is balanced and has acceptable RFV and you STILL have a vibration, it is NOT due to the wheel/tire. Again you would have to look at wheel bearings and steering/suspension components.

Don't be fooled by the fact that these machines do their analysis at a low speed. A balanced tire/wheel is a balanced tire/wheel regardless of speed. Also if it is imbalance or a stiff spot in the tire, it will show up at all speeds, not a specific speed.

If you have vibration at a specific speed, start checking suspension/steering/bearing components.

Best of luck and hope this helps,
Doc
ASE Master