When I go into local tire shops, I'm finding they have conflicting understanding of how to use the Hunter GSP9700 road force balancer. Some dealers are recommending a two step balancing procedure described below and others (including the Lexus dealer) only recommend step 2 be done and reserve step 1 only for when road force imbalance exceeds 20 lbs.

Step 1 is to have the Hunter analyze the runout of both the wheel and the tire to best compensate for assembly imperfections, variable tire stiffness and reducing the road force imbalance. After running the GSP9700, the operator makes a chalk mark on the outer sidewall of the tire and another on the wheel as directed by the GSP9700. He then deflates the tire, breaks the beads loose from the wheel, and rotates the tire on the wheel to align the two marks. Then he re-seats the beads, re-inflates the tire, and re-mounts the assembly on the GSP9700. They note that a "road force balance" has nothing to do with mounting weights on the wheel.

Step 2 is to weight balance the adjusted compensated tire/wheel assembly. Once the road force balance is completed in step 1, then the whole assembly is spun by the balancer with about 1400 lbs road force, its imbalance re-measured, and weights applied to correct the imbalance, in the usual manner. You gotta get 'em both right, and it takes a separate procedure for each one to do that.

They explain you can have a wheel/tire assembly that has significant road force imbalance, but is in perfect weight balance, and you can have a wheel/tire assembly that has significant weight imbalance, but is in perfect road force balance. Either condition can cause vibration that you can feel.

So when CL members say they got road force balance, did you get both steps done? Dealers charge separately for both steps. It costs about $150 for 4 tires for step 1 and about $100 for step 2.

 

Based on your definitions, I would say that my DT did this the last time (and I think they finally got it right) but honestly I think they try to do a quick impartial RFB on initial install to save money/time--that's why they put on my new wheels/tires in about one hour with a really busy garage on a Friday afternoon the first time.

The third time I went in and complained I noticed chalk marks on the tires and they took much longer to RFB it and had detailed % and used terms like runout, etc with me.

 

I went through training with a Hunter tech while Managing a "well known tire store". The easiest way I would explain the road force balancing to customers was to explain that even though both tire and wheel are round, they are not 360 degree perfect. So, the RF machine finds the low point in the tire and the high point in the wheel(or vice versa) and matches them together to make the best possible rolling circle. Theoretically it would be possible to balance a square block spinning on a regular balancer by adding or taking away weights, but that doesn't mean that it will roll smooth on a flat surface....
Pricing for this should be separated, regular balance which includes air check($0.00)...Then Road Force Balance, which includes all of the above plus the Force Variance test($00.00)

Hope this helps some guys...

 

Excellent explanation, you obviously paid attention throughout your training. Well Done

 

makinboost- - Great to hear from someone who knows how the machine works. What do you think of the Lexus dealers approach to take the wheel off the car and just weight balance the wheel/tire assembly with road force applied? Then only if the road force imbalance exceeds 20 lbs on the balanced wheel would they do step 1 and only on those tires that need it.