36 bucks for balancing two tires....

[ZebRuaj]

I share the sentiment that most of the in and out tire shops I've visited don't know how to utilize the fancy/pricey equipment they have in a road force balancer. It takes too much time or the techs are kids who don't know how to use it. Spin, place weights where computer tells em to, off the wheel comes.

They like having the honor of the label for those who might have any inclinations to give off the perceived confidence that their wheel/tire combo is getting the best balancing, but you're not.

 

[CapriRacer]

Perhaps I should explain what it means to "RoadForce Balance" a tire.

First, it is a bit of a misnomer, in that there is more going on than just balance. There is also measuring (and minimizing) Uniformity (Think "Runout" and you'll be close!)

A tire can have low Uniformity, and have bad balance - and vice versa. The 2 things are almost completely separate items.

What a RoadForce Machine does is apply a load to the tire and wheel assembly by way of a Load Wheel, then measure the variation in runout - followed by some math to get a high force value and location - and while that math is taking place, a spin balance is performed.

What comes out is a RoadForce value (in pounds-force), a location of the high point, and the location for balance weights.

If the Road Force value is too high (there are preset limits built into the machine - more on that below.), then the machine asks to have the wheel measured. After measuring the wheel, the machine does some more math and presents a value for the wheel, the location of the low point, a value for the tire, and the location of the high point. By reorienting the tire on the wheel, that assembly value can be minimized.

Please note: You can NOT correct bad uniformity using balance weights. (Not quite true, but close enough!)

And that is what the machine does. Please note that the term "RoadForce" is used by the maker of the RoadForce Balancer - Hunter Engineering - while the tire industry uses the term "Uniformity". There are other makers of balance equipment who also do these kinds of measurements and they use different terms

As can be seen, there is more involved than just slapping weights on.

Now onto some misinformation:

First, small, light cars are more sensitive to both balance and uniformity than large, heavy cars. So if you hear someone give a number that is "good", they need to specify what kind of vehicle that is for. Pickup trucks can tolerate more than cars. (and since it is more difficult to make larger tires, it is fortunate that that is true.)

Further, even within a group, there are overly sensitive vehicles. When I was working, there were some Cadillacs and Buicks that required very low uniformity. I don't know if they have fixed those vehicles or not. (It was in the design of the chassis.)

Another things is that the proper way to measure the wheel is with the tire OFF!!. Unfortunately, that requires a bit more time to perform (and thinking ahead), which is NOT something most tire busters do. So the measurement of the wheel is done in a location that might not yield a reliable value. This sometimes results in the tech thinking he has a good assembly when he doesn't (and vice versa!)

Further, the road surface is basically flat, but the load wheel is round. That means that the machine can give both false positive results and false negative results (False positive meaning the assembly has a larger value than what is measured.)

There are more things as well. but those are the highlights.

 

[CharBaby]

You are indeed the tire guru.

 

[JohnG]

Thank you for taking the time to explain this to those who have not had to deal with the Hunter machine. It is a very good general explanation of the process and clearly shows the difference from your typical spin balance that most people are familiar with.

I would like to elaborate on this one point:

Quote
Further, even within a group, there are overly sensitive vehicles. When I was working, there were some Cadillacs and Buicks that required very low uniformity. I don't know if they have fixed those vehicles or not. (It was in the design of the chassis.)


I've owned a couple of Cadillacs during that period. First was a 1999 STS and the other a 2008 DTS. Neither car was considered lightweight to my knowledge, but suffered from that uniformity issue.
My understanding is that the problem was due to how GM reduced unsprung weight by using cast aluminum suspension parts. This also enabled them to change the shock valving to give an exceptional ride.
They both rode very well as you can imagine.
More shock damping would have destroyed that ride, so we were in a catch 22 on tire balance. Those cars HAD to be BELOW 10# road force or the shake would be felt between 65 &72 mph.
Finally was able to convince my tire guy of all this and we both learned a lot from the experience.
One of his first comments in the process was "Even Jaguar only requires 14# RF!

 

[CapriRacer]

Originally Posted by JohnG
Thank you for taking the time to explain this to those who have not had to deal with the Hunter machine. It is a very good general explanation of the process and clearly shows the difference from your typical spin balance that most people are familiar with.

I would like to elaborate on this one point:

Quote
Further, even within a group, there are overly sensitive vehicles. When I was working, there were some Cadillacs and Buicks that required very low uniformity. I don't know if they have fixed those vehicles or not. (It was in the design of the chassis.)


I've owned a couple of Cadillacs during that period. First was a 1999 STS and the other a 2008 DTS. Neither car was considered lightweight to my knowledge, but suffered from that uniformity issue.
My understanding is that the problem was due to how GM reduced unsprung weight by using cast aluminum suspension parts. This also enabled them to change the shock valving to give an exceptional ride.
They both rode very well as you can imagine.
More shock damping would have destroyed that ride, so we were in a catch 22 on tire balance. Those cars HAD to be BELOW 10# road force or the shake would be felt between 65 &72 mph.
Finally was able to convince my tire guy of all this and we both learned a lot from the experience.
One of his first comments in the process was "Even Jaguar only requires 14# RF!



If I recall, the problem was that the resonant frequency of the chassis was near the resonant frequency of the suspension. That amplified the vibrations of any rotating component - not just the tires and wheels. I even had one where it was the brake rotors.

Someone proposed a fix by welding in a stiffening brace. This is HIGHLY outside the normal procedure and could only be implanted on a case by case basis at the dealership level, because no one in the GM corporate structure would authorize such a fix.

To make matters worse, GM was organized such that a fundamental change needed to be done to the chassis and that was the design guys job to do - BUT - the design guys NEVER worked on existing models - and the guys that worked on existing models weren't allowed to change the chassis. The good news is that this has changed.

 

[Traction]

Unfortunately even owning, and knowing how to use a road force balancer, sometimes there is nothing you can do to eliminate road force easily. I have a C5 Corvette and the front tires are over 35 pounds of road force, and it doesn't matter after trying over 4 different positions on both the wheels that are nearly perfectly round makes NO difference after spending lots of time trying. But, magically the car goes perfectly smooth down the road it seems mostly. I can't easily replace the Zo6 265/40-17 tires in the exact size, because there is basically nothing to pick from it that size for some reason. Probably because that was the only car to ever use that size. I would need to bend the wheels to make the road force to be in spec. The old cars of the past would run smoothly down a washboard road with bubble balanced bias ply tires! And back yo the OP, if you think $36 is too much to balance 2 tires, you should see what it cost to buy a RF balancer.

 

[Bighorn2500]

Belle was $30 plus tax to have one mounted and balanced when I carried a spare OE wheel and tire in to replace the factory donut spare.

 

[Traction]

I gave up on attempting to balance these tires, which are perfectly smooth at 45mph. These are the new Firestone 7.00-20 bias ply tires I recently bought that were $2000 for just 4 rear tires. They weigh like 120 pounds each.

 

[Rmay635703]

Originally Posted by Traction
I gave up on attempting to balance these tires, which are perfectly smooth at 45mph. These are the new Firestone 7.00-20 bias ply tires I recently bought that were $2000 for just 4 rear tires. They weigh like 120 pounds each.


That's nothing look up a 20r20 or 16r20 super single off road

 

[Zebra312]

Those prices are insane.

Last time I had carry in tires mounted and balanced at the local shop, I paid less than 60 for all four, mounted, balanced, new valve stems, and installed on the vehicle.

 

[CapriRacer]

Originally Posted by Zebra312
Those prices are insane.

Last time I had carry in tires mounted and balanced at the local shop, I paid less than 60 for all four, mounted, balanced, new valve stems, and installed on the vehicle.

That's $15.00 per assembly, but the OP was quoting $18.00 on a RoadForce machine and didn't specify what all was included.