I belive this was also a response to the diffrent stresses placed on the rims based on tire type. Radial stress is greater that bias ply. Conversion s not reccomeded on the GMC's I belive because the wheels were not designed for any thing else. I have Radials on my wheels and they are steel. I also know that the GMC COOP has the ability to "true" the tire and rim assembly to eliminate the vibrations that can occur with the radials. Here was his repsonse to my inquiry regarding tire balancing from Jim Bounds at www.gmccoop.com.
"Dynamic balancing does not work especially on the GMC or other larger vehicles. This type of balancing tries to take into account the out of round tire in the balance process. The problem here is that trueness of the tire can never be compensated with balancing, those are 2 completely seperate issues.
The trueness of the tire and rim assembly can only be accomplished by truing the tire and rim together. There are tolenance issues in the tire and the rim and both must be addressed before you will have a smooth, friction free ride. So, you must true the tire on the rim before the unit is balanced.
There are 2 ways to true tires and rims: on the coach or on a machine. While truing tires & rims on the coach may take the drum and rotor into the equasion, you will be totally unable to rotate the tires at all. Usually, the drum , if all of the weights are still on, will not go out of balance. If weights that were welded onto the drum fall off I would suggest that the drum has much age on it and should be replaced. Cracked or damaged drums are a real hazard. Rotors almost never go out of balance, they are spun to balance them.
While truing tires & rims off of the coach does not take into account drums or rotors, machines that do this are MUCH more accurate than on the coach machines and will assure an absolutely perfectly right job if it is used properly. A bonus to a truing machine is that the tire & rim can then be static balanced on the machine when the truing is complete for a perfectly balanced unit at ANY speed, not just the 3 speeds a dynamic balance machine does.
I tell you now that this works every time, it is not snake oil and if a seasoned tire man is honest with you will tell you truing and static balancing will yield the best results. As George Zimmer says, "I guaranty it"!
As far as truing trailer tires, there is no problem there when using the machine I have and if the drum is damaged, I would always suggest replacing it before it hurts someone.
I charge $25 per tire which is very reasonable when you look at the process and what it does for the tire and your ride.
Trued and statically balanced tires:
1. run cooler (less friction) which means they are safer
2. will yield more mileage (longer life)
3. smoother ride.
4. less wear on suspension components.
Why would you not want all of those.
Truing tires off of the coach is more involved in that the tire must be lifted from weight in a hot state (actually all truing should be done with the tire as round as possible with the cords lined up. The tires must be removed from the vehicle, worked over then reinstalled but I tell you it is the best way.
On the coach truers are much easier but all wheels must be taken off of the ground while hot or the job is not precise. This is why I selected to do my jobs with the equipement I have. I am not knocking on the coach truers but I feel and can prove my method is more accurate.
Hope I did not bore you with my long winded dissertation but, as the other guys, I too am intent that truing must be done for a good ride."