Boy, do not know where you guys get these crazy ideas from, relative to
balancing tires. Truing the tire has nothing to do with static or dynamic
balancing. One can true the tire and after truing, it will almost always be
out of balance both statically(at rest) and dynamically (when being spun).
Some facts about balancing tires (in addition you can read GMC Motorhome
news Sept 1996, page 4):
1. Truing the tire is nothing more than shaving off the high spots of the
tread (part that hits the road), so it is as near to a perfect circle as you
can get. The density of the various parts of the tire due to the molding
process and the fact that the belts not being perfectly placed on the tire
etc ensure that it is probably still out of balance.
2. Static balancing locates the heavy spot on the tire and there are
several ways to do it. In the early days ,mechanics simply spun the tire on
a very loose bearing shaft several times and marking where the heavy part of
the tire stops at the bottom of the circle with a chalk mark, than randomly
affixed small weights to the rim so that the tire when spun, never stopped
at the same spot. To say the least it was a random process. Later a balance
point was used and the tire and rim were laid on it in a horizontal plane
and weights added to the rim so it was level. Static balancing is fine as
long as the tire never moves out of one plane, ie; when it hits a bump and
the tire moves up or down and the caster or camber change, it instantly
becomes out of balance dynamically.
3. The modern computer based spin balancer does the whole thing at the same
time, locating the heavy spots in the tire and computing the three
dimensional axis point that the weight or weights should be placed to
properly balance the tire, and than recomputing the exact place to locate a
weight on the outside and/or inside of the edge of the rim to perfectly
balance it. Once it is computer balanced it can be dismounted and remounted
numerous times, re spun and still hold balance.
4. If you find a tire shop that tells you that this is not true, than find
another that understands the engineering principles behind the modern spin
balancer. What they are really telling you is that they do not have the
correct equipment and training to properly do it. In fact I will always ask
the tire shop to balance one tire first, than remove it from the machine,
remount it and spin it up again. If it does not show perfect balance take
your business elsewhere because they are not capable of balancing GMC
motorhome wheels
4. The correct sequence of tire balancing is:
a. Truing
b. Computer spin balancing
Now for the Cinabar article, they recommend the Hoffman 40, 60, or 80
balancers with the promatch feature and the dualie mounting adapter. If you
want to know if there is a dealer in your area that has the Hoffman
balancers call 1-800-251-4500 and ask them for the name of a dealer in your
area.
Hope this helps clear up this very important point.
>>
>> Jim,
>>
>> I was at Golby's in April and asked about balancing tires. They said the
>> only way to balance large tires is to have them "trued". When they are
>> shaving the tire you think there goes 10,000 miles of rubber.
>> But it is only a small amount and will extend the mileage.
>>
>> However if you have them spin balanced off the coach their centering device
>> is not true to the tire wheel combination. For experimenting have them
>> spin balance and remove them from the balancer. Then have them reinstall
>> on the balancer again. You will note that the wheel tire combination is
>> out of balance again.
>>
>> Hope this helps for you decision making.
>>
>> Bob
>>
>> >Jim,
>> >
>> >I've ordered the Alcoa's and Bridgestone R273 tires. You mentioned a
>> >couple days back to find a truck service center to "true" them. I also
>> >spoke to Zeb Fradey who recommended an alignment center north of Atlanta
>> >that balances the tires on the motorhome.
>> >
>> >Now I've got too many options. Should I have NTB balance the
>> >tires at all after mounting or just take the mounted tires straight to
>> >the truck center for trueing? Is there any advantage of balancing the
>> >tires on the motorhome after or instead of trueing?
>> >
>> >I figured that I'd ask these questions on GMCnet as others will face
>> >them eventually too. BTW, the R265 number is still active and is
>> >apparently a slightly different tread design from the R273, but from the
>> >catalog pictures I couldn't tell any difference. Paul and I will have
>> >to compare tires at Marion this fall.
>> >
>> >Thanks,
>> >Patrick
>> >--
>> >Patrick Flowers
>> >Mailto
atri63
>> >
>> >The GMC Motorhome Page
>> >
http://www.gmcmotorhome.com
>> >
>> >
>You are very right, a spin balance will come up different every time.
>That is why the tire is "static balanced right on the truing machine.
>On this point Cliff & I agree, the tires must be trued & static balanced
>off of the coach! It takes an expensive machine but Cliff & I both have
>one.
>
>
>
