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The Hummer Knowledge Base

Tires & Wheels/Balancing/Centramatic Wheel Balancer:

> Can someone describe what a Centramatic Wheel balancer is?? I've seen a
> few posts referring to it but I don't have a clue. Thanks.

It is a (galvanized steel, I think) tube bent in a circle with 20 oz. of lead BB shot sealed inside. Welded to a flat round plate, which is then drilled for the bolt pattern of the Hummer and other trucks. It fits between the wheel and the hub. The tube of shot is then located just inside the inner half of the wheel rim. The shot rolls to a position in the tube that will counter balance any imbalance in the wheel/tire.


> >The idea of spending almost $500 was not easy, and just
> >how well they worked I was not 100% sure about. After shopping around,
> >I found only two places to get them from, Centramatic (the mfg. of the
> >item here in Texas) and Stinger Accessories.
> Doesn't Terry at American Hummer Supply carry these?? If he does, his
> prices are usually better than Stinger.
> Also on the Centramatic note: Typical spin balancing involves weights
> being put on the outside AND the inside of the rim for balancing. What
> effect do the Centramatics have on this set-up and can't the wheel still
> get out of balance in the inside/outside dimensions?? Where are the
> physics majors out there??

I got mine from Terry @ American. They were a little bit less expensive than Stinger.

The computer spin balancing does, indeed, place two weights: one on the outside rim, one on the inside. I believe that this is to locate the effective center of the "net weight" near the center if the wheel. The Centramatic sits inside the wheel, closer to the center of the wheel. It should, therefore, be more effective than weights on either the inside or the outside, but not as good as weight at the exact center.

The Centramatic instructions specifically state that the tire/wheel should be balanced before being placed on the vehicle. The Centramatic can only overcome a limited off-balance problem (about 12 oz, I think).

Other opinions?

Dave Breggin
'95 Diesel Wagon

> The center of the rim is about where the Centramatic balancer are
>located. But, inside and outside weights are mounted on the edge for
>easy installation, would be a little harder for the every day garage to
>install weights in the center of the rim, True ?

The difference is Static VS. Dynamic. Your shop manual gives a good description of both these kinds of balance. Static is the wheel/tire bouncing up and down (the shakes) the kind of balance job a bubble balancer does.

The second is Dynamic (The Best) where a computer spins the wheel/tire and identifies the out of balance points on the inside and the outside of the wheel/tire. Dynamic corrects for the bouncing up and down, and the side to side (wobble) of the wheel/tire which is most detected by the shimmy in your steering wheel (that fast right to left shake in your steering wheel). Hummer wheels are wide. Imagine a barrel rolling down a hill, when it is not in dynamic balance (i.e.,. both ends in balance) it will develop a wobble and almost stand back upright, while rolling down the hill.

The Centramatics mainly fix the static problem, and a tiny bit of the dynamic problem, however it is not that magic bullet to all of your balancing problems. That's why they say to keep the existing weights on the wheel.

I had a set, and put them on/off my vehicle about 10 times testing them. What I found is that the Centramatics actually put in a shake at about 45mph and continued to 65mph. The verdict in my case was that my truck rode much smoother without the Centramatics. Another factor that may cause this result for me was the fact that my wheels were all trued (cut perfectly round). I have a very good truck tire center here in Pensacola, who does all the Guard tires for their HMMWVs including runflat installation etc. They have a great method of balancing wheels with CTI.

Another important factor, is to make sure you have the CORRECT type and quantity (flat and lockwashers) washers that fasten the CTI cover plate to your wheel. The CTI cover's center of balance is actually .5 in. away from the center of the wheel (really, next time you have your plate off, balance it with a flat screwdriver and see), so it is important to have all the correct hardware on the wheel to ensure that plate is somewhat center balanced. My truck is in great balance at all speeds without the balancers, I returned the centramatics and got my money back.

'95 383 Green DW

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