QuestionHello Barry! Can you please tell me what the best form of wheel balancing is these days? And why do some shops split the weights and apply them on opposing sides? Looking for the latest, simplest, state-of-the-art method to get the shake out of my Audi once and for all. Thanks!
AnswerStu,
There are really two issues here:
Balance and Uniformity (You could call it "Out of Roundness" but "round" is only part of the problem.)
Let's start with balance:
When a rotating assembly is balanced, it appears that the weight is concentrated in one spot (not really, it just appears that way!), and weight is either added 180 degrees opposite the heavy spot, or weight is taken away at the heavy spot (either works, but it is easier to add weight when dealing with a tire and a rim.
If the "heavy spot" is off center, then the added weight has to be off center, too!
Many old timers will do a "Static" balance. This is sometimes called "Bubble" balance because you can use an apparatus that has a bubble to indicate the amount of weight to be added. It operates a lot like a bubble level, except in 2 dimensions. Hopefully when someone does static balancing, they will
split the weights inside to outside.
However, "Dynamic" balancing is the preferred method, and that requires a machine to spin the assembly. The machine will indicate where the weights must be placed - and they aren't usually in one spot.
I should point out that when we talk about balancing a tire, we are really talking about the rim, too!. I have seen brand new rims that were horribly out of balance - and out of round.
I should also point out that there are other things rotating - brake rotors, hubs, etc - and they also can be out of balance.
Most tire (and rim) balancing is done with the tire (and rim) off the vehicle. But it is best to do it on the vehicle so those other parts are also balanced. Unfortunately, on-the-car balance machines are pretty rare - and usually not needed - which is why they are rare.
But there is one more aspect - Uniformity. As I said earlier, the term "out of round" is used, but that isn't quite it, but it will do for now.
There are some "balance machines" that have a feature that can measure the uniformity. Sometimes the words "Road Force" are used to describe the process.
Far and away the most popular "Road Force" machine is the
Hunter GSP9700.
Here's their web site. Notice they have the ability to locate a machine by zip code.
http://www.gsp9700.com/
But there is one more thing: Off center mounting of the wheel.
This is common in aftermarket rims, where the center bore of the wheel is larger than stock and the wheel isn't using the hub to center itself. If this is your problem, you need a hub ring - and that's a complex subject that should be dealt with with someone who has access to data from wheel manufacturers - I don't!
I realize this is a lot of information, but I hope it is helpful.
