As I've always got a more precise wheel balance by balancing on the car compared
with any off-car balancing, there must be some reason it's better. I also don't
believe it's anything to do with the balance of the disc etc, so all that leaves
is centering. The off-car balancing machines I've seen all centre the wheel on
the single hole in the middle of the wheel, but on the car the wheel studs/nuts
are used. You would only need a very small difference in the centering to throw
a good bit of weight to one side.
A very rough calculation on a 24" diameter wheel/tyre weighing 16kg shows that a
10 thou (0.25mm) error in the centering would need 7g added to balance it out.
That's the typical level of error I've seen between the 2 methods of balancing
coincidentally. Any dents in the wheel centre could give a bigger error than
this.
The other problem I've seen is operators doing the balancing correctly on the
machine, getting the weight and just wacking it on the wheel in the rough area
indicated; the weight needs to be within 1cm of the correct place in my
experience on a car that's fussy about balance, and there's no way a lot of
operators take the care to get it right, but this would be the same for off-car
and on-car balancing.
Post by Dave Plowman (News)Post by RobAnyone know anywhere in Hampshire (preferably in south hampshire) that
can do on car wheel balancing?
Can I ask why? The chances of the hub and disc assembly being far enough
out to cause problems are remote, and the only way to accurately balance a
wheel/tyre combination is off the car.
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