Balancing wheels

[jonno]

How do teams balance wheels if on a custom stud pattern (pcd of 81mm)? Most tyre balancing machines go off the 2" hole in the middle of wheels, but this will pretty much go to our stud holes. Other than knocking up[ an adapter with the 2" hole on one end and the studs on the other, how can we balance our wheels?

[markocosic]

Do they /need/ balancing? Most of your comp is <60mph isn't it?

[Denny Trimble]

That's correct Mark, we get up to about 70 in the acceleration event, and maybe 60mph in autocross and endurance.

We haven't ever balanced our wheels.

[jonno]

Cheers guys, we didn't think the speeds would require it, but it's reassuring to have it confirmed by others

[ben]

I wouldn't worry as others have pointed out. However if you do want to do it manually you can set the wheel spinning on a stand leave it to settle and add weight to the top of the wheel until it doesn't rotate freely when rotated to a different angle. Can take as little as a minute if the person has good experience of how much much weight to add by looking at the angular speed of the unbalanced wheel.

Ben

[Z]

Here is another easy "old-fashioned" way to balance wheels.

Make a "plug" that fits snuggly in the centre-hole of the wheel mounting flange. Machine (or drill) a V-shaped pocket in the centre of this plug. Mount the wheel and plug horizontally (ie. with "axle" vertical) on a sharp pointed vertical "needle".

If the wheel is unbalanced it won't stay horizontal, so add balance weights until it does!

A hardened steel needle and plug are best - minimum radius on the needle point and V-shaped hole (which together make a spherical joint) gives minimum friction. A "bullseye" type bubble level fitted to the top of the plug makes checking level easier.

This method is very quick and accurate but it only does static balance, not dynamic balance (ie. should be good enough in FSAE, as noted above).


Z

PS. Make the plug so that the needle point has a small axial "offset" (~1" or 2cm) from the geometric centre of the wheel. Too big an offset and you lose accuracy. Too small an offset and you will never get the wheel level (ie. too sensitive/accurate)!