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Balancing main wheel pants

Balancing wheel pants shouldn't be necessary. Many years ago some of the "Yankee" owners balanced their nose wheel pant to reduce shimmy. If you have a shimmy, you should address the cause of the shimmy rather than try to dampen it.
 
I balanced the wheelpants on my airplane before its first flight, so can't tell you anything about how it would behave without the balanced pants.

What I can tell you is that despite the balanced pants, the gear will shimmy if the tires are out of balance or out of round. A new, high quality pair of tires will completely eliminate shimmey from my airplane for 100 hours or so.

My experience is that cheap tires will shimmey "out of the box"...
 
My experience was just the opposite - no shimmy with the cheapo Van's tires, shimmy with both sets of new Michelins at 23 knots. The frequency is the square root of k/m, where k is the spring constant and m is the mass. The amplitude depends on excitation (rolling imbalances, out of round, etc.) and damping (lower air pressure).

I balanced my main wheel fairings to try to minimize twisting forces (about the axle) when rolling over rough ground.
 
Balancing Wheel Pants

My RV-4 operates of roughish grass strip, and with Mk1 wheel pants and mounting system I could not keep them tight. I balanced with some wheel nuts epoxied in the nose of the pant to eliminate the secondary twisting moment about the mounting scews. It seems to work.
 
I'd say add it later if you need it. I didn't balance my pants, and never had shimmy so never needed to go back add lead.
 
its not done to prevent shimmy but to keep torsion loads from tearing up the mounting points when the wheel bounces up and down on rough ground. It will make the pants last much longer on grass.
 
The original reason was shimmy dampening

Rick of Austin said:
its not done to prevent shimmy but to keep torsion loads from tearing up the mounting points when the wheel bounces up and down on rough ground. It will make the pants last much longer on grass.
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May be true in theory Rick but the original reason to "mass balance" the pants is similar to balancing the elevator and ailerons, to keep it from shimming, a mechanical version of the aerodynamic flutter if you will.

I like kevinh's advice, leave it off than add later. It does add weight.
 
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