Balance a flywheel after machining?

NYSpeed Automotive
1

Had some extra machining done on my Miata flywheel when I dropped it off to be resurfaced- milled off about 3lbs worth of a raised ring near the outside rim of the motor side.

The shop says that because they removed mass uniformly from the whole surface that it shouldn’t need to be balanced.

Thinking, just to be safe, maybe I should have them balance it anyway. They don’t mind doing it, they just don’t think it’s necessary.

Basically it’s their professional opinion vs. my anxiety about exploding flywheels. Cost for yielding to paranoia (getting it balanced) is like $90 and probably an extra week to get it back.

Thoughts?

2

you said it, their pro opinion vs your fear.

IMO, $90 is cheap insurance tho.

3

As long as they didn’t remove any material where a balance hole was, it won’t need rebalancing.

4

Is the engine externally balanced or internally balanced.

5

Internally.