Flywheel Identification Help

[ClayW]

What is the source of the light flywheel, and can I use it on my M30?

I pulled the dark one off the 88 535i M30. The light one came from a mystery parts stash. The flange-to-clutch face dimensions are are identical, and the starter gear rings are the same. All the bolt holes and dowels match.

The lighter one is lighter and has less material.

Does anyone know what the lighter one is from? Any reason why I can’t use it?

 

[HB Chris]

I wouldn’t use a flywheel with that much difference between the back of the flywheel and the crank, the one on the left will stand off too much.

 

[ClayW]

I wouldn’t use a flywheel with that much difference between the back of the flywheel and the crank, the one on the left will stand off too much.

That picture is deceptive. That's the back side of the flywheel, but the crank mating surface is on a different plane.

I measured the crank mating surface to the clutch surface on each, and they are within 0.4mm of each other.

 

[HB Chris]

It may be the pic but if thickness is that close it appears teeth won’t be in correct location. I regret lightening my flywheel, I would rather have a smoother idle.

 

[rsporsche]

the back side mounting point looks higher (more raised) than the one on the right. at first i thought that perhaps somebody just machined down the outer ring on the left one ... but it seems to me that the basics are different