We're talking a Factor of Safety of 200! The kind of heat and load that the flywheel typically experiences will not damage it.

Citing OEM's use of materials is a red herring. OEM's typically use a cast iron flywheel (not chromoly) for cost reasons, it's cheaper and easier to manufacture than a multi-piece Al flywheel.

Your primary reason for not recommending an Al flywheel is actually not directly related to aluminum vs steel, but to weight. If you were to leave out those last two sentences ("Buy a chromoly flywheel. I wouldn't recommend aluminum"), all would be good in the world.

 

The dissimilar metals comment from B had to do with corrosion, not performance.

The quip from me about coming apart has to do with any cracks or defects in the material, or in how the multiple pieces are joined, spinning at 9k rpm.

An 8lb AL flywheel weighs the same as an 8lb chromoly one. I'd much rather have a one piece flywheel.

But there is a difference between discussing the pros and cons of flywheels made of this material or that with someone that has already studied it and made an educated choice, compared to advising someone that is doesn't know much about flywheels and doesn't really want to, and just wants to make a reasonable choice.

 

Whatever corrosion the dissimilar metals may cause does not affect performance, strength, or even servicing. It's a moot point.

There can be cracks or defects whether the material is steel or aluminum. The relatively lightweight steel insert is joined to the Al flywheel with a bunch of high-strength bolts. They're not coming apart.

The point here is, choose your flywheel based on weight rather than fixating on the material it's made out of. You can advise the uninitiated all you want but at least give them valid advice, and not spread rumors of the perceived dangers of Aluminum flywheels. From what I gather, the pertinent advice here is don't go too light unless you know what you're in for.