Fidanza has a good reputation for their aluminum flywheels and overall I don't see a lot of troubles with them. I don't want to bag on anyone's product. Personally I don't care for aluminum flywheels for a host of reasons. Most of these reasons are more in principle than common problems. I say this right up front so hopefully you don't get the wrong idea. I don't want to come off with make-believe scare tactics like someone else is trying to do here.

Here are some of the main reasons ACT perfers to manufacture only forged chrome-moly flywheels:

Chrome-moly is much stronger, harder, and resists fatigue better than aluminum. Chrome-moly can be heat treated to suit the need where aluminum cannot.
Chrome-moly is three times more rigid than aluminum (Youngs modulus of elasticity).
Chrome-moly can serve all purposes at the same time: friction surface, gear teeth, and structural all in one piece.
One piece flywheels can be machined perfectly flat. Bolted on steel inserts are never perfectly flat to begin with and they warp easily. The more fasteners used = the smaller the bumps will be between the bolts.
One piece design will transmit heat more evenly and effeciently from the disc than muliple pieces.
One piece design allows more liberty to machine to the most optimum shape.
One piece design prevents anything like ring gears, bolts, etc. from ever coming loose.
Thermal expansion rate of aluminum is much different than steel. One piece = one thermal expansion rate.
Threads, bolt surfaces and critical dimensions wear quickly in aluminum compared to chrome-moly.
Our flywheels are less likely to need resurfacing compared to the need to replace the insert on the multipiece equivilent. This is because the surface the disc is riding against is probably three times as thick as the typical insert and much harder.
Resurfacing is economical: When necessary, it cost half the price of an insert, and usually no shipping costs.
Chrome-moly steel has a higher coeffecient of friction than aluminum so it adheres to the crankshaft better. On high hp cars, the flywheel has more difficulty staying on.


The stock flywheel is a very good part for being stock. It is a bit thin IMO, but it is made of good material so it won't likely blow up like most stock flywheels. It is very light for a stock flywheel so buying a lighter one for better response is not a big deal.

Fidanza flywheels: Once again, I am not trying to dog them for being made out of aluminum. They didn't get their reputation by selling junk. I have seen a lot of lesser copy-cat companies that give aluminum flywheels a bad name by not paying attention to details and cutting corners.

Pro Street flywheel: I haven't measured it or tested it to see how it compares so I won't speculate.

We don't have a lot of stake in the EVO flywheel market yet since ours wont be out for a couple months but I don't like to see false information spread around. Coming direct from ACT, take it for what it's worth. I don't claim to be un-biased, but I wanted to give our perspective.

 

Very informative post ACTman!

 

Our customers have had excellent success with our Pro Street Chromoly flywheels, and it is definately one of the best EVO 8 combos when paired with an ACT Clutch.

 

I have over 5k miles on my ACT and Prostreet combo! Great results! I didnt wanted an aluminum flywheel because some of my friends already had bad experiences with fidanza aluminum flywheels on 3000GTs and DSMs, and my mechanic also didnt recommended aluminum or a flywheel that is too light!

My friend also bought the same combo on his 2003 EVO and we are very pleased with the results.

My vote is for the Prostreet!