Really matters how much torque you are putting to the wheels. Currently have 15K miles on the Fx350. Got 37K out of the ACT HDDS; Got 48K out of the stock clutch (0-12k Stock; 12K-18K Stage I protune; 18K-48K Stage II Protune). Another note on the OEM clutch. It never put immediate power donwn to the wheels. Always a "delay". It was fried when removed.
Reposting from this associated thread: http://legacygt.com/forums/showthrea...DS#post4663409
have the CM Fx350. It feels like OEM with super grip. Break in did take some time. It was more like 2000 miles, of which 500 was local stop and go. It is a very driveable clutch for every day with no problems holding the TQ. Has a feel much closer to OEM. I installed with a resurfaced flywheel; not next time. The extended period to break in may have been for the for the grip of the clutch material to adapt to the flywheel surface. Perhaps a better initial surface would have yielded better results. Also, it's not the mileage for break in, but the engagements.
ACT HDDS break in was much better. However, the engagement point was not as forgiving. Easy to smoke this clutch on hill if you were only trying to move the car a little and not launch it, say parking... Second, the pedal force was way way more than OEM.
Note: There is no standard for clutch TQ ratings. I can say the ACT HDSS had to have been at or near the TQ of my Stage II 5th gen. In pouring through posts, the Fx350 should be much greater than the TQ of the car.
Southbend has a good rep. It cost a bit more, and I could not find much info on it when I had to make a choice.
In the end, the evidence shows:
OEM clutch with no engine mods - Sucks
OEM clutch with Stage I - Oh crap this thing sucks and is getting on my nerves
OEM clutch with Stage II - OEM clutch, YOU ARE AN ABOMINATION. Take your high engagement point and shove it. Take your long drawn-out down engagement to put power on to the wheels and take a hike. I will gladly BURN YOUR MATERIAL TO THE RIVETS!!!
ACT HDDS - Cool, AWD burn outs! Quick engagement. Hmmm, left leg is building muscle mass. Engagement point is narrow and still high. Easy to smoke this clutch.
CM Fx350 - Excellent holding power. Quicker to transfer power to the wheels than the ACT. Enjoying the lower engagement point with OEM-like pedal pressure. Much easier to engage the clutch. Break-in is a BITCH. It just takes longer. I even planned a 1000 mile trip to try and accelerate break in. If you don't drive a lot, then the time to break this clutch in will destroy you. The materials is so grippy, it sends the drive train and car into a judder; must depress the clutch and start again. Some of it is relearning. Just 100 more RPM over the ACT and engagement was much smoother.
Overall, I drive more so the Fx350 break in period, although aggravating, was bearable. IMHO, the Fx350 has been far superior. Got about 6K miles on the clutch now and it's all good.