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Kevin Butler · **Posted:** Sat May 03, 2008 10:00 am

Which do you think is more important. Clamping force or pad material coefficient of friction?

I'm split between the following 2 ACT clutches

ZM2 XTSS which provides 72% increase in clamping force with a standard single surface organic pad disk, rated at 307 ft-lb

ZM2 HDG6 which provides 33% increase in clamping force with a spring centered 6 puck ceramic pad disk, rated at 298 ft-lb

The ZM2 HDG6 can be had for about $100 bucks less than the other model.

I'm thinking the springloaded 6 puck disk wouldn't chatter.

Which one do you think would last longer for a track application? I'm currently putting out over 200 RWHP/175 ft-lb and will probably be increased by 50% within the next 12 months.

MarcusMcRae · **Posted:** Sat May 03, 2008 1:24 pm

From what I have learned in my search for a new clutch, the ceramic variety are supposed to hold up well to abuse but get really grabby as they heat up.

Ryan Holton · **Posted:** Sat May 03, 2008 2:20 pm

I have always been told to just say no to puck clutches.

Karl Shultz · **Posted:** Sat May 03, 2008 2:49 pm

Kevin, from my experience, you don't want one of those puck type clutches. The drivability is just horrible.

The thing is only making what, about 200hp, right? I can't imagine needing anything more than whatever ACT is calling their "street performance" clutch these days. Which I actually liked quite a lot - bought one of those two times for the Acura.

JamesFeinberg · **Posted:** Sat May 03, 2008 5:26 pm

That Star clutch I mentioned in your other thread was one of the puck-type clutches. It had plenty of holding power and never slipped once even when pushing 270+rwtq through it but I hated it and wouldn't buy one again for any car that sees street use. If it was a track-only car, it probably wouldn't be that bad but it can take awhile to learn to make smooth shifts with it.

Jim

Kevin Butler · **Posted:** Mon May 05, 2008 3:24 pm

I believe I have answered my own question after considering what I've experienced to date.

The Spec Stage 2+ clutch was a low clamping force, high friction type of unit. The high friction material wore in an accelerated fashion due to lower clamping force.

So this time I'm going with high clamping force and a more standard friction rate. After a little more thought, I believe that a higher friction disk will result in shorter flywheel surface life.

I think that also explains why the ZM2 XTSS(high clamping force, std friction rate) is $100 more than the ZM2 HDG6.

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