Inside ACT clutches

Industry Insider: Inside ACT clutches

By Mike Kojima, photos by Jeff Naeyaert

We have been familiar with the ACT clutch line for many years.  One of the race cars in the MotoIQ stable has been running an ACT clutch for the last 7 years which is probably over 20,000 racing miles with no problems at all.  This is real racing mileage on a track, punishing use probably 5 times tougher than street driving. Perhaps the motorsport that is the hardest on clutches is drifting. Our friends on the Formula D circuit Joon Mang and Tanner Foust use off the shelf ACT clutches in the brutal, abusive clutch kicking world of Pro Drifting. For street use, ACT clutches are known to be great at holding torque with good smoothness and light pedal effort.

Before reading this article, you might want to learn how clutches work, you can read all about how they function here!

Clutch tech part 1

Part 2

Part 3

Part 4

Inside ACT clutches

Ever wonder how a high performance clutch is made?  Do you think that some high performance clutches on the market are simply existing parts from other applications sprayed a different color?  Do you want to see the inner workings of a true performance clutch company?  Well follow us and see.

Inside ACT clutches 
 Stacks of received and inspected pressure plate covers await a trip to the powder coaters.

We recently visited ACT on a fact finding mission to see exactly how they make their line of excellent clutches.  We got a tour of the plant and engineering department and were quite impressed with their processes and capabilities.  The first thing we noted is that ACT has a Quality Assurance department.  Although this is common in the OEM manufacturing world, it is pretty unusual for an aftermarket performance parts company. 

 Inside ACT clutches
 Pressure rings await assembly into pressure plates on the production floor.

ACT's philosophy is that a higher quality part actually improves profitably and poor quality costs money.  The quality department analyzes warranty issues and feeds back information on every single failure to help improve the product.  Often this results in an immediate design change and improvement to a line of clutches. Since ACT is a small company, these changes can be integrated quickly into production.

 Inside ACT clutches
 Diaphram springs in stock await assembly .


Inside ACT clutches
Semi metallic friction material sits in inventory waiting to be riveted to clutch discs.
Inside ACT clutches
 Lightweight flywheels are ready for shipping.


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Thursday, September 23, 2010 5:35 PM
Very cool to see how there growing an doing things.
Thursday, September 23, 2010 8:00 PM
Very cool to know ACT balances their components. I always wondered if clutch companies did this... now I know that ACT does.

I had an ACT on my turbo Nissan SE-R back in the day. It lasted 80k miles with a 100-200 drag strip passes, a couple dozen auto-x's, and a couple tracks days thrown in. Great product!
Friday, September 24, 2010 5:38 AM
Hmm, I may never go back to Exedy again. Neat article, time to brush up on my clutch tech!
Friday, September 24, 2010 12:30 PM
All this technology and they still can't get a single plate evo clutch to shift at 8k rpms....
Mike Kojima
Mike Kojimalink
Friday, September 24, 2010 1:39 PM
Is this EVO's in general or your car? EVO's have a bleed orifice in the clutch hydraulics that sometimes hampers fast shifting. Also an improperly adjusted pedal can cause overcentering which hampers shifting seriously.
Friday, September 24, 2010 3:32 PM
I love articles like this. Pretty much made my mind up to get an ACT clutch for the next replacement in my S2000.
Friday, September 24, 2010 5:12 PM
Ah yes, I forgot about that stupid bleed orfice. The first mod I made to both of my Evo's was taking that thing out.
Friday, September 24, 2010 6:27 PM
The S2000 has the bleed orfice on the AP2's also. It's annoying as hell because the clutch slips badly on the upper gear shifts. I really have to baby the shifts on the 3-4 and 4-5 shifts. It would undoubtably slip on the 5-6 shift too, except I haven't gone that face on a road course yet.

I might take it out when I change out the clutch.

As for ACT clutches on Evos, I've never heard of this issue of shifting at 8k with it, and I've known quite a few guys with ACT clutches in their Evos.
Friday, September 24, 2010 6:28 PM
edit: face = fast in previous post. And for those unfamiliar with S2000 speak, AP2 is the second generation starting with the 2004 model year.
Matt Dennison
Matt Dennisonlink
Saturday, September 25, 2010 9:12 AM
I've been rocking my ACT HDSS since I hit 15k miles making 320-400awtq on my Evo... now with 68k and plenty of track days and daily driver miles to make a weekend warrior jealous, its still kicking strong...!
Saturday, September 25, 2010 9:55 AM
Mike it was at one point an issue I had with the clutch, regardless of pedal adjustment I could never get my mb7-HDSS to shift properly at high RPMS.

Mike where is the bleed orifice that you are referring too, was never aware that they had such a setup in the hydraulic system?

spdracerut, you are on evom, how have you not seen a lockout thread on there yet?

Mike Kojima
Mike Kojimalink
Saturday, September 25, 2010 4:33 PM
It's in the clutch MC. Removing it is a common trick that some EVO guys swear by. I left it in because I don't want to break my tranny and I am not really a drag racer. I do have to be careful with my high RPM shifts because it slips if I shift too fast. It might grind too.

Did you talk to ACT? They have a pretty good tech line and are pretty proactive in addressing issues with there clutches, especially if it's a common problem.

We will be putting an ACT single disc in our project evo IX soon so if we have issues we will report on it.
Saturday, September 25, 2010 6:59 PM
Mike it's a pretty well known issue with the Street disk offerings from ACT in the evo world, I am not a drag racer either most of the time I spend in my evo is on the road course or street but when you want to try to bang the lower gears it really hates high RPM shifts.

If you could reference a How-to or picture of what exactly is done to modify the MC i would be interested. So many clutch fix issues with this car whether it be pertaining to keeping the TOB in place, stopping the for from moving too far etc etc...
Saturday, September 25, 2010 9:17 PM
@Evo2nr, because I was still on the stock clutch on my Evo :)

I did a quick search on Evom about the issue. I found three catagories of guys: guys that don't have the issue, guys that due have the issue, and guys that had the issue but fixed it with a clutch adjustment.

As for the bleed orfice, Mitsu and Honda put them in so that even if the driver dropped the clutch on a launch, it still slowed the release of the clutch which prevented shocking the drivetrain to death.

If the lockout is clutch related, the only thing I can think of is that the clutch does not release completely. Why would this be any different at higher rpm vs lower rpm? Well, I know some clutches use the weighted fingers to increase the clamp load out higher rpms. I don't know if ACT does that, but perhaps that's the issue and why a slight clutch adjustment can help.

I do know that Ryan Gates, on his Evo X, stated that the stock synchros did not like shifting at high rpms; I think 8500 rpms +. So he went with a dog box tranny IIRC.

So I guess there are three main variables that can cause the lockout: improper clutch adjustment, improper tranny fluid (changed at the same time as the clutch) preventing proper synchro operation, or just a limitation in the design of the tranny itself.
Saturday, September 25, 2010 9:24 PM
Here's a link describing the removal of the clutch restrictor pill:

I use to reference www.evomoto.com for some install stuff too. There's an article on going to a braided clutch line and removing the restrictor pill
Street Surgeon
Street Surgeonlink
Tuesday, September 28, 2010 5:49 AM
I remember back in the early to mid 2000’s there was ONE go-to clutch for 500whp or less DSM’s and that was the ACT 2600 (Xtreme, or whatever they call it now…). That clutch was literally a no brainer, they were relatively inexpensive (around 340.00ish cost), tough as nails, and lasted forever. Fast forward to today and it’s just not the same. ACT’s been plagued with tons of failed units after they redesigned their pp springs/diaphragm, and discs. You have PP spring fingers snapping off, friction elements being torn from the discs, and springs jumping out of the clutch discs! It’s one thing if it were an isolated incident but this started happening more and more ‘til finally DSM’ers had enough. Warranty claims were met with the industry standard “Improper installation” bit, it’s a shame.
Tuesday, September 28, 2010 3:34 PM
I've had an ACT clutch (non sprung hub 6 puck) for 40k miles and 3 years in my turbo'd swift gt and I haven't been able to kill it. It sees mostly abusive daily driver use, and has had a couple drag outings and so far I like it. Would buy one again.....
Mike Kojima
Mike Kojimalink
Wednesday, September 29, 2010 6:36 PM
Did you see the improvements ACT has done in our story to reduce these problems? Induction hardening of the hub areas around the springs to prevent them from falling out, stamping a raised area into the fingers to strengthen them, doubling the hub rivets and bringing diaphragm heat treating in house to improve quality control?
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