flatsixforme

So, my friend with a F-355 and I were chatting and he said there was a buzz on FChat about a guy who had his clutch plate with kevlar (for a very reasonable price) and has had great wear results due to a decrease in heat. I've posted his results below. I'm interested to see what everyone's thoughts are on this and if anyone has tried it.
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After 15 months and 6000 miles the results are in. I did an inspection disassembly of my Kevlar clutch that I installed. I could see no sign of wear on either the clutch or the pressure plate (which was new 6000 miles ago). The flywheel was reground also 6000 miles ago and you can still see the grind marks on the surface with no smoothing of the grinding marks. The brownish surface was not there but that appears to be a rusty residue. The clutch wheel its self is the same thickness as we had at installation. While I never pop the clutch, I don't baby it either as most of my buddies will confirm.

Based on these results, I would recommend to anybody to immediately remove the OEM clutch disk and have it resurfaced in Kevlar. The OEM clutch disk leaves burn pits in these $6000 flywheels and pressure plates after the same number of miles. Don't wait until your OEM clutch is gone or you will be steering at $6000 for the mating parts.

The theory behind the good results rests in the fact that the OEM clutch material stores heat and the copper shards in the burnt wood compound the OEM uses actually gets so hot it burns the steel and creates "hard iron crystals" which destroys the part. The kevlar clutch material dissipates the heat so this doesn't happen.

FLA997

OK...where's Walrod? Steve W Or Bill V.... I'm sure one of them has an informed opinion.

chris walrod

The only other clutch materials I have experience with is multi-disc carbon-carbon race units about 5" in diameter. For road cars, just the typical OEM clutch disc is all I have delt with.

There have been Kevlar woven carbon clutch friction materials used in the past, but nothing pure Kevlar. Kevlar is a fabric and is a terrible material to bond just about anything to.

It does appear the above mentioned F-car guy is having good luck with it --

Cactus

Subscribed.

Bill Verburg

I've got a carbon-kevlar clutch in my '76, been ther since ~'94 seems to work ok. Last 993 clutch I bought is a .61 964RS/993RSCS unit that also seems to work well.

Rick Lee

Very interested in this. Even more so for my bike.

C4S_fan

"Don't wait until your OEM clutch is gone or you will be steering at $6000 for the mating parts" -- yikes. This is a good reminder of need to wait just a bit more before seriously considering an FCar!

Interesting thread. How would you go about coating the parts with Kevlar though?

flatsixforme

I'm trying to get info on the company that did it and cost...I think it's in Atlanta. I'll keep everyone posted. I'm surprised not more people have experience with this.

What are the potential downsides other than failure of the kevlar adhesion?

flatsixforme

Some more info below...still trying to get price

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The key to a successful Kevlar clutches life is using an SC 80 grit stone when grinding the flywheel. From Valeo, they are turn down using a single point tool, but after repeated heat cycles, the flywheel is too hard to use a SP carbide tool, and must be ground. It’s quite an extensive process to do it correctly, as you can only take .0002” off per pass. My experience with the 355 has taught me that it usually requires somewhere in the .008” to .015” total material removal to smooth the surface imperfections out.

Kevlar has a much higher coefficient of friction than an organic lining material, which is why you generally have a longer lived part; more of the energy is transferred to the wheels rather than making heat. Some concerns over what this extra “grip” will do to the related drive train components is valid, but can easily be addressed with a smoother flywheel (i.e 80 grit), and in the 355 / 348 DM flywheel absorbing the shock load.

Overall, the Kevlar setup is a better way to go, but the optimal install would be to purchase a new Flywheel / pressure plate combination, and have the flywheel immediately surfaced .004” as prescribed above. What this accomplishes is the best overall combination from the beginning of the components life. Preparing the components in this fashion could quite conceivably be a combination for a 60,000 plus mile clutch.

What would be interesting is to Dyno test before and after to see if there was any appreciable increase.

RallyJon

What problem are you trying to solve? Are you running significantly more than stock torque?

I've driven Clutchmasters kevlar clutches and they are fine if you carefully and diligently break them in. Like 500+ miles of painful stop and go trying to keep slipping to a minimum. Screw up the break-in and it'll never feel right. But that was in a car with about 70% more torque than the stock clutch was designed for.

Steve Weiner-Rennsport Systems

Kevlar clutches are very tough and durable in high-torque applications but can be finicky to bed in to maximize holding power.

As noted, the flywheel should be Blanchard ground to the correct finish to assist the bedding process.

IHMO, its not for everyone as few people have the patience to bed them and ensure the flywheel surface is properly prepared.

flatsixforme

Great info on the break in guys! I'm not trying to solve any problem and no, I'm not running any extra torque...just exploring the never ending quest to make our cars more affordable to own/opperate. Nobody likes to have to replace a clutch so the thought was to spend a little more up front and get significantly more life.

Sounds like it's not worth the hassle and there are certain risks involved.

Thanks for the input Steve and RallyJon.

gordo993

Do I have to take my car apart every 1500 miles to check on it, or is that an F-car thing?