Quote:
Originally Posted by acammer
McLeod RXT here. Been in for about 15-20k miles. It will chatter if you don't get your takeoff right. Mostly I can drive around it, once and a while it does catch me by surprise. I have a billet steel flywheel.
There are a few things that lead to that chatter on take-off with a clutch. The material used on the clutch has the biggest influence. Organic material, like that used on the factory clutch, Mcleod RST, and Monster "S" series clutches is very forgiving. Because it has a relatively low coefficient of friction, the discs are a "full face" which also promotes a smooth engagement. Finally, these clutch all also feature a "sprung" hub, which uses a series of torque dampening springs to help moderate any sort of spikes in torque delivery. That all combines to make for a clutch that operates smoothly, and has fairly gentle engagement characteristics.
More aggressive clutches, like the Mcleod RXT, use a ceramic material. This has a dramatically higher coefficient of friction, as well as much better heat resistance, which makes it ideal for handling big power and abuse. This type of material is arranged on a "puck" style disk to achieve the correct amount of contact area. The side effect of these performance benefits is that the engagement character is extremely fast and aggressive. You can slip a clutch like this, but the window within which you can do so is extremely narrow. These also are almost exclusively mounted on unsprung hubs to maximize their power transmission, responsiveness, and durability - but again that comes at the cost of a less desirable driving characteristic.
The flywheel material is altered to change the weight - the friction material is steel even on an aluminum flywheel, so the material itself does not impact clutch engagement behavior. However, with a light weight aluminum flywheel the engine can accelerate faster - and it also can decelerate faster. That sounds good, until you drive one on the street and find that it makes for a much more challenging take off. For drag raced stick cars, getting the 60' right with a very lightweight flywheel is a challenge, and I typically recommend to my customers to stick with a billet steel flywheel. This is already lighter than stock, but keep a little inertia in the flywheel makes the car easier to effectively 60', and the gain in performance there almost always outweighs the acceleration advantage an aluminum flywheel setup would have down track.
FWIW, here is some driveability video of my car with the Max Package 2.0, which includes a fairly good sized, aggressive camshaft, and a Mcleod RXT. You can see some of that tricky engagement behavior in a few places, but you'll also see that it's totally manageable with well coordinated feet.
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Long story but I got a Spec twin disc with aluminum flywheel that was installed wrong given to me.
I sent it back to Spec for inspection and had the discs changed to organic because I wanted zero chatter. I had to also replace the floater and the steel mating ring in the flywheel.
I was ASSURED it wouldn't chatter the many times I asked.
This MF'er is like a paint shaker at Lowes, I hate it.
I do my own work, I was a dealer tech for 12 years and have been doing car stuff all my life, but at damn near 60 years old my old bod is pissed it has to do another clutch.
The spec has an AEWSOME soft clutch pedal, grip is very very good but the drivability is shit. I can no lift shift it like butter. Make an outstanding road course clutch.
I have called Spec numerous times, I did the break in procedure. The told me to "be more aggressive with it" and I have, to no avail. It may be a tad bit better... maybe. Has about 3,000 miles on it now.
I am not going to mod the car anymore(I don't think) I like it at 600 wheel, fun and reliable.
A McLoed RST may go in it with a steel flywheel. I had one in my C5 Z06 and it never once chattered.
If I tried to do what you did in that video to take off without and added throttle it would die or shake your teeth out.
And FYI, the stock ZL1 clutch is 64Lbs, this clutch is 42 lbs, on a Dragy 60-130 in similar DA the car is not faster, although it feels like it is.