clutch questions

[rx7chris]

Just wondering what would make a stock clutch dissentigrate(sp?)? I was told only two things can make the material come off the disc.
1) over revving the motor, centrifugal force pulls the material off

2) over heating it, where it looses its bond with the disc itself

I had driven this clutch @ daytona in 1.5 hr enduro and +100 deg. temps and it came back for more. drove it in a 45 min enduro at sebring in 80+ temps. the clutch has gone through school and about 4 events counting the 2 above. 1st time out this year temps were around 60-70, 20 min. in it lets go. i was not driving at the time so anything is possible.

Any ideas?

and yes i've gone to a 4 puck since.

------------------
Chris
IT7 #88
PowerTrip Racing
http://www.geocities.com/ptripracing/

 

[joeg]

Any ideas?

Sure. The guy or gal you let drive it is the answer. People all act differently with stick shifts and clutch pedals.

Make 'em buy you a new one!

 

[dickita15]

a few years ago we put a first gen together from scratch and threw a used clutch in that was lying around the shop. we were on the cheap and it had plenty of material, may even have been new old stock. took the car to a test day and it ran great for a couple of hours. it then gave a mighty shudder and stopped moving. pulled the trans and there was absolutly no friction material attached. we assumed the material dry rotted.
dick

 

[rx7chris]

Anyone know the general rules of renting a car? Is it, If it happens when you're driving its your fault? or is the owner of the car supposed to prove you had something to do with it?

I know a little off topic, but still related.

------------------
Chris
IT7 #88
PowerTrip Racing
http://www.geocities.com/ptripracing/

 

[Speed Raycer]

FWIW... same thing happened to me on our 1st gen 7. Brand new, stock type clutch grenaded after a double drivers school/regional, and two more race weekends. The motor was never zinged, but there were early signs of trouble on botched 3-2 downshifts during practice that day. The friction material was completely wiped away from the flywheel side. Pressure plate side was fine. We've heard twenty reasons why it could have happened from 20 different people.

------------------
Scott
It's not what you build...
it's how you build it

E-mail me for deals on
Lightweight Replica Blocks!

 

[xr4racer]

Almost any time the material is wiped off the flywheel side of the clutch it is caused by not matching the revs on a downshift. When the motor falls to near idle when you are downshifting and then you let out the clutch without at least a blip, the rear wheels are forcing the motor to accelerate via the diff, driveshaft and trans. Also a missed upshift to a lower gear of course will yield the same result.

 

[balz]

I concur with the above statement...

HEAL TOE.....HEAL TOE...it will save your clutch and several gear box changes once you get the technique down.



------------------
Balz
#67 IT-7
www.balz.myip.org
"I live my life one Apex (seal) at a time"

 

[joeg]

Originally posted by rx7chris:
Anyone know the general rules of renting a car? Is it, If it happens when you're driving its your fault? or is the owner of the car supposed to prove you had something to do with it?

The person who drives it is 100% responsible.

That's the general rule.

If the owner feels bad about something he knew was about to break or fall off, he can volunteer to take responsibility--but that is only if he is a nice person (and he ain't required to be a "nice" person)

Caveat emptor.

Cheers.

 

[bill f]

In reply to the disc facing problem, I have an easy answer. This is based on personal experience.

Clutch facing comes off the disc due to the "working" of the material again'st the rivits that attach it to the disc enlarging the rivit holes. Cracks then appear, and eventually the facing failure will occur at the cracked rivit holes, and the facing will come off in pieces...usually with the round rivit holes easily identifiable.

Absolute solution is: Take a used disc (even one with loose lining) to a listed clutch re-liner in your area. Ask them to reline the disc, and BOND the lining to the disc. You will get it back WITH rivits, and bonding. Bonding will eliminate the stress at the rivit holes, and absolutely cure the failure problem. Additionally, the bonding process uses oven-heating to set the bonding agent, and the heat will flatten the marchall (sp) spring which is between the two disc surfaces. It has a wavy appearance between the two surfaces.

The advantage of "losing" the marchall spring is faster engagement during shifts. It will also affect the ability to smoothly start off from a dead stop (slipping the clutch depends on the spring for slow, progressive engagement), something not too important in road racing. The disc will now have a more "on/off" feel while shifting.

At the same time, ask the shop to replace the hub springs with stiffer ones, and they will not loosen up easily. The disc's ability to absorb shock loading at clutch-engagement will be retained, since the hub springs are not removed.

It is a win-win solution. I have been doing it for about 15 years. The discs even last years, since the lining is barely used during on-track racing, and it doesn't fall off prematurely.

Good racing. Bill