GTX
(Member)
10/14/16 08:48 PM
Clutch drag

Hi gurus,

Most likely you were through similar symptoms. In fact I was too

Long story short:

I have Exedy Stage 2 clutch with Fidanza aluminum flywheel. Runs like charm, no slipping on any RPMs. Pretty happy with it.
During last race I have noticed difficulty engaging the first gear, which very quickly evolved into not being able to use the first gear from the start.
Dragging clutch is obvious, you press the clutch and 2/3 of the way you feel something weird. Like it is hitting something soft. I had a bent pedal before and fixed it by extending the rod at the master cylinder. Worked for a few years...until now.

So, I figured, could it be a bent clutch fork or air in the system? Took the gearbox out... no signs of any abnormality. My clutch disk is 7mm (new is about 8mm), no signs of any damage on the fork, the bearing is fine. Am I getting the same issue with pedal? I was thinking about it and checked the pedal, even adjusted it to be tight with no gaps at the rod. Nothing. You raise the car, put it in neutral and the wheels are spinning... any ideas?
If I take the pedal box out, how do you check it?

Your ideas are highly appreciated!

Thanks
Alex


GTX
(Member)
10/14/16 09:03 PM
Re: Clutch drag

What is a normal size of the pivot bolt? Have anyone measured the length of the bolt inserted into the fork? I have two forks and two bolts, they measure the same, but both are old. I presume shimming the bolt might do the trick.

tektic
(Senior Member)
10/14/16 09:12 PM
Re: Clutch drag

Warped flywheel.

GTX
(Member)
10/14/16 09:48 PM
Re: Clutch drag

Looks ok to me
No colors. Ill measure it though
Thanks for the tip!


FlyingEagle
(Eager Beaver)
10/15/16 08:11 AM
Re: Clutch drag

Pull the clutch pedal back from rest, and check for movement.
If you have ended up like countless others, the pedal box assembly could have worn out; ie bushings.
There is a big thread about what was being done to repair them.


MuffinMan7580
(Member)
10/15/16 10:43 AM
Re: Clutch drag

I had a warped pressure plate that gave me a ton of trouble before I finally figured it out. It didn't feel like I was hitting something with the pedal, but the pedal never passed the "tight spot" that most pedals have before getting easier (difficult to explain). If it were me, I'd start from the beginning and double-check everything (hydraulics, warped PP, warped flywheel, make sure the fork sits at the right spot, etc...), especially if it's been a while since I'd been in the system.

Edit-I assume you've already checked your TOB? I'm not sure I understand your test with the car in neutral, but have you confirmed that it's actually the clutch (clutch drag test: 1st gear, clutch in, car on level ground, rev to 6k RPM, and if car moves, your clutch is dragging)?


GTX
(Member)
10/15/16 05:49 PM
Re: Clutch drag

Thanks for your replys guys. Much appreciate!
So I checked the flywheel for warpage. There is a runout of 5 thou. Around 0.125 mm. I guess I my case it is not a bid deal. I dont drive the car on the daily basis. Besides I already machined the flywheel once.

What I suspect is the pivot bolt. It was absolutely dry and made a nice dry landing area in the fork. I found a video where the guy explains how to check for a correct position of the fork. So as suggested I added a washer to raise the pivot bolt by 1.5 mm
Will let you know if it helps..
Btw: the test I did re:dragging
Raised the car on stands, put in first gear, press the clutch then start the engine. With healthy clutch the wheels not supposed to spin. In my case the were spinning like I did not press the clutch.


tektic
(Senior Member)
10/15/16 08:22 PM
Re: Clutch drag

What was the distance between the surface of the flywheel and the step? The step height.

GTX
(Member)
10/15/16 10:36 PM
Re: Clutch drag

Where? Pivot bolt, fork or flywheel?

FlyingEagle
(Eager Beaver)
10/16/16 10:02 AM
Re: Clutch drag

Quoting tektic:

What was the distance between the surface of the flywheel and the step? The step height.




http://www.roadraceengineering.com/clutchandflywheeltech.htm

Easier posting a link for exact information that I could not say better myself.


GTX
(Member)
10/16/16 02:44 PM
Re: Clutch drag

Excellent resource, Tim! Much appreciate!

EMX5636
(Carbon Fiber Cage)
10/28/16 08:41 PM
Re: Clutch drag

Jack's Trans has an excellent article on clutch drag and possibly checks/fixes. Check here

GTX
(Member)
11/02/16 03:02 PM
Re: Clutch drag

Yes, guys, it was the pivot bolt. Worked itself the nice semi-sphere in the fork. One 1.5mm shim under it fixed everything.
Measured the flywheel as advised. All within the specs. Many thanks for your help! As always, the community rocks!! Many Thanks to everyone!


FlyingEagle
(Eager Beaver)
11/04/16 11:21 AM
Re: Clutch drag

Question:

Did you put in a new pivot bolt and replace the fork?

Or, was just the pivot bolt shimmed and re-installed?


GTX
(Member)
11/10/16 11:51 PM
Re: Clutch drag

I shimmed the bolt using a thick washer. Verified the position of the fork and the amplitude of the movement. Was within the specs. Assembled everything, adjusted the pedal. Works fine now.

FlyingEagle
(Eager Beaver)
11/12/16 03:05 PM
Re: Clutch drag

This is good for clarification for others as they read throught the process of fixing their dragging clutch or identifying why they are having symptoms of a failure.

Also, a new pivot ball could be had for very little coin from RTMRacing, which is just down the road from you. This is one of those little items whereby replacing the ball at a minimum (with a good grease) and if the funds allow, but should happen anyways because the parts wear together, the fork. The fork is only available as a gen 2 revision, so a better part than the cars all originated with. The fork solves two problems, maybe three: Contact points at the TOB come back into spec, contact point in the fork where the pivot ball contacts are now back to spec, and if (for those that could suffer from it) the fork was bent for any reason, that would be brought back in line.

Glad to hear your transmission is back to shifting cleanly. Always hate to hear about transmissions with worn syncronizers as as result of long running, with lack of proper disengagement.



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