Where in the pedal travel does your clutch disengage? Top of pedal travel? Bottom? middle? Mine's at the very top. The pedal is stiff from the zero mark. This worries me that the pedal rod isn't adjusted properly and that there's un-necessary pressure on the throwout bearing. just curious. sjd
okay, so where should it disengage? i've had it all apart for the flywheel bolts coming out, and it measured and looked fine (numbers I can't recall right now) plenty of disc life left. sjd
perhaps I should clarify, there's a distinct overtoggle feel to the clutch pedal and full disengagement is about 1/3 of the way pressed. (i.e. everything is working properly) and engagement is naturally 1/2-2/3 from the floor. In other cars i've had there was always a bit of play at the top of the pedal...like the first 1/4" of pedal movement or so. some cars I've had had the engagement right at the floor and then play at the top (adjusted out with the pedal rod), some had 1/2 to 2/3 of pedal travel from the floor before the car would start moving. the 348 seems doesn't seem to have that little bit of play at the top. The concern is that the pedal rod is adjusted too "long" and is actually pressing the master at full height travel, thereby pressing the throwout bearing into the fingers prematurely. sjd
Everything you wrote indicates Plugzit has the correct diagnosis. While the clutch travel IS adjustable, what you have described is perfectly in line with the clutch friction disk being too thin. It is easy to check with a lift and a flashlight.
I'm not getting this. Clutch adjustment is limited to pedal height. It's a hydraulic clutch and clutch wear should not effect pedal throw or disengagement point.
I agree. The only caveat there is if the pedal rod is preloading the master, in which case, it shouldn't be...at least in my opinion. In theory, if you remove the clutch pedal and rod, the spring clip stop in the master to the piston bottoming in the master defines what the distance the hydraulic system travels. adding the pedal and rod into the equation allows for a too long rod to push the pedal against its up travel stop (presuming it's just like every other car i've worked on). if it were a too long rod, then the rod, with no place to go can only force the piston in the master down, creating preload on the throwout bearing. with a too short rod, the pedal has a tiny distance to travel before the tension of the system is felt. I really don't think i'm feeling that tension (hence the too long rod thinking). but all of this is just applying the general knowledge of working on cars for the last 22 years and not watching football. it doesn't feel weird, and I recall having measured the pressure plates to spec, but can't recall my friction plate numbers (maybe i just forgot to measure thickness). the ol' "well, it's not into the rivets yet, must be some life left" sjd
You comment about preloading the master cylinder is correct. The clutch pedal height is supposed to be adjusted using the push rod so that with the clutch master cylinder fully "relaxed" (piston all the way out) the pedal is at the same position as the brake pedal. Then there is a "top" stop which gets set to prevent the pedal from rising further. (It would be possible to preload the master cylinder by lengthening the push rod without first loosening the top stop, thus loading the master cylinder instead of allowing the pedal to rise further.) Next, there is another "bottom" stop which should be adjusted so that the pedal can only be depressed 115-120 mm. The throw out bearing is in constant contact with the pressure plate fingers. Thus, when correctly adjusted the pedal will always swing 115-120 mm regardless of clutch wear. (This is for the 355. I assume the 348 is similar.)
I agree. Becasue if you don't set the bottom stop correctly, you can over stress the pressure plate. sjd
arguably, it could swing less, all you really want is full clutch disengagement, and disengagement enough to be able to change gear. mine feels like I have way too much travel AFTER disengagement, hence the poorly worded original question. sjd
Likely, plus a certain amount of safety factor. I worked on an IMSA team for several years in prototypes. I know we'd set them up by having a guy leaning on the rear tire with the car in gear, and one of the mechanics setting the down stop on the clutch about 5mm after the clutch released. (but you don't really use the clutch in those cars except to leave the pits). sjd
I adjusted my clutch pedal/pushrod as follows: 1. Adjusted the pedal top stop to keep the clutch pedal level with the brake pedal, then 2. Adjusted the pushrod length so that I can feel a small free play (in the pedal pin through the fork) when I press the pedal by hand
i took a close look last night. There's less than 5mm free play by hand (pin movement like you describe), there's 110-120mm of full travel. I may adjust the downstop a little just to have the initial engagement in the clutch occur a little sooner. Thinking about what plugzit had originally said, wear on the friction plates would move the engagement point a little, but what i'm feeling isn't that drastic. I didn't have a chance to crawl under the car to see about friction plate thickness. sjd still in the neurotic area of the first 250 miles.
Disagree. It's a hydraulic system with constant contact throw out bearing. Clutch wear will not show up in the pedal. It is, in effect, self adjusting when set up correctly. You feel clutch wear in a mechanical or hydraulic system where there is "free play". That is, where the throw out bearing is not in constant contact with the pressure plate fingers. In those cases, as the clutch disk wears the gap between the pressure plate fingers and throw out bearing decreases and the free play is reduced with result that the throw out bearing engages with the pressure plate with less pedal movement and the clutch disengages higher in the pedal stroke. Miroljub's post on how he sets up his clutch is not the factory way. Factory method is to loosen the top stop. Then adjust the push rod so that the pedal height is correct. Then tighten the top stop so it just contacts the pedal. Then tighten the top stop one additional turn. No free play. The adjust the bottom stop for 115-120 mm travel.
ahhh... you're right. my bad. the fingers extend to hold the throwout bearing in place and it can't go any further in when the master is in its zero position. I talked myself in a circle. sjd
Hey guys I thought I would chime in. My clutch effort was absolutely awful it was so stiff that I was considering getting a clutch booster of some sort because I have a bad knee. I decided to inspect the clutch took it all apart and the plates were shot... they were worn down to the absolute minimum spec almost to the rivets. I just replaced them with brand new plates and it is unbelievable the difference it is literally half the effort now to push the pedal in. I can't quite wrap my head around as to why because I agree it is a self adjusting hydraulic clutch. I guess you could make the argument that the fingers on the pressure plate would actually be further "in" than before by virtue of the fact that the new plates are considerably thicker and therefore the amount of effort required to disengage it would be less not sure if that makes sense. My clutch before would not catch until the very very end when letting out the pedal now it catches about the halfway to 2/3 point
Yes, it makes sense. The clutch diaphragm disengages when it flips over - the feel on the pedal like going over the "cam". The effort pushing the diaphragm is higher when its cone is further away from the flip-over point (like the case with thinner clutch discs). The new thicker discs preload the diaphragm more bringing it closer to the flip-over point from where the effort to push the diaphragm further and over the "cam" is smaller.
Thank you for explaining that...it makes perfect sense. I couldn't wrap my head around the logic but that does make sense. One idea I had was to actually increase the thickness of the 3 shims to try to reduce the effort but then you might get into a situation where the clutch starts slipping. However with these new discs which by the way are AP Racing band, it is like I said half the effort that there was before it's unbelievable. What's even more unbelievable is the wear limit is only .8 mm so for the twin plate set up you're only talking 1.6 mm it's very hard to believe that such a small amount can make such a huge difference but it does
Just a crude example. 1.6mm at the pressure plate is much more at the fingers (thrust bearing). Image Unavailable, Please Login
