Question about air gap and throwout bearing

I am still finishing up my TOB system and I'm going to mock up the clutch in the car so I can set my pedal linkage in the correct spot. I want to confirm what a good air gap is plus the distance from the TOB and the fingers when the clutch pedal is against the back stops. Once I drill the pedal shaft and attach it, if I'm off any its going to be a real pain to redo it. From what I have read on this site when the clutch is fully engaged (pedal out) a good gap between the fingers and TOB is .370" min, plus an airgap of .070" is min.

Now I don't know which TOB carrier I need to get these numbers but I am going to put my shortest one in to start somewhere. I can't depress the clutch yet because all my brackets and so forth are only tacked in, my problem is how to simulate or check airgap if I can't push the fingers down. Can I carefully put feeler guages between the discs to simulate the air gap?

This is a triple disc crower and I'm only familiar with dual disc clutches. Am I way off base here or am I correct it my assumptions? If I can use feelers between the discs, is it .070" between each disc or is it .070" overall? I've never set up a Crower clutch before and any help would be great.

Hope that all made sense.

 

Sorry I was more concerned about telling the story I forgot to mention what type of clutch. Its a crower triple disc pedal, and its in a door car.

I hope thats all the info thats needed but if not i can try to answer any additional questions.

Thanks Again

 

If you are looking to simulate the lever tip height when the pedal is pressed at whatever airgap you anticipate (I would start with .100", and make sure you have adjustability +/-.070" in your linkage). You can zero the clutch like normal, only set it .100" past the actual "0" point. The top of the donut should damn near be touching the bottom of the hat. This should suck the levers down in the middle, similar to pushing the pedal.

My rule of thumb on most pedal clutches is that if I can get a fingertip between the zeroed clutch levers and the bearing without causing discomfort, it should be fine.

Couple things to be mindful of:

- If you're doing this with all new discs and floaters, remember, normally when the car runs you'll have used stuff in.. So lets say you've got an all new total disc and floater pack thickness of 1.810" (.370 on the discs, .350 on the floaters).. When you're running, you may only have an average of 1.630" (just say the discs are .350, .330, .310 and floaters are .310 and .330. So the total height of the clutch(including the lever tips) would be .180" lower than if all new stuff was in it. Usually you can account for that in the cross shaft setting(assuming this is a cross shaft bell housing)..

- The more long pieces you have in the linkage between the pedal and the cross shaft, and depending on how high you stage and how heavy on your clutch tune you are, the more air gap you'll generally need.

 

AWESOME ANSWER!!!!!! Thanks very much, you nailed my question on the nose!!!

As far as "long pieces" between my pedal and the cross shaft, I have a double pivot system from McAmis, very nice system but uses 2 quite long link rods because my pedal arm and cross shaft arm are almost on top of each other so I needed the double pivot.

When you say I need more airgap for long links is there any real way to know without just running it? I have rod ends on everything plus fairly fine spline on my cross shaft arm so I have pretty good adjustablity, should a guy just throw an extra .050" at it above the .100" airgap you recommended or is that to that too much?

Thanks

 

It just depends on the strength of the links(tie rods) and the amount of leverage you're using to push the pedal down. The longer parts have a greater chance to deflect when the RPM comes up and all the levers and counterweight really start pushing back, so while the pedal may not move, parts in the linkage bend under the stress and close up your air gap. So to answer your question, no, there isn't a really good way of knowing without starting it up and trying it.

You shouldn't need more than .100", .070" should be fine. If it still creeps hard with .100", you have a weak link in the linkage somewhere.

 

Sounds fair enough, thanks again for the great answer. Now I just have to read it 10 times so I can get it right

Corey

 

Depending on your launch RPM you air gap will vary as well. With our 3 disk crower we normally ran 45-55 air gap, launching at 6300 or so. Best way like Justin said is to try it. If the car tries to creep at stage RPM it needs more air gap. It does affect your r/t, so we found the tighter the better, as long as it doesn't creep.

 

Thanks Nathan, once I get this linkage all set and welded in so I have proper adjustment then I'm really going to bend you guys ears off for tuning advise