Flywheel machining for more pressure.

Hey guys,
Just wondering if anyone has had experience with this. I have to send a flywheel out for machining pretty soon and was think about getting them to machine extra off the pressure plate mounting surface to increase the spring force on the disk. They will already be there to skim off whatever material they took off the disk surface to even it out anyways, so it would a cheap modification I'm sure. What are your guys thoughts?

It will just make the clutch pick up closer to the floor, and if too much is milled off the clutch won't be able to fully release, making it rather difficult to drive...

Matt-98AHU said:

It will just make the clutch pick up closer to the floor, and if too much is milled off the clutch won't be able to fully release, making it rather difficult to drive...

Click to expand...

nope, hydraulics are auto-adjusting

ETA:
cut off too much of the step and you'll actually get lower clamp load, as the diaphragm does over-center partway through release bearing travel, and they carefully position this transition very slightly before the PP releases the disc, cut it the other way and you get a clutch that's tough to modulate as the pedal pressure spikes just before it bites. Really common mistake that aftermarket clutches have, exceptionally noticeable with a stiff PP.

Guys,

A standard (Not a self adjusting) diaphragm spring returns its clamping force over what you can describe as a bell curve. At new you get the initial clamping force, the disc wear a bit and the clamping force actually increases. Continue the wear to the discs worn out dimension and the clamping force is pretty much the same as new disc thickness.

If you do something to make the disc seem thinner you might gain some clamping force but you're also moving its service life to the worn out position.

This graph is a correct representation of a clampload curve for a standard diaphragm spring.

https://www.google.com/imgres?imgurl=http%3A%2F%2Fgrannys.tripod.com%2Fdiaphragmpressurecurve.png&imgrefurl=http%3A%2F%2Fclutchtamer.com%2F&docid=Evc2uH_dCQ1TnM&tbnid=zaWEF-OZAUSqbM%3A&vet=10ahUKEwiwyI3Uv5_VAhVDeCYKHUiyCt8QMwguKAQwBA..i&w=396&h=303&bih=638&biw=1366&q=clutch%20diaphragm%20spring%20clampoad%20curve&ved=0ahUKEwiwyI3Uv5_VAhVDeCYKHUiyCt8QMwguKAQwBA&iact=mrc&uact=8

[486] said:

nope, hydraulics are auto-adjusting

ETA:
cut off too much of the step and you'll actually get lower clamp load, as the diaphragm does over-center partway through release bearing travel, and they carefully position this transition very slightly before the PP releases the disc, cut it the other way and you get a clutch that's tough to modulate as the pedal pressure spikes just before it bites. Really common mistake that aftermarket clutches have, exceptionally noticeable with a stiff PP.

Click to expand...

Doesn't matter if the hydraulics are auto adjusting or not, you take off too much from the ring gear in an effort to keep more pressure on the springs, there will be less space to fully release the clutch. I've experienced what happens to a car when the flywheel isn't machined correctly.

Kind of strange, because it feels like the pick up point is about right for full engagement, but with your foot to the floor, the clutch never fully releases, thus making it very difficult to shift and impossible to get into gear at a standstill without first shutting the car off.

Matt-98AHU said:

Doesn't matter if the hydraulics are auto adjusting or not, you take off too much from the ring gear in an effort to keep more pressure on the springs, there will be less space to fully release the clutch. I've experienced what happens to a car when the flywheel isn't machined correctly.
Kind of strange, because it feels like the pick up point is about right for full engagement, but with your foot to the floor, the clutch never fully releases, thus making it very difficult to shift and impossible to get into gear at a standstill without first shutting the car off.

Click to expand...

How much did you take off? The usual amount of squeeze you'd add on a toyota where it's a pretty common mod is something like .01"

I guess I could see even that causing troubles on one of these though, they do only run about a sixteenth of an inch of clearance from the clutch cover to the inside face of the trans bellhousing.

Tis true, even on hydraulics, take off too much and they can't compensate, and you get the dreaded low pedal. Had it happen and it sucks, lol.

[486] said:

How much did you take off? The usual amount of squeeze you'd add on a toyota where it's a pretty common mod is something like .01"
I guess I could see even that causing troubles on one of these though, they do only run about a sixteenth of an inch of clearance from the clutch cover to the inside face of the trans bellhousing.

Click to expand...

*I* didn't take anything off. It was a new aftermarket flywheel that wasn't quite machined right from the factory...

what 486 said... too much off the ring gear and you approach the overcenter/release point of the diaphragm spring ... can cause high pedal slipping clutch