turning a flywheel

[Ray G.]

Can someone explain to me the reason to "turn" the flywheels when replacing the clutch? I have heard several stories in regard to this matter, some say just scuffing it up with sandpaper will suffice? Engineering answer? Thanks

[Clem Z.]

Re: turning a flywheel

Can someone explain to me the reason to "turn" the flywheels when replacing the clutch? I have heard several stories in regard to this matter, some say just scuffing it up with sandpaper will suffice? Engineering answer? Thanks

most flywheels will show some warpage from heat so grinding them will make them flat again.

[Jody B.]

Re: turning a flywheel

Not an engineer, but I wanted my new clutch to engage on a surface that had been trued. Get rid of the old wear patterns on the flywheel and start fresh. So, after $50 and .007" of removed material here's the before and after pictures. Way to much work to remove the transmission and not take care of all of the maintenance items at one time. I also turned the ring gear around so the starter would have new teeth to chew on.

[Gerry P.]

Re: turning a flywheel

Resurfacing helps correct clutch chatter or grabbing upon engagement.

[David B.]

Re: turning a flywheel

The flywheel can develop "hot spots", which show up as the dark blueish colored oval surfaces in Jody's photo. With successive heat build-up cycles on the flywheel surface, some spots can develop localized (relative) surface hardening, resulting in uneven wear, followed by clutch chatter. This is in addition to the potential warpage that Clem mentioned as well.

The hot spots and high spots cannot be remedied with sandpaper. Grinding is the preferred resurfacing in my opinion, even though they can also be resurfaced by cutting on a brake lathe with a flywheel attachment.

As far as an engineering opinion, I do happen to be a PE (Professional Engineer), but my comments on this topic are based on personal experience, observations, and learning from some elders who have shared valuable practical knowledge, rather than a metallurgical treatise based on engineering principles.

Short version - I would get it re-surfaced.

Hope this helps

[Joe L.]

Re: turning a flywheel

Can someone explain to me the reason to "turn" the flywheels when replacing the clutch? I have heard several stories in regard to this matter, some say just scuffing it up with sandpaper will suffice? Engineering answer? Thanks

Ray------

Re-surfacing is ok, but there is a downside, too. In a 63-81 Corvette, clutch adjustment is a "touch-and-go" situation. GM did a lot of "playing around" with clutch activation system components, mostly in the 63-75 period, but I don't think they ever got it exactly right. As a consequence, it can be very difficult to get a clutch adjusted so that there is specified free play as well as complete disengagement at full pedal travel.

Consequently, I am always extremely reluctant to do anything that would change the configuration of ANY part of the clutch actuation system lest I make the "inherent" problem worse. Surfacing the flywheel does change, albeit slightly, the configuration of the system. However, I think that a very small cut on a never previously cut flywheel on the order of the 0.007" described would likely be OK.

My preference is always to replace a flywheel rather than resurface it, though.

[David B.]

Re: turning a flywheel

Joe,

As you point out, while getting the optimum initial adjustment on a new clutch installation is sometimes difficult, keep in mind the influences of the cumulative effects of clutch linkages wear, cross shaft bearing surface wear, and clutch facing wear in the tolerance of the whole assembly. Clutch facing wear alone can account for more than a tenfold difference in the tolerances of contact of the mating surfaces between adjustments all by itself. (.007in. vs .07 in. for example) as compared to flywheel grinding. I don't think that grinding of the flywheel is a very significant influence, relatively speaking in the mechanics of the system. But, I concur that it is a component to be considered.

Dave