Warped dual-mass flywheel?
Thread Starter
Pro Mechanic
Joined: Oct 1999
Posts: 3,922
Likes: 1,468
From: South-Central Coast California
Warped dual-mass flywheel?
Forum members-
The general rule has been that the dual-mass flywheel used C4s with six-speed manuals from 89-96, including all ZR-1s, cannot be machined to fix warpage problems.
I've heard rumors that a few resourceful machinists were turning dual-mass wheels but had never actually seen it done...until today.
Mark DeGroff of "DeGroff Cylinder Head Service and Machine Shop" does all my machine work, except LT5 port work, has been machining BMW, dual-mass flywheels for a couple of years. I was out at his shop, today, doing a photo shoot for one of my web site customers and in walks this driver from a BMW repair shop with rush-rush flywheel resurfacing job. We had to take a break from doing image work to set this flywheel up and machine it. While he cut the BMW wheel Mark told me how he does C4 dual-mass wheels the same way. I observed his process and it works well, giving a dead-nuts accurate surface on the secondary mass.
No more do you have to scrap dual mass wheels which are warped but not too badly.
If you're interested in having a dual-mass flywheel surfaced, contact Mark DeGroff at 818-701-5274 or at mdchs3@verizon.net.
The general rule has been that the dual-mass flywheel used C4s with six-speed manuals from 89-96, including all ZR-1s, cannot be machined to fix warpage problems.
I've heard rumors that a few resourceful machinists were turning dual-mass wheels but had never actually seen it done...until today.
Mark DeGroff of "DeGroff Cylinder Head Service and Machine Shop" does all my machine work, except LT5 port work, has been machining BMW, dual-mass flywheels for a couple of years. I was out at his shop, today, doing a photo shoot for one of my web site customers and in walks this driver from a BMW repair shop with rush-rush flywheel resurfacing job. We had to take a break from doing image work to set this flywheel up and machine it. While he cut the BMW wheel Mark told me how he does C4 dual-mass wheels the same way. I observed his process and it works well, giving a dead-nuts accurate surface on the secondary mass.
No more do you have to scrap dual mass wheels which are warped but not too badly.
If you're interested in having a dual-mass flywheel surfaced, contact Mark DeGroff at 818-701-5274 or at mdchs3@verizon.net.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Hib -
How do I say this... DON'T DO THIS!
That should about cover it.
The face of the dual mass isn't the issue, it's failure of the retention springs inside. Sure, you can resurface, but the springs don't last forever. Figure no more than 120k miles, tops. Less if you race.
So, think of this, if the clutch is strictly street driven, and wears as normal at 100k miles, you just allowed yourself the privledge of delaying the replacement of the DM for about 20k miles AND you get to pay the labour twice! What a deal.
As for turning the BMW DMs, for the most part, the torque just isn't there, so cutting those might be worth the effort.
How do I say this... DON'T DO THIS!
That should about cover it.
The face of the dual mass isn't the issue, it's failure of the retention springs inside. Sure, you can resurface, but the springs don't last forever. Figure no more than 120k miles, tops. Less if you race.
So, think of this, if the clutch is strictly street driven, and wears as normal at 100k miles, you just allowed yourself the privledge of delaying the replacement of the DM for about 20k miles AND you get to pay the labour twice! What a deal.
As for turning the BMW DMs, for the most part, the torque just isn't there, so cutting those might be worth the effort.
Le Mans Master
Joined: Apr 2002
Posts: 5,726
Likes: 46
From: Waukesha WI
St. Jude Donor '15
I thought when you machined flywheels, you did it mainly to clean up the friction surface for the new clutch - kinda like new brake rotors for new pads. Am I wrong? I would think it would be hard to warp a 40+lb chunk of steel unless you got some serious clutch problems.
I agree with bogus on the 120k estimate...I would say closer to 100k tho. I could hear my dual mass clunk around a little since I got the car at 109k and it has gotten worse now that I am at almost 150k. I am not going to replace except for an LS1/T56 combo. I should have replaced it when I did the clutch at 115k or so but I did not know any better.
I agree with bogus on the 120k estimate...I would say closer to 100k tho. I could hear my dual mass clunk around a little since I got the car at 109k and it has gotten worse now that I am at almost 150k. I am not going to replace except for an LS1/T56 combo. I should have replaced it when I did the clutch at 115k or so but I did not know any better.
Drifting
Joined: Feb 2002
Posts: 1,952
Likes: 2
From: Little Rock Arkansas
Hibster!!! Glad to hear from you! Haven't spoken with you in a LONG TIME!!!
I've refaced dual mass flywheels in the past as well... I've turned them both on a lathe and have ground them with a Blanchard grinder as well. I'm with Bogus a little bit on this one, though, I don't think it's a particularly good thing to do. Plus, the damned things are so heavy I just prefer to can them and go with a standard f.w. setup. If you feel you HAVE to have the weight use a billet steel one; while they're a little more than half the weight of a dual mass they still have the mass to assist getting out of the whole and dampening the noises associated with the ZF better than a 12 lb aluminum f.w. (which I prefer).
-Jeb
I've refaced dual mass flywheels in the past as well... I've turned them both on a lathe and have ground them with a Blanchard grinder as well. I'm with Bogus a little bit on this one, though, I don't think it's a particularly good thing to do. Plus, the damned things are so heavy I just prefer to can them and go with a standard f.w. setup. If you feel you HAVE to have the weight use a billet steel one; while they're a little more than half the weight of a dual mass they still have the mass to assist getting out of the whole and dampening the noises associated with the ZF better than a 12 lb aluminum f.w. (which I prefer).
-Jeb
Thread Starter
Pro Mechanic
Joined: Oct 1999
Posts: 3,922
Likes: 1,468
From: South-Central Coast California
[QUOTE=bogus]Hib -
How do I say this... DON'T DO THIS!
That should about cover it.
(snip)
I'm sorry, but that doesn't "cover it".
I guess I did not clearly state that I was talking about dual-mass flywheels with friction surfaces which are warped. I was not talking about dual-mass wheels which have sustained broken springs or failed bearings. Obviousliy, surfacing the flywheel will not fix that.
How do I say this... DON'T DO THIS!
That should about cover it.
(snip)
I'm sorry, but that doesn't "cover it".
I guess I did not clearly state that I was talking about dual-mass flywheels with friction surfaces which are warped. I was not talking about dual-mass wheels which have sustained broken springs or failed bearings. Obviousliy, surfacing the flywheel will not fix that.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Hib - you are missing my point.
To start with, I don't see how warpage is going to harm anything. It's not like a brake rotor that has warped.
If the mileage is low, and the fw is that worn, the owner has been abusing the clutch, riding or racing.
the internal springs act just like the springs in a conventional sprung hub clutch friction disc. This is exactly why they wear out at the same rate as the rest of the clutch.
Add in the additional torque, I don't see any purpose to resurface the DM in this application.
I can't speak for this in other cars, but as far as the C4 is concerned, the DM is a one hit wonder... use it and recycle when you replace the clutch.
To start with, I don't see how warpage is going to harm anything. It's not like a brake rotor that has warped.
If the mileage is low, and the fw is that worn, the owner has been abusing the clutch, riding or racing.
the internal springs act just like the springs in a conventional sprung hub clutch friction disc. This is exactly why they wear out at the same rate as the rest of the clutch.
Add in the additional torque, I don't see any purpose to resurface the DM in this application.
I can't speak for this in other cars, but as far as the C4 is concerned, the DM is a one hit wonder... use it and recycle when you replace the clutch.
Burning Brakes
Joined: Aug 2001
Posts: 1,038
Likes: 15
From: Brick- Next to the land of Mojo NJ
Originally Posted by bogus
To start with, I don't see how warpage is going to harm anything. It's not like a brake rotor that has warped.
i agree with your main point though
