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1G Flywheel thickness

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
So i have looked and looked and cant not find what im looking for. Is there a minimal thickness for a flywheel? Im having clutch/trans issues and wondering if flywheel has been cut too many times. I have a new pivot ball and clutch fork, oem master cylinder and an aftermarket but new slave cylinder. I have also added a shim to pivot ball. I feel the fork still needs to be to driver side more. Ill add picture tomorrow. So leads me to believe flywheel has been cut too many times. Anyone have an answer to thickness? Thanks
 

dustyboner

DSM Wiseman
1,834
941
Mar 13, 2016
abq, New_Mexico
i can't find a minimum thickness anywhere.
could the step be wrong? If you have a new release fork and pivot ball you shouldn't need to shim it at all.


you would think a flywheel specs manual would have things like minimum thickness. But no, this is all it had:
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1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
I had it resurfaced at a shop that has done pletny of them so i didnt check the step height. I know i should have but tired of this car sitting and want it running and driving. Ill get a picture of where the fork sits in window. I didnt think i would need shim either but i did. Why im leaning towards flywheel being cut too much
 

dustyboner

DSM Wiseman
1,834
941
Mar 13, 2016
abq, New_Mexico
the step was just the first thing that popped in my head. I say just replace it since you have some doubt about its thickness. With a new one you won't have to worry about any of that shit.
 

NOSLO2PT0

Proven Member
2,666
221
Aug 31, 2002
Joliet, Illinois
I had it resurfaced at a shop that has done pletny of them so i didnt check the step height. I know i should have but tired of this car sitting and want it running and driving. Ill get a picture of where the fork sits in window. I didnt think i would need shim either but i did. Why im leaning towards flywheel being cut too much

The step height is the most important thing with the flywheel. And most shops don’t cut it right. You absolutely should have checked that first
 

Mech Addict

Supporting Member
716
271
Jun 9, 2019
Jackson, Wyoming
Step height and thickness from crank face to friction surface would both seem to play very important roles in the geometry of the clutch release. How much did you shim the pivot ball? Is it a stock flywheel or aftermarket?
As the friction face gets cut, it moves away from the fork's normal resting position, so even with the correct step, the whole clutch is too far from the tranny. a thicker shim could correct this. You mentioned "clutch/trans issues", can you describe the issues beyond the observation about the fork lever toward the d/s? Slipping? Grinding? Grabbing?
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
Im not sure what brand clutch is. Think ebay but its a sprung puck. Never had puck before. The pedal feels soft and seems to grab close to the floor. It doesnt like to really slip either. Its a stock flywheel. It shifted fine in 1st 2nd and reverse. Had issues with third so i parked it again. Here is pic of the fork in the window. Im not sure how thick the washer is.

You must be logged in to view this image or video.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
That looks ok to me. IIRC the fork should be center or towards the driver's side. This looks ever so slightly towards the driver's side. It might be something else. Did you adjust the clutch pedal and MC rod, and check for excessive play at the top? That was my issue and it probably trashed my trans forcing me to rebuild it as well as prematurely wore out the clutch disc, because the clutch wasn't fully disengaging. Did you also bleed the clutch, check for leaks on either cylinder and make sure that the mounts are good?

Btw I too was concerned about flywheel thickness after multiple resurfacings. In my case there was plenty of surface left and I also got a new fork and fulcrum, but to play it safe I shimmed with a very thin washer, probably a millimeter tops. When I put everything back together the fork was a bit more to the driver's side than yours, but not by much. I haven't driven it yet so I don't know if the shim was a bad idea.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
I have no leaks. Im pretty sure the mc rod its just about out of threads. I guess its possible my pedal assembly is wore out. I have checked free play of pedal yet. I have bleed and bleed the clutch line as well. The mounts are all new too. Im still feeling its flywheel related but i have no idea. Just trying to get ideas and figure it out. Im really tempted to order a new cheap xtd clutch of ebay just to see of it makes any difference.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
We both have 1G's which are notorious for a bad clutch pedal assembly. Google it, but the gist is that slop develops due to a poor design that can only be fixed by replacing the parts or having them welded together with a brass bushing.

Mine had a lot of slop which prevented the clutch from fully disengaging. I temporarily fixed it by tightening a bolt on the end of the clutch pedal shaft, but I now need to have it permanently fixed.

Before you order new parts or drop the trans first check this.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
Yes i remember this being an issue. I had it fixed years ago one on. I have been out of game for 5 years or so and have forgotten a lot. I was hoping not to have to pull assembly out but guess i should just order bushing and weld it. Then its done and shouldnt be an issue anymore
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Again, first check for play before yanking anything out. It might not be this.
 

dustyboner

DSM Wiseman
1,834
941
Mar 13, 2016
abq, New_Mexico
Think ebay but its a sprung puck. Never had puck before. The pedal feels soft and seems to grab close to the floor. It doesnt like to really slip either.
If anything like the name brand 6 puck spung hub clutch, they are not ment to slip. it is either engaged or its not.

If your trying to drive it like a stock or even a slightly upgraded clutch with a full faced disc, your gonna have problems.

I don't know if its the same for DSMs but on the K-series honda's all of the 6 puck clutches use the same pressure plate (made by excedy i think) , different companies have them powdercoated to match their color scheme.
The pressure plates on them are slightly shorter then the stock clutch setup. So you have to shim the pivot ball to correct the geometry when you use one.
 

Mech Addict

Supporting Member
716
271
Jun 9, 2019
Jackson, Wyoming
On my pedal assembly (which is a little worn at the pedal to arm fitting) if I remove my cruise control switch (or the stop bolt for those w/o cc) I can pull up on the clutch pedal with my hands and it will move up about an inch or so. This amount of wear results in running out of threads on the clutch m.c. rod. The best fix is a new pedal (no longer available), or welding the pedal shaft to the clutch lever (requires a bronze bushing). But another fix is to obtain a 2g clutch m.c. And swap the longer threaded rod in place of the one that comes on the 1g m.c. Then you simply get more threads to adjust. The donor 2g m.c. doesn’t have to be functional in any other way. The bolt wouldn’t wear even if all the internals have. So it can be an inexpensive and rather easy approach. Removing the m.c. Is way easier than the pedal assembly or the transmission. Swapping out the threaded rod is basically just removing a snap ring.
It might not improve grabby engagement if the puck-style clutch disc is part of the issue, but it should restore the correct pedal adjustment issue. Of course the pedal to lever clearance will over time get worse, and even welding it can still go wrong if not done with care.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
I think i might just order new brass bushing and rebuild/weld pedal assembly and get a full face clutch disc and see how that goes. I just want it driving for now. Down road ill get new flywheel and clutch kit
 

pauleyman

DSM Wiseman
7,179
2,097
Nov 19, 2011
oklahoma city, Oklahoma
If you're pulling the clutch it seems silly not to do the flywheel at the same time.
I'm betting on pedal assembly as well. At least check it. You don't even have to take anything apart and at least then you know for sure.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
I believe he did have it resurfaced, just didn't check the step.
 

RLSchwabe

Proven Member
115
22
Mar 21, 2014
Colorado Springs, Colorado
I chased issues on mine for a while, in the end I think it was the flywheel step height and free-play in my pedal assembly. The pedal assembly is easy to check. I would not try any extended master cylinder rods, slave cylinder shims/ext rods etc. I went down this path and destroyed a new SBC clutch and pressure plate.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
I chased issues on mine for a while, in the end I think it was the flywheel step height and free-play in my pedal assembly. The pedal assembly is easy to check. I would not try any extended master cylinder rods, slave cylinder shims/ext rods etc. I went down this path and destroyed a new SBC clutch and pressure plate.
As I mentioned above, with a stock AWD flywheel that's been resurfaced 2 or 3 times, a new SBC Stage 2 DD clutch & PP, and a new (Competition Clutch) clutch fork & fulcrum (and new OEM release bearing of course), I shimmed the fulcrum with a ~1mm washer, to compensate for the flywheel surface that's been removed in its several resurfacings. Was that a bad idea? The fork sticks out a bit towards the driver's side but not by much.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
If you're pulling the clutch it seems silly not to do the flywheel at the same time.
I'm betting on pedal assembly as well. At least check it. You don't even have to take anything apart and at least then you know for sure.
Money and time are the issue right now. I bought this car and was suppose to be a quick and easy fix. Year later here i am. Needless to say, the woman isnt very happy. Started out has a non turbo auto. Now its 5 spd swapped with a 90 fwd turbo trans. Have 90 cables and shifter too.
 

RLSchwabe

Proven Member
115
22
Mar 21, 2014
Colorado Springs, Colorado
As I mentioned above, with a stock AWD flywheel that's been resurfaced 2 or 3 times, a new SBC Stage 2 DD clutch & PP, and a new (Competition Clutch) clutch fork & fulcrum (and new OEM release bearing of course), I shimmed the fulcrum with a ~1mm washer, to compensate for the flywheel surface that's been removed in its several resurfacings. Was that a bad idea? The fork sticks out a bit towards the driver's side but not by much.
I think that's '..within spec...' RE the shift fork position in the window. However, as I remember I also had a shim added which ended up being taken out. Mine was also in the '..correct..' position in the window. I pretty much have the same set-up on mine minus the shimmed fulcrum.

Started with: Autozone master cyl, Autozone slave, SBC clutch + pressure plate, New ACT flywheel ( step height measured by someone who wasn't very familiar with DSMs or machining and flywheels specifically ), and a shim

Went through several autozone master cylinders, used a 2G rod in the 1G cylinder, made some hacked up extension on my pedal assembly, bled the system so many times

Discovered that my pedal assembly had free play in it, ordered the parts and had it welded back up then I reinstalled it. Still the same clutch drag issues

Pulled the trans again, by this time the clutch + PP were destroyed with only 1k miles on it. Removed the shim, got an OEM clutch master, OEM slave, OEM TOB, new SB clutch + PP, resurfaced the flywheel with a reputable machine shop and now it shifts well. It was definitely a journey and I feel ya. (2018 - 2021)
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Well, I replaced the leaking SC with an OEM when I replaced the clutch & PP with an SBC kit, just replaced the lower line & hose with SS braided, had a good shop machine the flywheel to the requested step of 0.610 which I verified, and will fix the clutch pedal slop issue soon. I figured that a 1mm shim was thin enough that it wouldn't hurt and might even help since pedal full disengagement is a bit low and the flywheel has lost some metal over several resurfacings.

Given all that you did to fix this, how do you know that the shim contributed to the issues you were having?

Money and time are the issue right now. I bought this car and was suppose to be a quick and easy fix. Year later here i am. Needless to say, the woman isnt very happy. Started out has a non turbo auto. Now its 5 spd swapped with a 90 fwd turbo trans. Have 90 cables and shifter too.
Money and time explain why you did things in the past and are tempted to do them now, but they rarely justify it by themselves. Not with these cars, where it's often do it right or don't do it at all and drive something else.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
I tried driving car without shim. I couldnt get into any gear without grinding. The fork sat too far to the left in the window. That is why i added the shim. Im going to check pedal assembly and go from there. If its not worn then im not sure what i have going on.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
From my and others' experiences such issues are often if not usually the result of multiple factors and not just one. In my case it was a worn clutch, unresurfaced flywheel, bad internal trans components, sloppy shifting linkages, old slave and master cylinders and a worn pedal assembly--and possibly a worn clutch hose. I've been gradually dealing with each problem separately but until I fix all of them I'll consider the matter unresolved.

These are old cars that came off the assembly line with some weaknesses that over time manifested themselves. A poorly designed pedal assembly was one of them. As for shims, if you literally couldn't get the car into gear without one then the problem is probably not just needing a shim, but at the very least also a bad pedal assembly and one or both cylinders. Have you replaced the stock clutch hose? That also loses some hydraulic power that makes full disengagement harder.

So this doesn't get lost in the text, here's what I've done or intend to do with my drivetrain, to get it back to stock performance if not better:

  • Rebuild trans with new 1-4 synchros, springs & keys, 1-2 hub/sleeve, shims, bearings, 1-2 & 3-4 forks, pins, lock ring, lock nuts, gaskets, interlock bolt, seals, select lever bushings, dust covers, washer & shoe, plus dressed chipped or word gear teeth
  • New fork, fulcrum (1mm shim), throwout bearing & clip
  • New clutch & pressure plate
  • Resurfaced stock flywheel, stepped to 0.610"
  • New SS braided line replacing short hard line & hose
  • New slave cylinder with speed bleeder
  • Tightened slightly loose pedal shaft nut after pulling pedal all the way up
  • Turned out MC rod as far as it would go
  • Cleaned, painted & rebuilt steering knuckles with new bearings & seals
I may have missed a step or two as I've done so much on the car. And I've yet to do these:
  • Rebuild or replace master cylinder
  • Rebuild & adjust pedal assembly properly
Lots going on there. You do it all (per your situation) or what's the point.
 
Last edited:

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
Fairly new oem master cylinder. New aftermarket slave cylinder. I have an oem awd slave cylinder but havnt tried it yet. New fork and pivot ball. Full length ss clutch line. Have steel bushings in end of cables and for shifter base. Oem throwout bearing as well. Think im going to pull assembly, rebuild it and weld it. Then go from there. I could have a bad trans. Was in a parts car that guy didnt get to drive.
 
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