TheRealMRDyno
10+ Year Contributor
- 46
- 5
- Aug 19, 2009
-
Akron,
Ohio
Just some info for anyone fighting with clutch disengagement issues, from my own painful experience.
The very short story when trying to sort this out is this:
1) Get a $10 digital caliper from Harbor Freight, etc
2) Have a friend help you with the clutch pedal, while you measure what the slave cylinder pin / release fork is doing. You want to measure how far the pin/fork is moving when the clutch pedal is pressed.
3) If you are not getting 0.351" at the slave/fork, you have an issue with your pedal assembly, hydraulics, need to bleed it, etc.
4) If your slave/fork is moving by 0.351", the clutch should release, and it should really, really release by 0.520" (see below). If it moves this much and does not release, you almost certainly have a bent/warped friction disk, or maybe a too-short step (<0.610") on your flywheel.
5) FYI, in 5th gear, when the clutch releases, you can for sure easily rotate the transfer case shaft with a pair of channel locks, very easily. you will not hurt the splines at all, might even be able to do this by hand. (The point of which is to check release before continuing assembly of your car.)
The reasoning here is:
1) I measured the slave cylinder pin to release bearing motion of the release fork (1991 Talon TSI AWD), total end-to-end travel of each end, and got a relative motion value of 0.569444:1. From ACT, the 2600 releases at 0.200", and can accommodate a maximum of 0.300" travel of the release bearing.
2) That means the slave cylinder pin / external fork needs to move by (0.200/0.569444 =) 0.351", and less than (0.300/0.569444 =) 0.526". On my personal car, with no slop in the pedals and the clutch properly adjusted, I measured 0.520" of motion at the slave/fork with my ACT 2600 installed.
Some other things that seem to come out of this are:
1) A longer slave cylinder rod only makes sense if you don't have the slave piston pushed back far enough in the cylinder when installed to give 0.500" or so of travel before bottoming out the slave piston, which seems unlikely, and probably means some other part is seriously out of spec.
2) Shimming the fork ball does not make a lot of sense to me at all. It will give you a tiny bit more travel, but if you are not hitting the transmission case with the shift fork, I think the slave has plenty of internal travel to make up for any flywheel machining and/or friction disk wear.
FYI, you can use thin shim stock between the end of the z-bar and the crank arm to the master cylinder to take the slop out of the pedal assembly. If the crank bar is not mushroomed, and the z-bar end is not actually rounded off, this is a pretty nice fix. I used (2) pieces of 0.003" shim, one on each flat surface. This is a place-the-shims, support the z-bar shaft, and pound-together operation.
Finally, some measured values for the clutch (from ACT) and the car (me):
From Dirk Sterson (?), president of ACT, about ACT 2600 clutch:
Min bearing travel to release 0.2 Inches
Max bearing travel, to not hit disk with fingers 0.3 Inches
(current design may handle > 0.3 inches)
Pedal Mechanism
Pedal length, center to tip 15.5 Inches
Crank lever, center to center 2.5 Inches
Pedal/Master Movement Ratio 0.161290323 :1
Absolute max pedal motion at tip 7.5 Inches
Master Cylinder
Diameter 0.625 Inches (5/8 stamp on part)
Radius 0.3125 Inches
Area 0.306795898 SqInches
Slave Cylinder
Diameter 0.75 Inches (from internet)
Radius 0.375 Inches
Area 0.441786094 SqInches
M/S Movement Ratio 0.694444444 :1
Throwout Fork
Slave Cylinder Pin motion 1.417322835 Inches
Bearing Motion 0.807086614 Inches
Ratio 0.569444444 :1
Overall Pedal -> Bearing Ratio 0.06378186 :1
Soooooo........
Required Bearing Motion 0.2 Inches
Max Bearing Motion 0.3 Inches
Required Slave Motion 0.351219512 Inches
Max Slave Motion 0.526829268 Inches
Required Pedal Motion 3.135687805 Inches
Max Pedal Motion 4.703531707 Inches
Joe
The very short story when trying to sort this out is this:
1) Get a $10 digital caliper from Harbor Freight, etc
2) Have a friend help you with the clutch pedal, while you measure what the slave cylinder pin / release fork is doing. You want to measure how far the pin/fork is moving when the clutch pedal is pressed.
3) If you are not getting 0.351" at the slave/fork, you have an issue with your pedal assembly, hydraulics, need to bleed it, etc.
4) If your slave/fork is moving by 0.351", the clutch should release, and it should really, really release by 0.520" (see below). If it moves this much and does not release, you almost certainly have a bent/warped friction disk, or maybe a too-short step (<0.610") on your flywheel.
5) FYI, in 5th gear, when the clutch releases, you can for sure easily rotate the transfer case shaft with a pair of channel locks, very easily. you will not hurt the splines at all, might even be able to do this by hand. (The point of which is to check release before continuing assembly of your car.)
The reasoning here is:
1) I measured the slave cylinder pin to release bearing motion of the release fork (1991 Talon TSI AWD), total end-to-end travel of each end, and got a relative motion value of 0.569444:1. From ACT, the 2600 releases at 0.200", and can accommodate a maximum of 0.300" travel of the release bearing.
2) That means the slave cylinder pin / external fork needs to move by (0.200/0.569444 =) 0.351", and less than (0.300/0.569444 =) 0.526". On my personal car, with no slop in the pedals and the clutch properly adjusted, I measured 0.520" of motion at the slave/fork with my ACT 2600 installed.
Some other things that seem to come out of this are:
1) A longer slave cylinder rod only makes sense if you don't have the slave piston pushed back far enough in the cylinder when installed to give 0.500" or so of travel before bottoming out the slave piston, which seems unlikely, and probably means some other part is seriously out of spec.
2) Shimming the fork ball does not make a lot of sense to me at all. It will give you a tiny bit more travel, but if you are not hitting the transmission case with the shift fork, I think the slave has plenty of internal travel to make up for any flywheel machining and/or friction disk wear.
FYI, you can use thin shim stock between the end of the z-bar and the crank arm to the master cylinder to take the slop out of the pedal assembly. If the crank bar is not mushroomed, and the z-bar end is not actually rounded off, this is a pretty nice fix. I used (2) pieces of 0.003" shim, one on each flat surface. This is a place-the-shims, support the z-bar shaft, and pound-together operation.
Finally, some measured values for the clutch (from ACT) and the car (me):
From Dirk Sterson (?), president of ACT, about ACT 2600 clutch:
Min bearing travel to release 0.2 Inches
Max bearing travel, to not hit disk with fingers 0.3 Inches
(current design may handle > 0.3 inches)
Pedal Mechanism
Pedal length, center to tip 15.5 Inches
Crank lever, center to center 2.5 Inches
Pedal/Master Movement Ratio 0.161290323 :1
Absolute max pedal motion at tip 7.5 Inches
Master Cylinder
Diameter 0.625 Inches (5/8 stamp on part)
Radius 0.3125 Inches
Area 0.306795898 SqInches
Slave Cylinder
Diameter 0.75 Inches (from internet)
Radius 0.375 Inches
Area 0.441786094 SqInches
M/S Movement Ratio 0.694444444 :1
Throwout Fork
Slave Cylinder Pin motion 1.417322835 Inches
Bearing Motion 0.807086614 Inches
Ratio 0.569444444 :1
Overall Pedal -> Bearing Ratio 0.06378186 :1
Soooooo........
Required Bearing Motion 0.2 Inches
Max Bearing Motion 0.3 Inches
Required Slave Motion 0.351219512 Inches
Max Slave Motion 0.526829268 Inches
Required Pedal Motion 3.135687805 Inches
Max Pedal Motion 4.703531707 Inches
Joe
