greekgodchaos
15+ Year Contributor
- 513
- 126
- Jul 4, 2007
-
Vancouver,
Washington
Hey all,
I am currently in the process of my Omega build, and when it comes to the PTT Twin Disc clutch I got, its muddy waters for me. So I am collecting all the useful information here (much of it is circa 2006-2013, so expect outdated and mostly wrong information from those who never bothered to contact PTT for help), including a Q/A I had with Steve (President of PTT), who was kind enough to answer some of my questions and then some. I decided to put all the information I found here so it can be found by anyone else wanting to use a PTT Twin Disc in the future.
A TON of misinformation is out there regarding PTT and their Twin Disc Clutches just bashing their product, and all because an end user heard from a friends-friend or followed what opossumlover69420 posted on DSMtalk in 2007 based on an incorrect installation using their backwoods mechanic skills.
-------------------------------
This is my email to/from Steve on 04/24/2022:
Subject: Installation Questions (91 Eclipse 6-bolt AWD)
Hi, I recently purchased a PTT Twin Disc/ Flywheel from ExtremePSI, and at the moment I am having a local shop assemble my motor, but its going to be a while before I get it all back.
I have been searching high and low for any in-depth how-to articles pertaining to the PTT Twin Disc Clutch installation besides what was included with the clutch itself. I have the information I need in regards to the Isuzu Trooper slave cylinder and the modifications that need to be done to it in order for it to fit and operate properly. That's all pretty straightforward.
What I am hung up on right now is the use of a clutch pedal stop; some say it's necessary, while others advise against it. I found one post that references a Steve at PTT that supposedly said, quoted from their post:
"Yes I did have a pedal stop in there but Steve @ PTT told me to take it out and extend the clutch as far down as it will go and since they use a regressive spring it gets hard then soft then it would get hard again and that is there built in clutch stop so the fingers aren't over extended. He told me I should push down until the built in stop and the clutch should be fully disengaged. I did that and it was disengaging properly but the pedal assembly was way past the "auto adjust" to get it to go to the stop. I can't get the clutch to fully disengage without being past what is acceptable. I did think I was over extending the fingers until I talked to the owner of PTT." Original thread/post found here
Here is a how-to posting regarding the custom pedal stop.
Any information you can provide for me to make this installation go as smoothly as possible would be great.
Signed,
Alex
-------------------
(NOTE: I bolded/colored key points IMO are critical)
Subject:RE: Installation Questions (91 Eclipse 6-bolt AWD)
Alex,
Like a lot of info posted to the interweb, some of the info you have is correct, and some of it is mis-interpreted, and wrong.
Proper clutch release is all about having the proper motion ratio between the clutch pedal, and the release bearing pushing the diaphragm spring fingers of the clutch. The following points should always be adhered to:
1. The quote you sent from the post you found is a little wrong. Someone was trying to incorrectly quote me form memory, or they simply did not fully understand my original explanation.
2. You always want to be able to depress the clutch pedal fully. Use the full pedal stroke to your advantage. More leverage is GOOD.
3. The motion ratio should be: One full stroke of the pedal = 3/8” (10mm) movement of the release bearing.
4. Stock clutch release bearing ratios are usually approximately: One full stroke = ¾” (19mm) movement of the release bearing. This is because stock style, large diameter clutches use that much movement of the spring fingers to fully release.
5. PTT clutches are high performance, small diameter, multi-disc RACING clutches. As a result, they are engineered to have a very short spring travel for full release (disengagement).
6. When installing a PTT clutch in a car with a stock clutch release mechanism, you must alter the motion ratio. If you do not, you will over-travel the PTT clutch (potentially most likely damaging it), the pedal force will be quite high (potentially damaging the thrust bearing in the engine), and the clutch will feel like an ON/OFF switch, resulting in a very difficult driving experience. (You will NOT be happy with the driving experience)
7. The Isuzu Trooper slave cylinder was developed as a low-cost way to change the motion ratio of the early Mitsu clutch release mechanism. It works, BUT, because this is a racing clutch, you should always check the installation for proper clutch release, without over-travel. Something we found difficult to get across to all end users.
8. You should always have the factory specified amount of pedal free-play (1/2” (12mm)), at the top of the pedal stroke. Some end users were too lazy to get the proper slave cylinder, and PTT bearing, and adjusted the master cylinder pedal clevis to have 3-4” of pedal free play instead. Do not do this. It is difficult (unsafe) to drive.
9. Upon installation (of a PTT clutch, release bearing, and Trooper slave cylinder), you must check for clutch over-travel. IF your particular installation results in over-travel (all installations are slightly different) you must install a pedal stop on the floor of the car to prevent clutch damage.
10. You must run the PTT supplied release bearing with the Trooper slave cylinder. This will result in a smooth, more linear clutch release. If you run the Mitsu release bearing, it will result in high pedal force, and increased force on the engine thrust bearing (potentially damaging the engine).
11. PTT racing clutches (like ALL diaphragm spring equipped clutches) use a regressive rate diaphragm spring. When the clutch pedal is fully depressed (at the floor) the pedal effort is reduced from the amount of effort it took to push the pedal to the floor. Halfway to the floor the pedal force peaks. All the way to the floor, there is a substantial force reduction. (OEMs do this to make it easy to hold the clutch pedal to the floor while sitting at a stop light.)
12. If you push the clutch pedal to the floor with your arm (which is much more sensitive) instead of your leg, you will feel this force difference as you stroke the clutch pedal from fully engaged (up) to fully disengaged (at the floor). Yes, there is a travel limiting stop built into every PTT clutch cover. IF you do not have the motion ratio correct, you can feel the pedal force go back up again a second time as the clutch pedal nears the floor (checking with your ARM). You must install a pedal stop (or lower the clutch release mechanism motion ratio) to prevent the release bearing from going so far that you hit the internal stop built into the clutch cover. If you can feel the pedal force go up a second time as the clutch pedal nears the floor, STOP, and correct the problem. You risk damaging the clutch if you over-travel it so much that you hit the internal stop.
13. One way to check for complete clutch release: Engine Off. Car on jack stands. Put the car in gear. Have a buddy try and rotate the driveshaft, as you sloooooowwwwwlllly push the clutch pedal. Clutch release occurs when your buddy can rotate the driveshaft. If release occurs too early in the pedal stroke (near the top of the stroke), you need more motion ratio. If the clutch release occurs too late in the pedal stroke (near the floor) you need less pedal ratio.
14. There are other variables involved in the design and proper adjustment of external slave cylinder clutch release mechanisms (such as pushrod length, proper fork geometry, ball stud height, etc., which I will not get into here). For your installation, all of those stock components will work just fine. IF a previous car owner has replaced or modified any of those components………
15. ALL of the above info pertains to a clutch in brand new condition, being properly installed for the first time. Used clutches have other difficulties I do not have the time to get into.
16. THE most common tech question we answer, here at PTT, is: Why won’t my clutch release? OR Why is my car so difficult to drive (because the clutch release mechanism is like an ON/OFF switch? It is almost never the clutch at fault. It almost always (99% of the time) is a mis-matched component, or incorrect adjustment in the clutch release mechanism, resulting in an incorrect motion ratio.
It sounds to me like you are properly gathering (from me, at least) all the info you need for a seamless clutch installation, and you have a pretty good handle on what you are doing. Do not over-think it. Gather good advice from known, reputable sources. All reputable manufacturers have an engineer or tech person on staff, who will answer questions. Be very suspect and afraid of answers gained from the internet, especially forums… Good luck. We are always here if you have questions.
Regards,
Steven Fox
President
POWERTRAIN TECHNOLOGY, Inc.
---------------------------
I myself will be posting more when I have more information to share.
I want to keep this thread free of any "I think", "I heard", "I read somewhere" comments, without anything to back them up.
If you have had a successful first-hand installation without issue with the PTT Twin Disc specifically, please post any information you wish to share to make this an easier installation for future users.
Useful Links
Pedal Stop DIY
Info and Review
PTT FAQ
PTT Resources
Pedal Stop DIY Photos
Isuzu Trooper Slave Fitment Modifications
I am currently in the process of my Omega build, and when it comes to the PTT Twin Disc clutch I got, its muddy waters for me. So I am collecting all the useful information here (much of it is circa 2006-2013, so expect outdated and mostly wrong information from those who never bothered to contact PTT for help), including a Q/A I had with Steve (President of PTT), who was kind enough to answer some of my questions and then some. I decided to put all the information I found here so it can be found by anyone else wanting to use a PTT Twin Disc in the future.
A TON of misinformation is out there regarding PTT and their Twin Disc Clutches just bashing their product, and all because an end user heard from a friends-friend or followed what opossumlover69420 posted on DSMtalk in 2007 based on an incorrect installation using their backwoods mechanic skills.
This is not a brand comparison thread.
-------------------------------
This is my email to/from Steve on 04/24/2022:
Subject: Installation Questions (91 Eclipse 6-bolt AWD)
Hi, I recently purchased a PTT Twin Disc/ Flywheel from ExtremePSI, and at the moment I am having a local shop assemble my motor, but its going to be a while before I get it all back.
I have been searching high and low for any in-depth how-to articles pertaining to the PTT Twin Disc Clutch installation besides what was included with the clutch itself. I have the information I need in regards to the Isuzu Trooper slave cylinder and the modifications that need to be done to it in order for it to fit and operate properly. That's all pretty straightforward.
What I am hung up on right now is the use of a clutch pedal stop; some say it's necessary, while others advise against it. I found one post that references a Steve at PTT that supposedly said, quoted from their post:
"Yes I did have a pedal stop in there but Steve @ PTT told me to take it out and extend the clutch as far down as it will go and since they use a regressive spring it gets hard then soft then it would get hard again and that is there built in clutch stop so the fingers aren't over extended. He told me I should push down until the built in stop and the clutch should be fully disengaged. I did that and it was disengaging properly but the pedal assembly was way past the "auto adjust" to get it to go to the stop. I can't get the clutch to fully disengage without being past what is acceptable. I did think I was over extending the fingers until I talked to the owner of PTT." Original thread/post found here
Here is a how-to posting regarding the custom pedal stop.
Any information you can provide for me to make this installation go as smoothly as possible would be great.
Signed,
Alex
-------------------
(NOTE: I bolded/colored key points IMO are critical)
Subject:RE: Installation Questions (91 Eclipse 6-bolt AWD)
Alex,
Like a lot of info posted to the interweb, some of the info you have is correct, and some of it is mis-interpreted, and wrong.
Proper clutch release is all about having the proper motion ratio between the clutch pedal, and the release bearing pushing the diaphragm spring fingers of the clutch. The following points should always be adhered to:
1. The quote you sent from the post you found is a little wrong. Someone was trying to incorrectly quote me form memory, or they simply did not fully understand my original explanation.
2. You always want to be able to depress the clutch pedal fully. Use the full pedal stroke to your advantage. More leverage is GOOD.
3. The motion ratio should be: One full stroke of the pedal = 3/8” (10mm) movement of the release bearing.
4. Stock clutch release bearing ratios are usually approximately: One full stroke = ¾” (19mm) movement of the release bearing. This is because stock style, large diameter clutches use that much movement of the spring fingers to fully release.
5. PTT clutches are high performance, small diameter, multi-disc RACING clutches. As a result, they are engineered to have a very short spring travel for full release (disengagement).
6. When installing a PTT clutch in a car with a stock clutch release mechanism, you must alter the motion ratio. If you do not, you will over-travel the PTT clutch (
7. The Isuzu Trooper slave cylinder was developed as a low-cost way to change the motion ratio of the early Mitsu clutch release mechanism. It works, BUT, because this is a racing clutch, you should always check the installation for proper clutch release, without over-travel. Something we found difficult to get across to all end users.
8. You should always have the factory specified amount of pedal free-play (1/2” (12mm)), at the top of the pedal stroke. Some end users were too lazy to get the proper slave cylinder, and PTT bearing, and adjusted the master cylinder pedal clevis to have 3-4” of pedal free play instead. Do not do this. It is difficult (unsafe) to drive.
9. Upon installation (of a PTT clutch, release bearing, and Trooper slave cylinder), you must check for clutch over-travel. IF your particular installation results in over-travel (all installations are slightly different) you must install a pedal stop on the floor of the car to prevent clutch damage.
10. You must run the PTT supplied release bearing with the Trooper slave cylinder. This will result in a smooth, more linear clutch release. If you run the Mitsu release bearing, it will result in high pedal force, and increased force on the engine thrust bearing (potentially damaging the engine).
11. PTT racing clutches (like ALL diaphragm spring equipped clutches) use a regressive rate diaphragm spring. When the clutch pedal is fully depressed (at the floor) the pedal effort is reduced from the amount of effort it took to push the pedal to the floor. Halfway to the floor the pedal force peaks. All the way to the floor, there is a substantial force reduction. (OEMs do this to make it easy to hold the clutch pedal to the floor while sitting at a stop light.)
12. If you push the clutch pedal to the floor with your arm (which is much more sensitive) instead of your leg, you will feel this force difference as you stroke the clutch pedal from fully engaged (up) to fully disengaged (at the floor). Yes, there is a travel limiting stop built into every PTT clutch cover. IF you do not have the motion ratio correct, you can feel the pedal force go back up again a second time as the clutch pedal nears the floor (checking with your ARM). You must install a pedal stop (or lower the clutch release mechanism motion ratio) to prevent the release bearing from going so far that you hit the internal stop built into the clutch cover. If you can feel the pedal force go up a second time as the clutch pedal nears the floor, STOP, and correct the problem. You risk damaging the clutch if you over-travel it so much that you hit the internal stop.
13. One way to check for complete clutch release: Engine Off. Car on jack stands. Put the car in gear. Have a buddy try and rotate the driveshaft, as you sloooooowwwwwlllly push the clutch pedal. Clutch release occurs when your buddy can rotate the driveshaft. If release occurs too early in the pedal stroke (near the top of the stroke), you need more motion ratio. If the clutch release occurs too late in the pedal stroke (near the floor) you need less pedal ratio.
14. There are other variables involved in the design and proper adjustment of external slave cylinder clutch release mechanisms (such as pushrod length, proper fork geometry, ball stud height, etc., which I will not get into here). For your installation, all of those stock components will work just fine. IF a previous car owner has replaced or modified any of those components………
15. ALL of the above info pertains to a clutch in brand new condition, being properly installed for the first time. Used clutches have other difficulties I do not have the time to get into.
16. THE most common tech question we answer, here at PTT, is: Why won’t my clutch release? OR Why is my car so difficult to drive (because the clutch release mechanism is like an ON/OFF switch? It is almost never the clutch at fault. It almost always (99% of the time) is a mis-matched component, or incorrect adjustment in the clutch release mechanism, resulting in an incorrect motion ratio.
It sounds to me like you are properly gathering (from me, at least) all the info you need for a seamless clutch installation, and you have a pretty good handle on what you are doing. Do not over-think it. Gather good advice from known, reputable sources. All reputable manufacturers have an engineer or tech person on staff, who will answer questions. Be very suspect and afraid of answers gained from the internet, especially forums… Good luck. We are always here if you have questions.
Regards,
Steven Fox
President
POWERTRAIN TECHNOLOGY, Inc.
---------------------------
I myself will be posting more when I have more information to share.
I want to keep this thread free of any "I think", "I heard", "I read somewhere" comments, without anything to back them up.
If you have had a successful first-hand installation without issue with the PTT Twin Disc specifically, please post any information you wish to share to make this an easier installation for future users.
Useful Links
Pedal Stop DIY
Info and Review
PTT FAQ
PTT Resources
Pedal Stop DIY Photos
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Isuzu Trooper Slave Fitment Modifications
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
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