Ride of shame and the reason why

[Sdonnel]

The weather finally cooperated and my son and I got the car out today. We had done a bunch of changes and wanted to double check everything. 10 minutes into the ride, the clutch pedal went completely soft and we coasted to the side of the road. I had a feeling right away it had to do with the external slave, but needed to look to be sure. Sure enough, the piston had come out of the body of the cylinder. I believe the cause of this was that I had the slave cylinder shaft angled back to the piston. That, or I should have put some washers under the slave cylinder for better alignment. I went with the external in case I had issues (to avoid pulling the transmission with an internal slave). I'm hoping those of you using Forte's external slave will comment on a potential solution. I am in NO WAY saying this is an issue with the slave. It's more the mechanic that installed it and how short he cut the actuating rod. I took a pic of the current state of the external slave as well as the required pic on the roll back.

Scott


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[Scott Zackowski]

As you discovered, the external slave piston does not have a stop. If the travel of of the Clutch Pedal itself or the Master Cylinder is too much the external slave piston will be pushed out.

In my build I prevented this by putting a stop bracket on the clutch pedal. But you have to make sure you are getting enough travel in the external slave push rod to fully disengage the clutch. So the length of rod is important as well. I set up mine so that the front edge of the slave piston came just to the edge of the housing. I think it is okay to have it protrude no more than 1/8 inch, but I am not sure about that.

Maybe EdwardB will chime in.

[mcwho]

I have an extenal slave as well, have wondeed about a stop backet also. How many miles do you have on the car now? I used Ford Ruby Red.

Bob

[GTBradley]

It happens to the cable guys too. Mine popped at about 1000 miles - same ride home.

[phileas_fogg]

If you cut the slave push rod too short, you can easily make another by cutting the head off a 5/16"-24 bolt (assuming that's the size of your current pushrod). Not that I had to do that...:p

I've added the description of what I did for a clutch stop below. It's worked flawlessly for the past year / 3000 miles.


John

--------------------------------------------

Clutch Stop Part 1

A late add for my build was a clutch stop. Now that I’ve got my pedals set where I want them (for now anyway), I realized that at max extension the clutch arm is roughly 2 1/2” away from the forward foot box wall. That means the only thing stopping my clutch was whatever retaining ring or jam nut was inside the Wilwood clutch master cylinder.

I don’t weld, so I decided to beef up the forward foot box wall with a backing plate. Then I’d use some 1/2”-13 bolts and a coupler to make the stop.

I made the backing plate out of 16 gauge steel.

https://farm1.staticflickr.com/981/41058815975_9d6e1a5e45_k.jpg (https://flic.kr/p/25yeawg)IMG_4410 (https://flic.kr/p/25yeawg) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

I used a generous amount of JB Weld and some rivets to secure it in place. Note that the backing plate goes inside the foot box, not outside as shown in the picture below.

https://farm1.staticflickr.com/950/41239444374_7aaba7efdc_k.jpg (https://flic.kr/p/25QbW41)IMG_4410 (https://flic.kr/p/25QbW41) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

I placed my stop fairly high off the floor to take advantage of the slight bend in the foot box aluminum. The bend adds stiffness, and I want as much as I can get.

The stop itself will be made of 1/2"-13 bolts and a coupler.


John

----------------------------------------

Clutch Stop Part 2

With the carpet in place, I was able to mock up the post for the clutch stop. It took a couple of tries, but I found a combination of bolts and washers that will work.

https://farm1.staticflickr.com/965/27174642927_7b102f0136_k.jpg (https://flic.kr/p/Hpk9Ak)IMG_4445 (https://flic.kr/p/Hpk9Ak) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

For those interested, I used two 1/2”-13 x 3/4” bolts with a a 3/4” coupler. I used two SAE washers (on the outside of the foot box panel and on the inside next to the backing plate) and two USS washers under the inside bolt. I may have to add or subtract a USS washer depending on a drive test.


John

[Sdonnel]

John,
I plan to replicate your stop as well as making a longer extension rod from the bolt. I appreciate the responses to my situation. I was originally thinking internal slave. I like the idea of not pulling the transmission. Again.

Scott

[edwardb]

Hey Scott and Zach. Hate to see that. My ride of shame a year or two ago was a similar distance. Completely different issue though. But also a bit self-inflicted. I'm not following how cutting the pushrod too short caused that. You want the pushrod cut (and the Heim joint adjusted) so that it's just lightly loose with the pedal at rest. Ideally it should be lined up. So if you need to add spacers so it's a straight push, sure won't hurt anything. With the clutch pedal pushed all the way down as far as it can go, you shouldn't extend the slave any more than the absolute max of it's rated travel. The CNC's I've used were rated for 1.125 inches. Can't tell if you have a CNC or whatever Forte replaced it with. Both of the CNC setups I did maxed at 1.0625 inches and never had an issue. Adding a stop isn't a bad idea if needed. Just keep in mind (Mr. Obvious here...) that if you're stopping short of the back wall, e.g. max travel possible, then the effort is higher for the same clutch travel. For mine, I changed to a Wilwood 1 inch MC. That, along with the CNC 7/8 inch slaves I used, pushing the pedal hard against the back wall still didn't exceed the CNC travel, fully released the clutch, and gave me the lightest possible clutch effort. Hopefully something in there is helpful.

FYI, the Tilton 6000-Series Hydraulic Release Bearing in my Coupe is awesome. Some exact flywheel, clutch, and pedal box as my Anniversary Roadster with the Forte external setup. The effort is considerably less in the Coupe and it's glass smooth. I'm super impressed with it and was simple to install. Of course holding my breath if anything should happen because it's a teardown as you said. But so far I'm loving it. Just had to throw that in. ;)

BTW, that's with the 115 miles I've got on the Coupe. Come on Michigan. Give me a break.

[boat737]

My clutch stop. Wilwood 1" master, CNC 7/8" slave. The carriage bolt contacts the back side of the actual pedal, not the pedal arm. Also, my clutch pedal is adjusted about an inch aft of the brake pedal.

[CraigS]

If the slave piston comes out of the cylinder I would think about a smaller MC or larger slave to reduce the amount that the slave piston moves. This would also give a lighter pedal effort. Not that I don't think a pedal stop is a good idea, but both a stop and a different sized cylinder could be a good solution.

[rich grsc]

If the slave piston comes out of the cylinder I would think about a smaller MC or larger slave to reduce the amount that the slave piston moves. This would also give a lighter pedal effort. Not that I don't think a pedal stop is a good idea, but both a stop and a different sized cylinder could be a good solution.
And here you have the correct reason for the failure, and the fix.

[Jeff's First FFR]

Practice driving without using the clutch. You will save the cost of a tow. Old Volkswagons had a propensity of breaking their clutch cable.
and my 1965 Mustang had a clutch problem. I have become proficient in starting the car in gear and shifting by matching revs. That is the main reason i did not wire the clutch switch. Made it home every time.

[mike223]

The CNC's I've used were rated for 1.125 inches. Can't tell if you have a CNC or whatever Forte replaced it with. Both of the CNC setups I did maxed at 1.0625 inches and never had an issue.




If the slave piston comes out of the cylinder I would think about a smaller MC or larger slave to reduce the amount that the slave piston moves. This would also give a lighter pedal effort. Not that I don't think a pedal stop is a good idea, but both a stop and a different sized cylinder could be a good solution.


And here you have the correct reason for the failure, and the fix.

Not to disagree with Craig or Rich - but back to Edward's statement and to the OP:

A big part of the problem is that with many SBF clutch / pressure plate / clutch fork combinations - you need (nearly) a full 1.125 of throw to go from just clear of the throwout bearing to full release of the clutch.

It can be a very ticky adjustment - you need the least amount of "full release of clutch" you can live with.


SN95 fork and cable clutch here (with a slightly oversized aftermarket quadrant to provide enough throw).

[mike223]

Out of curiosity I went and measured.

I'm running a full 1.375" throw on a SN95 fork via cable/quadrant.


Not saying you can't get it done with 1.0625" - obviously many have.

Just saying the setup and adjustment on 1.0625" (or not to exceed 1.125") is a lot more critical.

[edwardb]

Out of curiosity I went and measured.

I'm running a full 1.375" throw on a SN95 fork via cable/quadrant.


Not saying you can't get it done with 1.0625" - obviously many have.

Just saying the setup and adjustment on 1.0625" (or not to exceed 1.125") is a lot more critical.

Your point is totally valid. But with one additional variable. For the hydraulic setups, the connection to the clutch arm is often in a different location than where the cable attaches. Not sure where you're measuring the 1.375 inches. This is the setup on my 20th Anniversary Roadster. The outer bolt holding the bracket onto the clutch arm is through the hole where the cable would normally connect. So the 1.0625 inch slave movement I referenced would measure as a higher value at the actual cable connection location. Even more if measured at the end of the clutch arm. This setup releases the clutch just fine. With a 1 inch MC as mentioned earlier, and the clutch pedal aligned with the brake pedal when released.

https://hosting.photobucket.com/albums/ab234/edwardb123/Factory%20Five%2020th%20Anniversary%20Mark%204%20R oadster/Coyote%20Engine/IMG_4308_zpsbs6rkvtm.jpg?width=590&height=370&fit=bounds (https://app.photobucket.com/u/edwardb123/p/9a6a3d9e-2667-45cb-96e1-1a9d119099b0)

[mike223]

Your point is totally valid. But with one additional variable. For the hydraulic setups, the connection to the clutch arm is often in a different location than where the cable attaches. Not sure where you're measuring the 1.375 inches.

The outer bolt holding the bracket onto the clutch arm is through the hole where the cable would normally connect.

So the 1.0625 inch slave movement I referenced would measure as a higher value at the actual cable connection location. Even more if measured at the end of the clutch arm.



All agreed - that definitely changes the math, I'm not sure exactly how much - probably easier for you to measure. :p

My 1.375" is actual cable/fork movement measured at the (SN95) fork where the cable attaches.

[mcwho]

Your post intrigued me...

My 2 cents worth. I apologize fo the quality of this video but I just got the gopro last week. My thow looks to be about 1 1/4 to 1 3/8. I dont have a stop but it seems to be ok, I have 1800 miles on the car.

video link
https://www.youtube.com/watch?v=UnaKOP-YbXw

Bob

[Sdonnel]

Thank you for all the input and suggestions. I pulled the boot forward and the piston is protruding as expected. The o-ring is about 3/16 inch clear of the slave cylinder. Before any disassembly, my son and I will get the piston back into the bore and check travel. Once we know that dimension, I can start to plan the next steps. My pedal assembly is the trio that Mike Forte sells along with his external slave kit. I'll give Mike a call Monday if I find anything out of ordinary once I get the car up in the air. While there are always things that can come up, this forum and it's members make solving the issue a great and learning experience.

Scott & Zach

[mcwho]

I agree with your recommendation to practice driving wo using the clutch. Had many fists and alfas and even a sunbeam tiger when I was younger. Never had a tow!

[Railroad]

I need to look into a larger bore slave cyl. I have the Forte kit, but the pedal is pretty heavy. My clutch engagement is at the top, so it should not create a problem. Maybe Mike knows what bore I have so, it will be an easy swap.

[ThickCobra]

Hey Scott and Zach. Hate to see that. My ride of shame a year or two ago was a similar distance. Completely different issue though. But also a bit self-inflicted. I'm not following how cutting the pushrod too short caused that. You want the pushrod cut (and the Heim joint adjusted) so that it's just lightly loose with the pedal at rest. Ideally it should be lined up. So if you need to add spacers so it's a straight push, sure won't hurt anything. With the clutch pedal pushed all the way down as far as it can go, you shouldn't extend the slave any more than the absolute max of it's rated travel. The CNC's I've used were rated for 1.125 inches. Can't tell if you have a CNC or whatever Forte replaced it with. Both of the CNC setups I did maxed at 1.0625 inches and never had an issue. Adding a stop isn't a bad idea if needed. Just keep in mind (Mr. Obvious here...) that if you're stopping short of the back wall, e.g. max travel possible, then the effort is higher for the same clutch travel. For mine, I changed to a Wilwood 1 inch MC. That, along with the CNC 7/8 inch slaves I used, pushing the pedal hard against the back wall still didn't exceed the CNC travel, fully released the clutch, and gave me the lightest possible clutch effort. Hopefully something in there is helpful.

FYI, the Tilton 6000-Series Hydraulic Release Bearing in my Coupe is awesome. Some exact flywheel, clutch, and pedal box as my Anniversary Roadster with the Forte external setup. The effort is considerably less in the Coupe and it's glass smooth. I'm super impressed with it and was simple to install. Of course holding my breath if anything should happen because it's a teardown as you said. But so far I'm loving it. Just had to throw that in. ;)

BTW, that's with the 115 miles I've got on the Coupe. Come on Michigan. Give me a break.

Edwardb, did you mention the pushrod should be slightly loose at (pedal) rest?

Jay

[Jeff Kleiner]

Practice driving without using the clutch. You will save the cost of a tow. Old Volkswagons had a propensity of breaking their clutch cable.
and my 1965 Mustang had a clutch problem. I have become proficient in starting the car in gear and shifting by matching revs. That is the main reason i did not wire the clutch switch. Made it home every time.

And that is EXACTLY why I put a toggle switch under the dash of every one I build which bypasses the clutch safety switch and I explain it's purpose to the owners! As far as I know no one has ever had to use it but they're ready just in case. I had an old hydraulic clutch Toyota Celica that I had to limp home 2 or 3 times after the slave cylinder puked. RE: speed matched shifting... I'd say that if I'm just cruising a good 25% of the time once my car is rolling I don't touch the clutch again until coming to a stop---you gotta' love those smooth shifting T5s :)

Jeff

[Sdonnel]

Good Afternoon Guys,
I got under the car and started to evaluate what happened. Based on the original photo, the piston was protruding from the bore and cocked in the opening. I took a C clamp and compressed the shift arm enough to realign and re-insert the piston into the bore. Released the C-clamp slowly and it went right back into position and worked as desired. While I had everything compressed, I took some measurements. Piston diameter on the slave is 3/4" and the piston front lip rests 3/4 inch inside the housing. Once we bled the clutch pedal, my son cycled the pedal to the bottom of the travel. Each time he did this, the piston protruded from the bore of the slave by 1/4 inch and the O-ring was clear of the housing by about 1/8 inch as well. This is where my problem occurred. One of the measurements we took was the amount of movement of the shift arm. It traveled 15/16 of an inch from start to finish. I have attached a photo of the piston at the point where the clutch pedal is fully depressed.
I also wanted to respond to those that said rev matching would have gotten me home. When the piston came out of the piston and jammed, the clutch was hung in the open position. There was no power going to the driveshaft. Had it gone south with the clutch engaged, I would have learned to rev match pretty quickly. Apparently, my son has mastered the technique with his Accord coupe, as he doesn't touch the clutch after first gear ( so I'm told). I still have to determine which master cylinder I have from Forte to know that last piece of the puzzle.

Keep the responses and solutions coming. I'm headed back out to shim the slave for better alignment and then start working on the pedal stop.

Scott

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[edwardb]

Edwardb, did you mention the pushrod should be slightly loose at (pedal) rest?

Jay

Yes that's what I said. Are you concerned that's not a proper setting?

[ThickCobra]

Yes that's what I said. Are you concerned that's not a proper setting?

My concern is mine is not set properly. I recently removed my CNC slave cylinder and its mount while needing to separate the transmission from the engine. That was fun...not! Reinstalling the mount and slave required me to compress the pushrod to tighten all bolts. Again, not fun. As such I have no play whatsoever at pedal rest. I'll be working on that today.

Just one more reason to read up on forum posts. Some of us (me) are never really done with adjustments.

Thanks, Jay

[nelsond003]

Hey Scott and Zach. Hate to see that. My ride of shame a year or two ago was a similar distance. Completely different issue though. But also a bit self-inflicted. I'm not following how cutting the pushrod too short caused that. You want the pushrod cut (and the Heim joint adjusted) so that it's just lightly loose with the pedal at rest. Ideally it should be lined up. So if you need to add spacers so it's a straight push, sure won't hurt anything. With the clutch pedal pushed all the way down as far as it can go, you shouldn't extend the slave any more than the absolute max of it's rated travel. The CNC's I've used were rated for 1.125 inches. Can't tell if you have a CNC or whatever Forte replaced it with. Both of the CNC setups I did maxed at 1.0625 inches and never had an issue. Adding a stop isn't a bad idea if needed. Just keep in mind (Mr. Obvious here...) that if you're stopping short of the back wall, e.g. max travel possible, then the effort is higher for the same clutch travel. For mine, I changed to a Wilwood 1 inch MC. That, along with the CNC 7/8 inch slaves I used, pushing the pedal hard against the back wall still didn't exceed the CNC travel, fully released the clutch, and gave me the lightest possible clutch effort. Hopefully something in there is helpful.

FYI, the Tilton 6000-Series Hydraulic Release Bearing in my Coupe is awesome. Some exact flywheel, clutch, and pedal box as my Anniversary Roadster with the Forte external setup. The effort is considerably less in the Coupe and it's glass smooth. I'm super impressed with it and was simple to install. Of course holding my breath if anything should happen because it's a teardown as you said. But so far I'm loving it. Just had to throw that in. ;)

BTW, that's with the 115 miles I've got on the Coupe. Come on Michigan. Give me a break.

What size master are you using with your Tilton-6000? I have the same set up, clutch works fine, but it is a little firmer than I thought it would be.......Compared to the Hydraulic clutch in my C7/Z06.

[Railroad]

Moved by railroad.

[edwardb]

What size master are you using with your Tilton-6000? I have the same set up, clutch works fine, but it is a little firmer than I thought it would be.......Compared to the Hydraulic clutch in my C7/Z06.

Wilwood 260-10373 13/16 inch MC with a Tilton 6000-Series Hydraulic Release Bearing 60-6104. This specific HRB is for a T-56. Other part numbers for TKO, etc. The instructions from Tilton describe how to size the MC. I followed them and happy with the result. Obviously I have no way to know what your C7/Z06 feels like. Many OE's (like Mustang, for example) have spring assists on the clutch pedal. May not be possible to get this setup similar. My comparison is to the exact setup on my Roadster with the Forte external slave. The HRB is considerably lighter.

Little off topic from the thread. Happy to respond to PM's if you have more questions.

[Scott Zackowski]

Here is another option for clutch pedal stop.

It was designed by my son, a mechanical engineer, who calculated the stresses and forces that would be applied by the pedal and developed this minimalistic bracket. We slipped a piece of left over silicone hose for padding. It gives a great feel when the pedal is bottomed out. The forward bolt is tapped in and the rear bolt goes all the way through.

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[Sdonnel]

I was able to resolve the piston extending out of the slave by making a longer push rod and for good measure, also installed a pedal stop. When the pedal hits the stop, the piston is 1/16” behind the lip of the cylinder body and the clutch pedal comes up about 1/2” before the it catches.

Thank you for all the ideas and solutions.

Scott

[Avalanche325]

I had my ride of shame recently from the same issue. I am not using the Forte setup. But the same thing happened to me. I popped the piston out and jammed the clutch completely disengaged. It was fun sitting at a light, no propulsion and cars coming up behind me at 70+mph. I pushed her off the road in record time.

Called AAA and waited for 4 hours. The first tow company bailed on me after two hours. Of course my wife was with me. It was the first time in my life that I have ever had a car towed. I have always been able to at least limp home.

When I was installing my slave, I noticed that there was a groove for a c-clip in the bore. I thought about putting one in, but I didn't. One day I am going to learn that if I am not 100% happy with something, take care of it NOW. So that was my non-existent safety interlock.

The other issue was my own manner of nit-wittery. My piston has a spring behind it. I obviously did not get it pushed far enough in when I did my initial setup. On my redo, the rod went in much further. My replacement slave also came out of the box with a c-clip.

I also added a pedal stop. Mine is a steel plate that bolts through the firewall and sits behind the carpet. It is threaded for the stop bolt. That bolt does not go though the firewall. I found the length bolt that I was happy with and that is done.

The worst part of the whole ordeal????? I had to listen to country music for two hours while in the tow truck.

[RoadRacer]

Practice driving without using the clutch. You will save the cost of a tow. Old Volkswagons had a propensity of breaking their clutch cable.
and my 1965 Mustang had a clutch problem. I have become proficient in starting the car in gear and shifting by matching revs. That is the main reason i did not wire the clutch switch. Made it home every time.

This has come up so many times in this thread that I have to ask.. I've been driving (lol) 40 years and never heard of this before. I have never even considered trying to start a car in gear! I feel dumb now, and I grew up in UK where a stick was normal.

I'm fascinated, so would love to know the "tricks" if there are any. I'm amazed you can get the engine cranking fast enough to start while in 1st... and as for 'matching revs' are you saying that you pull out of gear, blip throttle then put it in gear? I do that anyway when changing down, since "double de-clutching" as we used to call it makes the shifts smoother.

Sorry for being slightly off-topic, but it seems a good place to learn about this :D

[Gromit]

back in the day my 86 Iroc had the Hydraulic clutch slave cylinder fail, I drove it home shifting it clutch less. and yes. you can even start a carbureted car in first. it just lugs a bit. no AAA at the time and it was still under warranty so I have know idea what the root cause was. up shifts are easy. its a bit harder to get the correct engine speed on the down shifts.