Clutch pedal force

[chevynut]

As I mentioned in my build thread, my clutch pedal force is higher than I expected it to be. I may be spoiled by the ease of effort to depress the clutch in my Porsche, but i believe it has a dual disc clutch and pedal effort is really nice. I have read posts here from a couple of members complaining about pedal effort in their tri5 cars.

I also went out and depressed the clutch pedal in my 56 parts car and it's a lot lighter than my Nomad. However, it has a 6-cylinder engine and the clutch is smaller at 9.5", and it's a stock setup. I can't find anything in the 56 Chevy specs about clutch effort/ force needed at the clutch fingers. BTW, Chevy did offer a heavy duty 11" clutch in both 6-cylinder and V8 cars.

I'm using a Centerforce Dual Friction clutch setup, disc and pressure plate. It's an 11" diaphragm type clutch and they claim "light pedal effort". I'm now thinking that maybe I should have investigated dual disc clutches more at the time I got my setup.

I designed my pedal and hydraulic clutch system to give about .6-.65" of throwout bearing movement including about 1/16" of gap between the TO bearing and clutch fingers. This is per Novak Conversions, where I got the info. They state that it takes about 0.550" of TO bearing travel to disengage the clutch. Then they add the .063" to get 0.613" total travel needed. They did tell me that their testing was with a new, not broken in clutch disc so it's likely conservative.

McLeod says "Typically with OEM applications the throw-out bearing travel is .440” -.445”. I've read other sources with conflicting information.

Have any of you actually measured your clutch pedal force, or fork travel, or have info on what it should be?

[55 Rescue Dog]

On my Camaro I used a Howe hydraulic throwout bearing which has a travel of .688 inches and it has been working perfect for 10 years. Every pivot point adds resistance to the pedal force and the hydraulic bearing eliminates 3 pivot points. It's never needed adjustment and the pedal pressure is smooth and light, easy to modulate with perfect travel. I even had to go to a 7/8' master cylinder to get less travel and it added little to the pedal force using a 7:1 pedal.

Throw Out Bearings - Howe Racing Enterprises, Inc (https://howeracing.com/collections/throw-out-bearings)

[chevynut]

On my Camaro I used a Howe hydraulic throwout bearing which has a travel of .688 inches and it has been working perfect for 10 years. Every pivot point adds resistance to the pedal force and the hydraulic bearing eliminates 3 pivot points. It's never needed adjustment and the pedal pressure is smooth and light, easy to modulate with perfect travel. I even had to go to a 7/8' master cylinder to get less travel and it added little to the pedal force using a 7:1 pedal.


Thanks for the info. I thought about using a hydraulic TO bearing but decided against it after seeing so many of them leak in other projects. Maybe you got lucky. I didn't want to be pulling the transmission out again and again like one of my friends had to do. I also read a lot of horror stories online about leaking problems with them, even the Howe ones. The hydraulic TO bearing only reduces a master/slave setup by one pivot point, which is the fork/ball which does have a lot of force on it. Another friction location using a fork is the TO bearing sliding on the transmission yoke but I don't think that's significant since it's axial movement. It does all add up though.

I used an external slave and a Lakewood 15500 clutch fork with a lakewood pivot ball. Yes that linkage adds a friction point from a hydraulic TO bearing, but it was a tradeoff to deal with any leaks. I can easily change the slave if it fails, and a simple fork/pivot is a proven design over decades of use. The rest of my linkage from the pedal to the master cylinder has heims and the bellcrank is on bushings. I'm not sure, but I don't believe at this time that friction in the clutch linkage is a big problem.

Howe says the maximum travel for their 82876 GM TO bearing is .536" and their 82870 is .688" so you must have the latter. Typically a hydraulic TO bearing uses a 3/4" master cylinder for a 1 to 1 ratio.

Also going from a 3/4" master cylinder to a 7/8" one INCREASES the travel of the TO bearing. So it makes no sense to increase the MC size to get a shorter TO bearing stroke.

You probably have around 6" or so of usable pedal travel, and that means you have .86" of pushrod travel at the master cylinder with a 7 to 1 pedal. The TO bearing should move that same amount with a 3/4" MC. To decrease the stroke at the TO bearing you'd have to go to a smaller bore MC.

It really doesn't matter how you get there, mechanically or hydraulically, as it's the amount of work done that matters. So if you need to push say X pounds Y" at the clutch fingers you need to do X*Y in-lb of work.

I calculated my TO bearing throw based on actual measurements and it's theoretically .637" now with 5.5" of usable pedal stroke. With an assumed 400 pounds needed at the pressure plate, my pedal force is theoretically 46 lb ignoring any friction. I haven't figured out a way to measure it yet but some kind of spring scale might work.

[chevynut]

By the way if you read the 2 reviews on that 82870 Howe TO bearing, they're both complaining about leaks.

https://howeracing.com/collections/throw-out-bearings/products/82870-hydraulic-throw-out-bearing-stock-clutch


(https://howeracing.com/collections/throw-out-bearings/products/82870-hydraulic-throw-out-bearing-stock-clutch)The other issue I was concerned about was trying to adjust the clutch if needed, and using shims wasn't attractive to me. Once it's installed, you get what you get. I do understand they're somewhat self-adjusting once they're set up as the clutch wears. I see pros and cons.

[Rick_L]

I don't think the hydraulic t/o bearings used in OEM GM applications have a big complaint list regarding leaks. Pretty much anything with a T56 has one, as well as S10s etc. I don't know what full size pickups with manual transmissions use, but they're also rather rare. The T56 t/o bearings are shimmed for initial setup, similar to the aftermarket t/o bearings. I don't regard that as a big deal.

[chevynut]

I'm going to assume you actually went to a smaller .625" bore master cylinder to reduce the TO bearing travel. Also, I think you have Tilton pedals and they only have a 5.0 or 6.2 ratio available as far as I can tell.

So if you have 6.2:1 pedal ratio and a .625" MC bore you would have an overall ratio of 8.95 which is about the same as mine at 8.64. So our pedal forces with the same clutch would be almost the same, with only a 3.5% difference. With an assumed 400 pounds at the pressure plate, you would theoretically have 44.7 pounds at the pedal, and I would have 46.3, both assuming no friction.

[chevynut]

I don't think the hydraulic t/o bearings used in OEM GM applications have a big complaint list regarding leaks.

Bruce went through 3 OEM GM throwout bearings on his LS engine before he got one that didn't leak. He's the one who finally changed my mind on using one. I know there's millions in use but there are lots of complaints online about leaking throwout bearings, some OEM. I opted to avoid the issue altogether and the master/slave setup was used successfully for many years on GM and many other cars. What did you use?

[55 Rescue Dog]

I am using the Wilwood reverse mount clutch/brake pedals with the reservoirs and compact Howe master cylinders under the dash which suck for adding fluid. I went to a bigger master to reduce pedal travel. With the 3/4 cylinder and the pushrod adjusted to engage the clutch just slightly off the floor my clutch pedal was a lot higher than the brake pedal with a light effort and long travel. I could push it down by hand. Going to the larger master I was able to lower the pedal travel and the clutch/brake pedals are even and it still has light effort, but I didn't use a heavy-duty clutch either. The throwout bearing travel is controled by pedal travel adjustments.

[55 Rescue Dog]

A good way to ruin a hydraulic release bearing is to let it overtravel, which is most likely to cause a leak banging on the snap-ring stop from not having a lower pedal stop that a lot of people don't consider important, but it is.

[Rick_L]

What did you use?

For my T56, I have an 02 Camaro t/o bearing, along with a Tick Perf. speed bleeder and a Tick Perf. clutch master which uses a slightly bigger bore Tilton cylinder than GM used. Slightly increased force but also a bit more t/o travel vs. pedal travel than the Camaro m/c.

[chevynut]

I am using the Wilwood reverse mount clutch/brake pedals with the reservoirs and compact Howe master cylinders under the dash which suck for adding fluid. I went to a bigger master to reduce pedal travel. With the 3/4 cylinder and the pushrod adjusted to engage the clutch just slightly off the floor my clutch pedal was a lot higher than the brake pedal with a light effort and long travel. I could push it down by hand. Going to the larger master I was able to lower the pedal travel and the clutch/brake pedals are even and it still has light effort, but I didn't use a heavy-duty clutch either. The throwout bearing travel is controled by pedal travel adjustments.
I misinterpreted your "reduce travel" comment because the TO bearing travels FAR more than you need it to travel per the experts. I assumed you were reducing TO bearing travel, not pedal travel.

Looking at Wilwood's site the maximum pedal ratio they list for their reverse mount pedal assemblies is 6.25:1. I thought I saw pics of your Camaro with the master cylinders on the firewall. They do offer 7:1 ratio in that configuration, but not with the reverse mount.

So your overall ratio is actually only 4.59:1 with the 7/8" master cylinder and the 6.25:1 pedal ratio. That should make your pedal force with an assumed 400 pound clutch 87 pounds, which is way more than mine. And you max out the TO bearing's .688" stroke at only 3.1" of pedal stroke. Even with the 1:1 master/slave ratio your clutch force with that 400 pound clutch and 6.25:1 pedal would be 64 pounds. At 7:1 it would be 57 pounds which is still higher than mine is.

Either you have a really weak clutch or a very strong left leg if you think 87 pounds is light.:eek: And pushing 64 pounds by hand isn't easy. That's nearly twice the pedal force as I theoretically have with the same clutch. Do you have any way to measure it? I really don't know what the clutch pressure plate force is but I've read 400 pounds is in the right range.

My overal ratio is increased by 2X due to the 2:1 clutch fork even though my pedal ratio is only 3.92:1. So I have a 7.84:1 effective pedal ratio with equal sized master and slave.

Here's an interesting read on the subject of pedal force....

https://www.gt40s.com/threads/clutch-pedal-pressure-what-do-i-want.32131/

[chevynut]

For my T56, I have an 02 Camaro t/o bearing, along with a Tick Perf. speed bleeder and a Tick Perf. clutch master which uses a slightly bigger bore Tilton cylinder than GM used. Slightly increased force but also a bit more t/o travel vs. pedal travel than the Camaro m/c.

Any idea what your pedal force is with that setup? I'm trying to figure out if mine is typical or if I need to tweak it some. It seems that my TO bearing travel is in the right range at .637" per Novak, but it's more than Mcleod says you need. I guess I won't know til I drive it, but it's easier to change now than later.

[55 Rescue Dog]

I didn't know what it calculates out to, but the clutch pedal force feels nearly the same as all the other hydraulic bearing cars I've owned over the years, and my setup works even better than a most of those did. Yes, the reverse mount was a 6.25 ratio. I forgot after buying it like 20 years ago. My 55-brake pedal is 7:1. I originally set up the clutch with the recommended cylinder and it needed to be tweaked for a bigger one to not have such a long pedal travel was all I needed to do. The only friction point is the pedal pivot and just fluid power from there making it very smooth.

[55 Rescue Dog]

I adjusted my clutch disengagement/take-up point by having someone turn a rear tire and adjusting the pushrod on the master cylinder. It was pretty simple and haven't touched it since.

[chevynut]

I sent Centerforce an e-mail yesterday asking 1. how much does the throwout bearing have to move to disengage the clutch. 2. What is the force on the throwout bearing as the clutch is being disengaged. 3. What is the clutch finger ratio (pressure plate versus TO bearing movement) and 4. What is the clutch clamping force for my model. All questions relate to part number DF148552.

I got a reply from a tech saying it took 3/8" of throwout bearing motion to disengage the clutch. That's all he answered. So I asked again about the force at the TO bearing and he said it takes 400-450 pounds to release it. He never did answer the other two questions, but they're not critical for my work. Getting technical info from these guys is like pulling teeth.

So I only need 0.375" of TO bearing travel plus say .063" of free play which is 0.438" total, which is consistent with what Mcleod says you need. None of these companies are very clear about what their dimensions actually mean. I told centerforce that I assumed their 3/8" was after the TO bearing contacted the fingers, and he didn't acknowledge anything.

According to these numbers, I'm over-driving my clutch per my calculations. I'm going to put a dial indicator on the clutch fork and see what I'm really getting there, and make adjustments based on that and how the clutch actually feels when I drive the car. I estimated I was at somewhere around 50 pounds at the pedal when I first depressed it (based on my gym workouts, LOL) and my calculations using the quoted 400-450 pounds at the fingers give me 46-52 pounds at the pedal.

If I can drop the TO bearing stroke by using a smaller master cylinder, the pedal force will move lower accordingly. That assumes I have room to drop it and still maintain adequate TO bearing stroke.

Another thing I did a little research on is whether or not the TO bearing should be in constant contact with the clutch or not, which affects how much stroke you need. Some guys say it's designed to rotate continuously and should last as long as the clutch. They say that by only rotating when the clutch is disengaging, it has to make contact with the fingers and get it spinning, which wears the clutch and the TO bearing face. The other camp says that the finger wear isn't an issue and they are adamant that that the throwout bearing should not spin all the time. Some say you need as much as 1/8" -0.3" of clearance!! Not sure which is better, but I've always assumed there should be a small gap between the TO bearing and the clutch fingers unless the clutch was depressed. RAM Clutches says their hydraulic throwout bearing always rides on the clutch fingers. Someone else said that new modern TO bearings, like modern wheel bearings, are made better and are packed with better grease and are made to spin constantly.

Here's an interesting thread on the issue....

http://www.clubcobra.com/forums/transmission-talk/103889-throw-out-bearing-always-makes-contact.html

[chevynut]

I didn't know what it calculates out to, but the clutch pedal force feels nearly the same as all the other hydraulic bearing cars I've owned over the years, and my setup works even better than a most of those did. Yes, the reverse mount was a 6.25 ratio. I forgot after buying it like 20 years ago. My 55-brake pedal is 7:1. I originally set up the clutch with the recommended cylinder and it needed to be tweaked for a bigger one to not have such a long pedal travel was all I needed to do. The only friction point is the pedal pivot and just fluid power from there making it very smooth.

Do you know what clutch you have? if you have a 6.25" pedal ratio, a 7/8" master cylinder and a 3/4" slave cylinder the calculations say that you have a pedal force of 87-98 pounds with a 400-450 pound force at the TO bearing. That seems really high. Also with just 4" of pedal travel you'd drive the TO bearing forward .87" which is far more than the specified maximum travel. You must have a large air gap between the TO bearing and the clutch fingers.

[chevynut]

Bottom line in all my research on the subject is that clutcha pedal force in the 40-50 pound range is typical. I may try to figure out how to measure it just to see where I am. The math says 46-52.

[55 Rescue Dog]

Do you know what clutch you have? if you have a 6.25" pedal ratio, a 7/8" master cylinder and a 3/4" slave cylinder the calculations say that you have a pedal force of 87-98 pounds with a 400-450 pound force at the TO bearing. That seems really high. Also with just 4" of pedal travel you'd drive the TO bearing forward .87" which is far more than the specified maximum travel. You must have a large air gap between the TO bearing and the clutch fingers.
I don't have a slave cylinder since it is a hydraulic TO bearing. There is no free play. There is no pressure on it since it just gets pushed back out of the way like a brake caliper piston, so it isn't really spinning if at all, and has no load on it. I have no idea what the actual stroke on the bearing is and really don't care since it works perfect with travel room to spare as the clutch wears. All I would need to do at some point to keep the engage/disengage point the same is turn the master pushrod in as the clutch wears. Instead of spending a bunch of time trying to overcalculate everything, just hook everything up, adjust it and see how it works and make a change is needed after testing it. No math needed to measure pedal force, since I can just feel it and it is easy to push. I've driven a few cars with stiff clutch pedals and know what that feels like without any calculations. The clutch I'm using is a stock 10.5-inch diaphragm with the fingers bent on the ends, which is designed for a hydraulic release bearing. Also using a lightweight L-88 flywheel that I think is around 18 lbs.

[chevynut]

I don't have a slave cylinder since it is a hydraulic TO bearing. There is no free play. There is no pressure on it since it just gets pushed back out of the way like a brake caliper piston, so it isn't really spinning if at all, and has no load on it. I have no idea what the actual stroke on the bearing is and really don't care since it works perfect with travel room to spare as the clutch wears. All I would need to do at some point to keep the engage/disengage point the same is turn the master pushrod in as the clutch wears. Instead of spending a bunch of time trying to overcalculate everything, just hook everything up, adjust it and see how it works and make a change is needed after testing it. No math needed to measure pedal force, since I can just feel it and it is easy to push. I've driven a few cars with stiff clutch pedals and know what that feels like without any calculations. The clutch I'm using is a stock 10.5-inch diaphragm with the fingers bent on the ends, which is designed for a hydraulic release bearing. Also using a lightweight L-88 flywheel that I think is around 18 lbs.

A hydraulic throwout bearing IS a slave cylinder. Many of the hydraulic throwout bearings are held by pressure against the clutch fingers and they turn constantly. Maybe yours doesn't. They're supposed to work assuming the master and slave are the same size (3/4") since 1" of travel at the master gives 1" of travel at the slave, as I understand it. If there's no play, where is that .877" of travel going that you pedal stroke of only 4" causes? Maybe you should have done some calculations first and you wouldn't have ended up with too much travel at the pedal. Now you end up with limited pedal travel and your must have some gaps somewhere because your throwout bearing only travels .688" max. Do some simple math and prove it to yourself. If you like it, that's fine. I prefer to design my systems to work using simple calculations. But those calculations are dependent on good information.

I did assemble my clutch and tried it, and this thread was asking about what the pedal force should be. You gave me a bunch of numbers from your car that I thought might help, some of which were not right. As usual, you never even answered my original question, you just threw a bunch of stuff out there about your car which wasn't even right. Sources say an OEM 10.5" clutch takes about 400 pounds to actuate. Do your own calculation as to what your pedal force would be with your setup. I appreciate your "trying" to help but as usual your last comments are typical of how these discussions end.

[chevynut]

Maybe I'm misinterpreting the size of the hydraulic throwout bearing slave's equivalent bore. I had assumed it was equivalent to a 3/4" master cylinder based on the stuff I read online.

[55 Rescue Dog]

You can put me down all you want as to how smart you are and how dumb you think I am. All I did was follow the stupid instructions and understand how it works. The master and TO bearing both operate well within the maximum travel ranges. The master never bottoms out on the internal stop, and the bearing which doesn't use any spring return is setup with a max 1/16in clearance, so it doesn't bottom in the return position. In operation the bearing just floats on the clutch fingers with zero clearance and no pressure. I went with the recommended 3/4 master, and it would have been fine, but I wanted a little less travel so I could keep my heel planted on the floor which makes it much easier for modulating initial engagement, so I tried a bigger recommended 7/8 cylinder which I determined by observation instead of just math which sometimes is important but doesn't always work out that way in the real world, until you try it. Plus, the travel specs are in the instructions.
And how can you calculate the friction added by your pivot points? Also, unless your slave cylinder has a spring return it should be setup so the slave doesn't bottom out in the return position and then your bearing will float on the fingers with no pre-load which is the way most hydraulic clutch setups operate and self-adjust for clutch wear.
I have a C5 Corvette and have learned a lot from dealing with that hydraulic setup and there was nothing you could calculate to deal with their issues, which you are finding out. A hydraulic TO bearing is still the best way to go. I didn't have t worry about any of it by installing an auto in my 55 which was the best choice for that car. A 4-speed computer-controlled auto transmission would have been a huge hit back in 1955.
13326

[chevynut]

Okay RD, I think I now understand where I went wrong on the calculations for your clutch setup. I remember reading somewhere that you needed a 3/4" MC with most hydraulic throwout bearings, and that gave a 1:1 correlation between master cylinder stroke and slave (hydraulic TO bearing slave) stroke. In doing some more research I think that 1:1 was bad information or a bad assumption on my part.

I looked at the Howe HTOB installation instructions and they say that for a 3/4" master cylinder, you get .43" of TOB stroke with 1" stroke of the master cylinder. That makes the equivalent bore of the HTOB slave cylinder 1.144" in diameter.

I also found this at Modern Driveline:

Here are the volume displacement requirements for the Tilton bearing assembly:
Travel Volume (cu/in)
0.4” 0.483
0.45” 0.543
0.5” 0.604
These numbers give a bore area of 1.208" and an equivalent bore diameter of 1.24" for the throwout bearing slave cylinder. So these numbers vary quite a bit from one HTOB to the other.

Now it all makes sense. With your original 3/4" master cylinder your pedal force with an assumed 400 pounds at the clutch fingers would only be 27.5 pounds. You would only have .413" of TOB travel with 6" of pedal travel, which is what I think you were having problems with. When you changed to the 7/8" bore the pedal force went to 37.4 pounds and you get the same .413" of TOB travel with only 4.4" of pedal travel. Sorry for the mistake.

By the way, Mcleod says you can't use their HTOB with a clutch that has weights on the fingers like the Centerforce diaphragm clutches have. I didn't know that. I'm not sure if that's a limiter with other HTOBs.

I think my TOB could be traveling too far, but it's just about exactly what Novak said to use and what I designed for. Mcleod and Centerforce both say you need far less. I'll probably try to go to a smaller bore slave which will drop my pedal force and still operate my clutch correctly. Part of it depends on how much pedal travel I actually want when the clutch is released.

[55 Rescue Dog]

How far off the floor is your pedal when the clutch disengages? You can check while someone turns a rear tire, push the clutch pedal in/up and check the engage/disengage points. I like mine around 1 inch or so from the floor, adjusted with the threaded pushrod.

[chevynut]

Today I checked the slave pushrod travel at my clutch fork. I tried setting up a dial indicator to do this but there's no room so I used a 6" steel rule. I have about .1" of movement of the clutch fork before the throwout bearing touches the clutch fingers. Then pushing the pedal to the floor I get 1" of additional travel at the fork. I'm not sure if I'm actually hitting the floor or if I'm bottoming out the master cylinder. I need to check that. My master cylinder has 1.4" of travel.

Those fork travel measurements correspond mathematically to about 0.43" of free pedal travel and .050" clearance between the TOB and the fingers. The additional 1" corresponds to 4.30" of pedal travel. So I mathematically have a total of about 4.73" of pedal travel from the up stop. Also, the 1" of fork travel should give me 0.500" of TOB travel.

However, I think I have closer to 5.25-5.5" of actual pedal travel so I'm either getting some deflection or slack somewhere, or I still have some air in the system. I hope it's the latter.

Funny that my wife, who pushed the pedal when I measured, doesn't think the clutch is too stiff. LOL :eek: :D

According to my numbers, I have a 8.64 overall ratio between the pedal and TOB with the .750" master cylinder. So for a 400# clutch my pedal force is theoretically 46 pounds, and for a 450 pound clutch it's 52 pounds. That seems to be in the higher range of what my research suggests it should be.

The .500" of TOB travel I'm getting with 4.3" of pedal travel after touching the fingers is 1/8" more than what Centerforce says I need. But I don't think I want to have to push the clutch all the way to the floor to disengage it, so it might be just about perfect where it is. Theoretically it should engage 1 1/8" off the floor. I could possibly move to a .700" booster that would drop my pedal force about 6 pounds if I can still get enough TOB travel. I think I'm going to wait to see where it engages before I try to do anything with it but I may try bleeding the system again and see if fork travel changes.

I could also decrease the pedal free play by tightening up the TOB gap. Some TOBs are meant to run all the time but I'm not sure mine is. Lots of guys say the TOB will outlast your clutch running against the fingers all the time. That's another .050" of travel I could gain.

Maybe I need some kind of clutch booster. There actually is such a thing. ;)

[chevynut]

How far off the floor is your pedal when the clutch disengages? You can check while someone turns a rear tire, push the clutch pedal in/up and check the engage/disengage points. I like mine around 1 inch or so from the floor, adjusted with the threaded pushrod.

I think that's a good idea and planned to do it since I read that's how some guys suggest doing it. I can adjust free play two places on mine, at the master cylinder pushrod and at the slave pushrod. I think I'd rather adjust the slave pushrod. I also need to install a clutch pedal return spring to bring the pedal up against the stop because the master cylinder doesn't seem to do it like I thought it would. That also might indicate that there's still some air in there. I have a small spring pulling the clutch fork toward the slave.

[chevynut]

I did a little research on clutch boosters and springs and found out why my Porsche has such a light pedal...

https://www.youtube.com/watch?v=YfjD4a_m900

Also occurred to me that tri5's have a "clutch helper spring" as well. I always thought it was a return spring, because that's what everyone calls it, but it works in both directions just like the Porsche spring. Looks like this is a really common setup and my car doesn't have one anymore. I'm not even sure I have room to put it back in if I wanted to. I imagine those springs reduce the clutch pedal force quite a bit.

https://www.55-57chevys.com/tech/56/6-13.gif

[55 Rescue Dog]

Pictures of your pedal and linkage setup would help. Shouldn't need any power assist if setup right.

[chevynut]

Pictures of your pedal and linkage setup would help. Shouldn't need any power assist if setup right.

I could show you a picture of my linkage, and it wouldn't make any difference. You probably would ask why I did this and that and whatever, and tell me how good yours works and how simple it is. Mine is working as-designed. I had specific objectives, one of which was a hidden master cylinder. And I've posted some pics of it before.

The only question left is whether I can get by with less travel at the TOB so I can use a 0.700" master cylinder instead of the 0.750" one. I won't know that until I try it out driving the car. I can't put a stock "helper" spring on it because I have too much stuff under the dash, like a bellcrank to move the brake master cylinder over, and my clutch switch, and Raingear. I may want to try to design something different if I think the pedal is too stiff.

Like I said you can't get something for nothing. You trade off pedal force and travel for throwout bearing travel....it's that simple. If I need to move the TOB 0.375" against 400 pounds, it takes 150 inch-pounds of work. If you want to move the pedal 3" to disengage the clutch by moving the TOB .375", it takes 50 pounds of force to do it. There's nothing you can do to change that but add a booster that uses an outside source of energy like vaccum, pressure, or a spring (which stores energy). You can change levers, master cylinders, slave cylinders, etc. all you want and it's still going to take 160 inch-pounds of work. A smaller master cylinder will decrease the pedal force, but it will increase the pedal travel needed.

With the same clutch and the same pedal travel, your car is going to take exactly the same force as mine to work the clutch unless you have an assist spring. It doesn't matter if it's mechanical linkage, a cable, a master and slave, or a hydraulic TOB. It's simply physics.

The only tradeoff is how far you have to move the pedal. I want the clutch to have a slight amount of free play, but I might eliminate that if I feel comfortable with the TOB spinning all the time. So the question is where I want the clutch to engage and disengage. There's a total of 6" of possible travel between the pedal and the floor as far as I can tell. I think I want it to engage about 2" off the floor. That leaves 4" of travel to disengage it, and if I add any free play it's reduced further. The only way I'm going to know for sure is to drive the car.

[55 Rescue Dog]

Sounds like you have it all figured out all by yourself, and that you shouldn't have chosen a heavy-duty street/strip clutch.