Triumph Repair: Spitfire 1500 clutch, clutch installation, piston cylinder

Question
QUESTION: We replaced the clutch and slave cylinder and rebuilt the master. Im pretty sure all the air is out, bled x 3. The clutch will only disengage at the very bottom of the pedal travel. It will stay disengaged so I don't think the problem is the master cyl. Is it possible I have installed the clutch plate the wrong way round? 50% chance right or wrong and does it make a difference?
Thanks. I do not want to pull the engine unless I have to.
Roger

ANSWER: Hi Roger,
I have found that many of the Spitfires and TR-6s suffered from that same problem, in that you had to have the pedal on the floor to disengage the clutch. Especially new or a new clutch installation. I believe Triumph (BLM) engineers designed it too close to not working. In most cases after driving the car a couple thousand miles the disk will flatten out a little and thus give you a higher engagement on the pedal travel. The spring plates that separate the two linings of the disk in some cases are too wide, making the disk too "Soft" and thick causing the problem. The TR-6 in some cases was easy to correct due to two different size pistons in their master cylinders, so if a car has the small piston master you could just install the larger piston cylinder to gain more travel, thus a higher engagement on the pedal travel.

I don't think the Spitfire had any different size master cylinders so that won't help you. If you can get the clutch to disengage by putting the pedal all the way down, I would advise not to do anything except use it that way. As the disk wares and gets flatter and thinner it will engage higher.

It is not anything you did wrong and you can't install the disk backward. The disks are just too soft and thick for the design of the rest of the system. It is a Triumph/BLM design flaw.
Howard

---------- FOLLOW-UP ----------

QUESTION: Thank you thats very helpful. One thought would it be worth enlarging the slot for the pinch bolt on the slave cyl. by say 1/4 inch so the slave can go that much further forward in the bell housing?
Thanks Roger

Answer
That will not work as there is no free play in that area and if the slave cylinder piston is already bottomed out you will just put a preload on the release bearing and it will be worn out in a week. The problem is length of travel and you can't change length of travel by moving the slave cylinder since the piston is up against the clutch arm already.
Howard