Clutch master and slave "my experiance"

[Dragonfly]

Since I am now on my 3rd clutch master cylinder (and it works now) I am going to let everyone know what I have learned. I started out with a stock 5/8" clutch master and a stock 3/4" clutch slave, with a stock clutch that works great... but I am not running a stock clutch. The stock clutch needs aprox. 3/4" inch of travel at the slave to disengage the clutch, my new clutch needed about 1.2" of travel from the slave to disengage the clutch. After doing a lot of reading about what others had done to overcome this problem I went out and purchased a new 1" Wilwood master cylinder, this was master #1...

 

Master #1: I had enough travel at the slave but the pedal effort was extream, after about 15 miles of driving with this setup I managed to bend my clutch pedal and bend the master cylinder actuating rod (from master to pedal) into the shape of a "J". A couple of days after that I was at the Good Guys car show and Wilwood had a booth there and I had the chance to talk with one of thier techs about my problem and he told me that my problem was not a volume issue but rather a stroke issue and that I needed to go back to a 5/8" bore master but with a 1.4" stroke and he gave me a part number for the master cylinder I would need... #2.

 

Master #2: It arrived a few days later and I did not get a chance to open the box for about 3 days because of other things going on. When I opened the box I imediately noticed how much this master looked like my stock master. I laid the two side by side and took a few measurements and found that they were dimensionaly identical including the stroke. Before putting #2 on the car I called Wilwood and asked to speak to an engineer, I was given over to a tech rep who when confronted with my situation asked if he could call me back after talking to a real engineer... #3.

 

Master #3: After being called back and talking to the tech rep and the engineer this is what I learned: I will explain this in a manner in which I hope everyone will understand. When a system is designed it is done so with a small bore master using a long stroke and a larger bore slave that uses a shorter stroke, this allows you to have a moderately light pedal with engagement adjustability throughout the range of the pedal. When this system is modified as in the case of increasing the force of the clutch and requiring a longer travel from the slave you need to increase the size of your master cylinder bore or the length of stroke or both in order to increase the stroke of the slave. Since the length of the stroke on most masters is no longer than 1.4" it was necesary for me to resort to a 3/4" bore in my master with a 1.4" stroke which provided me with a 1:1 bore and stroke ratio, since I only needed 1.2" of stroke on the slave I now have .2" of room to adjust the pedal (thats not much) and the pedal effort is noticably greater than stock but definately less than I had with the 1" bore master.

 

I will be putting this setup through its paces over the next few weeks before Motorsport and then I will be racing at Motorsport on Saturday and showing the car on Sunday. Any one who is going to be there on either day is welcome to come up and say hi and take a look etc. I will keep you guys posted.

 

Dragonfly