Brake master cylinder

[alaric]

Steve - you must have spotted my deliberate mistake above - of course a smaller bore on the master cylinder gives more mechanical advantage - I've edited the post to try and save more embarrassment.

Sean.

[CBUEB1771]

If someone that's had the opportunity to try the +2 with and without the servo could give an estimate of the gain from the servo, that would be great.

The servos fitted to the +2 and the Elan have gains of approximately 3:1 and 2:1, respectively. I have posted before about my experiences with removing the servo from my +2. I went all the way down to a 5/8 bore master cylinder, the smallest available from Girling. I found the pedal effort to be much too high and completely out of balance with all of the other required inputs, steering, gear change, clutch, etc. It was not simply a matter of balance of control input. The fiberglass to which the pedal box is mounted was also cracking under the required force. I did this many years ago, without the benefit of the more recent high coefficient brake pad materials. Nonetheless it is hard to make up for the 3:1 boost of the servo.

[Expat+2]

The high friction Greenstuff pads made all the difference on my +2, with standard pads the pedal effort was too high. I had the standard boosted system before and I found the pedal effort very light, now it's firm but not heavy - comparable to other non-servo cars I've had. There is certainly some flexing of the fibreglass around pedal box, but as to it failing... I guess I've decided it's strong enough.

Another thought, is it possible to use a tandem cylinder with a single servo?

[alaric]

Thanks for the benefit of your experience. My plan is to retain the servo and standard master cylinders until the car is on the road. I'll keeo an eye out for a replacement master cylinder that offers a fail safe solution.

Off out to the garage now armed with the servo and a whole load of brackets and pipes... Earlier today I managed to move the car backwards and forward under iits own steam for the first time in 10 years. So I need brakes next.

All the best.

Sean.