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Fitting a Bulkhead servo (2 replies)

MGMiniman
5 years ago
MGMiniman 5 years ago

I want to fit a bulkhead servo to a non servo car. It already has 8.4 discs and have a servo/master cylinder/bracket assembly. I know that the brake pedal for the servo'ed cars is different but I can't see why provided a suitable push rod is fabricated to connect the brake pedal to the servo bell crank the brake pedal or pedal assembly needs to be changed. The servo pedal has a non removable clevis pin on the actual pedal. I realise that the servo brake pedal does not have a return spring but it will be easy to cut this without removing the assembly. This function is built into the servo assembly.
Has anybody tried this? Why did Rover in their wisdom change the brake pedal? Is it that the leverage ratio on the pedal different between the two types?

MGMiniman

MGMiniman
5 years ago
MGMiniman 5 years ago

Now I have discovered that the difference between the servo and non servo pedals is as I suspected a different leverage ratio.

How much is the question. I suspect that the ratio is reduced for the servo version as you have the servos help.

So will this make that much difference in using the non servo pedal on a servo. Will it make the braking effort too fierce?

Modern cars have "light" braking pedal pressure so it may be worth a try.

The only thing I need to know now is the length of the rod between the pedal and the servo bell crank.

I had to cut the existing rod off the master cylinder to get it out as the clevis pin is seized in the brake (non Servo) pedal, never seen this before. So I've got the bottom end of the rod.

Can somebody please measure this servo rod and give me the dimension centre to centre between the clevis pins.

MGMiniman

MGMiniman
5 years ago
MGMiniman 5 years ago

Further update.

I now have both types of pedal unattached to a car to look at.

There is no difference between the two except the size of the clevis pin (hole).

Non servo pedal is 3/8" - Servo type pedal is 1/2"

Early servo'ed car had the operating push rod from the pedal to the servo permanently fixed with a non removable clevis pin.

Later servo'ed cars had a traditional removable 1/2" clevis pin and therefore a separate operating rod.

So answering my own question a non servo pedal assembly can be used to operate a bulkhead servo if a suitable operating rod is made with the appropriate clevis pin forks on each end. The only other issue is to cut off the end of the pedal return spring as this is catered for on the servo itself.

MGMiniman

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