The V8 Owners Forum -

Based on the calliper piston sizes given above, I have calculated the following, based on 10 thou brake pad movement.

Your 1" dia master cylinder is moving 0.32".

So pedal movement
at 1:4 ratio = 1.32"
at 1:5 ratio = 1.62"
at 1:6 ratio = 1.92"

Now the servo with a 5/8" bore will in theory move 0.785"
This will be slightly less because some fluid goes through the servo before the piston seals and the assisted pressure is applied.

Now if the realistic pad movement is say 15 thou then all the above go up by 50% and I think in this situation the 5/8" bore servo may not like moving 1.2" and may even bottom out.

I'd go for a 7/8" bore servo even if the require pedal force will be slightly higher.

It would be good to get someone to verify the likely brake pad movement.

Cheers Denis

Thanks Ian, thanks Denis, my pedal ratio is barely 1:4 !

Devonrod wrote:Thanks Ian, thanks Denis, my pedal ratio is barely 1:4 !

Out of interest, How much does you pedal move?

I thought I would put this post to bed, I fitted the Wilwood 1 inch master cylinder, and got a new Lockheed 1.9 ratio, some were saying keep the 2.3 ( which needed replacing anyway due to sticking brakes) others said go for the 1.65. well a guy was selling brand new 1.9 for £115 on ebay so I thought I would get one to try as if it didn't work out I know this is the right size for my other project and I could use it on that, the brakes feel lot better now, you still have to push fairly hard, but before they just felt not right, I think it was down to the cheap repro Land Rover 1 inch master cylinder I used.