Re: Thinking of fitting a servo....
Posted: Sat Jul 23, 2016 9:59 pm
The link to the table is one that I created from the AP Lockheed brake design principles.
In practice we have Metro 4-pot calipers at the front and standard Minor 7" drums at the rear (with the later, smaller, 1098 3/4" cylinders). The immediate problem we had when the restoration was completed 18 years ago, with the new brake set up, was locking of the rear brakes under heavy braking.
The front pads are Mintex 1155 and the rear shoe linings are Mintex 'competition', but not sure exactly what the shoe material is. The line pressure required to get either the standard 8" drums or the front calipers to work, means that it is too much for the rears, so they lock up. Our solution was to fit an adjustable pressure limiting valve in the rear circuit to prevent lock-up. It is a standard Mini pressure limiting valve, modified to be adjustable. Although the line pressure is much the same as for the standard 8" drums, the discs continue to work long after the front drums will have faded.
For our set-up there would be not point in fitting as 'bigger' rears, as the standard 7" are already too much, even with 'competition' linings. It has raised queries on the MOT, as the handbrake is far more 'efficient' than the footbrake rear, as this is deliberately restricted.
The standard 7" front brake set-up is very badly balanced at 63%/37% front/rear, far too much to the rear, and a very high pedal pressure required (143lb for 1g braking). The 1098 8" front drums with smaller rear cylinders is much better balanced, with lower pedal pressure (74%/26% and 119lb), and is fine for a standard engined car.
If fitting discs I would suggest retaining the standard 7" Minor rear drums, with the later 3/4" diameter rear cylinders and see what the actual performance is.
In practice we have Metro 4-pot calipers at the front and standard Minor 7" drums at the rear (with the later, smaller, 1098 3/4" cylinders). The immediate problem we had when the restoration was completed 18 years ago, with the new brake set up, was locking of the rear brakes under heavy braking.
The front pads are Mintex 1155 and the rear shoe linings are Mintex 'competition', but not sure exactly what the shoe material is. The line pressure required to get either the standard 8" drums or the front calipers to work, means that it is too much for the rears, so they lock up. Our solution was to fit an adjustable pressure limiting valve in the rear circuit to prevent lock-up. It is a standard Mini pressure limiting valve, modified to be adjustable. Although the line pressure is much the same as for the standard 8" drums, the discs continue to work long after the front drums will have faded.
For our set-up there would be not point in fitting as 'bigger' rears, as the standard 7" are already too much, even with 'competition' linings. It has raised queries on the MOT, as the handbrake is far more 'efficient' than the footbrake rear, as this is deliberately restricted.
The standard 7" front brake set-up is very badly balanced at 63%/37% front/rear, far too much to the rear, and a very high pedal pressure required (143lb for 1g braking). The 1098 8" front drums with smaller rear cylinders is much better balanced, with lower pedal pressure (74%/26% and 119lb), and is fine for a standard engined car.
If fitting discs I would suggest retaining the standard 7" Minor rear drums, with the later 3/4" diameter rear cylinders and see what the actual performance is.
