I've still go a soft pedal even after bleeding more than once with no air the last 2 times. Sierra callipers front and rear twin master cylinders with 0.625 front and 0.75 rear. Anybody tried 0.7 front 0.75 rear to reduce pedal travel?

I'm running 0.875 / 0.7 with very good results (using Wilwood calipers at the front and golf calipers at the rear).

Depends on your calliper piston sizes and pedal ratio - big calliper pistons or a higher pedal ratio than normal will increase mechanical advantage and you will need to compensate for this with a larger master cylinder.

I'm aware of that - I also run a Mallock Mk18b race car. I've got the equations but just wondered if anybody had actually tried it out to see what it feels like. I've got a selection of cylinder sizes so could just swap and see but then would have to reset the bias too. I'm having difficulty heel and toeing due to the length of the travel and that annoys me ( although is probably completely pointless on the road anyway).

I used one of the brake calculation spreadsheets to work out what to use - I was a bit skeptical when it came out as 0.875, but gave it a go and it feels spot on, so if you have done the calculations then I would just trust them and make the appropriate changes.

I'll do as you suggest then and see what happens! Braking ratios front to rear are a function of the cross sectional area ratio of the master cylinders assuming the callipers remain the same so if the ratio remains the same but with bigger m/c both front and rear travel should reduce without affecting balance I suppose.

Simples don't get side tracked down blind alleys this a well known issue when Sierra rear calipers are mounted at dfferrent orientation from the original Sierra. rear calipers to bleed unbolt and turn them so the bleed nipples are at the highest point then bleed.



[Edited on 4/8/15 by britishtrident]

[Edited on 4/8/15 by britishtrident]

BT is correct

I had to unbolt my rear sierra calipers and roll them around the disc so as to achieve the highest point for the bleed nipple.

If you search on here for rear sierra caliper bleeding ..... i'm sure more info will appear.

Already done that twice. Will do it again though