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Master Cylinder Sizes: What the crack?
omega0684 - 26/3/10 at 11:55 AM

right guys, here's one for the LCB masterminds

What is the crack with master cylinder sizes? i currently have a 0.625 & a 0.75 for my front and rear brakes, but which one goes on the front and which one goes on the back?

i have been told by some that the 0.625 goes to the front and others have said 0.75 on the front, so which is it and why is it so?

thanks

Alex

flak monkey - 26/3/10 at 11:58 AM

0.625 on the front and .75 on the back

The .625 will create higher line pressure which is what you need for the front brakes.

Bluemoon - 26/3/10 at 12:02 PM

Depends on calipers/drums slave cylinders balance bars ect...

arrow-engineering - 26/3/10 at 12:05 PM

thats true, it does depend, but generally with standard set ups and cars converted from drums to discs its 0.625 for the front. tell us what brakes you have.

omega0684 - 26/3/10 at 12:42 PM

sorry,

running 4 pot Hi-spec's on the front and std cossie rear calipers

pewe - 26/3/10 at 12:47 PM

As above ^^ but also bear in mind if using a balance bar the push-rod to the front m/c probably needs to be adjusted so that it's shorter than the rear one i.e not just a question of m/c size but piston travel.
Again as above both m/c size and push-rod adjustment are a function of the braking set-up i.e. caliper piston sizes.
Since brake imbalance was a common cause of SVA failure (mine included and presumably now an IVA issue) I'd recommend having the brakes set up professionally or at least by yourself on a private roads pre-test.
HTH
Cheers, Pewe

omega0684 - 26/3/10 at 12:57 PM

what company can i get in touch with to have the brakes set up properly?

Mr Whippy - 26/3/10 at 05:06 PM

quote:
Originally posted by omega0684
what company can i get in touch with to have the brakes set up properly?


do a road test in a car park in the wet and that will soon let you know if you have the brake balance right. Then try braking will turning too and if the back end locks up and sends you in a spin, reduce the back pressure.

britishtrident - 30/3/10 at 01:26 PM

quote:
Originally posted by pewe
As above ^^ but also bear in mind if using a balance bar the push-rod to the front m/c probably needs to be adjusted so that it's shorter than the rear one i.e not just a question of m/c size but piston travel.
Again as above both m/c size and push-rod adjustment are a function of the braking set-up i.e. caliper piston sizes.
Since brake imbalance was a common cause of SVA failure (mine included and presumably now an IVA issue) I'd recommend having the brakes set up professionally or at least by yourself on a private roads pre-test.
HTH
Cheers, Pewe



Here be dragons, adjusting push rod length needs extrem care.

coozer - 30/3/10 at 01:30 PM

Sierra had abrake bias valve as standard, this reduced pressure to the back brakes.

Two ways to do it, put a bigger cylinder on the back or bigger size wheel cylinders. Thats with drums.

With dics its harder, not done it so don't know.....