Hi all,

I run the standard Sierra master cylinder (two outputs to the front and one to the rear, I think) on my MK Indy R. I was wondering if anyone could tell me the bias ratio between front and rear on the standard Ford part?

I'm looking to fit an AP Racing single circuit item. I know dual circuit are better on the grounds of safety, but apart from that are there any other negatives to having one - such as MOT testing or anything?

Thanks,

Carse

I think you need to stop and seriously think about this.

Why do you want to go to a single circuit system as it brings absolutely no advantage but ha s potentially serious safety and legal implications. It is not without reason that single circuit brakes have not been banned from being fitted to new vehicles for 40 years. Some of us are old enough to remember total loss of brakes due to a simple hydraulic leak.

Because it is has the role of emergency brake the handbrake efficiency requirements for classic cars fitted with single circuit brakes are much higher than for vehicles with dual circuit brakes. Reverting to single circuit brakes is a very grey area, but I am pretty sure most MOT testers would be very reluctant to pass a modern vehicle that had single circuit brakes .

An AP Racing cylinder is just an ordinary master cylinder nothing magic about it if you have a standard 22mm bore Ford master cylinder to get better more responsive brakes ie lower pedal pressure then all you need to do is fit a smaller bore tandem dual circuit cylinder.

If you really want to go single circuit first do an ebay search on "Girling Master Cylinder" as old fashioned Girling types or close copies are more or less standard in the racing car world.


[Edited on 22/1/13 by britishtrident]

Hi,

I appreciate your advice and believe me, I'm thinking about this. I was only provisionally looking at fitting a single-circuit type (I too had my reservations) but after a bit more research I'm decidedly against the idea.

I'm after better pedal feel, hence why I've gone for the machined AP Racing item - plus it was offered to me at less than the price you'd pay for a second-hand Sierra one.

I'll be fitting another generic single-circuit master cylinder for the rear and a balance bar system to adjust.

On the subject of the front to rear ratio on the standard Sierra type master cylinder: it's so I can get the master cylinder bores roughly right and then work in some adjustment with the bias bar - it's no good if one is too big and the other too small as to counteract it I'll be out of adjustment on the bias bar, if you see what I mean?

Any help much appreciated here - as it was from you Britishtrident. Thanks for taking the time to reply.

All the best,

Carse