What's the best, easily found, affordable master cylinder for a Haynes locost type kit car, sierra donor?

doesnt this depend on what brakes you are running? bit more info is needed me thinks. presumably sierra calipers on front? are rears drums or discs?

[Edited on 1/5/11 by mads]

yep, sierra brakes. front and rear disc. maybe i'll change calipers, but much later on... for now, sierra calipers will do.

many tend to use the standard sierra mc as appears to be sufficient in a seven.

from what i read, the sierra's mc does not offer much sensitivity. some say the fiat 124 is a good choice or a lada niva's...

yeah, fiat 124 is an alternative. its what i am planning to use on mine though i am running wilwood 4 pot calipers all round. not seen anything about the lada i'm afraid. hopefully someone with a bit more knowledge will be able to come and add to this.

[Edited on 1/5/11 by mads]

I started wth the standard sierra item, but i found pedal effort to be a liitle harsh. Changed it for the fiat item and now ime happy !




Tony

what do you mean by harsh? To much pressure on foot needed? To much sensitive (lock at first touch)?
What would be the best choice for a later calipers upgrade? I'm also thinking using an instant adjustable bias valve for brake rear/front balance...

[Edited on 1/5/11 by Tilo]

Is this not down to bore size rather than make ?

smaller diameter = more pedal travel ,less pedal pressure, more progressive feel?

What are the sizes of the Sierra and Fiat 124 m/cyls

I spent some time this afternoon sanding the sierra's donor MC and I might go with it... Just need the resevoirs and the rubber seals.

Sierra is fine, but make sure you get a sufficiently high pedal ratio. See also this discussion from last year: http://locostbuilders.co.uk/viewthread.php?tid=111925

Another vote for Fiat 124 MC. I couldn't get the pedal ratio high enough on the Sierra MC. It worked fine but was very solid and needed a big push to approach the point of locking the wheels.

The Fiat one was about £20 plus another £20 ish for MC and hoses.

The pedal travel is longer but I get a lot more braking effort for a sensible level of leg effort and the brake force is easier to control.

Stu

I have a mini one with *I think* 0.7" primary and 0.625" secondary cylinders inline which I hope will work nicely, not got it plumbed yet tho!

If you ever get excess pedal travel on a new build the first port of call after checking every single joint for leaks (always check for wetness at joints while system is under pressure) is to check the brake callipers don't have stuck pads or pistons (Cortina/Escort M16 callipers were particularly prone to both even when brand new), then check the callipers are correctly aligned to the disc this especially applies to any calliper mounted on specially fabricated brackets. Custom mounting multi-pot callipers needs especial care as the length of the calliper makes pedal travel problems due to mis-alignment worse.

To explain a bit; Calliper misalignment or a stuck pad/piston causes a spongy ( actually it feels "springy" pedal because the calliper brackets must deflect under pressure to bring both pads in full contact with the disc. When the pedal is released the calliper springs back knocking the pad and piston back from the disc in the process.

In an M16 style calliper with a stuck piston or jammed pad after fitting new pads the brake pedal travel may initially feel OK but the springyness in the pedal travel gets worse with normal wear and eventually the brakes become less effective and start to pull to one side.

The pistons in M16 callipers are quite prone to seizing after the piston has been pushed fully home to fit new pads.

Because they float Sierra callipers are much less prone to spongy pedal problems however if you get a spongy pedal with Sierra style callipers and it isn't due to the well known problem bleeding the rear callipers then check all the anti-rattle clips are still in place.

[Edited on 3/5/11 by britishtrident]

[Edited on 3/5/11 by britishtrident]