Larger brake master cylinder options

[dylanp]

Evening all..
Don't suppose anyone here changed their brake master cylinder for a larger bore one and if so do you maybe have a part number or donor car make/model? I know the standard master is 22.2mm so looking for an option with 23.8 or even 25.4 bore.

(I've upgraded my Chimaera front brakes with brembos from bmw e38 which work amazingly well, however the pedal is now feather light and pedal travel is way too long - hence the intention to put a larger bore master cylinder to shorten travel and firm up the pedal).

Thanks!
Dylan

[steviegtr]

I will watch this thread as I have done the exact same with my MK3 Chim. Using 300mm front discs Focus st. & Bmw 7 series 4 pot calipers. Awesome result but a slightly long pedal. I came to the conclusion that if the larger girling cylinder will fit. The problem being the servo fitting points to the cylinder. Wish I had a spare servo to experiment with. Funny as there are lots of 4 pot conversions that have been done , but no mention of a larger master cyl.
Also all the complete upgrade kits available show all the parts , but no new master cylinder. ????.
Steve.

[phillpot]

Four pots but far smaller than the one big one in a standard caliper (that has to move twice as far) I wonder if the volume of fluid moved is actually any greater . . . .

[steviegtr]

phillpot said:

Four pots but far smaller than the one big one in a standard caliper (that has to move twice as far) I wonder if the volume of fluid moved is actually any greater . . . .

Looked at this & yes the single is a huge piston. Not worked it out but clearely from 1 large to 4 smaller must still require a bit more fluid.
Bearing in mind that once fully bedded in the pad only moves a few thou . Mine are not fully bedded yet. Something like 125 miles of short journeys, so maybe I need to give it a chance. Although the MOT is due so will have to see what they say.
Steve.

[dylanp]

Yes, I've also only done about 500 miles whilst running in a freshly rebuilt engine, so haven't really given the brakes much of a workout yet.

Might improve a bit but I still think a larger master is the right thing to do - in my mind long pedal and super light = bigger master needed.

[phillpot]

steviegtr said:

Not worked it out but clearly from 1 large to 4 smaller must still require a bit more fluid.

But the one large moves twice as far as it is doing both sides on a sliding caliper arrangement

Edited by phillpot on Sunday 15th September 17:55

[hansdaal]

Hallo Dylan,

If you are after a larger bore brake master.
Fiesta MK3 partnumber 7117261/ Delphi LM39003 is 23.8 mm
Did quite a few brake upgrades in the past with 4 pot AP/TVR calipers with 300/ 324 mm discs but never changed the brakemaster.

REgarsd Hans.

[dylanp]

Thanks Hans, that's super useful!
😁