240 staggered bore master cylinder

There is a proportioning vavle on each of the lines that goes to the rear callipers. Id imagine that would keep the pressure to them evenish regadless of feeding from the big or small bore. Pressure to each of the front calipers would be the same due to the dual circuits to them. Attach pic explains the purpose of a stepped bore.

jrhendo

Thanks for that, but I’m now more confused! The diagram seems to show both bores that feed the brakes are actually the same size and the bigger bore just pushes fluid up into the reservoir once the piston has moved past the right side feed.

I guess the bigger bore could push fluid past the rubber cup if the yellow thing is some sort of one-way valve?

FYI, for my 144 rally car, I use a 240 master and booster. I’ve changed the pipe work to feed the front cylinders only from the rear outlet of the M/C , and use a single line from the front outlet to the rear brakes through an adjustable pressure valve. My reason for this was that the surface area of the front caliper pistons was close to twice the surface area of the rear ones and the cross section of the 7/8” bore in the M/C is close to twice the cross section of the 5/8” bore, giving similar fluid volumes front and rear.

From the diagram, that now seems rubbish! But the braking system is well balanced.

The background to all this is to see if I can delete the booster without needing huge leg muscles. One issue is that the standard brake crossbar setup on my 144 has the LHS actuation lever (that pushes the booster and M/C) on the bar is twice as long as the RHS lever that the pedal moves. This effectively halves the input into the booster (which the 1974 brochure says is 3:1).

So if I can move the M/C to the RHS (if it fits) maybe I can delete the booster and only have a 50% increase in legwork. Maybe...

I'm currently a long way from home so I can’t measure, just think - and ask questions!

I think the image @VolvoHordz posted is generic...not the actual 240 one, so I would not make any decisions based on the one image. The Greenbooks have a good diagram of the 240 braking circuits and master cylinder IIRC, so might be worth a look there. If you don’t have access once of us can post some pics.

jrhendo

Thanks Greg, I'd realised i was generic but haven't been able to find a 240 one on the net. I don't have a 240 green book, so if someone could post a 240 master cylinder diagram, I'd appreciate it.

I’ll have a look out in the shed today and post if I find anything useful.

@jrhendo here’s an image from the Greenbook. Hope it helps. If you need any more images from the book, lemme know. Greenbooks courtesy @deleted_user_1622 :)