I can't source reasonably priced 0.7" master cylinders for the rear circuit so will be using 0.625" cylinders with balance bar for front and rear.

I am using standard drums on a Cortina live axle and as I have to replace the wheel cylinders thought I would re-size them to suit the Master Cylinder but need some info to get things approximately right.

Does anybody have the formulas for calculating brake and hydraulic forces for drum brakes. ( I believe they are different to disc brakes because there is some servo effect due to drum acion)

Otherwise does anybody have the sizes of the Cortina Dual Master cylinder - in which case I will use the Brake Calculator found here http://www.locostbuilders.co.uk/viewthread.php?tid=53413
to compare wheel forces for Cortina and Locost and size wheel cylinders accordingly.

At least using the above method I might be in the ballpark and if brake balance is hopelessly wrong i can replace the wheel cylinders to correct problem as they're reasonably cheep - just a mission to replace.

[Edited on 10/3/07 by Ivan]

http://www.rallydesign.co.uk/catalog/product_info.php?products_id=4052

I'd have thought that was quite reasonable

ATB

Simon

quote:

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Originally posted by Simon
http://www.rallydesign.co.uk/catalog/product_info.php?products_id=4052

I'd have thought that was quite reasonable

ATB

Simon

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email rally design and see what they'd charge for delivery to S.A.
i don't know what customs import charges etc might be (if any) but might work out about the same price? (bearing in mind i don't know what the prices there are...)

Thanks for the advice - I did the maths before purchasing the one's I have - but given the potage costs, 50+% import duty and high risk of the parts never getting here but being appropriated by some postal worker the ultimate cost were similar.

An interesting point is that I could have got Willwood ones from the USA for about 50% less than from the British suppliers but the risks above put me off.

[Edited on 11/3/07 by Ivan]

Drum brakes tend to have very non-linear friction characteristics so calculating the "ideal" wheel cylinder size isn't easy.

I am fairly sure that you balance bar should have more than enough adjustment range to get the front brakes locking first, as long as you use wheel cylinders from the saloon version.