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MG Midget and Sprite Technical - Brake pipe advice please

Hi

given the problems I've been having with my fierce clutch pedal I have decided to bite the bullet and change the system and get rid of my old style combined master cylinder.

John has donated a twin outlet 1500 brake master pedal box so I now have (not yet fitted) a single clutch and a dual outlet brake master to fit.

I am happy enough to adapt the upper panel to suit, but.

What to do with the brake system?

Should I completely change a system that works by fitting the shuttle valve unit and splitting the brakes?

OR will the new master run a single line system if I blank off the "spare" feeder hole?

OR should I "split" the system into front and back with a pipe for each direction without the pressure warning doodah.

I would welcome thoughts and ideas on this.

At present I am considering fitting a tee piece to feed nearside front and the rear end at one outlet and a separate single feed to the offside front caliper.

And next question...

Now I have the later pedal box am I better off to stick with my relay and hydraulic brake switch or should I use the mechanical one in the "new" pedal box? Still no doubt with a relay, once bitten (twice bitten me!) etcetera...
Bill sdgpm

c'mon you know the old adage - change as little as possible and even then change only one thing at a time.
A couple of us have used the 1500 dual-line m/cyl without shuttle valve on the race cars, but always seemed to get a softish pedal that started halfway down, even with a brand new unit. Personally I'd try a single brake m/cyl per 67-74 cars. And leave the brake light switch alone until later. If you do go for split system then go front / rear.
David Smith

You must run your brake lines in a symmetrical setup. Either fronts together and rears together, or one front and the diagonally opposite rear together. Imagine the case where one circuit fails. The idea is that braking with the remaining circuit won't cause the car to spin. eg if you have frotn left and rear left together and that circuit fails, all the braking is on one side of the car and you'll spin. Don't put one wheel on it's own either - if the other circuit fails you end up with one wheel braking and again you'll spin.

Personally I'd use the mechanical brake light switch, but keeping the hydraulic one in one circuit would be fine too. If a circuit fails then losing the brake lights are the least of your worries!

And finally, don't just block off one outlet on the M/C. If you did then that circuit would go rock hard when you press the pedal, and you'll get no braking pressure in the other circuit at all. If you have a dual circuit M/C you have to put two wheels on each circuit, with either a diagonal split or a front / rear split.

Ant
Ant Allen

Oh, I suppose you could connect the two M/C outlets together in a 3 way join with the third connection going to the existing single line circuit. That would be the least effort to fit I guess. It's a waste of a dual brake M/C though.
Ant Allen

Thanks for that

I sort of thought in that way anyway, but "given" a late master thought I'd work out some possibilities.

The "run one side separately" option wasnt even a starter, 'cos just after I posted I realised how stoopid that was...
(say RED backwards Bill....)

So its earlier master then, ta David.
Bill sdgpm

This thread was discussed on 24/02/2009

MG Midget and Sprite Technical index

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