Brake proportioning valve

[Bitsilly]

IIRC there are two valves used in the single line system to reduce the rears stopping power.
And the difference is the spring.
Does anyone know how much of a reduction these valves make?

As I am putting some very heavy batteries in the boot it will not be a normal weight distribution, so I was thinking rather than mess about with springs etc. I could just fit an adjustable valve accessible inside, and adjust to suit.
The problem is most of them only reduce down to about 60% and I have no idea what I will need!

Thanks again.

Ed

[InnoCooperExport]

I could just fit an adjustable valve accessible inside, and adjust to suit.
The problem is most of them only reduce down to about 60% and I have no idea what I will need!

AFAIK an adjustable valve accessible to the driver in the cab isn't legal if you're going for an IVA approval. I don't know what is going to be best for you though, just thought I'd put that out there.

[111Robin]

I don't think you will need a valve. It's there to prevent the rears locking due to the centre of mass shifting to the front when standing on the brakes, with no rear passengers to keep some mass above the rear axles. Your batteries will ensure the mass centre remains near balanced under braking so far less likelihood of locking the rears. Infact you might even tend to lock the fronts if your mass is biased to the rear.

[Bitsilly]

I see what you mean, it would be a good idea to see 'how is' functions .
And there is no requirement for IVA as only the 'engine' is being changed.
Cheers

[Polarsilver]

I fit fully adjustable Brake Bias Valve from Compbrake.. a quality alloy item ..then adjust to suit my needs

[indigo]

For a comparison I run a Twin engine Mini.
Estimated extra 150kgs in the rear.
Standard 7.5 inch discs on the front.
850 style 1 inch cylinders on the rear (single cylinder each side)
No proportionng valve.
Single master cylinder with barke booster as per Mk1 setup.
Brakes are excellent, better than standard Cooper S, no locking of the rear under heavy emergency braking (not sure about the wet).
And passed all the engineering tests for registration.

So depending on the mass of your batteries, compared to my 150kgs, you may not need a valve, and may be able to fit larger rear cylinders to improve braking. (also depends on what you choose for the front).

[Spider]

IIRC there are two valves used in the single line system to reduce the rears stopping power.
And the difference is the spring.
Does anyone know how much of a reduction these valves make?

There was at least 4, maybe 5.

The ones I can ID are;-

250 PSI
370 PSI
390 PSI &
450 PSI

I * think * there's also a 300 PSI type.

They all make a difference, but you need to fit something that's going to shut off the rear brakes before they lock, under all conditions.

As you'll have a boot full of batteries (?), you can likely afford to have more rear braking than a normal Mini.

Fitting an adjustable type might be the answer here.

[Bitsilly]

Thanks everyone.
I will try and find an adjustable valve that has more range, but if 50-50 works with an extra engine in the back then I would guess a valve that can cause a reduction of 60% is more than adequate.