Adjustable Brake Proportioning Valves.

[simonr]

The kind of thing which lets you reduce the pressure to the rear (or front) brakes to improve the balance of your braking.

The reason I ask is that all the suppliers of such devices say something like 'for track use only'. I spoke to one establishment who said they were not suitable for SVA.

The reason I'm interested is the SVA seems to include testing to see that the proportioning of the brakes match the weight distribution of the vehicle. My front and rear calipers are the same - so I have 50/50 braking but not 50/50 weight distribution.

I have a proportioning valve from a Disco (kindly donated by Mark) which at low pressures allows the same pressure through to the back, but at higher pressures the rate of increase at the back is lower than the front. I'm not convinced this is sufficient - at least for SVA - so how does one 'fix' it?

Si

[Guest noggy]

yes, they're installed on old mini's, infact they're on a lot of cars, i believe ford escorts have them as standard aswell.

it should be alright for an SVA i cant see why not. they're a fairly normal thing.

they're more commonly called brake bias valves.

[western]

the in cab adjustable brake valves may not be road legal, but the standard factory ft type are.

[steve_d]

SVA accept that adjustable valves are required in order to correct the brake balance in kitcars but insist that they be completely locked once adjusted. There have been test centres that insist the balance-bar type be welded once adjusted rather than just locknuts.

If you used an inline type you could make a box to go over it and tack weld that to the chassis. It would seem permanent enough for the tester who may not realise the grinding unwanted bits off of a chassis is an every day thing for LR owners.

Steve

[FridgeFreezer]

They say for track use only because they don't want to take the insurance risk of some idiot setting it wrong and killing someone on the public highway. All sorts of stuff has the same caveat on it - calipers, wheels, steering bits, lights (too lazy to get an E mark), etc.

[simonr]

SVA accept that adjustable valves are required in order to correct the brake balance in kitcars but insist that they be completely locked once adjusted.

Thanks Steve, that's a relief.

To be honest, because it's never going to be used for racing or track days, I don't thing the precise balance is going to be all that critical. Once it's set - I'd be happy to lock it off. It's going to live inbetween the chassis rails anyway - so not convenient for adjusting on the fly.

I presume I need to set it up on a rolling road having measured the corner weights?

I take it also that if there is for example a 60/40 weight distribution, the brakes need the same ratio front to rear?

Si

[FridgeFreezer]

Si - you could use a master cylinder with a different split, I think 90's have 50/50 split and 110's have 60/40 with no biasing valve, my master cyl is 110 and seems to stop the 109 very nicely.

[simonr]

Si - you could use a master cylinder with a different split, I think 90's have 50/50 split and 110's have 60/40 with no biasing valve, my master cyl is 110 and seems to stop the 109 very nicely.

Good idea. No idea what a Suz<cough>uki has though. Might be OK as is!

Si

[Hybrid_From_Hell]

My mate across the road has a much modded Suzi

He has made rear disc brakes, asnd when he drove down the road for a test drive and stmped the brakes the rears locked up

He had to fit an adjustable bias valve - he paid £££££££££££££££££s for some bling from Demon S£qeaks

The std Suzu unit didn't like discs Its fine now

HTH

Nige