Wanted - Brake Pressure Reducing Valve
 

Hi

Has anyone got one of the standard brake pressure reducing valves they don't want?

I've got discs all around and need something to reduce the rear line pressure.

Thanks
Matt

Scrappy,vauxhall corsa and most fords have them either in the cylinder or at the rear pipes.

Are they the straight pressure reducing valves, or the deceleration sensitive ones?

try get one off MK2 fiesta, there's a link on locostbuilders, that's what I've bought cost me a tenner bolts straight into master cylinder... don't know if it will work but it's been used a lot on robin hood set-ups with discs all round

Late reply,pressure reducing personally I would avoid anything speed sensitive as it would be for a larger heavier car and possibly a problem.

Fiat Uno ones are available from factors very cheaply, they can be made adjustable very easily, made unadjustable for IVA, and then returned to the original state!

If its the ford sierra deceleration valve i have one you can have.

Thanks. I've PM'd you with my contact details - let me know what you want for it.

Matt

I bought one of those (from Brakeparts, part #HRV1013), but I can't work out what I would need to do to make it work correctly - do you have the details?

That's why I was looking for the standard Sierra one - as far as I can tell it just shuts off the rear brakes when the decelleration reaches a certain rate. It may not be optimal, but seems from comments that as long as it is mounted identically to the Sierra then it is enough to pass the IVA.

Matt

Roller brake tester does not take into account deceleration only brake effort/force so could cause a fail at test/IVA.

Reading the IVA manual I think it's covered under Brake Performance 09E - Note 6: Decelerometer test – This method must only be used where the vehicle cannot be tested in the roller brake tester due to a design characteristic.
...
Drive the vehicle on a level road at a steady speed of approximately 20mph and apply the service brake sufficient only to obtain wheel lock. Observe whether all the wheels of the rear axle(s) lock prior to both wheels of the front axle.

Having a deceleration sensitive valve would mean that was the only way the brakes could be tested, and it's definitely a design characteristic.

Still I haven't been through the IVA so this is all theory

Matt

Decel is used for 4wd etc and has no bearing on the Sierra valve if used for the Roadster.

Every MOT station in the land has a decelerometer for 4wd.

Better to use a pressure reducer as per previous post's and alter after IVA.

Someone on here posted on this. They fitted 4x4 sierra front calipers which are a slightly bigger piston diameter which got round the imbalance thing and it passed sva. No gadgets needed so try and keep it simple.:)

Bob

Hi all
I am going to agree with Flyerncle on this thread, these devices were fitted to the donner car which were much heavier and carried 4 passangers, so big differnce in weight to the roadster and therfore not suitable!!!!

However I am not sure what is avaliable from any of the specialist to fit either and to be IVA compliant ?

It seems there's no good way out of this - either I have to pick a random pressure reducer and hope that the balance is good enough, or rely on a valve from the donor which was designed for a completely different weight of car.

I've got an MOT station within 1/2 mile of my house so once I get that far I can see myself taking a quick trip over there (on a trailer of course) and getting them to let me know what the balance actually is.

At least that way I'll have some hope of getting through

Matt

thats rubbish.

simple physics here the action of the proportional valve will be relative to the inertia/mass of the vehicle. the iva man asked me why i didnt fit the ford valve to my car so its quite apparent that its not an issue to use them.

if it were me knowing what i know now i would be fitting the valve to avoid the roller test. much simpler to drive the car round the iva station and slam the brakes on and see if it locks up at the back first than it is for them to mathematically calculate it on the rollers over 4 points. you can also test it at home easily by driving down the road and slamming the brakes on while a mate watches :D

No need for the limiter
 

Hi Ash
I am not sure what you mean by rubbish? Further discussion with a few other builders and then your goodself it looks there is no need for the limiter at all, on either disics or drum system. Do you agree and hope Matt can prove this when he takes this to his Mot station?

Cheers

No maths involved,brake tester does it all for you and on average I use one up to ten times a day testing vehicles.

At the end of the day if the mate who is watching which wheel locks first is as good as the roller tester in the IVA he is wasted standing on the side of the road.

the iva man doesent use mot spec brake testers for a start
also the foot pressure on the pedal is monitored along with braking effort at all wheels totaly diffrent kettle of fish to the mot brake test im afraid

Cheers Ash. that's good to know

Thanks to kj71 I now have a Sierra valve so I'm going to fit that and move on.

Matt

Going to disagree Baz,spoke to tester first hand the other day at length and having attended the VOSA facillity on many ocassions the equipment is the same as I have in my test station and is in a couple of others I have been to.

Only difference is I apply the brake and not a given load,I still go by what I said previously and reading what has been posted and quote .
"simple physics here the action of the proportional valve will be relative to the inertia/mass of the vehicle."

There is no inertia involved in a static roller brake test and a straight pressure reducer would be better suited if needed at all.

flyerncle

when i had my iva they stuck the car on the brake rollers then applied 4 different pressures measured with a device on their foot. while applying the different amounts of pressure they make a note of the efficiency front and rear from the rollers at each pressure.

they then go and put all the data into an excel spreadsheet that works out the front to rear balance at the four different pressure points they then use that data to work out if the overall brake balance is correct.


now if you fit the ford valve they cant do the test on the rollers as the car needs to be moving for the pressure valve to work. the ford valve controls the rear brake pressure through inertia.

so if you have the valve fitted they have to drive the car around the test station and physically test the brakes. they still try it at all four different pressures but they dont have any rollers to give them the data for the spread sheet so the only test they can do is visual to see if the rears lock under breaking.


i didnt fit the valve to my car as i had the small 1.6 sierra drums. but knowing what i know now i would have fitted it. i believe adrian had the bigger 1800 drums and had issues with brake balance. he didnt fit the ford valve he used smaller rear cylinders to reduce the pressure.

at the end of the day there are lots of solutions to the problem none of them are wrong as long as the balance is correct and it passes the iva

In theory then it would be of use to know what pressures are being applied to the pedal and what percentages in terms of balance they are looking for. That would remove the black art.

Bob

i believe it is all on adrian h's website

sorry im only going on what my local tester is telling me and he is telling me the brake tester is not the same as mot one and tests all 4 wheels brake effort at the same time while monitoring foot pedal pressure.
as i mentioned to him if i could go to my old garage where i used to work to check and set my car up pre iva (brakes, exaust gasses etc)
when i used to do mot's there was no foot pedal pressure monitoring to braking effort so mot set up was no good to set up a ballance bar i was planing on going for. also mot is a 2 roller job and there was no front-back effort at the same time so no good for doing my brake testing pre iva
long and short of it he said it would be best just to fit a normal master cyl and inertia valve and as long as the fronts lock first its a gooden

Hi Baz,can only speak as I find and as posted the effort of each wheel is gained by a certain amount of effort applied to the pedal to give four different readings,it may not need any type of valve at all if the brakes are ok and these discussions have been food for thought for one and all.

If fitted with Sierra valve expect a decelerometer to be used,if not it will be static test.