Wanted - Brake Pressure Reducing Valve

[flyerncle]

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.

[AshG]

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

[robo]

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

[AshG]

i believe it is all on adrian h's website

[baz-r]

Originally Posted by flyerncle

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.

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

[flyerncle]

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.