tractorboy
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| posted on 17/3/04 at 05:33 PM |
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brake deceleration valve
as some of you may have read i have just failed my sva on the first attempt. the main problem i had was with the brake deceleration valve. this is the
valve that i thought was just a pressure reduction valve for the rear wheels. but apparently it isnt! it works on inersia and has to be facing fore
and aft at the same angle as that in a sierra to work properly. it works by the fact a ball bearing inside moves foward as you decelerate ,allowing
fluid past it to the rear brakes.
but in good tiger tradition i had followed the book! so now have to go to a scrappy and see what angle the sierra one sits at to keep mr sva happy.
by the way bloke at norwich is very helpful and seems like a nice bloke . if anybody has a sierra sitting on the drive and could save me a scrappy
trip could you tell me what sort of angle the valve sits at i would much appreciate it. and i hope having read this i can save you the same trouble as
ive had but not to worry ill get there in the end  
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jonti
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| posted on 17/3/04 at 06:37 PM |
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I suspect the angle of dangle for a lightweight like a Locost will be different from what is required for the much heavier Sierra.
There was a thread on this quite recently and I'm pretty sure the concensus was to throw the bloody thing away.
Others will confirm or ridicule what I've just said no doubt
OFROK
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JoelP
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| posted on 17/3/04 at 07:04 PM |
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as jonti says, that is what was recommended by members whose opinions i respect. fiat bias valve is the usual recommendation, and some have said it
isnt needed on all cars.
i personally wont be using one because i have a drum brake rear end and my weight is maybe even mostly on the back wheels. time will tell though...
Beware! Bourettes is binfectious.
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JohnN
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| posted on 17/3/04 at 07:27 PM |
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If you want to fit it then the attached photo may help
John
 
Rescued attachment brake valve.jpg
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Dave_the_sparks
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| posted on 17/3/04 at 10:36 PM |
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Well done JohnN, good pic! I can got about modifying mine now, i have only just fitted the damn thing!
mobile auto-electrical specialists www.hammondauto.co.uk
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elitewiring
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| posted on 18/3/04 at 01:32 AM |
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how will mr sva know that its fitted at the correct angle, this will effect the safe operation of the brakes, so surely you will need some evidence
(upon request) that it is fitted in the manner to make it function correctly, surely it cann't be a case of any angle will do, some body correct
me!!!
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Peteff
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| posted on 18/3/04 at 10:36 AM |
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It works on the suspension dive in the Sierra which you do not get with a locost type car. What brakes are fitted to the car? The system works without
the valve in most cars or use the fiat or volky one as others do.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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tractorboy
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| posted on 18/3/04 at 07:57 PM |
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ive got the standard cortina front end and rear sierra drums from a 2LTR estate .mastercylinder is from same sierra and all new pipework from tiger.so
the general concensus seems to be towards the fiat or vw .is that just a straight reduction valve then? and is there any particular model best suited
to get one from? and thank for your help on the subject ( i was ignorant and blissful !)
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britishtrident
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| posted on 27/3/04 at 07:23 PM |
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quote:
Originally posted by Peteff
It works on the suspension dive in the Sierra which you do not get with a locost type car. What brakes are fitted to the car? The system works without
the valve in most cars or use the fiat or volky one as others do.
Its a shut off valve shuts off completely any increase in pressure (and flow) to the rear brakes at a give rate of deceleration, it workks by a ball
rolling up a slope under the "G" force of braking This type of valve was used for years by larger BMC/Austin-Rover fwd models. Valve must
be fitted fore-and aft Increasing the angle of mounting (ie raising the front of valve) increases the value of G the valve shut off cuts in at.
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ayoungman
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| posted on 13/9/04 at 08:56 AM |
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Brake valve
If the valve works on enertia, when they test the brakes on a rolling road, the valve shouldn't work since the car is stationary. I phoned Tiger
and they said it doesn't make any difference what direction the valve is mounted as long as the angle is about right. To me this seems to make
sense !!??!!
 
Rescued attachment DSCF0004.JPG
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DaveFJ
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| posted on 13/9/04 at 01:52 PM |
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First off, makes sense to me... if the valve relies on intertia during decelleration then the valve must be orientated correctly to work.
secondly, a lot of people have binned the sierra valve and fitted one off a fiat Uno. this is adjustable and seems to be a better solution.
Finally.... A PINK CHASSIS !!! that's just wrong !
but seriously - any chance of a pile of piccies in your archive.? all sources of information are extreemly helpful and you seem to have done a few
things differently from your photo.... What is the steering column from? why the ally bulkhead ? etc etc
Cheers
Dave
Dave
"In Support of Help the Heroes" - Always
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andrew.carwithen
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| posted on 13/9/04 at 03:44 PM |
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On page 217 of Sierra Haynes manual, it shows the deceleration valve with an installation angle 'A'. I've measured this angle with a
protractor and it is exactly 25 degrees.
It will have to line-up fore and aft in order for it to work!
I'm fitting the ST/Luego type pedal box with seperate master cylinders for front/rear brake circuits to my Avon c/w bias bar. I'm unsure
if I need to incorporate the deceleration valve into this set-up. What have others done? (Northy etc?)
Cheers,
Andy.
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supercat
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| posted on 13/9/04 at 04:24 PM |
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Another thing worth mentioning is make sure you put the pipes in the right way round. The pipe from the m/c needs to go in the back (fat end) and the
pipe to the brakes come out the front (thin end). Guess who made that mistake first time
Hope this pic from John Ferguson's Cat helps...
Cheers,
James
[Edited on 13/9/04 by supercat]
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Northy
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| posted on 13/9/04 at 06:26 PM |
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Right guys,
If you fit the Sierra device as per "the Book" and SVA at Beverly, YOU WILL FAIL!!! You have been warned. I didn't fail on this,
that is what the SVA inspector that Pat (Avoneer) told us.
I think he said if it was fitted as per the Sierra it would pass.
This cam about by him passing a car that had it fitted as per "the Book", that car was involved in an accident, and he had the accident
investigators asking lots of questions!! Since then, they don't pass, no questions asked.
He told me he phoned Jim, told him what I just told you, and Jim aggreed and said they were aware of this problem, and it had ben altered in the new
book (allegadly  Don't sue me!). I'm not sure if it was altered or not.
I think this message will have been passed onto other test centres, as the SVA inspector got backup from head office over the whole thing.
Hope that has answered your questions.
Cheers
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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Northy
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| posted on 13/9/04 at 06:36 PM |
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quote:
Originally posted by andrew.carwithen
I'm fitting the ST/Luego type pedal box with seperate master cylinders for front/rear brake circuits to my Avon c/w bias bar. I'm unsure
if I need to incorporate the deceleration valve into this set-up. What have others done? (Northy etc?)
Cheers,
Andy.
Nope, you don't need it!
My set up, std Cortina front with Greenstuff pads, and std 2L Sierra rear drums passed SVA with the Bias bar set to max rear braking! 
'Tis a long story....
Cheers
[Edited on 13/9/04 by Northy]
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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