flange nut
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| posted on 2/3/03 at 10:31 PM |
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Rear brake bias valve
The one thing that struck me when reading the Avon book ( OK there's lots of things) is the position of the rear brake pressure reduction valve. It
appears to be mounted across the chassis on the rear panel. ( Pages 86, 87)
This type of pressure reduction valve works by the deaccelertion of the car producing an inertia force sufficient to roll a steel ball up the sloping
cylinder and closing a valve to the rear brakes. That's OK when it's mounted correctly in a fore aft position but I can see problems arising when
braking on sweeping bends. In theory it would produce too much rear brake in one direction and a lot less in the other. It also appears to be
plumbed up the wrong way round in the photographs! I'm I right or is this a cunning trick on the part of Tiger Racing?
Have any Tiger Avon builders/owners used this system?. Am I right? I would like to know as I might use my Sierra's valve.
Just another thought, as this type of pressure reduction valve works by inertia how do you get the rear brakes throught the SVA brake test when the
car doesn't move?
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Viper
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| posted on 2/3/03 at 11:19 PM |
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As far as the sva goes i believe you tell them you have a reduction valve fitted and they then drive the thing?? sounds a bit odd to me because the
valve is there to reduce the risk of rear lock up so the brakes should still work fine on the rollers bear in moind they don't stamp on the brakes,
if this system didn't work on the rolers there is no way a sierra would pass an MOT
As for the tiger book....best place for that is in the bin...as tiger so often say "it's not a build manuel"
major cop out?? did i say that?? perhaps i ought to state that this is just my opinion or even retract my earlier statement just incase it incurs a
court case......
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kingr
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| posted on 3/3/03 at 09:39 AM |
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Not a build manual??? What is it then? A coffee table book? Art? Fictional? What a load of crap.
Kingr
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flange nut
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| posted on 3/3/03 at 02:19 PM |
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In my opinion it makes a great coffee table book, all those glossy colour photos are nice to look at, but as for putting a car together in my opinion
it shows how good old Ron's book really is. Sorry about all the "in my opinion" stuff but I believe you can't be sued for expressing your own
opinion.
In reply to Viper I would expect the rear brakes to work fine to pass an MOT. The problem is in the SVA, the tester, when testing the brake efficiency
uses a pressure transducer between his foot and the pedal. For a certain pedal pressue the rear brakes should show a lower efficiency then the front.
Without any deacceleration affecting the rear bias valve the rear brakes could show up as being far to effective.
Maybe I should play safe and use a modified Mini or Uno bias valve.
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Viper
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| posted on 3/3/03 at 05:46 PM |
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i think Kingr's last description of the book was the most accurate "what a load of crap"
as far as the reduction valve goes i am not using one at all, i am going with a bias pedal box, at least that way i will have all the adjustment i
could want without putting something in the line that cuts off the flow..
i think the best thing to do bout this is phone the sva bods if they can't tell you what to do then throw it in the bin and fit an alternative..
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theconrodkid
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| posted on 5/3/03 at 07:44 PM |
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flange nut,i have a few uno valves left,£20 inc p+p,mail me if yr interested.
who cares who wins
pass the pork pies
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donut
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| posted on 20/3/03 at 07:30 AM |
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I was also surprised when i saw the reduction vaulve going left to right, it would only work when you braked round corners!!!! I have put mine facing
forwars high in the g/box tunnel out the way as requested by MAC#1 Motorsports. That's what they do and their cars pass SVA no probs. It faces
forwards in the donor too so i'm told. I can not beleive a top company like Tiger making such an error, it makes you wonder about the rest of
the car!!
Andy
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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bruce
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| posted on 29/3/03 at 12:31 PM |
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eljays
I had a problem with this, so I went and saw the tiger demo. The valve is as in the book accross the back and facing down (normally rear to front
facing slightly up). Fixing this way would have the effect of reducing pressure to the rear permanently, which is the general idea. For this reason
on a rolling road where a sierra would lock up at the rear because there is no deceleration, this set up would work. I have asked several people and
most are of the opinion that reducing the pressure permanently would not be a problem.
I bought the avon and so far am very pleased with it, and the book although not a build manual has got me this far (with help from other forum
members). You get what you pay for, tiger does not claim the avon is a caterham and only a fool would expect it to be.
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flange nut
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| posted on 30/3/03 at 01:34 PM |
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Thanks Bruce, I can see now that the valve is upside down and probably would reduce the pressure to the rear brakes while stationary and if you get
the angle of the valve right get you through the SVA.
The fact still remains though that the pressure to the rear brakes would change depending on the direction of the curve the car was travelling along
while braking.
A few words of wisdom from Jim Dudley in the book about how he expects the Sierra valve to work in this application would have helped. In my opinion
the book raises more questions then it answers and is too vague in so many important places. If it's not be a build manual then it's a
pity it's call "How to build your own Tiger Avon...."
Perhaps you can answer a question. What is purpose of the square plate "B" as shown in drawing 6.3a?
The book of course doesn't mention it.
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gjn200
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| posted on 30/3/03 at 06:34 PM |
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I'm going to put the vin plate on it.
<- Me!
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bruce
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| posted on 31/3/03 at 05:53 PM |
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I believe this to be for a zetec mount. There is only about 6mm clearence between this and sump on the pinto. Some people have told me they have
removed it, but double check first. My pinto is in and I cant see any use for it.
The bearing in the valve is very sensitive, and even when the valve is level it would still have the effect of reducing pressure. If the valve is
faced down, at an angle shown in the book, even on a bend at high speed the gravity would not be enough to push the bearing up the valve because the
fluid is also having the effect of putting pressure on bearing. I was told by tiger that the pressure of the fluid is enough to close the valve, even
if the valve is level. Again I am only repeating what I have been told by tiger and other builders, so do what you feel is the best way.
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Viper
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| posted on 4/4/03 at 06:24 PM |
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If it is for the zetec then why is there a number welded onto it?
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