Brake bias valve.
Discussion
Or is that brake pressure valve, proportioning valve, or control valve ?
Yes, I know it what it basically is & what it supposed to do..... but !
Being as I am doing an S3 total restoration....
What is the failure rate/are they a known problem part?
What/where was it sourced from, is there a readily available replacement ?
Is that seemingly silly angle its mounted at, a functional requirement for correct operation ?
IE. It carries some form of inertia control ?
TerryB.
Yes, I know it what it basically is & what it supposed to do..... but !
Being as I am doing an S3 total restoration....
What is the failure rate/are they a known problem part?
What/where was it sourced from, is there a readily available replacement ?
Is that seemingly silly angle its mounted at, a functional requirement for correct operation ?
IE. It carries some form of inertia control ?
TerryB.
Then I guess it should be really called... A Gravity Activated Brake Proportioning Valve.
I haven't been able to locate the same one as 'ours' unless its the same as fitted on Escort Mk4 (x2 of them on that car apparently !).
I'll just give mine a external clean, & maybe flush it out too.
Although (in theory) to prove basic operation, if held in your hand vertically (outlet UP), fluid should flow. And if held 180o the other way (outlet DOWN) fluid should not flow.
But it may need a little pressure behind the fluid to prove this....
Read. Oily floor & hands.... Again !!
And for my second theory... If it did fail, then being as its 'normal' state is open to allow fluid flow, it could be more likely that the back brakes will continue to work if it goes faulty/inoperative (thus giving too good rear brakes under sudden braking).
I'm surprised you 'S racers' out there haven't played around with this, or swopped it out ?
TerryB.
I haven't been able to locate the same one as 'ours' unless its the same as fitted on Escort Mk4 (x2 of them on that car apparently !).
I'll just give mine a external clean, & maybe flush it out too.
Although (in theory) to prove basic operation, if held in your hand vertically (outlet UP), fluid should flow. And if held 180o the other way (outlet DOWN) fluid should not flow.
But it may need a little pressure behind the fluid to prove this....
Read. Oily floor & hands.... Again !!
And for my second theory... If it did fail, then being as its 'normal' state is open to allow fluid flow, it could be more likely that the back brakes will continue to work if it goes faulty/inoperative (thus giving too good rear brakes under sudden braking).
I'm surprised you 'S racers' out there haven't played around with this, or swopped it out ?
TerryB.
Edited by Blue 30 on Thursday 11th February 12:39
Edited by Blue 30 on Thursday 11th February 12:41
Edited by Blue 30 on Thursday 11th February 14:03
My thoughts right now have turned to why, & what work TVR did in picking the inertia valve from Sierra, to fit onto the S.
Was it just 'well it was reqd on Sierra', so we'd better fit it to our car !!!!
And if so, what if any effort did they go to in creating their own mounting bracket, to get the angle right for the dynamic bias to kick in. Or again, is it just a standard Sierra bracket. (Anyone created & fitted a variable angle bracket ??)
Apparently on Sierra the valve was mounted at 25o. But on a shorter lighter stiffer car, is that too much of an angle ? And are they fitted in the same relative position on the car, based on front end 'dive' & rear end lift. Then there's all of those S cars that have had brakes, suspension, wheel & tyre changes, which will all have an effect. Maybe enough that in normal public road driving and braking, the valve rarely, if ever comes into play. But don't forget the master cylinder by design gives front/rear brake bias anyway. This is all leading me to wonder if a standard road only going S really needs it !!! As there are many 'like' sized & weight sports cars that don't have such a thing fitted.
And I don't think a preset or adjustable pressure limiter would be any better, or worse, not on the road anyway. Maybe fitting one of those in some respects would even diminish any advantage in fitting rear discs. Or is it needed more, being as the standing bias would have been changed.
Its all getting very subjective....
TerryB
Was it just 'well it was reqd on Sierra', so we'd better fit it to our car !!!!
And if so, what if any effort did they go to in creating their own mounting bracket, to get the angle right for the dynamic bias to kick in. Or again, is it just a standard Sierra bracket. (Anyone created & fitted a variable angle bracket ??)
Apparently on Sierra the valve was mounted at 25o. But on a shorter lighter stiffer car, is that too much of an angle ? And are they fitted in the same relative position on the car, based on front end 'dive' & rear end lift. Then there's all of those S cars that have had brakes, suspension, wheel & tyre changes, which will all have an effect. Maybe enough that in normal public road driving and braking, the valve rarely, if ever comes into play. But don't forget the master cylinder by design gives front/rear brake bias anyway. This is all leading me to wonder if a standard road only going S really needs it !!! As there are many 'like' sized & weight sports cars that don't have such a thing fitted.
And I don't think a preset or adjustable pressure limiter would be any better, or worse, not on the road anyway. Maybe fitting one of those in some respects would even diminish any advantage in fitting rear discs. Or is it needed more, being as the standing bias would have been changed.
Its all getting very subjective....
TerryB
phillpot said:
....... Sometimes I think you can over think things, just drive it 
I did.... A whole 3 times including driving home after purchase. I only unscrewed one bolt & this fell on the floor !
Maybe its just one of those things that is surplus !
Re - Over thinking things... That was the whole idea of this topic. Great to see the results of you guys 'grey matters' in action. And we all gain from it. Thanks all.
My chassis is now at the blasters, getting rid of what's left of the powder coating, plus giving it a zinc thermal metal coating before I paint it.
And then take a sharp intake of breath, & garage spring clean before I even think about the rebuild including mods.
TerryB
Oops, I forgot the piccy.
And my chassis has gone to Applied Surface Treatment of Wolverhampton. Very helpful guys.
And 'yes' yours truly has spent the winter doing the cutting, welding, & grinding !!
And my chassis has gone to Applied Surface Treatment of Wolverhampton. Very helpful guys.
And 'yes' yours truly has spent the winter doing the cutting, welding, & grinding !!
Edited by Blue 30 on Friday 12th February 20:11
Edited by Blue 30 on Friday 12th February 20:27
Well spotted..
Yes, I have squirrelled away a near brand new AJ30 jag 3.0 V6 engine, plus a never used, not even had any oil in it matching manual gearbox, & to finish the drive train off, a remanufactured 3.14 LSD diff. All ready to fit once it back as a rolling chassis. My jag engine is complete with all ancillaries including the engine bay wiring loom. Of which I will be plumbing that into a high spec programmable ECU.
Maybe it will be totally finished this time next year.
Oh, the chassis is currently missing a removable lower mid-point cross brace. That can only be planned fitted once the engine position gets finalised.
And of course there's the more normal modsto fit such as brakes, suspension, new hood etc etc, plus some Terry'isms as I call them...
TerryB.
Yes, I have squirrelled away a near brand new AJ30 jag 3.0 V6 engine, plus a never used, not even had any oil in it matching manual gearbox, & to finish the drive train off, a remanufactured 3.14 LSD diff. All ready to fit once it back as a rolling chassis. My jag engine is complete with all ancillaries including the engine bay wiring loom. Of which I will be plumbing that into a high spec programmable ECU.
Maybe it will be totally finished this time next year.
Oh, the chassis is currently missing a removable lower mid-point cross brace. That can only be planned fitted once the engine position gets finalised.
And of course there's the more normal modsto fit such as brakes, suspension, new hood etc etc, plus some Terry'isms as I call them...
TerryB.
Edited by Blue 30 on Friday 12th February 22:35
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