Dickyboy
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| posted on 11/6/09 at 09:39 AM |
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Sierra master cylinder/diagonal split brakes
As I understand from the gurus on the site the IVA needs 30% efficiency from each side of the split brakes (how do they measure it?). So front/rear
split will not give the rears 30% of the brakes.
Can I re-plumb to put the two front Sierra master cylinder outlets to go one side forward and opposite side rear, tee the rear m/c outlet to do the
other front/rear?
If not can I still use the Sierra m/c?
I have RS200 drums (9" on the rear but still doubt it will suffice, and if it does I suspect it will lock the rears before the fronts!.
Any advice welcome.
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cd.thomson
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| posted on 11/6/09 at 09:43 AM |
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brake bias valve?
Craig
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l0rd
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| posted on 11/6/09 at 09:56 AM |
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Didn't someone mention that brake bias valve are not allowed any more?
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Charlie_Zetec
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| posted on 11/6/09 at 10:17 AM |
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Brake bias valves are still allowed, but they have to be permanently fixed in place. ie. the old measure of drilling and using a pin is no longer
allowed - they suggest welding the bar to lock it.
I'm currently using a sierra m/c, and am preparing for IVA. The way I look at it is this; the front/rear brake proportion is split 60/40.
With the twin fronts, they should be equalling 30% each as a rule of thumb. Thus, is either one of the front pipes fail, you should still get the
minimum 30% from the other front brake and rear units.
Dickboy, the way you are suggesting splitting the braking would not create equal force. My understanding of the Sierra m/c is that the front
section/2 outputs has a smaller bore than the rear, allowing for the bias itself. If you did it how you suggested, one diagonal would technically put
more braking force than the other, something I think you'd not be too keen on! If anoye wants to correct me, please feel free.
Someone who has a copy of the IVA might be able to give us the technical definition, but I don't intend to split my brakes diagonally in a
specific manner, other than that of the standard sierra setup!
Artificial intelligence is no match for natural stupidity!
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MikeRJ
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| posted on 11/6/09 at 10:21 AM |
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quote:
Originally posted by Charlie_Zetec
Brake bias valves are still allowed, but they have to be permanently fixed in place. ie. the old measure of drilling and using a pin is no longer
allowed - they suggest welding the bar to lock it.
That's a bias bar. I believe adjustable bias valves are not allowed for the IVA.
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Charlie_Zetec
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| posted on 11/6/09 at 10:26 AM |
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Sorry, mis-read that!
My understanding is that bias valves and bars are both acceptable, as long as they are fixed in place.
Again, someone who has passed IVA or has a manual might be able to shed more light than I.
Artificial intelligence is no match for natural stupidity!
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l0rd
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| posted on 11/6/09 at 11:46 AM |
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You can lock a bias bar
but a valve??
Hard to believe that this can be done.
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MikeRJ
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| posted on 11/6/09 at 11:54 AM |
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Straight from the horses mouth.
quote:
Note 4: Hydraulic valves that only operate automatically and react to vehicle loading or braking forces are permitted (Load Sensing and Gravity
valves) Manually adjusted valves (other than to permit presetting the automatic function of a valve) are not permitted to be fitted even if they are
rendered un-adjustable.
Note 5: Bias bars and other mechanical adjusting devices fitted to twin master cylinders must have no means of adjustment. However they will be deemed
acceptable if the all nuts etc are fully welded to their relative threads and all the threads originally intended to provide adjustment are welded
along their length i.e. permanently rendering them un-adjustable.
So you can only use a bias valve design to work at one pressure, not an adjustable one that has been 'fixed'.
[Edited on 11/6/09 by MikeRJ]
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Dickyboy
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| posted on 11/6/09 at 12:02 PM |
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Charlie_zetec, just checked my master cylinder, the front two outlets are both into the same chamber, one pipe/brake loses pressure then both are
dead!
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MikeRJ
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| posted on 11/6/09 at 02:45 PM |
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quote:
Originally posted by Dickyboy
Charlie_zetec, just checked my master cylinder, the front two outlets are both into the same chamber, one pipe/brake loses pressure then both are
dead!
That is perfectly normal on a front/rear split system; the master cylinder normally has two front outlets, and a single rear outlet which feeds into a
T piece somewhere near the rear of the car.
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