donut
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| posted on 12/9/05 at 01:29 PM |
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Brake bias valve...where to put it?
Ok i have got a Wilwood break bias valve but i don't know where to put it. (ok no one tell me to shove it up my a***!  )
I believe that if it goes in the tunnel the SVA man won't see it so that would be ok. If it's in the boot or engine bay then i think
i'm right in saying that it needs to be set at a deturmined setting and then fixed so an adjustment can't be made.
Anyone got any ideas?
it looks like this:
[Edited on 12/9/05 by donut]
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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Hellfire
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| posted on 12/9/05 at 03:49 PM |
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Stick it in the bin......... 
Or back on e-bay. 
[Edited on 12-9-05 by Hellfire]
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Surrey Dave
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| posted on 12/9/05 at 04:34 PM |
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If you look at the posts on brake bias ,you'll see that everyone seems to adjust the bias valve to a point where it does nothing ,so why
bother?
Another job I've saved you!!!!
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Bob C
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| posted on 12/9/05 at 04:59 PM |
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Interesting replies! I disagree, a proportioning valve like this can give better braking over a wider range of conditions than a bias bar & 2
master cylinders BECAUSE it automatically compensates for weight transfer. A balance bar fixes the front /rear bias at one setting.
Bob C
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donut
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| posted on 12/9/05 at 05:07 PM |
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I have now been told that it's not an SVA requirement to have a brake bias valve as i have the correct Sierra brake master cylinder. Therefore
i'm not going to fit it. If i am locking the rear up alot then i'll fit it.
Hellfire, do you not have a brake bias valve on your car?
ignore that... i have just found a thread about bias valves that are not fitted and it seems many have not done so.... so i won't either.
Another job i don't have to do!!!
[Edited on 12/9/05 by donut]
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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MikeRJ
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| posted on 12/9/05 at 06:15 PM |
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quote:
Originally posted by Bob C
Interesting replies! I disagree, a proportioning valve like this can give better braking over a wider range of conditions than a bias bar & 2
master cylinders BECAUSE it automatically compensates for weight transfer. A balance bar fixes the front /rear bias at one setting.
Bob C
The Wilwood bias valve is (AFAIK) a simple pressure regulator that can reduce pressure to the rear brakes (exactly like the ones fitted to early
minis). It's not an inertia operated valve like the stock Sierra one, so it can't take into account weight transfer etc.
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Bob C
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| posted on 12/9/05 at 07:03 PM |
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Doesn't have to be inertia operated - the braking acceleration(deceleration) is proportional to the pressure in the brake line!
Or else you're skidding, then all bets are off anyway!
Bob C
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Bob C
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| posted on 12/9/05 at 07:08 PM |
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I did a spreadsheet to work out the prop valve characteristics I wanted for my car (tried to work out height of centre of gravity of my unborn car -
not easy...) Here's a link, someone might find it interesting (or at least work out what the hell it means!!!)
Cheers
Bob
http://freespace.virgin.net/bob.carter/files/brakecalc.xls
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MikeRJ
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| posted on 12/9/05 at 08:59 PM |
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quote:
Originally posted by Bob C
Doesn't have to be inertia operated - the braking acceleration(deceleration) is proportional to the pressure in the brake line!
From that point of view there is no difference to an adjustable bias bar then. In fact a bias bar is better as the front and rear pressures are
proportional to the pedal pressure, the simple adjustable proportionaing valves simply limit the maximum pressure to the brakes, i.e. above a certain
point pressing the brake pedal harder won't acheive any more pressure after the valve.
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Surrey Dave
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| posted on 12/9/05 at 09:44 PM |
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Rear Brakes
Does anybody have an MK or Locost that locks the rear brakes (not counting bias bar setups)?
Mine never has and never will........
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Bob C
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| posted on 12/9/05 at 11:20 PM |
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___________________________________
From that point of view there is no difference to an adjustable bias bar then. In fact a bias bar is better as the front and rear pressures are
proportional to the pedal pressure, the simple adjustable proportionaing valves simply limit the maximum pressure to the brakes, i.e. above a certain
point pressing the brake pedal harder won't acheive any more pressure after the valve.
___________________________________
No what I'm saying is a bias bar will always give (say) 70% front 30% rear & this may be ideal for a 1G stop wher 70% car weight is on front
wheels & 30 on rear. Put the same car on a slippy surface where only 0.2G is possible and there's now 50% front 50% rear weight
distribution. If you brake so the fronts are on the point of locking there's less than half this on the rear . So only 3/7 of the 50% braking
available from the back axle is being used. In other words the brakes IN TOTAL are only 70% as effective as they could be
.
Unless you continually adjust the bias bar.
The proportioning valves let full pressure through up to an actuating pressure, after which a reduced proportion is allowed through, on the wilwood
one the pressure is adjustable from 100psi up and the proportion is 57% reduction thereafter. These valves allow the pressure in front and rear
circuits to approximately follow the weight transfer due to deceleration. That's why I think they work better over a wide range of conditions
than a bias bar.
For SVA the bias bar will be set to a 'dry tarmac' setting of 70/30 or so FR/RR & that will give excellent performance for track days
& sunny drives. I just think a properly set up prop valve would also give better performance on slime, grass or snow.
Who goes out on that in their locost ? ? ?
cheers
Bob
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