bilbo
|
 posted on 14/8/10 at 09:49 PM |
|
|
Wilwood Bias Valve – Dumb question
I have a Wilwood Bias Valve like this one in-line to my rear brakes:
 
Wilwood bias valve
I'm just head scratching a bit as to which way is which. It says 'Decrease' on the handle with an arrow – does this mean decrease line
pressure, i.e. reduce the rear braking , or does it mean decrease the restriction in the line, i.e. increase the rear braking?
Reading a few threads on here, I probably won't need it anyway, but seeming as it's already fitted, I want to set it to leave the pressure
unaffected – I can always then change it if the rears lock up first.
Told you it was a dumb question 
Oh, and before anyone asks, it's in the engine bay, so there is no way you can adjust it whilst driving.
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
|
|
prawnabie
|
| posted on 14/8/10 at 09:53 PM |
|
|
I have used one like that and with the handle fully bent over the rear brakes were locked.
Wherever you put it it will fail assuming you haven't passed IVA yet.
|
|
|
bilbo
|
| posted on 14/8/10 at 09:54 PM |
|
|
quote:
Originally posted by prawnabie
I have used one like that and with the handle fully bent over the rear brakes were locked.
Wherever you put it it will fail assuming you haven't passed IVA yet.
Why fail? I thought they would want me to get the brake balance correct?
Also, which way did you do it to get the wheels locked - that doesn't seem to happen to me?
[Edited on 14/8/10 by bilbo]
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
neo2
|
| posted on 14/8/10 at 10:13 PM |
|
|
It should'nt lock the brakes totally which ever way you fit it its bias valve not a line lock..
Mines the screw type and decrease means decreases the pressure to the rear brakes ie less braking, and its also a willwood item..
Iva dont allow adjustable brake valves if i remember correctly, but as you cant reach yours from inside im not 100% sure if yours is ok or not...
Rob
|
|
|
bilbo
|
| posted on 14/8/10 at 10:20 PM |
|
|
quote:
Originally posted by neo2
It should'nt lock the brakes totally which ever way you fit it its bias valve not a line lock..
Mines the screw type and decrease means decreases the pressure to the rear brakes ie less braking, and its also a willwood item..
Iva dont allow adjustable brake valves if i remember correctly, but as you cant reach yours from inside im not 100% sure if yours is ok or not...
Rob
Thanks for that - That answers my question re which way it should go.
I wonder if the it will be OK for IVA if I somehow pin it in position, like you would do with a bias bar assembly?
Might just be easier for me to remove it - I'm just a little worried as I have a disk conversion on the back, but using a sierra M/C original
for drums.
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
Rod Ends
|
 posted on 14/8/10 at 10:52 PM |
|
|
www.wilwood.com/PDF/DataSheets/ds489.pdf
|
|
|
snapper
|
| posted on 15/8/10 at 05:28 AM |
|
|
IVA requires the fronts to lock before the rears, if you don't know what happens without the bias lever, how can you set up the lever?
You could fit it and pin it but still need to address any problems at IVA.
Perhaps using locking wire would convince IVA man that it permanently fixed but you could at IVA cut the wire reposition lever and rewire if you
failed on bias
[Edited on 15/8/10 by snapper]
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
|
|
|
bilbo
|
| posted on 15/8/10 at 08:55 AM |
|
|
Thanks for the replies.
I simply don't have any way of testing what wheels will lock first, before I get it on the road - what have other people done to set up brake
balance before the test? I was hoping to do as Snapper says and alter it at the test if it fails, but if this isn't an option I'm stuffed
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
interestedparty
|
| posted on 15/8/10 at 09:28 AM |
|
|
quote:
Originally posted by bilbo
Thanks for the replies.
I simply don't have any way of testing what wheels will lock first, before I get it on the road -
You don't have any way of testing that after either Im afraid!
Thing is at IVA they test braking effort at several different pedal presuures, so even a MOT station cant test that, nor would driving it on a road,
unless you had a road with lots of different surfaces.
If a car was being driven on a slippery road (maybe slightly oily wet road, for instance) and the rears were more efficient at LOW pedal pressure
(which they might well be, even though less efficient at full pressure) then the car would spin if the driver braked gently in a curve.
The only answer is to try it on full pedal pressure (at MOT for instance, or on a private road, or even a gravel drive) and go woth your best guess,
and go to the IVA. Your chance of passing first time is low anyway, so budget £90 for a retest .
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
|
|
|
bilbo
|
| posted on 15/8/10 at 09:37 AM |
|
|
quote:
Originally posted by interestedparty
quote:
Originally posted by bilbo
Thanks for the replies.
I simply don't have any way of testing what wheels will lock first, before I get it on the road -
You don't have any way of testing that after either Im afraid!
Thing is at IVA they test braking effort at several different pedal presuures, so even a MOT station cant test that, nor would driving it on a road,
unless you had a road with lots of different surfaces.
If a car was being driven on a slippery road (maybe slightly oily wet road, for instance) and the rears were more efficient at LOW pedal pressure
(which they might well be, even though less efficient at full pressure) then the car would spin if the driver braked gently in a curve.
The only answer is to try it on full pedal pressure (at MOT for instance, or on a private road, or even a gravel drive) and go woth your best guess,
and go to the IVA. Your chance of passing first time is low anyway, so budget £90 for a retest .
Thanks for that. I guess my best bet is to see if I can do it on the drive and take it from there. I'll also put one of those stickers near the
valve as per bias bars, and hope they are happy.
I already suspected it wont pass first time, but the more I get right before I go, the better.
Thanks again,
Bill
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
RazMan
|
| posted on 15/8/10 at 10:07 AM |
|
|
Another factor to consider is bedding in the pads & discs makes a LOT of difference to braking performance and balance. When my car was tested
(SVA) everything was brand spanking new and the tester allowed me to do a few laps of their 'circuit' to try and get a bit of heat into
the brakes. Needless to say it was a bit of a gamble and I was gobsmacked to pass - the car had never been run before the test! The force needed on
the brake pedal was actually painful 
Later, with a few miles on the clock, the braking performance was vastly different from the test. I needed to reset the bias bar to stop the fronts
locking up. Sometimes the test parameters don't make any sense .....
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
bilbo
|
| posted on 15/8/10 at 10:16 AM |
|
|
Good point on the bedding in. I'd planned to drive the car to IVA to bed everything in, but then that messes up any tests I do on my drive.
I have to say, I'm bricking it a little re IVA before I've even got a date.
After 4 years of build, I'm finally almost there and I'm getting paranoid about everything.
Doesn't help as well that I started building to SVA regs, then had to rethink stuff when IVA came in
[Edited on 15/8/10 by bilbo]
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
ReMan
|
| posted on 15/8/10 at 10:31 AM |
|
|
Bear in mind therre are pleenty of our cars out there without adjustable bias pedals and without an in line device like this that are working
perfectly well.
I'd say if in doubt leave it out
|
|
|
matt_claydon
|
| posted on 15/8/10 at 05:48 PM |
|
|
Bias valves are not allowed for IVA, doesn't matter if it's locked.
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.
|
|
|
bilbo
|
| posted on 15/8/10 at 09:40 PM |
|
|
quote:
Originally posted by matt_claydon
Bias valves are not allowed for IVA, doesn't matter if it's locked.
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.
Well, that's clear then. I'll have to remove it. I'll just have to hope it will be OK?
Personally, I think this is a stupid rule - to me, a manually operated valve is the perfect solution to get the bias set correctly.
So why, then are bias bars still OK?
[Edited on 15/8/10 by bilbo]
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
|
|
|
procomp
|
| posted on 17/8/10 at 10:20 PM |
|
|
Hi
If you get completely stuck with whats happening at the calipers with differing pedal pressures and fancy a trip to Brum. I can run our brake bias
gauges on the car. It measures line pressure at the calipers giving percentage or actual line pressure readings.
Cheers Matt
|
|
|
