Brake bias valve & brake pipe connections
Discussion
I was just looking at David H's Griff project site (it's extremely useful for finding out where all the random bits in the garage actually go!)
I noticed that his Griff has what appears to be a Sierra brake bias valve near the rear diff.
Mine doesn't have this at all, so I wondered what the arrangement was?
Is the biassing built in to the master cylinder or is it in the bodywork near the pedals or does mine not have one for some reason? The pipework looks original, so I very much doubt anyone has messed with it in the past.
Also, on the brake & clutch pipe attachemnt block in the driver's inner wing, what wheel goes where? I know the clutch is at the bottom, but do the rest actually matter? I know I should have written this down, but I forgot to
I noticed that his Griff has what appears to be a Sierra brake bias valve near the rear diff.
Mine doesn't have this at all, so I wondered what the arrangement was?
Is the biassing built in to the master cylinder or is it in the bodywork near the pedals or does mine not have one for some reason? The pipework looks original, so I very much doubt anyone has messed with it in the past.
Also, on the brake & clutch pipe attachemnt block in the driver's inner wing, what wheel goes where? I know the clutch is at the bottom, but do the rest actually matter? I know I should have written this down, but I forgot to
It should have a brake bias valve but it has been known for them to be removed. Not sure I agree with that as it will increase the bias to the rear on a car which is rear biassed already. Without it, the brake balance is defined by the calliper piston sizes and the ratio between front and back. I would recommend fitting a manual adjuster rather than nothing at all.
As for the block, I can't remember either. Probably a case of following the connections through...
As for the block, I can't remember either. Probably a case of following the connections through...
shpub said:
It should have a brake bias valve but it has been known for them to be removed. Not sure I agree with that as it will increase the bias to the rear on a car which is rear biassed already. Without it, the brake balance is defined by the calliper piston sizes and the ratio between front and back. I would recommend fitting a manual adjuster rather than nothing at all.
It's important to keep the distinction clear between static balance and dynamic balance. The static balance is determined purely by the overall effective leverage of the pedal, master cylinder, caliper, disc. This is the brake balance you get under gentle braking, for example if you dab the brakes gently while cornering hard or try to stop in very slippery conditions. The static balance should be close to the static weight distribution of the car. To change it, you need to change the geometry or leverage of the brakes, for example with a balance bar.
The dynamic balance determines how the brake distribution changes as you apply the brakes harder and harder. This is usually achieved by putting a bias valve in series with the rear brake circuit, which limits the amount of braking going to the rear wheels as you apply the brakes harder and harder. The dynamic balance should match the amount of weight transfer you get under braking. If you have changed the calipers/discs and are now running at a different line pressure than the bias valve was set up for then you will need to change the bias valve to match. You can get aftermarket adjustable bias valves that make this easy to achieve.
If you remove the bias valve you will lose the ability to cope with weight transfer - you can set the brakes to be balanced under light braking, or heavy braking, but not both. This can be quite dangerous but is frighteningly common with people who have upgraded the front brakes and find the rears aren't doing enough work. Cars like this are an accident waiting to happen imo.
It is possible to use a bias valve to mask the effects of the static balance being wrong (e.g. after upgrading the brakes at one end of the car only) but again this is the wrong approach, you should get the static balance right first and the bias valve doesn't do that.
Hi dnb
I asked this question before,and didn't realize it was just the small cylinder(about 20mm x 40mm) in front of the T junction which I didn't think was a valve.
Edited to add,hydraulic body block,from bottom ,Clutch,rear brakes,front near side,front off side.
I asked this question before,and didn't realize it was just the small cylinder(about 20mm x 40mm) in front of the T junction which I didn't think was a valve.
Edited to add,hydraulic body block,from bottom ,Clutch,rear brakes,front near side,front off side.
Edited by v8sag on Thursday 5th April 22:26
A big box arrived from Speedflow this afternoon, so I can fit the new lines in the right place now 
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