Porportioning valve needed?
I would only run one if it is needed, and you won't know that until you drive it. It is better to size the calipers to achieve the correct bias than it is to use a prop valve. On a 4 disc system I would be much more inclined to use an LBS than I would to use a p-valve. Think of it as a pressure delay valve, it slows the pressure rise to the rear brakes so that when they have the least traction they have the least braking pressure, but when they have more traction they have more braking pressure.
http://www.dpiracingproducts.com/lock-resistant-brake-system-lbs/
Adjustable p-valves do not adjust the rear brake pressure. I know everyone thinks that, and everyone is wrong. They have a "knee" in their pressure-in/pressure-out curve. P(out) = P(in) until you reach the knee point. Once past the knee point P(out) = ~.6*P(in) What you adjust is where that knee point is, not the pressure ratio.
I would only run one if it is needed, and you won't know that until you drive it. It is better to size the calipers to achieve the correct bias than it is to use a prop valve. On a 4 disc system I would be much more inclined to use an LBS than I would to use a p-valve. Think of it as a pressure delay valve, it slows the pressure rise to the rear brakes so that when they have the least traction they have the least braking pressure, but when they have more traction they have more braking pressure.
http://www.dpiracingproducts.com/lock-resistant-brake-system-lbs/
Adjustable p-valves do not adjust the rear brake pressure. I know everyone thinks that, and everyone is wrong. They have a "knee" in their pressure-in/pressure-out curve. P(out) = P(in) until you reach the knee point. Once past the knee point P(out) = ~.6*P(in) What you adjust is where that knee point is, not the pressure ratio.
