specific question on brake bias setup (front/rear setup)

[Grubester]

(Mk IV roadster; IRS; 11.65" rear disc, etc.)

Okay, here's a specific idea to "quantify" the process for setting the two master cylinders (front/rear) bias.

Use a hand-held IR pyrometer. Drive at say 50mph, brake with medium effort perhaps three times, then quickly record the temperatures of the front vs. rear discs.
Do this a couple of times and consider the temperature delta. Maybe repeat with higher-effort braking (allowing some driving in between for a little disc cooling).
Maybe the experience with this (temp data) from the forum, will help to "quantify" what otherwise is a very subjective effort of trying to "just lock the fronts before the rears lock" or other techniques.
Ideas...?

[CraigS]

I don't think temp matters except on an endurance race car. My thinking is that, just for the sake of discussion, you could have really large brakes on the rear of the car. Since they are so large they will not get as hot for a given amount of deceleration as smaller brakes. But when you really get on them, they will actually have more stopping power than smaller brakes. My method for adjusting brake bias is find a good road w/ minimal crown and little traffic and hit the brakes at 40mph. Keep adjusting and testing until the rears lock first. It is a good idea to drive a couple miles w/o brakes so they can cool between tests. Be aware that, the first time the rears lock first it can be quite a surprise (which is why I do it at just 40). Then adjust bias back just slightly to the front. Also note that, if you set bias on a good surface, then any reduced traction surface will cause the fronts to lock first. That happens because the reduced traction means you can't brake as hard, so weight transfer to the front is reduced, so the fronts lock earlier.

[Avalanche325]

I did the same method as CraigS and also agree that temp is not going to help you set up bias. In an ideal world, the rears never lock.