I found this post on another forum, and I thought you all might find it interesting/usefull.
Original post here: http://www.nsxprime.com/forums/showthread.php?t=57074
Ouote:
"Xavier's question has prompted me to pull out my copy of Going Faster from Skip Barber Racing School and to review Chapter 14 on brake bias adjustment. My thinking is that using different brake compounds on the front versus the rear is similar to adjusting brake bias. Here are some excepts, not the full two pages.
"Load Transfer
First some basics about grip....More download delivers more grip....Under braking, for example, deceleration transfers load off the rear tires onto the fronts.....When the braking system is .....adjusted, a key consideration is the increased grip available to the front tires because of the increased download. Brake bias adjustments are an attempt to adapt the braking system of the car so that braking effort is proportioned correctly to use the different levels of grip available to the front versus rear tires........
Setting the Bias
....first run the car for a few laps, getting to the point where the tires and brakes are up to temperature. If you set the bias when the tires are cold and the grip is less than you'll experience under racing conditions, there will be less download on the fronts than there will be when everything is warm. Then you are likely to have too little braking at the front and too much at the rear when things finally heat up. This rear-bias situation can get overly exciting, so it's something you should avoid.
......after carefully checking the mirrors to avoid being run over. From high speed, squeeze the brake pedal on...until either the front wheel or rear wheel gets just to the edge of lockup.......
In an open wheel car, you should be able to notice the strobe-like effect of the front tires slipping across the road.....With rear bias, focus the mirrors on the rear tires while doing the brake testing to confirm the physical sensation of rear bias (the rear darts around during braking). In closed wheel cars, you have to trust your sensitivity and back it up with evidence of buffs of smoke out of the wheel wells.
With either type of car, you are aiming to get the brake bias adjusted so that the fronts begin to lock marginally sooner than the rears. You would rather have a little excess bias toward the front because it is the more stable of the two extremes. Going too far to the front, however, will compromise the overall braking ability of the car.
Bias and the Clutch
.....In most cases of threshold braking, the car will be decelerating in gear with the clutch engaged, except for the moments you dip the clutch for downshifts. In this case the brake bias should be set by braking the car with the gear engaged. In most cases the engine compression...is contributing to the braking of the rear pair of tires. If you set the brake bias with the clutch disengaged, you'll end up with too much rear bias if you slow the car with the help of the engine during the race.....
Brake-turn Bias
Once the bias is close in straight-line stops, it's time to try it under simultaneous braking and turning conditions (trail braking). If there is any possibility that the bias is too far to the rear, it will show up here. You may find that a bias that was perfect for straight-line braking will be biased a little too much to the rear for comfort under brake-turning. Under the combination of pitch and roll, which takes place while braking and turning, the inside rear tire is substantially unloaded and the drag of the rear brakes contributes to the rear losing cornering traction, allowing the rear of the car to slide slightly more than the front.
.....Anticipate that if there is a lot of aggressive braking and turning needed at a particular track, the bias may end up a turn or two more toward the front."
Obviously the author is writing about race cars without ABS but the desired result is the same. Similarly, I think that electing to use different brake compounds front versus rear (effecting a change in bias) should be approached in a similar fashion. It appears to me that the major reason for using a "stronger" compound in the front would be to correct for too much rear brake bias i.e. the rear darting around during braking; oversteer during trail braking."
Original post here: http://www.nsxprime.com/forums/showthread.php?t=57074
Ouote:
"Xavier's question has prompted me to pull out my copy of Going Faster from Skip Barber Racing School and to review Chapter 14 on brake bias adjustment. My thinking is that using different brake compounds on the front versus the rear is similar to adjusting brake bias. Here are some excepts, not the full two pages.
"Load Transfer
First some basics about grip....More download delivers more grip....Under braking, for example, deceleration transfers load off the rear tires onto the fronts.....When the braking system is .....adjusted, a key consideration is the increased grip available to the front tires because of the increased download. Brake bias adjustments are an attempt to adapt the braking system of the car so that braking effort is proportioned correctly to use the different levels of grip available to the front versus rear tires........
Setting the Bias
....first run the car for a few laps, getting to the point where the tires and brakes are up to temperature. If you set the bias when the tires are cold and the grip is less than you'll experience under racing conditions, there will be less download on the fronts than there will be when everything is warm. Then you are likely to have too little braking at the front and too much at the rear when things finally heat up. This rear-bias situation can get overly exciting, so it's something you should avoid.
......after carefully checking the mirrors to avoid being run over. From high speed, squeeze the brake pedal on...until either the front wheel or rear wheel gets just to the edge of lockup.......
In an open wheel car, you should be able to notice the strobe-like effect of the front tires slipping across the road.....With rear bias, focus the mirrors on the rear tires while doing the brake testing to confirm the physical sensation of rear bias (the rear darts around during braking). In closed wheel cars, you have to trust your sensitivity and back it up with evidence of buffs of smoke out of the wheel wells.
With either type of car, you are aiming to get the brake bias adjusted so that the fronts begin to lock marginally sooner than the rears. You would rather have a little excess bias toward the front because it is the more stable of the two extremes. Going too far to the front, however, will compromise the overall braking ability of the car.
Bias and the Clutch
.....In most cases of threshold braking, the car will be decelerating in gear with the clutch engaged, except for the moments you dip the clutch for downshifts. In this case the brake bias should be set by braking the car with the gear engaged. In most cases the engine compression...is contributing to the braking of the rear pair of tires. If you set the brake bias with the clutch disengaged, you'll end up with too much rear bias if you slow the car with the help of the engine during the race.....
Brake-turn Bias
Once the bias is close in straight-line stops, it's time to try it under simultaneous braking and turning conditions (trail braking). If there is any possibility that the bias is too far to the rear, it will show up here. You may find that a bias that was perfect for straight-line braking will be biased a little too much to the rear for comfort under brake-turning. Under the combination of pitch and roll, which takes place while braking and turning, the inside rear tire is substantially unloaded and the drag of the rear brakes contributes to the rear losing cornering traction, allowing the rear of the car to slide slightly more than the front.
.....Anticipate that if there is a lot of aggressive braking and turning needed at a particular track, the bias may end up a turn or two more toward the front."
Obviously the author is writing about race cars without ABS but the desired result is the same. Similarly, I think that electing to use different brake compounds front versus rear (effecting a change in bias) should be approached in a similar fashion. It appears to me that the major reason for using a "stronger" compound in the front would be to correct for too much rear brake bias i.e. the rear darting around during braking; oversteer during trail braking."
