@LasseA Thanks Lasse
It's true that I care quite strongly about getting everything just right.
About the 49% brake bias, I think what you said is pretty much spot on. I mean, let's say you use 50% brake bias. That means the brakes at the front and the rear have equal braking power - let's say 1000N front / 1000N rear. By adding throttle, I presume you are simply reducing the braking ability of the rear tyres so it's now more like 1000N/850N. The brakes in default GPL are pretty strong, so reducing the front brake bias will make them less sensitive to locking as well.
Another factor is the diff settings, which prevent the rear wheels spinning independently of each other. If you are using say, 30/60/2, then your locking % is 13% under throttle and 8% when off the throttle completely. By adding any amount of throttle you are increasing the locking percentage to 13%. This greatly increases the stability of the car as you enter the corner.
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About the front/rear grip differences vs. brake bias. Actually this is a pretty complicated topic, but it is mostly down to what I wrote in the GPL Tyre Physics thread. The more weight on the tyres, the lower the tyre's peak friction coefficieny. A Lotus 49 with a 40/60 weight balance will have roughly 115kg on each front tyre and 180kg on each rear tyre when stationary and there's 5% loss of grip per 100kg.
If the front and rear
base friction coeff was the same, e.g. 1.00:
- After calculating the car's static weight, friction coeffs are approximately 0.95F/0.90R
- When you enter a corner, weight is being transferred to the outside tyres so entering the Parabolica, at 1.2G, the left side tyres will now be 0.92F/0.88R.
- Since there is more weight on the rear, the rear of the car will roll more than the front. More roll increases the camber, which also reduces the grip. So, accounting for this, tyre friction might now be 0.90F and 0.85R.
With a 50/50 brake bias, the rears are going to lock easily and you'll have a lot less grip on the rear when cornering in general, so you'll need to move the brake bias forward. This is obviously ignoring longitudinal weight transfer, slip angle, temperature, pressure etc. It also ignores the various inertial factors which we were talking about earlier, because although I haven't done any testing on it, I am pretty sure these also increase how much weight is transferred around the car.
Default GPL uses more like 1.00F and 1.05R for the base tyre grip. So, in the above situation:
- Static grip will be 0.95F/0.945R
- Cornering at 1.2G (excluding camber change from body roll) - 0.92F/0.925R
- Now including body roll: 0.9F/0.895R
Hence you can get away much lower front brake bias.
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I haven't done too much reading on it myself to be honest
A lot of this is from 2 years of playing around with GPL's physics engine, comparing with the physics in Assetto Corsa and my own real world racing experience. I recommend continuing to watch the various videos on YouTube, especially those from Driver61. They are pretty easily digestible.
I don't think GPL needs that exactly but I already found a setting I am happy with so you'll see it in the mod.
