Smooth Braking and Turning

[Eclipsor]

Because if I trail brake with 1000+ lb rear springs the car spins

Heh, yeah... like I said up there... rotation is the goal. Just be a bit more smooth.

Trail braking helps you rotate the car into a corner by controlling the transfer of weight onto the front tires, giving them more stick, and thus compensating for any understeering tendency the car would otherwise have.

The alternative is: do all of your braking in a straight line, then release the brakes entirely, then turn in. The trouble with this technique is that when you release the brakes, weight - and therefore stick - will be removed from the front tires, just when you need them to be loaded enough to turn the car into the corner. So - unless the car is set up to be driven like this - it will understeer away from the corner. This is typical behavior for 'street' (aka massively understeering) cars that have been adapted for racing.

On the other hand, a 'proper' race car will probably oversteer if you don't trail brake. If you turn into a corner with your feet off both brake and throttle, the front tires will have all their traction budget available for turning while the back wheels will be doing some (engine) braking. Net result: oversteer. Application of the brakes settles down the oversteer by substituting a proportionately balanced loss of steering traction (because the brakes are biased towards the front). In fact, you use the brake pressure to control the rate at which the car rotates into the corner.

How much trail braking you do at a particular corner - i.e. what percentage of the corner is taken under braking - depends on the angle of the corner. For a 60┬░ corner, you'd typically only trail for a few percent of the corner, for a 90┬░ corner, you'd typically trail brake for maybe 25% of the corner, and for a bigger corner, you could do it for up to 50% of the corner. You are aiming to trail off the brakes until they are released completely at or before the throttle application point (which typically occurs somewhere before the geometric apex).

Another way of looking at trail braking is: what you're doing is braking so late for a corner, that you're never going to make it if you carry on in a straight line. In order just to stay on the track, you have to release a little of the pressure on the brake pedal and bend the car into the corner, just to give yourself a little more road - enough extra road to finish the braking. If you find that you've finished braking before the throttle application point in these corners, then you didn't brake late enough. (BTW, if the car won't turn in when you release a little brake pressure, then you probably need to reduce the front brake bias; likewise, if the car swaps ends when you turn in, add some front brake bias).