[Georges]

After 10+ years of AutoX I still get to learn...

Today's event in the rain and low 40 degree F with some snow flakes at the end of the event...

Pivot turn at the end of a straight (close to red line). You'd think find your brake point and threshold brake with ABS kicking in when you'r not perfect, make the slow turn and back on the gas.

However, I noticed that after the finish, also close to the red line, I seem to stop faster with less "urgent" braking. So, back to the course, I use less brake pressure; not even close to ABS and guess what? The car slows faster and much more stable and perfect around the pivot. Tested it with 3 runs and am a bit shocked. Less brake means you can slow faster and more stable.

I've got a couple of theories. Comments?

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[rhudeboye]

Less = more normally doesnt apply when your talkin brakes.

As far as being steady, I get that. At least in theory - Light brake pressure allows the wheels to move more freely giving you more control.
Turning a corner w/ 70% brakes, locked or ABS, and the car becomes a bit jerky and wheel response is white knuckled.

Braking faster with less pressure on the pedal. That I just don't get. Wonder if it's a feel thing.

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[benspeeder]

Hi - what you describe doesn't add - must be a feel thing. Have somebody put a watch on you and let that be the measure.

Threshold braking is what you want on a road race course. Using the brake distance marks or pick an object like a tree or a sign and use that to set a braking point and each lap go a little deeper using the brakes as hard as you can without activating the ABS. You will find your correct braking point for that corner and be able to modify your brake point depending on traffic, conditions etc. Once you get one corner figured out start working on other corners on the track.

Eventually you will have brake points figured out for the entire track and feel really confident going in deep or letting a guy pass you under braking so you can get a better run off the corner and smoke him down the straight :-)

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[Georges]

I don't think it's a feel thing, I've been out racing (autox) long enough to tell.

My theory is that once you exceed threshold and the ABS kicks in it's equivalent to using less brake. For example, 101% of threshold is equivalent to 85% of threshold. Here 85% is just a number I picked. Once the ABS kicks in under freezing rain with bold tires, you just cannot recover the grip quickly. Assuming 85% is the right level, better to aim at 90% of threshold and not be punished for a mistake than to aim for 98% and have the ABS kick in when you're wrong. In the dry the 85% figures is a lot higher. In my autox conditions I wouldn't be surprised if it was less than 85%. The grip was so poor you had to be careful with the gas on the straights.

But I wonder if there's more to it than than. Conditions across the contact patches are not homogenous. With four wheels on the ground you average grip over all four tires. With just two wheels the average occurs over 1/2 the surface area and if you hit a bad spot one of the wheels will lose grip abruptly and after the other wheel. Yes, all right, with weight transfer is more than 2 wheels but I hope you see what I mean. I remember in the days of my air cooled VW using engine braking on black ice to get the best result of control and braking. So a bit of AWD reasoning applied to braking.

I can't wait for the next time it rains to go out and try a few things out. I'll bring a watch too.

BTW, I'm not very impressed with the 968's ABS. In the days of my 944 w/o ABS my braking skills were better due to necessity, now I get lazy at times.

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