Folks,

A brief background:

Autoxing back in mid 90s, switched to open track days and time trials. Instructor for BMWCCA/PCA since 01, CCA Club Racer since 06. Presently in Dubai for an international assignment; head of motorsports for BMW Club UAE and chief instructor (if you will).

On Topic:

I had been trail braking to pretty much help rotate the car (depending on corner/speed) car in question was an E36 M3.

Since then, I decided to experiment with AWD cars and ended up getting an STi. Its a front heavy AWD car weighing in 3160 without me in it. The brake bias is towards the front (326mm front disc vs 300mm rear). Running DTC 70s all the way around.

After re-reading Speed Secrets 1, FWD (technically thats what my car is with an added rear diff so to speak) would need to trail brake much more for weight transfer up front, hence more grip during turn in and rotation. In my case, I had been overheating the front pads (450 degrees on the caliper as measured by Alcon heat stickers). And I was told NOT to trail brake by a reliable source (former Time Attack champ in CA).

His argument: there is plenty of grip up front, when you apply more brake, you end up losing grip (too much weight). Plus you are putting more heat on the front outside caliper/rotor. When braking in a straight line, you minimize the negative effect of front brake bias, ensuring all four corners are doing the job on slowing down the car.

Its counter intuitive and wanted to get some feedback from you guys.

Thank you in advance.

Regards,

Lutfy

 

I don't have a lot experience in FWD or AWD but hopefully my advice is still stands.

From my experience instructing, people that come from an autocross background tend to over drive a fair bit. Driving an autocross is a lot more violent than a road course. On a road course you need to be super smooth and have seamless transitions. In autocross you just don't have the time.

So my first bit of advice is to change your mind set. You are probably braking hard, chucking the car sideways, then powering out. This is not the fastest way around a road course. And it's quite hard on the equipment. On a road course, you should squeeze the brake, then ease off it gentley as you enter the corner. This will keep the front suspension loaded as you transition into cornering.

In an AWD (your is front biased), you can use the power to pull you through the corner. So I would not trail brake as much as I would in an M3. However, I would still trail brake a bit to keep the front suspension loaded. If you don't trail brake a bit, the front suspension will bounce back from braking and unweight the front of the car. Good luck turning in with the front of the car unweighted. 

I recommend you practice not braking, or not braking much. Start slow and see how much speed you can carry without braking at all. Then add braking back in a bit at a time. This will force your brain to think through the corner and plan your weight transfer carefully.

Visualize driving in the rain, or even better on ice. Imagine if you apply the brakes too much your will brake traction and slide. This will force you to be super smooth. You will be amazed what you can do after praticing this exercise a few times.

I just got a Porsche Cayenne as a tow vehicle. I couldn't resist trying it out at VIR this weekend. It's a 5000lb 4WD truck (rear biased). I found myself trail braking maybe 1/3 into the corner then using the front end power to pull me through from there. Considering what it is, it's quite a remarkable vehicle.

In a fwd, you want to be a little more rotated before you exit because putting the power down costs you grip. If you pull yourself out of the corner with brute force, spinning the front tires, you will burn up the tires faster than you ever thought possible. For instance, in a mini it is quite possible to cord 4 brand new pilot sport 2s in 2 1/2 days. I know this for sure (my first real track event in a fwd).

For speed, fwd cars tend to have aggressive alignments for good rotation. As an example, I had toe-out in the rear of my mini for a while. This is widely felt to be suicide. The car rotated amazingly, and was very fast with no understeer issues at all. Oversteer I could cope with using power. Unfortunately it was just too tiring to drive, and I had a hard time shifting because of the strength required to keep the car going straight at all. So, this is overshooting, but you get the idea.

If your car is stable enough you can also TB to rotate early. I'm disagreeing with peter here, but I might have more fwd experience and the front tire wear issue is very serious if you use fwd to claw your way out of corners.

Hi, Lutfy.

I ran a moderately-modified Evo VIII for 3 or 4 years. It wasn't a dedicated track car, but it did see an awful lot of track time. I found that it really needed a VERY different driving technique than a well-balanced RWD car. The contrast between my E30 and the Evo couldn't have been more stark.

In the E30, it's all about being as smooth and seamless as possible. When you try that in the Evo, you get nothing but understeer all the way around the corner. Boring, slow, and very hard on the front tires. And the STi is even worse than the Evo in this regard. On top of the inherent understeer in any FWD/AWD chassis, we've also got considerable turbo lag to deal with, which adds another level of "fuzziness" between turn-in and apex.

What seems to work best is to slow a bit more than usual, rotate a bit more dramatically at corner entry, then ease onto the power a bit earlier while aiming just to the inside of your apex. If you time it all right, the car will be on-boost just as you nail your apex (right on target) and you'll 4-wheel-drift all the way to track out.

For most corners, this will involve varying degrees of trail-braking. Generally, it'll be a tiny, tiny bit of trailbraking just to keep the front-end tucked in. But in the slower corners, it often pays to trail-brake quite aggressively to the point where you start to feel the outside rear tire really load up. Then, once you're back on boost, the rear will slowly let go and help you round the corner. It's quicker and far more elegant than understeering like a pig all the way around.

Like John, I favored a suspension setup that would be considered quite bizarre by RWD standards: I had a massive rear sway-bar and I was running a small amount (1/16") of  toe out in the rear, in addition to a moderate amount (1/8") of toe out in the front. That really helped to keep the rear-end mobile. Made it easy to bring the rear around in slower corners and allowed me to use less steering input in faster corners. Any time I felt the car slipping into understeer, a quick brush on the brakes with my left foot could get the rear moving. Gives you a lot more control over the car's cornering attitude.

EDITED: Photographic proof that you can nail your apexes in an AWD car.

Part of the problem you were having has to do with that LSD up front. Most AWD cars (including almost all Scoobies and Evos) have an open diff up front. That, coupled with the fact that most of the power is shifted to the rear wheels under hard acceleration anyway, means torque steer isn't really an issue with these cars until you get up into the 500hp range.

When my Evo VIII was making 400hp, I had no noticable torque steer. Even at that power level, your Mini Cooper GP would be putting more power through the front wheels under acceleration than I would. Plus you've got an LSD.

Also, I guess AWD cars are just more stable under acceleration in general. Even with all my toe out and big sway bars, I never had any problem putting the power down nor had to fight to keep the car tracking straight. The only time the car felt twitchy was under hard braking on uneven surfaces. That's when you REALLY feel the rear toe out!

When I had toe out I almost spun braking in a straight line a couple of times, for instance into the bus stop at wgi where it is pretty bumpy. With toe out, trail braking was very interesting. Separating rotation and power seemed to be the fwd key.

Funny you should mention that corner. The first time I drove WGI with my new suspension settings, I had a BIG slide at the entry to the bus stop when the rear end snapped out. Later that weekend, I had a scary spin entering the boot. I'm honestly surprised I didn't roll.

It took me some time to figure out how to get the most out of that suspension setup. After a while, I was able to use the tail-happiness to my advantage. But it was a real mess at first