winders

I don't think that is reality any more. Today, roll is controlled mostly by springs with anti-roll bars uses mostly to adjust chassis balance. Softly sprung cars tend to squat and dive too much.

zzyzx

So, a friend stated that if you outbrake your competitor by 2 feet once every lap for a 10-lap race, then by the end of the race you will be 20 feet ahead. I told him that I thought this was incorrect but I had trouble explaining how. What's the best way to explain this? Or am I wrong?

Related to this, can anyone tell me how much time you would lose each lap if you were to brake 10 feet early going from a 100 mph straight into a 50 mph corner?

ProCoach

As said before, it's not the application point, it's the duration and release that makes more of a difference. I don't have data indicating any driver who is that repeatable over the course of a ten lap race, especially if passing and repassing is involved... Although I am sure there are math geeks that could give you an answer to this problem.

Veloce Raptor

Agreed. In addition, braking 10' later does not save time per se, and does not mean that driver will be ahead at the end of that lap. Braking super late also can mean a lot more forward weight transfer...and thus it may take longer for that car to settle enough to apply power. So it might be an advantage at entry but a hindrance at exit.

AdamBrouillard

Good question. Doing exercises like this is a good way to test your knowledge of line theory. The later braking car wouldn't be 20 feet ahead assuming the drivers are doing everything else correctly. There's not anyway to say the exact difference though. Let's say car A drives the corner perfectly at the limit and car B brakes 2 feet earlier, but also drives at the limit. Car B would run off the inside of the track in that scenario. Basically, 2 different braking points necessarily change what happens afterwards so you can't directly compare how they affect times.

Instead, this 2 foot earlier braking point would require car B to drop below the limit for at least a moment to stay on a good corner entry line to set up for a perfect apex and exit. Car B would ideally be constantly correcting their corner entry to achieve the best exit they can. Done well, the time difference to car A would be in the neighborhood of 1000th or 100th of a second. It's best to stick with time differences because distance differences change with speed.

The car B scenario is much more realistic as well to what a driver typically does. Car A would only make the apex if their entry was flawless. If it wasn't, they would miss the apex and end up losing a lot more time than car B did. Certain types of corners punish missing the apex much more than others.

Also understand that this is assuming the 2 cars have some distance between them. Everything changes when cars are nose to tail because of the distance compression with reduced speed.

Matt Romanowski

In non aero cars it's my experience with a pretty broad range of cars. As soon as the car makes lots of downforce, then you have to keep the platform stable, but with maybe the exception of Scott's 914, that is not any car here.

winders

While what I said is certainly true with cars with lots of aero, it is also seems to be true with cars running modern racing radial tires. Modern racing radials abhor having the contact patch change. A car with soft suspension changes wheel geometry (toe and camber, specifically) a lot more than a car with stiff suspension.

Plus, the stiffer the anti-roll bars get, the less independent the suspension gets.

If you control roll to the same degree with ant-roll bars versus springs, you tend to hurt your ability to accelerate coming off of a corner. Again the suspension is less independent. I have experienced this with my race car. Going up in spring rate to control roll, and squat, was better than just adding more ani-roll bar. The rear end was better coming off corners and was more stable in the high speed stuff.

Kevin Fennell

So after talking to my main vendor (BOE) it has come to my attention that with my large wing I can't really run any softer rear springs, so the roll bar seems like it is unlikely to help much if it is just going to make me stiffer...

This brings me to my next question. My car is all the way to the class limit in weight, in fact I have a few lbs in the car to make weight. My question is how much is it worth it to remove weight from the high points, and also from the ends of the car. Let's treat this as two separate questions I guess.

1. How important is moving weight from the roof of a very low car to the floorpan? I could move about 30 lbs between the roof and the hatch a total of about 30" lower.
2. How important is it to remove weight from the ENDS of the car to reduce polar moment? I could bring about 30 lbs from the ends of the car into the center (light buckets and associated hardware + remove exhaust + lighter splitter).

This is on a TT3 Exige that weighs about 2230 lbs for next year.

Veloce Raptor

I would do both if at all possible

ProCoach

Kevin Fennell

everything is possible but money is a thing!

is it more important then ~6 hours of extra track time to practice for example?

is reducing polar moment that important in a car that wants to spin already? Or does it help since you would be catching less momentum. These things are hard to think about

Veloce Raptor

If it were my car, I'd lower the weight first. Then test and adjust set up if necessary. Then work on moving weight inboard

zzyzx

Interesting video on driving sims from the perspective of a pro driver.

Vettett15

Read through the entire post, do much great info, now if I can only learn how to apply it....


First I think I need to get a proper seat and harness in the car, I'm all over the place on my last track day (sebring couple weeks back).

bldn10

"I need to get a proper seat and harness in the car, I'm all over the place"

Back in the day when I autocrossed I bought a belt that wraps around the seat and your torso, pretty effectively holding you in. I still use it on the track. No substitute for a 5-pt. harness but you won't be all over the place. And $14 is a lot cheaper than seats, harness bar, and harness. :-)

http://www.soloperformance.com/SPS-U...ss_p_1279.html