4 Wheel Drift

[Zeke]

A theoretical question: If your front wheels are straight and you are pointed straight, is the car at it's least rolling resistance and accelerating at it's maximun even if you're are still finishing a turn in a drift? I seem to remember Milt Minter driving the RSR like this.

[Vintage911Racer]

Milt does drive that way. Driving against him in 67 911S I watched closely as he 4 wheel drifted through every corner.

My theory would be ( not that it matters) if your front tires are pointed straight, and the car is straight, but you are still finishing a turn in a 4 wheel drift--------- You technically would be scrubbing speed because you still have lateral movement fighting forward progress. I have raced against many drivers with many different styles. I guess it all depends on who you talk to.

[HarryD]

Vintage911,

I am not a physicist, but...I am not sure you are really losing power if you are drifting as long as your wheels are continuing to turn. I figure that you are converting linear motion to angular motion but (according to physics) total momentum is conservered and when you are straight, most of that energy is returned to you. That is why you can turn fast when you drift.

This seems to fit what I read in Henry Watts book about a slight slip angle actually allows you go faster through the turn.

Love your car by the way.

[Zeke]

The way I see it, you can go throught the turn one of two ways: either a true arc in which your are turning until you finish at the exit tangent, with more or less the same throttle position; or an eliptical arc, where you can stand on the gas and unwind the wheel as you gain speed. In the second method, you can pitch the car sideways so that it lines up with the exit tangent and stand on the gas before the apex. The question remains, which has the highest exit speed at a pre-determined point? I think Minter thought the latter because of the balance of the 911.

Racing enduro karts, we didn't have enough HP to make up for mistakes, so we had to maintain the highest possible speed in all segments of the corner. (This is on full size road race circuits where the slowest corners were around 50mph and the highest ranged up to 90 and 100 mph turns.) So there wasn't much pitching it sideways type of driving because the things would bog down. However, there was a lot of drifting because karts have a solid rear axle and only roll free when all wheels were in line traveling in the same direction and covering the same exact distance. Any arc bound up the kart. Very fine line in driving style.

[David Bahr]

I have a slightly different take:

Sliding scrubs speed no matter what. But a four wheel drift means you are carrying a higher speed. I think Milt's thinking is, while his acceleration at that instant may be marginally less, he is maximizing his speed through the corner which more than makes up what he loses in scrub. His exit speed is faster because he carries more momentum through the corner.

Racing is all about drifting, to me!

[ttweed]

Originally posted by Vintage911Racer
Milt does drive that way. Driving against him in 67 911S I watched closely as he 4 wheel drifted through every corner.

Hey Vintage911Racer-

Your pic gives you away- hope you weren't trying to maintain your anonimity. You're Mark Scott, no? I met you and your Dad at Buttonwillow during the University of VARA in 1999. You were just shaking the car down, then, I think. It was very nice looking. I was driving my white street 1967 911S in the school that weekend, but haven't really been able to afford to go vintage racing myself.

I saw by the article in the Aug. 2002 Excellence mag that you went on to great success in VARA and actually kicked your Dad's butt one year. Good on ya, mate! VARA is a great group- Phil van Buskirk turned me onto it, and if I was going to go wheel-to-wheel racing, that would be my first choice. For now I'm just sticking to autox and time trialing as much as my budget will allow.

To get back on topic, though, as I remember from Fred Puhn's book, the ideal slip angle of most tires is between 5-10 degrees or so, depending on type and construction. This is where the compound will develop the most grip, and the curve drops off dramatically beyond that. If the slip angle in your "drift" is greater than that, then I would say you are sliding and losing grip, i.e., not going as fast as you might thru the corner. You're probably also being harder on the tires than you should, heating them up and wearing them out faster.

To apply that to the exit, which is what Zeke's original question asked about, it seems to me that if your wheels are pointed straight and your car is still proceeding sideways at greater than a 10-degree angle from straight ahead, then you probably aren't accelerating out of the corner at the maximum possible rate, since your tires probably aren't developing their maximum grip, according to their ideal slip angle.

Of course different corners may require different techniques with different cars to optimize the lap time (say, getting the car to rotate thru a slower corner where it might otherwise push), and when you add traffic into the equation and are trying to get around somebody, all bets are off- I'm just talking about the ideal "Time Trial" or qualifying line.

YMMV,