It sounds like your near spin was mostly throttle induced which is significantly different than much of the material covered. Once you're loose they are much the same, but if you are asking about the
cause I would guess it is simply a case of having the car approaching the limits of adhesion while still accelerating. You have only so much traction available. You can spend it to accelerate, brake, or turn. Of course those limits are much lower on wet pavement, and as already noted, the amount of tread becomes critical. When you accelerate, your rear tires have less traction for turning than your fronts. (Although the get some back due to rearward weight transfer.) With the power of the NSX it takes very little throttle to spin the tires on wet pavement, much less if most of your traction is already spent on cornering, and before you realize what happened it can be stepping out on you.
Although the other posts here were very good, I’m not entirely comfortable with some of the points made so far. For example, it seems that the importance and impact of polar moment was not thoroughly explained.
Keep in mind that the skater analogy applies after traction is lost and the spin started, and even then I think it’s cheating a bit. Pulling the arms in while already spinning does not so much “allow” them to spin faster as force them to. I’m also not sure you covey the right meaning or mental image when you say that a car with more mass in the center will spin faster. I’m having trouble putting it into words myself (and I’m no engineer or physicist) but perhaps more discussion of polar moment will help.
Of course polar moment can be very significant in an autocross slalom or even tight esses where you have relatively abrupt transitions in direction, but otherwise it is probably less significant than overall balance
if you’re in control. Where a high polar moment really comes into play is how forgiving the car is in terms of catching it after things go wrong. With a car like the 944 or C5, the F/R balance is very good as noted above, but when it does get loose, catching it can be tough. Rather than a skater, imagine a simple barbell. Slide the weights near the center then grasp the bar in the middle with one hand and spin it first one way and then the other. Now slide the weights out to the ends. It will be noticeably harder to start it spinning, but really tough to stop it and get it going the other way. This is where the laws about a body in motion can bite you fast and hard. That too is over simplified because a car has tires at the corners rather than a literal fulcrum at the center, but it gives a reasonable picture of why once you start to spin in a high polar car, a slight over-correction can quickly escalate into a several oscillations and a very hairy spin. That’s the worst danger of polar inertia.
I think overall F/R balance is more important than you give it credit for in terms of turn-in and controlled cornering. Although being nose-heavy certainly is a factor, that an M3 understeers coming into turn is as much due to suspension tuning as weight distribution. Even the NSX and rear engine Porsches are designed to understeer in normal conditions. The problem with a tail heavy car is that when you lift or brake in a turn, a significant amount of weight transfers to the front. Since available traction is closely linked to the weight on a given tire, that means you just shifted some of your traction from the back to the front. If you were approaching the limits of adhesion already, the back is going to break loose as the front digs in and serves as your new pivot point. The more tail heavy the car, the more weight there is to shift and the faster it snaps. That sounds a bit like the skater analogy, but I don’t think it’s really the same. (Obviously, the suspension plays a role in how much weight transfers to the front, as does brake balance if you’ve made the mistake of braking with the wheels turned.) It’s important to note that on street cars of all configurations this often
starts as understeer, prompting the lift or brake. (remember the recent video of the S2000?) A tail heavy car like the 911 can understeer from too little weight up front (and therefore traction) unless the driver knows how to set the suspension with a little lift or tap of the brake just before turning in. That’s one reason many people complain the old ones are rather vague at turn-in, the nose is so light.
I’d also recommend caution on the statement that with a front engine car you need to lift or brake if you’ve come into a corner too hot. Depending on how and where you got into trouble, the same weight transfer can still cause the back end to come around. If you’re in a bad understeer situation and really have no choice but to slow down or dive headlong off a cliff, it is sometimes possible to straighten the wheels briefly so you can use a little brake, then turn in again. The sooner you recognize that you aren’t going to make it, the better your chances of pulling that off.
While the standard answers about how to get out of trouble in a front engine Vs. mid/rear engine car are certainly not “wrong”, there are so many variables in terms of how/why you got loose, road conditions, corner shape and camber, suspension setup, etc. that the actual best response in a given situation can easily be the reverse.
OK, rant away!
[This message has been edited by sjs (edited 28 March 2002).]
