Snap, why am I going backwards? A thread about loosing grip on the rear wheels

Magnus · #1 02-01-2006, 09:10 AM

So,

Have you ever spun your car?

Here is what happened to me at Mantorp Park.

Heading to the Chikane is a slight left hander. So I step on the brakes and avoid trail braking due to the wet conditions. Downshift 3-2, rev match and suddenly my ass breaks loose...

Now this could have been solved with the gas, but I'd probably end up in the barrier in the chikane cause of over speeding and I had no intentions to test my grip to the limit in the wet.

So the catch was simple clutch, light light light opposite steer to avoid the fish tail, soft brake, brake slam. I ended up missing the line by 4-5 feet, but it was way better than smacking the car.

Lesson learned? Rev-match was the cause, it was too aggressive for the rear to keep the grip. Weight transfer caused the rear to loosen up to much and the grip got decreased. Taking a less aggressive line was my saviour in these conditions.

So, bring it on, who else got a rear end on the loose that made them think twice afterwards?

billy · #2 02-01-2006, 10:56 AM

Thats interesting for me because the couple of times I've had a tank slapper, it fish tailed on me. So, you're saying be more gentle trying to catch it to avoid it coming back around on you?

Magnus · #3 02-01-2006, 02:43 PM

In general, depends on how quick you're going and the difference between direction of your vehicles body mass and where your butt wants to go. A rear that steps out when you're braking almost straight is a small difference, to much oversteer and you'll Sushi all over the place..

But you have a tiptronic don't you? Have no idea how they react, sorry..

uwaeve · #4 02-01-2006, 03:26 PM

I grabbed 2nd instead of 4th going into the bus stop at Watkins Glen last year. The back snapped out on me and I caught it. I have in-car footage that I'll post as soon as I find a place.

Thankfully the gearbox has pretty close ratios, so it might have been ok even going straight without the weight transferred forward. The whole reason I got second was that I was late with the shift AND was having trouble finding the gear (hit the gate edge a few times I think). So by the time I was letting the clutch out, I had just about turned in. So the rear was still a little light under braking, and as soon as the clutch grabbed, I turned, and the rear lurched.

I guess those car control schools helped. After all, you fight like you train. Which is why I feel very strongly that it should be mandatory to drive cars out of control in a safe environment before getting a license. I spent a lot of time in snowy parking lots when I was in high school, and I will force my kids to do the same. You can have your soapbox back now.

billy,

Not that you asked me, but I'd be glad to offer my opinion! I think that timing is the most important aspect for spin correction. Clearly, you need the right magnitude of steering input to recover from a spin. However, there is a delay in the process. From when an event happens (the spin starts), the butt and eyes have to send information to the brain, which needs to process it, then determine the appropriate action, then send info to the hands and feet, which then implement the actions. The inputs then go through all the tolerances in the steering and suspension as well as the elastic properties of the components and tire before getting to the contact patch, where they can actually influence anything. The point is, if this whole delay starts to approach anything close to the time it takes to start the spin in the first place, you have to be dialing in the right amount of steering you're going to need in the future. This is also another reason it's sometimes easy to go back and forth in a slide. By the time you realize you've put too much correction in, you've already got too much polar inertia going the opposite way (you're about to spin in the other direction). By the time you realize this, you are spinning the other way. And so it can go, sometimes growing in magnitude.

Long winded, but I guess my point is: get out of control a lot on purpose. The fastest and smoothest you will be able to correct will be if you've done it a lot before.

uwaeve

Conan · #5 02-01-2006, 03:51 PM

Quote:

Originally Posted by uwaeve

I guess those car control schools helped. After all, you fight like you train. Which is why I feel very strongly that it should be mandatory to drive cars out of control in a safe environment before getting a license. I spent a lot of time in snowy parking lots when I was in high school, and I will force my kids to do the same.

+1. I attribute all of what little ability I have regarding car control to tossing around cars as a teenager on the family farm and in parking lots in Michigan. I was lucky enough to live out in BFE and my parents taught me to drive at age 12 (I'm now 37) on a '78 Celica GT 5-speed

. I lost control then many, many times. And since it was a safe environment, the experience taught me what it feels like and how to deal with it.

uwaeve · #6 02-01-2006, 03:56 PM

Good meeting you, Conan. I hear that you, too, have the good fortune of driving around a 3,400 pound bundle of joy?

uwaeve

Conan · #7 02-01-2006, 04:01 PM

Quote:

Originally Posted by uwaeve

Good meeting you, Conan. I hear that you, too, have the good fortune of driving around a 3,400 pound bundle of joy?

uwaeve

Nice to meet ya.

Yeah, I'm a Z owner. It actually dresses out at closer to 3200 lbs, but it still needs to drop a few

She definitely will kick out the tail if you so desire.

jstecher · #8 02-02-2006, 12:05 AM

Its funny how all the midwester guys learned to drive early. I just did doughnuts in my dads field in his old S10 after learning to drive the tractors to help him out. If you can drive a tractor you can drive anything I feel.

Rassel I have actually done what you are talking about a couple of times but never had it bite me in a turn. Going into turn three at BIR last year I did it actually chasing Conan around the track. Basically hit the gate on the shift and didnt get it in on first shot...since everything is timing with me it seems it threw me off for a sec til I got it in BUT then I let the clutch out without rematching revs. Boom locked up the back end, car got loose but never rotated and eventually the wheels caught back up.

Rev matching on the down shift of a really high speed straight seems to do a lot of people in. I am still working on getting it right. Its funny because I rad once that this was a common problem back when F1 still used real transmissions. A good deal of crashes were caused by drivers locking the rear wheels on a missed shift in the heat of a tight battle.