Turned a Little Sideways Shifting into 2nd!

[RGCohen]

I was already in sport mode when the new yellow Turbo Porche pulled up next to me at the light. I turned off DSC. The launch was great, we were right together. The road turned slightly to the right as the shift to second came up. When I shifted I guess I was a little too throttle happy for the shape of the road, as the back started to come around . Of course, I lightened up on the throttle and steered into it. In just a moment the car was fully under control. But it did scare me, and certainly was an embarassment.

I am off to the M5 Experience shortly. Will they teach me to avoid such mistakes?

What advice do you experienced performance drivers have for me? Particularly, since with DSC on the launch is slower and the shift to second seems to have a serious power cutout. On the other hand, one runs the risk of my dangerous situation with DSC off. Even a great driver might hit some oil or gravel, right? Can I learn to launch and shift to 2nd with DSC on and still be very fast?

Thanks for any advice!

[greg]

You just need to feather the throttle a wee bit more. You don't WANT to spin the wheels shifting into 2nd (A little is OK if you're in a straight line, but if you had to shift in a turn on a track you'd want it REAL smooth so that doesn't happen.

[kgk]

Here is my NON-EXPERT guess:

The rear tires were beyond their traction limit, and were slipping. When you entered the turn they had nearly no lateral grip, so they started to slide around. You did the right thing by easing off the throttle---they regained grip and you made the turn with no problem.

I think that the recipe is this: Always stay away from crossing the tire's traction limit if you're on a curve, or if you actually want to win the drag race. Of course you will look much cooler laying down rubber and smoke, so it's not as if you did something wrong....

The secret to winning drag races is to have a computer manage the gas for you, of course. Sadly, DSC does not do a very good job. The SMGII (that comes with the 2002 M3) will launch for you, however!

I haven't been to any of the BMW schools, but I would be astonished if they taught you anything useful, like how to drag-race.

[brettcoon]

It will always be easier to slide your tires in a corner than in a straight line, since cornering forces are "using up" some of your available traction. Thus, you'll need to back-off a bit on the throttle to compensate. Other than just leaving DSC on, which actually isn't half bad of an idea when corners are involved, I'd bet you just need to keep practicing your accelleration through corners, until you get a good feel for what the tires can stand. If you routinely spin the tires (even just a bit) in straight-line accelleration, that doesn't bode well for your ability to maintain traction on a corner.

A little slipping is probably OK, but of course that suggests really aggressive driving for a public road. The possibility of oil, sand, and other traction-reducers on the road makes it a good idea not to get too close to your limits when you aren't guaranteed a nice smooth runout area...

-Brett

[Stallion M5]

It's always a good idea to maintain the steering wheel in straight position when you launch and shifting gears. Just a little movement to the left or right on the steering wheel could make or brake the race, especially on the high powered vehicles such as our beasts.

Last night I had a blast with it, made a really nice and long chirp on the second gear transfer. The rear end squad down good, especially with a passenger in the rear (my buddy loves the feeling back there).

[AndyMenard]

RG:

I've been there and done that my friend - and with a fellow enthusiast in the car with me! Besides being shaken a bit, I was obviously embarrased. It did however make me quite a bit more conscious and careful while taking turns. It is amazing how quick the rear end of the car gets sideways if you are not paying attention.

Glad to hear you came out ok - even though your ego got a little bruised?!

[JFB]

The winner of the race is not the car that enters the turn ahead of the other cars -- it is the car that exits the turn ahead of the other cars.

You said there was a slight right turn, but you nonetheless lost traction. Next time, you might take the turn wider to the left and delay your turn entry in order to straighten out your exit and maximize the time you are on the accelerator.

See this link.

[JEM]

I haven't seen anyone else comment on this part of your statement: you upshifted in the turn?

Shifting in a turn is something that should be saved for situations where you're nowhere near the limit of adhesion, and even then you need to be careful.

The upshift is a destabilizing operation; as you back off the gas and depress the clutch to upshift, you transfer weight forward, and off the rear wheels. If you're at the limit already and carrying any real speed this is probably going to spin you. Even if you're not, as you re-engage the clutch, you're dumping torque back into the unloaded rear wheels and the results can be unpredictable.

The best approach here would probably have been to upshift before the turn, and on the street it's yet another reason to leave the DSC on.

[Rahim]

Great link Jim, thanks.

[fais2000]

COOL .

sorta like the guy who spins out of control, right into a tight parallel parking spot

fas

[JFB]

JEM

Good observation. I'm not an expert in this, so could some of you race track pros tell me if my understanding is correct?

In the turn, wouldn't the outside rear tire be weighted relative to the inside rear tire? Thus, the outside tire would not be as close to the loss of traction, and an application of power to the rear wheels (without DSC) would result in a loss of traction on the inside tire earlier than the outside tire.

Thus, the problem likely developed because (1) the rear tires were unweighted (due to depressing the clutch and/or braking), (2) the rear tires were approaching their lateral traction limit in the turn, (3) the inside rear tire was unweighted relative to the outside tire, (4) power was applied to the unevenly weighted rear tires, (5) DSC was off, (6) the relatively unweighted inside tire lost traction sooner than the outside tire, (7) the outside power wheel pushed the left side of the car toward the inside of the turn, fishtailing the rear end.

Possible solutions: (1) DSC on, (2) wider turn entry, (3) brake and heel-toe downshift before entering the turn, (4) late apex turn, (5) accelerate smoothly as the car straightens out and lateral forces decline.

(BTW: I'm not advocating street racing. Just enjoying a theoretical discussion. )

Jim