Why is the Rain Line different in Champ Cars than Skippy Cars?

[Andrew]

Another question.

While watching the Champ cars and the Atlantics at RA this past summer, I noticed that while driving in the rain, everyone took a different line through turn five than we were taught.
We were shown that riding the rim would provide the area of greatest grip. Basically side step the braking zone, cross the dry line, pick up the rim and follow it around until you exit on the dry line again and carefully accelerate to keep from inducing a power on oversteer spin.
The pros side stepped the braking zone, crossed the dry line, picked up the rim but then turned in early and crossed the dry line again and exited the corner 'side stepping' the dry line on the exit.
It appeared to me that this allowed them to get on more throttle sooner.
Is this a new development in driving technique or just germaine to the much more powerful Champ cars?
Do you think this is better than running along the rim?

[J Goring]

The higher the horsepower, the later the apex. Im no champ car driver, but I find tracking out on the dry line usually is fine in a Skip Barber car. Maybe the higher horsespower and downforce has a different effect, I am not too sure.

[Pork Chop Willie]

I had the same question watching one of the Formula One races this year in the rain (I think it was Hungary). Everyone other than Alonso was pretty much staying on the dry line. I will say that Alonso was going a couple of seconds faster than everyone else on the "rain line". So why was everyone else driving the dry line in the wet?

[AZRCD]

I cannot answer why no one moved to the rain line, but I can say that the downforce creates grip so there is an advantage to driving on the biggest radius. However, when I did the '04 Rolex 24 I was getting grip on the rain line in the hairpins and hanging or catching the DP's in the corner. So grip is still grip, but I think the best summation is sometimes there is enough grip because of the downforce that driving the ideal radius is best and other times the dry line is really slick and you need to go to the race line.

[dalyduo]

With no memory of which tracks had rain this year... Another explanation might be the surface age of the track. If the track is brand new or the track is old but newly surfaced there may be little difference in the surface grip from racing line to wet line because the track, for all practical purposes is completely uniform.

Some of the great old tracks we run on still have their great old track surfaces that are now highly polished and that's where you'd normally see big wet and dry line differences.

Just a thought.

[rgreist]

Good point about track surface variability, Pat.

My understanding is that softer tires make a big difference in the rain and might allow a driver to take a more traditional dry line through a corner. Or at least softer tires begin to make it less worthwhile to travel the greater distance required to perform a rim-shot.

[Rossi]

I think the main reason is the fact that there is SO much downforce on a Champ Car that they don't need to take such an extreme race line as we skippy guys do because I believe that the water is almost thrust out from under the can creating an almost "dry" surface. I know that Formula One cars barely need to take a rain line at all, so I think its similar with the Champ Cars.

[PT Cruiser]

Originally Posted by rgreist

My understanding is that softer tires make a big difference in the rain and might allow a driver to take a more traditional dry line through a corner. Or at least softer tires begin to make it less worthwhile to travel the greater distance required to perform a rim-shot.

I'm guessing that tires have a lot to do with it. I have had one experience with rain tires, at a Malibu Grand Prix in New Jersey, of all places, but it was really eye opening.

I was about 3 laps into the 40 laps I had purchased when it started to rain. If you've ever been lucky enough to drive a Malibu car on its normal slick tires in the wet, you'll know it is an absolute blast. The cars slide like a banshee, 30 degree power slides are the norm, but it is all easy to keep under control if you've got halfway decent car control skills. Anyway, just as things were getting really good, they pulled me over, and insisted that I get into a car with rain tires. And it was no fun whatsoever!! The car wouldn't slide at all, even on a polished track in full wet conditions. The darn tires had more grip in the wet than the standard Malibu slicks in the dry. It was an absolutely astonishing experience. I suppose there is a chance that the car with rain tires also had a detuned engine, but I don't remember feeling that the car was down on power in any way. After about 3 laps, I begged them to put me back in the car with slick tires, as driving around on rails was no fun at all. But of course, the kids minding the track weren't about to risk getting fired to break the rules.

Ever since, I've had a very healthy respect for rain rubber!!