THSCC Forums

I know that the roostertails are very impressive (very photogenic, Kevin ) but it occurs to me that the more dirt you throw into the air the less energy you have to push the car forward.

Class, the topic is open for discussion.

Simon

Au Contraire, As we all know, dirt on a road surface is a "lubricant." Thus, the more of this "lubricant" that the drive wheels eject from beneath the tires, the more that tire comes into contact with the earth core and provides thrust.
Actually, a lot of the "rooster tails" were from the front tires of many cars as they used the plowing technique in the soft dirt as a braking device. Imagine a farmers disk attachment at triple its intended speed.
The rooster tail from my car was probably caused from the bottom dragging on everything. Lesson 1: don't bring a seriously lowered track car to a rallycross. I actually got stuck once when I got high centered. The car kept going, but the seconds were ticking by quickly.
Charlie Guthrie

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1998 BMW Z3
1987 BMW 325is
2000 BMW
1996 F250 Turbo Diesel

I saw a show I think on TLC about tractor pulls, there always going with wheels spinning and roostertails flying. In the end it said that since grip was so hard to get in the dirt without slipping, just do the same thing but allot more. For every action there is a equal and opposite reaction. Meaning the more dirt you throw up the more forward motion your going to have. Was something along those lines.

As Charlie pointed out, Vincent's big dirt spray photo shows what I would call a "splat" more than a roostertail. He slid sideways off line into the deep soft stuff and sent it flying. Definitely absorbing energy.

I think the real answer for the best way to accelerate on dirt may depend on the actual surface. If it's quite firm, I'd expect you'd be best to keep wheelspin down. If it's loose but there's a firm base not too far beneath the surface, then if you can dig down to that hard base that would be the ticket. But if the surface is soft and deep (like sand), any digging you do with the wheels would just create a hole for you to climb out of, so if you can stay on top that would yield the best acceleration.

The power available to most cars is so much greater than the traction available on most dirt surfaces that we're probably better off talking about how to find/make traction than worrying about where we may be dissipating energy...

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Carl Fisher

Be Cool to the Pizza Dude:
http://www.npr.org/templates/story/stor ... Id=4651531

Yeah, but I ran out of GRASS before I ran out of GAS. This event gave new meaning to the term "plowing".
Charlie (too low & too heavy) Guthrie

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1998 BMW Z3
1987 BMW 325is
2000 BMW
1996 F250 Turbo Diesel

Thanks for pointing that out Carl. That pic looked really cool until you told everyone that I screwed up! You are exactly right though. I slid off line, out of the ruts, right into a big pile of the soft stuff. It felt like dropping a boat anchor I slowed so fast! I learned my lesson though.

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Vincent Keene
'06 Ford Mustang GT (track rat)
'15 Dodge Charger R/T (yeah, it's got a HEMI!)
'07 Ford Fusion SE (205,000 miles and counting)
'98 Chevy Z-24 (retired)
'93 Acura Integra (Team SWB 24HOL Car)