Dirt track versus paved track

[nonetoosmart]

I am perplexed by the differences between dirt and paved track setups. For instance, a paved track stock car stays as flat as possible, whereas a dirt stock car (dirt late model, actually) transfers quite a bit of weight to achieve maximum lateral acceleration. On corner exit the cars also have much different attitiudes, with the dirt car "hiking" the left rear corner, driving that tire into the surface to produce longitudinal traction. A dirt team will increase right front spring rate to loosen the car on entry, and a paved track team does the opposite. Why?

Im wondering why similar cars have such different setups - is it due to the compliances associated with an unpaved (usually soft) surface? Perhaps due to different tire design?

[SidewaysFeltham]

On a dirt track, since there is no effective grip between the tyres and the surface, in order to go quickly, the car has to be set up to slide sideways in a power-steered drift.

Mordern suspension and steering geometry aims to create the highest possible level of G force and thus grip without the car sliding, since at the point of slide, the car has lost adhesion, the tyre treads "Shuffle" and all the careful work expended on geometry is wasted.

"Black Jack" or "Sideways" Brabham cut his teeth on Australi's dirt racing circuit and always wanted his car set up with the "Arse hanging out", as Ron Tauranac was reputed to have said!

The American driver Maston Gregory, also apparently came from the US dirt track circuit and on one occasion he was driving a Jag Mk VII saloon for the works and as Maston appeared at one particularly tight corner, sideways, tryes squealing and smoking, after a few circuits, the Jag Racing Manager, Lofty England, having watched Maston circulating in total silence and completely bemused, simply went back to Coventry!

I did some dirt racing in the late 60s and we always used to increase tyre pressures to promote slide, as part of the setup.

Ideally also, the last thing you want are wheels waving in the breeze! You want the car to sit flat, with no roll induced steer and as little lateral weight transfer as possible.

No suspension might help!

[trikesrule]

If I may add. Adding spring rate dosen't loosen the car it actually creates a 'push'. Assuming the car was dialed in earlier in the night. Adding rate to the right rear loosens the car. I've now established my credentials by answering the trick question. Just because it's dirt dosen't mean we don't keep bitumen setups in the back of ones mind. When the clay goes 'black' I take weight out of the right rear and put some of that into the left rear thru use of the winders. Because I come from a bitumen back ground when the track (usually in the Feature) goes 'black' our car(s) are a bullet. (Never lost a black track Feature). At the start of the night a sedan may lift three wheels off the deck but as the 'cush' builds and the night progress's you will see the cars suspension / stagger being altered so they can stay flatter and ride the cush as in 'lean' the right rear against it. Next thing - probably the most important is tyres. When the cush builds the grooving irons come out and an extra circumference groove (or 2) is added to the shoulder with inter linking cross cuts. Each cross cut provides forward bite whereas when the track turns black one has to think bitumen and look for more bite from the left rear so as the right rear dosen't go 'off' as in overheat. When racing on the black stuff as in the V8 Supercars I've noticed that some of the 'Engineers'(?) set the cars with Speedway (clay) in mind then change to a black set up as the bitumen warms. Confused? Just think backwards ha!............trikes