[FitFlowjoe]

Originally Posted by raton

I was thinking...what mod (other than changing driving tech) would've caused both rears to stay on the ground?


However, I see other experienced drivers that have their car go on 3 wheels too. So maybe 3 wheeling is no big deal?

Well in reality it is not that big of a deal, b/c most FWD car that autocross or race tend to want to do this. The main reason is Weight Transfer to the front tire that the car is turning against (eg. right turn, left front tire), more logic behind this is our cars have about 62% of the weight on the front tires just standing still. Add to that Cornering forces this can go up to say 75% weight on the front, making the car practically a see-saw.

I guess a way to see this is imagine your car in a full force right turn, the front gets loaded up on weight (due to weight transfer), the front left (FL) tire takes most of the force, this force then travels up the shock and spring, compressing the front left spring displacing the car in this direction, the rest of the weight move to the left rear (LR) tire and front right (FR) tire; the rest gets transfer to the right rear (RR) side. So basically the weight (eg. force) cause the car to see-saw, making the pivot point to be between the LR and RF with most of the weight (eg. force) on the FL, hence up goes the RR… and BAM!! instant Three-Wheelin’ AutoCross Action!!

But back to the mods… The biggest suspect for this 3-wheelin’ action is the Rear Sway bar.. which basically works by transferring the loaded rear tire force (eg. Weight) to the other side… in order to plant the rear end. But due to imbalances in the forces per tire side that downward force is not enough to compensate for the upward force of weight transfer to the front and hence that RR tire goes up even higher in the air.

I guess the only real cure for this is… Is to transfer weight to the rear of the car… aka putting the gas tank back in the rear (instead of under the front seats)!! Or adding died weight to the rear (battery, subwoofer, actual iron weights, etc.)…. BUT!! This also has a negative effect since it adds weight to the car making it slower in general, even if you are using all your tires contact patches.

Mods to cure this… hmmmm tough one but I would go with:
1) Higher Spring Rates in the front, so that corner force doesn’t displace (compress front spring) the front end so much
2) Lowering the rear might work.. but that might have a negative effects on the weight transfer due to lack of weight (aka. grip) in the front
3) Installing roll center adjusters, might work… since it changes the position of the center of gravity
4) Making rear tire width smaller so it slides more instead of grips… but that could cause snap oversteer

Not sure how a LSD would fit in this. C-pillar bar doesn’t really do much, If I could get away with another bar I would use the Miracle X-Brace to tie the corners of the rear hatch together. And corner-weighting, Which I’m totally gonna do, only make the weight transfer rates even no matter which way you turn. Basically just makes there be exactly the same amount of weight side to side & diagonal to diagonal.

Enough ranting… Sorry I get carried away about this stuff, I’m a Mechanical Engineer who lives and breaths cars, I did the suspension for my schools SAE Mini Baja car.