WAIT hold on guys, I just took a land vehicle dynamics class last semester and if I find my notes.....
Oh here they are one sec let me find the section on Camber caster, and kingpin inclination angles
alright first off rolling resistances
influenced by:
applied load
inflation pressure
tread design
compound
The primary cause of rolling resistance is hysteresis (or internal friction) of the tire material, which occurs as the tire flexes
it increases with
higher load
higher tread design agressiveness (net to gross footprint ratio)
higher tread depth
and decreases with
increasing tire pressure (i.e. less contact patch)
it can be calculated at the contact patch as
F_r= [(s+1)(t_in/R_l)-F_x]cos(a)-F_y*sin(a)
where
F_r is the rolling resistance
s is the slip ratio= (Omega*R_l/V_0)-1
F_x is the longitudinal force (+ driven - braking)
F_y is lateral force
Omega is the angluar velocity of the wheel in rads/second
V is the forward velocity (in ft/s)
a is the slip angle
R_t is the tire radius
and T_in is the driving torque
so on to camber angle
camber angles is the tilt of the center of the tire patch axis from vertical
camber is positive (if viewing from the front of the car) if the tops of the tires are further away from each other than the bottoms
Trucks run positive camber to account for different loads
a small camber is used to account for road crown
some trucks have different camber settings to account for the huge torque their engine can output (this counteracts the torque of the engine's affect on the suspension
mechanics used to bend axels to give cars positive camber ( they shouldnt be doing this anymore >)
so some reasons why camber angle would increase gas efficency
well for one, it makes the effective tire radius larger (by a tiny bit) which should decrease rolling resistance, also, it makes the contact patch smaller, however, depending on the sidewall strength of your tires, this could merely cause more internal hysteresis friction and decrease your effective gas milage
one of the big reasons you probably should not do this is... most consumer tires are manufactured assuming no camber angle, so you'd probably run into some issues with tires wearing out quickly. Also, if you, like most people, forget to check tire pressure before every ride, it would probably be fairly easy to blow out your sidewall in a tight corner, especially if you were running with a heavy load
and if you're especially stupid, and put too much negative camber, you could probably screw up your suspension geometry enough to make your tires move further than the designed rattle space in you car (the open area where the suspension can move) and perhaps your tires would rub on the inside of the wheel wells before the suspension bottomed out.
but it really depends on the type of suspension your car has (and there's wayyyyy to many to list) to get a definite answer as to whether this is doable or advisable. I would go with the factory recommended settings personally and just firkin keep your tire pressure high enough (the recommended amount) and you'll save a TON on gas
oh and a warning, ALWAYS REPLACE REAR TIRES if you're only gettin 2 tires, if you replace the front tires (regardless of a front or wheel rear drive car) only, you could potentially put your car in an oversteer condition, and that is what causes people to lose control, and spin out, unless you're a formula 1 driver and you know WTF you're doing, always keep your car in an under steer condition (i.e. more traction in the back dawg)
This is what i got for taking a land vehicle dynamics class, i hope you find some of it useful