vehicle vs wall

let's say you drive a 4 wheel rc car towards a wall. what's the force required to drive the front wheels up the wall?

i've been told that each tire needs to produce LESS than 1/4 the total weight of the car. i just can't work it out that way.

this is a design project problem. they don't make motors torquey enough to produce 1/4 the weight of my little car, but it's close. if it's slightly less, i'm saved and i can find some motors. see if you guys can work this out better than i can. save my life.

It would depend also on the height of the front fender.  If it was higher than the front wheels by much, the forward force would produce an upward force as well....but if the front fender is no higher than the front tires, friction against the wall may make it impossible.