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.

I doubt diamond tires would get much traction on diamond walls.