4wd – does it offer more grip?

[monthefish]

I was always under the impression that (as well as offering more traction) 4wd offers more grip in corners etc, hence the good reputation in this respect for Audi Quattro, Scooby/Evos, Porsche 911 C4 & Turbo, etc etc

However, I’m also aware that a tyre has a finite amount of grip which I believe is shared between forward/backward motion (i.e. acceleration/braking) and directional changes, so from that respect a 4wd should have less grip (as some of the tyres’ available grip is being used to drive the car forwards).

What’s the real story and the correct physics behind it?

Cheers.

[monthefish]

BigLepton said:

monthefish said:

However, I’m also aware that a tyre has a finite amount of grip which I believe is shared between forward/backward motion (i.e. acceleration/braking) and directional changes, so from that respect a 4wd should have less grip (as some of the tyres’ available grip is being used to drive the car forwards).

Errr, no. A 2WD car shares its lateral grip and braking grip between all four wheels, but two of the wheels get all the torque, reducing the amount of the other two forces they can handle, dependent on throttle opening. A 4WD car shares all three forces (lateral grip, braking and torque) between all four wheels which means you should be able at any given point of a corner to apply more throttle without the driven end giving up gripping before the none driven end.

What I was meaning was that each tyres only has so many 'daves' of grip available at any given time, so if some daves are being used for propulsion, there will be less daves available for lateral grip.

Also, how can a tyre be trnsmitting braking and torque at once?