what the difference between multilink vs double wishbone?
which one is on the rx8?

 

I believe the RX8 has double wishbone front and multilink back

 

The RX-8 rear suspension is a multi-link design. The front suspension is double wish bone. With the exception of Audi, which uses a mult-link front suspension in a attempt to reduce front wheel/all wheel drive's inherent torque steer, cars generally don't have multi-link front suspensions. They use double wish bones, strut suspensions with a single A arm, or a solid axle on big trucks.

Multi links usually have 5 links: 4 of them are essentially two pairs of split wish bones (or A-arms, as they are also referred to) and then a single trailing link for fore/aft location. The combination of links is usually configured to allow some passive steering/toe control that can help keep the car from spinning as the rear of the car reaches its adhesion limit. I must emphasize that rear toe control won't always save the car from spinning - but it can help if it comes into play under the right conditions.

If you're close to losing control because you've entered a corner too hot or have accelerated too hard, slamming on the brakes is a classic way to make the car spin if it's already near the limit. Rear toe control can help keep the rear from coming around in a situation like this, but only if you're not too close from spinning once it comes into play.

I once entered a corner too hot in my old '94 BMW 325is and was amazed that I didn't spin - the rear toe control saved me. I was lucky though - if I'd been going much faster I would have spun regardless of the toe control. Moral of the story - scout the route and know the curves.

Someone correct me if I'm wrong, but I believe that, ideally, a toe correcting/passive rear steering suspension will toe out the outside rear wheel during low G's and then toe in the rear outside wheel when the limit is approached.