New VRC RX8 Buggy & Updated Physics

The RX8 is a complete new buggy chassis featuring the very latest suspension geometry technology and narrow chassis layout. As both the RX8 and the NX8 use 3D suspension geometries and animated suspension, our physics expert Todd ‘Doc’ Wasson was faced with a new challenge of making both chassis work well, maintaining their own character and keeping both of them competitive when racing together. The RX8 chassis not only has completely different suspension geometry, the chassis also has a much narrower lay-out, which means that the engine is in a different location. 

So keep in mind that the engine, exhaust and body components are not interchangeable with the NX8 chassis, or at least they are not an exact fit. Make sure to select engine, exhaust, body and transponder components which are for the R-series chassis. The different chassis lay-out has affected the center of gravity and the roll, pitch and yaw moments of inertia which, besides the different suspension geometry, make the RX8 chassis handle very different from the NX8 chassis.

With the release of the RX8 chassis also the physics engine was updated. This update affects all the off-road chassis which use 3D suspension geometry so also short course trucks. The handling of all the off-road cars has changed significantly, and for the better, although to some extent this reflects personal preference.

New VRC RX8 Buggy & Updated Physics


So how different are these 2 chassis and is the RX8 the faster one? In potential the RX8 is probably the faster chassis as it uses the latest suspension specs and chassis lay-out which are now common in today’s buggies, but this depends very much on the skill level of the racer and the personal preference of how sharp and responsive he wants his car to be. We expect the NX8 to still be the choice of many racers, because it is a little less ‘edgy’ and more forgiving. The RX8 is sharper and more responsive. It may also depend on the track which car you prefer. You should really try both, work with setup and see which one fits your driving style best. And don’t forget, it’s not about the ultimate lap time you can squeeze out of the chassis, but how many laps you have completed after 5 or 20 minutes… David Ronnefalk stated in one of our forums that he prefers an easy car over a fast car…!

It has already been mentioned, the short course trucks also benefit of the improved physics, you will definitely feel the difference and will enjoy the SC truck ride even more. The short course trucks were already using the 3DS suspension, but now they also feature animated suspension even though this can only be seen from close by and in replays. Still another important step towards more realism, both in handling and in looks!


To try to understand the difficulties this has presented to Todd, you have to understand the difference between the real and the virtual world. In the real world everything complies with ‘natural’ physics which are simply there. In the virtual world the physics need to be described by an immense set of formulas, algorithms and logic drawn from what we scientifically understand of physics laws. So virtual physics are always an approximation of real physics and are never 100% accurate in all areas.

It is a never ending process of making ‘virtual’ physics ever more accurate. Our chassis model is probably the most accurate, since all the necessary data is known and available, like geometry dimensions, masses, moments of inertia. The big ‘unknown’ (also in all other car sims) is always the tire physics. With over 50 parameters the tire physics model is extremely complicated, and with little tire testing data available (and believe me, we have a lot more tire data than any of the tire manufacturers) we had no other option than to fine tune the tyres towards the chassis.

The tyres control a lot of the car behaviour and especially the ‘feel’. Now imagine optimized tyres for the NX8 chassis also to work on the RX8 chassis which has a completely different suspension geometry, center of gravity and weight distribution. It speaks for the physics engine quality and depth, that Todd has managed to make both chassis work ‘perfectly’ with the same set of tyres!

In the process several refinements and optimizations of the physics engine were implemented, among them how the suspension jacking forces are being computed, improved algorithms for the differentials and some modifications to the camber effect of the tyres. Now also keep in mind that every little change in the physics engine also affects how the short course truck behaves! With all the off-road cars clearly benefiting of the physics update it’s nearly miraculous what Doc. Todd has been able to achieve!