The three differential system used in many RC cars is a great way to keep the power on the ground, but it often requires careful planning of differential oil viscosity distribution according to the driving conditions. Furthermore - each oil change requires you not only to have the proper viscosity of silicone oil, but to reach the differential insides - meaning you need to disassemble the whole car. The most obvious problem is how to avoid locking the central diff in order to gain the advantages of having it without loosing too much power wasted in spinning and blowing tires. That is, if you are using regular open differentials of course.

Now that we have the Tactyl II light differentials available for Hot Bodies/HPI models though, we can assemble another kind of beast - one that will rarely need attention, no matter what the conditions are. Tactyl diffs lock in certain on-power conditions and unlock when off power - that means they actually act as an open differential in corners and lock almost immediately after you exit a corner and apply throttle. Of course, they do not work as Torsens - a Torsen differential would transfer most power to wheel that have the best grip, which is usually the outside wheel in a corner (you wouldn't use Torsen as a rear diff). Instead the Tactyls might even hurt a bit your cornering if you apply too much power while steering, but they will help you exit at full throttle wasting only a second to properly align the car - and it will not bring the car's nose up or spin a wheel as a balloon. On a loose track your car will put power on each an every wheel - see for yourself:

Back on the beginner's needs - these differentials help a lot on loose surfaces, as in snow, sand, mud, dirt on any other surface that would otherwise make wheels loose grip. In the snow, where most 3-diff cars could struggle to get a grip and often spin a wheel too fast (you can see it in our Bullet with CD video here), the Tactyl-equiped car will act as if every wheel has a power source. Again - see for yourself in the following video: