short arms.
I will preface my comments with the fact that I am not an engineer for 1:10 cars.
Now for what I know, there 2000 lb bigger brothers.
Before anyone pans or promotes the short / long arm you need to know which is relative. Is short, short because its just not long? I know I am playing with words, but stick with me here.
Roll up under your car. If you can, take a look under a vette, mustang, viper, or some other higher performance vehicle. You will find striking similarities to the width of the suspension compared to the JRXS. Since I do not have access to the measurements of the JRXS, I can't be specific.
Yes, an arm too short would require different suspension tuning techniques than a "long" arm.
With the 2000lb cars, you don't want long arms like they have on the offroad cars. The longer the arm, the more mass you need to move for the equivelant movement of a smaller arm.
If you've ever raced a 3000# car on a road coarse, you will know that on a track where you need a responsive car, one that has fast longitudinal movement, you move your arm pivot points closer to the wheels.
You can't simply just use a shorter arm. Everything has to change, camber links, shock locations, steering setup. Everything.
To sum things up a bit: it's about the longitudinal movement. Short arms on a car with the battery / motor mounted off the centerline would require some serious magic to work. Remember the shelf weapon? I had one too.
If you have nearly all the weight centerline, short arms will allow you to adjust your car without changing everything. I would take a guess that the Losi drivers use camber link / length and ride height (tire diameter) to do most of the adjustments. Once a driver finds the spring / shock oil/ piston he likes, I don't think he would change them. Maybe only a "tight" setup and a "loose" setup.
The most important thing is the overall design. You cannot simply use arm length. Its nearly like comparing apples to oranges. You need to talk about the tree they grow on, too. I am guessing Losi engineered this car like we engineer real street cars. With specific tuning options in mind. When you get to a track you don't have time to mess with everything. You know what you like, get a nuetral setup and go from there.
Since I am not a team driver, nor do I drive like one (hence I be mechanic), team drivers comment please.