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As the spec says, you can use any 2WD 1/10th scale stadium truck chassis as the basis of a J-SPEC car. If you have an old Kyosho Sandmaster laying around, use it! If you need to get something new to start with, though, I would recommend that you pick up a Traxxas Rustler RTR. Aside from the fact that I like Traxxas products, the Rustler truly is a rugged, reliable truck that is painfully inexpensive, making it the perfect platform for J-SPEC.

Follow me as I whisk you through the straightforward steps of transforming a box-stock RTR Rustler into a J-SPEC racer. This whole process should take about 1 hour plus the time it takes to mask and paint a lexan body.

What I used:

Chassis: Traxxas Rustler RTR (comes assembled, with radio) $129.99*
Body: HPI Super Nitro Subaru Impreza WRC 300mm wheelbase $33.99*
Tires: Pro-Line M2 Step-Pins (rear) $16.99*
  Pro-Line M2 Hole Shots (front) $16.99*
Battery: Dynamite Dyna-Sport Sport 1500 (4) $55.96**
ESC: Duratrax Spike $27.99*
Other: RPM wide front bumper $6.69*
  Battery charger (you would need one if you're just
starting out; I already had two of my own)
Totals:   $288.60
* At Tower Hobbies. Other vendors' prices may vary
** Estimated

Making the conversion

** Be sure to click on the images below to see the large, zoomed-in versions **

Click to enlarge Step 1: Open the box!

I literally started with a completely stock Rustler RTR, taken right out of the box. Some people laugh at the included Traxxas TQ radio, but hey, it works! Trust me, it's more than good enough -- I have 8 of the darn things and with one brief exception, I have never used anything else.

Install your antenna tube now before you forget like I did at first ;)

Click to enlarge Step 2: Work that body

Make sure your body meets the spec. It needs to be at least 215mm wide and passenger car, not a truck! The 300mm wheelbase bodies work perfectly with the Rustler. This one is a Super Nitro Subaru Impreza WRC rally body from HPI. It is more expensive than your typical Rustler body, but the construction is very tough and the lexan is thick, so I won't need to replace this any time soon.

Be sure to put some time into decorating your body and feel free to be creative and try wacky ideas. Personality is a good thing! Take your time and enjoy this step.

Click to enlarge Step 3: Bring things under control

This is not a crucial step, but I think it's worth it. I got the cheapest ESC (electronic speed controller) I could find, the Duratrax Spike, to replace the stock Rustler MSC (mechanical speed controller). You'll want to remove the MSC assembly, which includes the resistors mounted above the motor, the rotor assembly and the acutator servo. While taking all of this apart, you'll come across a mount that holds the rotor. This is a flat piece of black plastic with two screw posts sticking up. Leave that in place -- it helps to hold the battery in place.

Attach the new ESC to the floor of the left side of the chassis with double-sided servo tape. Most household double-sided tape isn't strong enough and will wiggle loose, so use the strip that comes with your ESC. Use the stock "bullet" connectors to hook it up to your motors if you wish, or splice the wires together. The blue ESC wire is negative, so connect it to the black motor lead.

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Step 4: Get posted

This is the single trickiest step, though there is no single right way to do it. Obviously the super-sized rally body is taller than the stock Rustler body, so you'll need to use some extended body posts (like the Duratrax ones shown at left). Up front you can just unscrew the stock body posts from their horizontal cross-member and screw on the new, long posts. I bought 4"+ posts just for overkill, knowing it's easier to cut off excess than to try to add on missing length that you need.

For the rear, I got a Stampede body mount set. Take the part that looks like a really short football goal post and carefully cut off the posts at their base, parallel to the flat surface below (see the 3rd picture at left). Discard the short post stubs. You can then drill a hole (3/32" or so) through the center of each of the cut sections of the remaining mounts to form screw-holes through which to bolt your new, longer mounts. Mount the entire assembly to the rear of the stock Rustler shock tower using the screws provided and the holes that are already pre-drilled in the tower.

For each of the new posts, start a set screw into one of the height adjustment washers (I don't know the official name -- they're the donut-like things that comes with the body posts) and slide it over the post. Don't tighten it down yet. The end result is what you see in the bottom picture at left.

Click to enlarge Step 5: Trim & mount

At this point you're going to need to do some trial and error work. First trim out the wheel wells of the body using the lines molded into the shell. This will give you a good sense of exactly where to mount the body relative to the chassis (tricker than it sounds... just play with it for awhile and you'll catch on). The wheelbase (distance between the front & rear axles) of most stadium trucks (like this Rustler) changes as you compress the suspension, so start with something that doesn't change by mounting the body such that the rear wheel wells arecentered over the rear axles. This would be a good time to form holes for the rear body posts and stick them through. Slowly trim out the front & rear wheel wells, staying as symmetrical from the left side to the right as you can. The rear wells will need to be made large enough to fit the tire up into them a bit when the rear suspension is compressed. The fronts will need to be trimmed far enough forward so that the tires don't rub when the suspension is uncompressed, and far enough back so that they don't rub when the suspension is compressed and the wheels are turned to steer. The key point to remember is to take your time.

When you're happy with the trimming job, set the height adjustment stops where you want them to be and tighten them down. Trim off excess body post material, but leave at least 1/4" to 3/8" sticking up above the body. Drill a horizontal hole through each post for your body clips, if necessary.

(You may note in this picture that I actually put on some aftermarket Losi 2.5" springs in the back -- just to lower the car a little.)

Click to enlarge Step 6: Feel the power

By now you should be just about ready to hit the road. Be sure to read and follow the guidelines in your original Rustler owner's manual. Pop in a spec 1500mah pack and follow the instructions that came with your ESC to set your neutral point and high/low range. That's about it... you should be ready to race!

There are, of course, many other things you can do to customize your J-SPEC car and improve its handling. In my case, I put on some better tires, Pro-Line Step Pins on the rear and Hole Shots on the front. Remember if you get new tires that you must not run ribbed tires up front. For protection against collisions, I installed an RPM wide front bumper. Finally, as mentioned above, I put some Losi blue springs on the rear to lower the stance of the car a bit.

If you want to go all-out, bring your chassis up to Ultimate Rustler specs!


This is just one way to make a great J-SPEC racer. You can just as easily start with a DuraTrax Evader, Losi XXX-T, Team Associated T3, or any other stadium truck. Hey, a Stampede would work great as well!

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