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Online Illustrated Assembly Instructions
As soon as you buy your Micro RS4 kit, be sure to see our latest website feature, Micro RS4 Assembly Instructions. These step-by-step written, fully illustrated instructions show you exactly how the "pros" at HPI built their Micro RS4 kits.

Front Diff Gear Update
The small brass gears (#73403a) that fit into the front diff case may need to be slightymodified to fit onto the silver pin (#73403b). If the brass gears won't slide easily onto the pin, use a sharp hobby knife to gently ream out the inside of the gear so the pin will slide in. See the picture below for an illustration of how to modify the gear. The gear is made of softer metal than the hobby knife blade so it is easy to cut away too much - make a few passes at both ends of the gear with the knife (you should have some brass shavings) and test-fit the diff shaft. If it is still tight, make a couple more passes and try it again.

You can also send your gears to us (see the Contact page at left) for free replacements.

Bend Those Body Clips!
Use pliers as shown below to bend the ends of each body clip slightly. This makes them easier to grab off a table and off the body or upper deck.

As you can see below, it will be much easier to take the clips off if they ends are bent up slightly.

Step 12 Update
When removing the large plastic gears for the front gear diff (#73403-5), use a hobby knife to remove the gears from the part tree. Do not twist them off without trimming the part carefully, because you may accidentally leave a small piece of the tree on the gear, which will cause the front diff to click when turned. This will make the diff bind and could cause damage to the diff, requiring new gear parts. See the picture below for a close look at what should be trimmed off.

Changing the Wheelbase on your Micro
When looking for new bodies for your Micro RS4, remember that if you change the wheelbase of your car, you must install a new belt as well. If you don't already have a spare belt to change wheelbases, the part number for the 140mm (short) WB belt is #72314 and for the 150mm WB (long) WB is #72316. The wheelbase for each car is noted on the header card of the package and in the Micro RS4 Bodies page.

Wheel Hub Widths for Each Body
The Micro RS4 allows you to use different width settings for each body you choose. This lets the cars be more realistic in scale appearance. The front wheels have three settings; the rear wheels have four settings, plus you can add 1mm spacers on each side for an extra 2mm of rear width. Here are the settings we recommend you use for each body:

Mounting the Body
Listed in step 30 of our Micro RS4 Assembly Instructions, these are the starting body mount positions we suggest for each body that has been released for the Micro RS4. Count the number of holes specified from the top mounting hole on each front or rear body post to achieve a well-proportioned body height.

Body Height Adjustments
Each hole in the body posts is 2mm apart, however if you use the second body post mount position you can adjust the posts up or down in 1mm increments.

Direct-Solder the ESC to the Motor
It is unlikely you will be replacing the motor very often; in this case it is recommended that you directly solder the motor wires to the ESC. This helps to "clean up" the chassis of the car by removing excess wire and also helps you lower the weight of the car. After all, on an off-road truck or touring car the extra wire doesn't make that much difference, but on a car the size of the Micro RS4 removing excess wire weight really does help!