Shimming The RC Cars

One can increase the speed of an RC car by shimming. One very exclusive speed tip is to use shims to remove any unnecessary slop in your RC car. Excess slop reduces an RC car's speed and makes it handle erratically. Shimming a trans simply means that the have the correct tolerances on each shaft or cluster of gears

If there is a gap between the hub and the axle pin, it causes undesired side to side movement; robbing an RC car of speed and making it handle erratically. One place to remove excessive slop is between the rear hub and the axle pin. We can do this by using thin plastic shims.
If you take a look closely at your model you shall find a thin plastic shim next to the ball bearing.

The inner hole and outer diameter should match the ball bearing's dimension for good results. You shall need to assemble the rear hub, but to get result as your desire of increasing the speed, this time insert the plastic shim before inserting the ball bearing. The final assembly should result in a minimal amount of gap between the axle pin and the ball bearing inside the hub.

Too much shimming will cause binding. Better to have some amount of slop rather than have binding. You can test for binding by removing the dogbone temporarily and spin the tire with your hand. The tire should spin freely for at least 30 seconds. If not, there is binding, better to reduce the amount of shimming.

It is important to learn how to make plastic shims. A step by step guide to making cheap plastic shims for the rear axles is helpful. Details on shimming can also be researched from other resources. You can also ask an old hobby expert in RC Cars.

First step is to find a thin piece of plastic and punch a hole which is slightly bigger than the axle diameter. Next is to cut out the outer diameter that matches the outer diameter of the ball bearing. You can easily do this by first finding a spare axle and then insert the plastic shim and a bearing. Then use a cutter to mark the outside diameter.

You can then cut out the outside diameter using scissors to get the final result. If you wonder why the RC cars of top drivers are so fast, it is because their cars are built with almost no slop.

In case of Tamiya Championship series the use of thin shims to space out the slop or play in suspension arms, steering bell-cranks and wheel axles is now permitted in all vehicles except in the specific class. Shimming the aforementioned components of the car in a way that alters the geometry of the car or its basic geometry design is not legal. In case of shimming the tranny or t-maxx, if you want to get the slop out of it, you should stick a 5x8x.1 mm shim or more between the bearing and the tranny case where there is e-clip.