Choosing the Optimum Gear Ratio for your car


The TSR24 and TSR32 cars are supplied with a gear ratio representing the optimum set up for their size, weight and use. However and in certain circumstances, it may be necessary to change the gear ratios to get the maximum performance from the cars.

In each case, the criteria are the following: if the car reaches its top speed very quickly on a very long straight, the car may need to be geared with a taller ratio, meaning a larger pinion with a smaller spur gear.

If the car fails to reach its top speed quickly and appears to be sluggish at normal operating voltage, it may be necessary to install a shorter ratio.

In any case, the TSRF chassis requires a change of both the motor pinion and the spur gear, just like a full-size racing car.

To proceed, you will need a quality pinion puller such as a Hudy or similar. TSRF with soon offer its own pinion puller in our tool line.

Once the pinion is removed, the new pinion needs to be pressed in place and this can be accomplished in a precision machine vise or a pinion press The motor shaft may be trimmed with a Dremel disk and chamfered prior to installation, so as to facilitate pressing.



The Home-Racing cars come with either a steel or glass-filled Nylon pinion, and a glass-filled Nylon spur gear, both in 64-pitch. You may use the available Nylon pinions (part number T2405 for the 11-T and T3205 for the 14-T) as press-on, perfectly adequate for home-racing use. We recommend to clean the motor shaft with a degreaser, place a tiny droplet of synthetic motor oil in the bearing, place a tiny droplet of red Loctite inside the pinion's hole and gently push in place while placing a U-collar spacer made of adequately thick cardboard to retain the pinion from bottoming on the motor bearing. You must leave a clearance of 1.5mm between the bearing and the pinion.

We like the plastic spur gears that come in both the chassis kits and RTR models, and while it is un-necessary on the 1/32 scale model, red Loctite should be used to affix the spur gear permanently on the rear axle of the 1/24 scale model. The Club-Racing models are supplied with a metal or glass-filled nylon pinion and a setscrew aluminum spur gear. This gear has exactly the same width as the Nylon units and requires the use of a .035" hex wrench. A small flat may be ground on the axle but it has been shown that this is really not necessary.

TSRF offers 4 different gear ratios. The car are fitted with the following from the works:

TSRF24 kits and RTR: 11/48

TSRF32 kits and RTR: 14/45

Other ratios available: 12/47 and 13/46.

If using the aluminum spur gears, combinations of 12/48, 13/47 and 14/46 may be used if too much clearance is noted between pinion and spur gear. Some breaking-in time may be necessary.

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