Geared for Speed
All 4-Tec models roll out of the box geared for all-around action, and get an extra gear ratio in the accessory bag just for goin’ fast. The difference in ratios between the brushed and brushless cars, and between the stock and “speed” gears, is pretty interesting. Check it out: The VXL’S “speed ratio” is twice as tall as the brushed car’s stock ratio—that’s a big gear. If we factor in the 4-Tec’s 2.85:1 drivetrain ratio and 68mm tire diameter (I’ll spare you the math), we get a “rollout” of 48mm. That means for every revolution of the Velineon 3500 motor, the 4-Tec VXL (with speed gearing) covers a tick less than two inches. At the motor’s peak speed of 50,000rpm, that works out to 1.5 miles per minute, or 90mph! That doesn’t account for drivetrain friction, rolling resistance, and aerodynamic drag, however—that’s how 20-ish mph gets scraped off for a final top speed of 70+mph.
When the pinion is nearly as big as the spur gear, you know some serious velocity is about to go down. This is the VXL’S “speed gearing,” a 35T pinion and 55T spur gear.
The VXL model gets the same motor plate and 70T spur gear as the Titan-powered cars, but the pinion is a 29T—that’s an 8-tooth jump up from the brushed 4-Tec.