TurboTimmy 88 Posted September 16, 2019 I have a Lunchbox that is stock except for a Sport Tuned 540-I do plan to put on CVA shocks all around....... What is the recommended pinion size (number of teeth) for that motor in that chassis? Thanks for all replies. Share this post Link to post Share on other sites
waterbok 1282 Posted September 16, 2019 Stock pinion is ok for the sports tuned. 1 Share this post Link to post Share on other sites
Juggular 4964 Posted September 17, 2019 To expand a bit on what waterbok already said; other pinion than the 10t stock will not fit. The other gear you could theoretically install is 18t Hornet/Grasshopper pinion. But that would be a bad idea. That 18t pinion was made for much smaller + lighter 77mm tires (not for 105mm Lunchbox tires). When Tamiya made Lunchbox big and heavy, it had to reduce the gear ratio. That's why there is a collar between motor and the gearbox. 10t is smaller, so it wouldn't even touch the spur gear. To close that gap, there is the collar (red circle below). Also that's why the pinion is so tall. Tamiya went through a lot of trouble to make the pinion small. If you take off the collar and installed the 18t Hornet pinion, I'm afraid you'd lose the benefit you get from Sport Tuned. It will feel like it would take forever to reach the top speed. Going from 10t to 18t? That is asking the motor to do 180% of the work. It will run much hotter as a result. Heat will kill the magnets in the motor, making it weaker and weaker every time. (People install heat-sinks on their motors to cool it down, even when the motor doesn't even get that hot) The other option is to use a custom motor mounting kit. That will allow other gears, probably anything between 11 and 18t. But even if I had a custom motor mount, I'd still use the 10t pinion. If I replaced the plastic shell with a very light lexan body? Then I might use 12t or 13t, because now it is like 30% lighter. Still not as much as Hornet/Grasshopper. So... long story short, I would stick with the stock pinion. If you forced anything other than 10t pinion (or 18t after taking the collar off), it will either not mesh at all, or chew up the gears. Shocks are a good idea. (If you want, double wishbone suspension for the front is also a good idea) 1 Share this post Link to post Share on other sites
TurboTimmy 88 Posted September 17, 2019 Thanks!!!! Now that you mentioned the gearing issue with the big tires, the 10t pinion is obviously the only one to use...... Here is another footnote: Is the gearing for a Rising Fighter the same as a Grasshopper 2? Probably a dumb question...... I am looking at both for potential purchase and plan to use a Sport Tuned with a 17t pinion. Thanks again for any advice. Share this post Link to post Share on other sites
