[classicchrisk]

I have started measuring rpm on the running cars back wheel using a tachometer, which has been interesting, one car seems to have slightly exceeded the max 23k, I measured 24.5K (although it was declared as 21.5k  which is correct according to the brand tech details) on the registration sheet. My set up may not be perfect in this aspect, although I am working on improving the consistency of this testing.

That's roughly 10% over. I'd count the teeth on the pinion. If it's out by 1 tooth, that could account for the error at the back wheel. Gear is easy to check, with its colour code, but pinions aren't as obvious. After all, most of us rely on the rpm quoted on the motor wrapper, and that our power source is giving its stated voltage.