Not to burst anyone's bubble, but what is everyone talking about?
If you keep the same gear ratio, regardless of pinion/spur size, your top speed will remain the same (simple physics and mathematics). By increasing the spur AND pinion together, you ARE increasing the rotating mass, but it's by a very small amount. I'm not convinced you will notice that change on the track, because the mass is not where you will feel the changes, unless you go to the extreme. At the same gear ratio, whether using small gears or big gears, the motor will always spin at the same RPM in relation to your final drive RPM. CHANGING your gear ratio is what you want to experiment with...Why? read below:
Electric motors never produce peak power at the beginning or end of their RPM range. Take one of my P2K's, which produces it's most power (63 watts) at around 15k RPM. BTW, Don't EVER trust labels put on by motor companies. So, let's look at how this relates to on-track experience when using a 93t spur, 24t pinion, T1FK04 with low-ratio pulley set (1.77)...
Gear Ratio = 93/24 = 3.875 (the pinion turns 3.875 times for every revolution of the spur)
15,000RPM/Gear Ratio = 15,000/3.875 = 3,870.97
3,870.97/Pulley Ratio = 3,870.97/1.77 = 2,186.99
So far, at 15k Motor RPM, we are spinning the axles and wheels at 2,186.99 RPM. Using my Sorex 28R tires, I find the circumference of my tires are approx. 7.875". So, how fast am I going on the track?
2,186.99 x 7.875 = 17,222.55"/min or 1,435.21'/min, which is 15.71mph. If you are saying, at this point, so what! I don't care how fast in mph my car is going! You are correct, it doesn't matter in mph how fast your car is going, but what kind of track are you running on?
If you are constantly driving the car at 3/4 to full throttle around the track, then you want to gear the car to place your motor's peak output in the 3/4 to WOT range, which you can easily find by knowing how fast your are going at WOT. The reason is because you will accelerate faster out of the corners because you are in the motor's power band, thus increasing your average speed...and on-road is all about raising that average speed. However, keep in mind what Big Jimmy G said, the lower the CG the better the car will feel. Also, don't everheat the motor...I usually run mine in the 150-170 range at the end of 5 minutes on an outdoor track. But I also know someone that's pretty quick running in the 200 range. These temps are stock motors.
(DISCLAIMER) These are just my opinions and I don't expect anyone to agree. Your driving style and car condition may affect your specific situation!
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