Short Course Truck Gearing 21/87 too much?
 

Changing the gearing a little, is this too much with a 13.5t brushed motor?

I run 22/87 with my SC10 indoors with a 13.5. Would run 23 but it won't fit.

Going to change over to an 84 spur to give me a wider range to choose from.

Cool, so I'm in the right ball park then... That'll do for starters!