hmmmm, I think a 44 or 45 pinion can be run with the 105 spur. I currently run a 102/46 combo with my 13.5 and it's close. A 47 might rub the top deck with a 102. I would switch to a 96 or smaller spur if you are gonna run 17.5. 105 spur is only good for brushed motors and mod brushless.
bboy, you didn't have to mod out the chassis to get the 115 spur to fit?? My 108 seemed to be my limit on mine. I'll have to recheck later on. I could of swore a 108 would "almost" rub the chassis opening.