That gearing is fine I run 15/48 on my brushless 8ight-t (1515 2.5d w/ 5s 5k packs) , and I run 14/48 on my 8ight-e w/ Medusa 2000kv, 4s 5k packs. Zero speed issues and now that they are tuned a bit better even faster than before! I hope to be hitting 29sec laps on thursday night