I've tried the following setup for the race-only bike:
- 14/40 - too large of a delta from stock IMO. Gears 1-3 revved up way too fast and too much top end lost even on tight tracks
- 14/39 - good setup for tighter tracks with shorter front and back straights such as Sonoma
- 14/38 - I felt the perfect setup for all-around track riding. Better drive out of corners, especially improved mid-range in 2nd and 3rd gears and worked very well for acceleration on straights when used together with reverse quick-shifting.
- 15/40 - not enough of a difference for track use IMO but would be the way I'd go for all-around, spirited street riding. Will likely make the change on my Tri with this gearing.
With regards to a 15/41 set-up, while I haven't ridden that exact setup, obviously I've danced around close enough to that gear ratio to feel that 2 teeth up in the back would give you a short-term "solution" to the low-end and mid-range issues but I believe would also introduce handling issues and riskier corner drives on public roads where road conditions aren't near what they are on a track.
*Note - The bike is a base, non-abs with Termi slips, S wheels, CRC race plastics, and a few select carbon pieces for lighter weight and protection.
- I use the AFAM quick change kit with 520 chains and alum sprockets. Personally, I think the weight savings are minimal and for a street/track bike I would use steel sprockets and consider a 525 chain.
- You need to make sure to log, track, and adjust ride height and wheelbase changes as it will have a fairly significant effect on handling characteristics. I have a very knowledgeable team mechanic that understands these things much better than I and would be apprehensive to make these changes otherwise.
- Also note that the testing was all done prior to the new upmap and bazzaz tuning and have yet to be able to test it out on the track with the new upmap installed.
