Instead of trying to tell you how to find this; I'll paste it here:
45 tooth rear sprocket evaluation on pavement
I may not do anything more off-pavement soon, other than dirt/gravel roads; so thought I'd test a 45 tooth. Only required: switch sprocket and shorten chain one set of links. No new chain required until I try a 55 tooth rear.
2014 TW, no performance mods, 2,300 elev, 185 lb rider, 87 octane NON-ethanol. Not to compare mine to yours, just 50 tooth vs 45 tooth.
Test #1: 60 miles, mostly flat with a few short hills, paved back country roads, 10 stop signs, steady 45 mph.
50 tooth held 5th gear throughout.
45 tooth had to use 4th gear once or twice for 5 seconds to maintain 45 mph on hills.
Result: Smoother more comfortable ride due to less buzz/vibration and fuel mileage improved 6 mpg over 50 tooth.
Test #2: 60 highway miles (30 each way), some slight grades, steady 60 mph.
50 tooth held 5th gear throughout.
45 tooth had to use 4th gear quite a bit to hold 60 mph on the grades, especially into the wind.
Result: 4th gear 45 tooth had a little more buzz/vibration than 5th gear 50 tooth -but-
45 tooth 5th gear was a MUCH smoother and more comfortable ride than 50 tooth.
Even using 4th gear on the grades; fuel mileage improved 5 mpg over 50 tooth.
Test #3: 2 miles, 6% grade, full throttle test.
50 tooth 5th gear - 58 mph at bottom - 55 mph through middle - 58 mph at top.
50 tooth 4th gear - 56 mph at bottom - 57 mph through middle - 58 mph at top.
45 tooth 5th gear - 52 mph at bottom - 42 mph throughout most - 40 mph at top.
45 tooth 4th gear - 57 to 59 mph with almost no fluctuation off 58 mph.
45 tooth 3rd gear - 55 mph bottom to top.
Test #4: Maybe 1/2 mile, steeper grade, full throttle test.
50 tooth 5th gear - low of 46 mph - high of 48 mph.
50 tooth 4th gear - low of 48 mph - high of 54 mph.
45 tooth 5th gear - USELESS at steady 31 mph.
45 tooth 4th gear - steady 50 mph.
45 tooth 3rd gear - steady 52 mph.
My opinion: For "street only bikes" or "those whose off-pavement riding may only be hard packed dirt, gravel, fire-roads etc.", a 45 tooth is a winning improvement. With a simple down-shift to 4th you pretty much give up nothing to a 50 tooth (even in 4th), and gain a much smoother, more comfortable bike with improved fuel economy.
A lot of non hard-core off-road situations (and some hard) stock gearing, you may find 2nd gear a little too high and 1st gear a little too low. This might make 1st a sweet spot; like gearing lower and 2nd becoming perfect. -J-
Update: February 2017: (my testing above had been done in calm weather) Have had a 65 tooth on for quite awhile. Tested a 35 tooth (failed) and then put the 45 tooth back on. Went out in strong winds and could barely hold 55 on a flat road into the wind and could barely hold 45 up a slight but long rise by shifting to 4th. So I am amending my opinion to: the 14-45 is lacking in very windy conditions. I put the 50 tooth on and got to 60 on the flats. In the future, I hope to try 14-47 or the equivalent 15-50.
Update: March 2017: Tested 14-45, 15-50 and 15-45 (equivalents of 14-47 and 14-42) on the freeway. No gearing setup higher than stock would hold 60 mph in the wind in some sections regardless of being in 4th or 5th gear.
So I just ordered a 42 tooth rear. The 15-42 is equal to a 14-39 setup.
Update April 2017: Tested 15-42 which is equal to 14-39. My motor is totally stock - unlike some who have gone to this gearing set-up. I do not recommend these gear set-ups with a stock motor, as I felt there was too much lag (bogging taking off from a stop) for everyday use. I switched to 15-45 and had no problem - and was holding 60+ on sections I had problems before.
Update June 2017. Admiral loaned me his 44 tooth and I tested it today 15-44 which is equal to a 14-41. It did not have the bogging problems taking off from a stop like the 15-42 did; and was able to hold 65 with a shift to 4th if necessary (where the 42 tooth wouldn't hold 60 in 5th or 4th).
So: 15-44 / 14-41 is the highest gearing I can recommend for a stock motor - unless I get a 43 tooth to test with my 15 front (equal to 14-40 "within 15rpm").
So, knowing 15-44 or 14-41 is good - and 15-42 or 14-39 fails with my stock motor:
Anybody have a loose 43 tooth sitting around that I could borrow to complete this test. I would pay shipping both ways.