Just replaced front sprocket (JT 15) chain and rear sprocket(JT43) stock is 46 tooth. My speedometer is spot on with GPS and mileage is 6% off 100 miles on GPS = 94 on odometer. I love the difference much smoother at slower speeds don't notice power loss if I keep RPM at or above 4500 RPMG
I see Speedy posted last year, however I question how it could be smoother? I had a 07 with the 16 tooth, yes I could still start off in second gear, 0 to 100 KM/Hr in second gear, gear shifts wider apart. Let me say the 2015****is a different animal, below 4000 RPM it sucks, so unless you are moving at 100 to 150 KM/HR all the time and never need to run in the 50/60 KM / HR range I can see it.
For me if I am on the back roads, 80 to 90 KM/HR is common, with a 16 tooth I would need to run in fourth gear. My understanding is the 2015 has been changed in many ways, low RPM performance has not been enhanced over the MK1 and MK2, in fact if it wasn't for the many other improvements on the 2015, I would sell it and go back to the 07
I sold my 16 tooth sprocket and don't see myself returning to it, FYI the 07 had a lot more get up and go over the 2015, and much smoother between 1500 and 4000 RPM, I could easily hold it at 3000 RPM with a 16 tooth sprocket and crank it, O vibrations, try that on the 2015, even at 3800 to 4000 RPM it hesitates and vibrates.
I have changed the main throttle sensor to 0.90 VDC from 1.034 ( shipped from dealer) I set it at 1.05 in May, this won't improve performance, just fuel mileage.
Last thing I need to do is a vacuum sync, and unlike the 07 which could be done without removing the gas tank, the 2015 is impossible to do without removing the tank, so that is my next project, possibly this week.