1- 17 on the TA
2- the Triumph has rubber on both sides that is supposed to dampen any chain vibrations, but most people can't tell the difference.
3- 18 is much better at highway speeds with less vibration, but there is a trade off in dead start acceleration. Exhaust upgrades, carb and airbox mods offset a lot of the loss.
4- You can get quality sprocketes at Brent"s (http://www.newspeedmaster.com/index.html) or at BellaCorse (http://www.bellacorse.com/index.html).
