Thruxton Rear Sprocket On A Bonnie

Hello again!

One of the mods that I really enjoyed making to my 2018 Bonneville is replacing the rear sprocket with one off of the Thruxton. For most of the type of riding I do I felt that I was in the wrong gear much of the time, and that the Bonnie was geared too high. I replaced the stock 37 tooth with a 42 tooth rear sprocket, which is just right for me. A lot of times it is as equally important to see how low in the RPM I can go without straining the engine as much as how fast. And since I have a straight 1:10 multiplier for every gear, I just get 10-percent more torque across the board. RPM, as expected, is 10-percent higher than stock for any given gear, so that 6th is now closer to the stock-gearing 5th.

About the only time I miss the stock gearing is on freeway drones, but I rarely have to do any of those for my "pleasure" riding in and around the South Bay area of San Jose and surrounding mountains.

Another significant change is that the wheelbase is reduced by at least an inch. I have attached a photo to show the change, where the axle adjuster was at the rear of the swing arm in the stock configuration. High speed stability is undisturbed, but in the low-speed twisty stuff I sometimes feel like I am on a big (heavy) dirt bike!

This is a fairly inexpensive mod, too! I paid $45 for the Thruxton sprocket.

Great fun!

 

In theory I agree with you, but my experience on two of my previous bikes is that any front sprocket less than 18 tooth really accelerates chain wear.