Wheel size

[twangin4u]

I got an 18" wheel on the back of my '91 1200. I'm curious how that effects the performance of the bike as far as acceleration and top end. Seems like it may bog it down some. Just a thought.

[Capn Ron]

I got an 18" wheel on the back of my '91 1200. I'm curious how that effects the performance of the bike as far as acceleration and top end. Seems like it may bog it down some. Just a thought.

The size of the wheel has nothing to do with the final drive ratio.  Assuming that you have the same front and rear sprocket sizes between the original setup and your now-new 18 rear wheel, all other factors remain the same.  The overall diameter of the tire that is mounted to the 18" wheel will determine difference (if any) in final drive ratio.  You can easily look up the specs of a manufacturer's tire in regards to diameter, overall circumference and even revolutions per mile.  If it's the same specs as your old setup, the final drive ratio is the same.  If it's different, do some quick math as to the percentage of difference in...let's say...revolutions per mile.  If the new tire rotates 5% fewer times per mile, then your final drive ratio is 5% higher...and you'll get "5% more 'bog-down'".

[TexasDave]

Like Capn Ron said--the overall diameter of the tire will determine if it makes any difference what so ever. As an example I was riding next to Pat Conlon who has 17inch wheels on his 84FJ and I have the stock 16inch on my 84. When the engine rpm's were in synch (wonderful sound) I was gaining very slightly on him. We both have 18/40 gearing. This indicated that even though he has 17inch tires my 16inch tire with a taller profile had a bigger diameter. The difference between us was insignificant. After a mile I might have gained 5 feet on him.   Dave

[Charlie-brm]

This site might give you some idea. It's one just about everyone should bookmark.

http://www.gearingcommander.com/

Just curious, what's the reasoning for an 18" rim? How is the selection of tires at that size?