Gearing

[GavD]

I'm in the process of fitting 6 spoke Trident style wheels, and thought that the change from 17" to 18" rear would mess the gearing up quite a bit such that I would need a different rear sprocket and possibly a longer chain.
After a bit of pondering I came to the conclusion that the important thing is the circumference of the tyre, not actual wheel size. The Tiger circumference measure in at 79" and the Trident wheel at 79.5".

So with a standard 18/48 sprocket - one rev of the front sprocket = 0.375 revs of the rear = 29.625 inches of travel.

With the Trident wheel and the same 18/48 sprockets (which does fit ok) - one rev of the front = 0.375 rev of the rear = 29.8125"

If i was going to try to compensate by fitting a 49 tooth rear;
one rev of front = 0.3673 revs of rear = 29.2 inches of travel.

my assumption is that the standard gearing is pretty close and there is no need to change the rear sprocket and so I've saved myself a few beer tokens.

Would anyone care to comment and see if I've made any mistakes in my calculations, and/or assumptions.

Gav

[Mustang]

you will be fine with the 18/48 combo

[NeilD]

think I came to pretty much the same conclusion when I was thinking about doing this..  8)
one thing I did wonder though with the larger rearwheel was the affect on the height and wether the sidestand would end up beign too 'short'... although I noticed you are lowering your bike so should be ok..?

[GavD]

With the overall circumference only 1/2 inch greater the height of the wheel will only be .16 inch higher. I'm primarily lowering the bike because I'm on the balls of my feet anyway and I'm looking to get my seat upholstered and it'll probably be higher because of that.