[python] Re: gearing on small pythons / wheel sizes

Hi all,
I have a 20" drive wheel on my trike with a 44t / 60t chainring combination with 150mm Bulletproof cranks and a 11-28 six speed cluster. My maximum speed is about 48kph at full clip on a short down hill slope on my commute. I can cruse at 33kph in a cross wind and about 22kph in a head wind, and up short hills. I had to make a custom adapter out of a 44t bmx chainring to fit the 60t which was 135bcd. 

http://jetrike.com/chainring-adapter.html
The combinations seems to work well, I can certainly cruse down hills in top gear, but if I put the hammer down quickly top out -- maybe one more high gear would be better. The bulletproof cranks come in sizes from 145mm to 170mm in 50mm increments -- I bought them after reading about Dirk's short cranks. I agree with Dirk, you end up with a much higher cadence than normal 170mm cranks, but now that I am used to it I prefer it. Going back to regular 170mm cranks feels decidedly awkward.
With regard to wheel size differences, here is a recent post by Aaron from the JETalk list on this subject... 


On the rolling resistance question though I have some experience from the 
mountain bike world. some companies are starting to build bikes with upsized 29 
inch wheels and claiming all sorts of improvements. Opinions were strong on 
both sides so Bike magazine did a detailed test and review and here are the 
basic results...

Weight difference isn't huge, but the larger wheels have a rotational inertia 
that is enough higher that you can feel the difference in effort needed to 
accelerate them.

The 29 inch rims also carry speed through slightly rough terrain noticably 
better though. Especially when cruising at higher speeds.

The conclusion was that the effect larger wheels would have on your ride 
depended heavily on what kind of ride you do. Lots of stop and go or speed 
changes favored the smaller rims. Lots of high speed cruising with lightly 
rough terrain favored the larger rims.

Some companies are now building mountain bikes with 29 inch front ad 26 inch 
rear wheels to try to capitalize in both benefits. Im not soure how thats 
working out for them. Probably more marketing hype than anything.
I can certainly confirm that my 20" rims appear to give me superior straight line acceleration to other riders on 26" rims. 

-h
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