- Mar 14, 2011
Seems you put very small wheels on very large frames. The way most bicycle frame sizes are measured is by the seat post length. However frame geometry can still be very different depending on model and manufacturur for the same size seat post tube. Still generally speaking a 24" inch frame would be for someone around 6'4"+.i have the 49 c.c. slant head 2 stroke engine on a 20" frame with 20" wheels and a 44 tooth sprocket. My friend has the 80 c.c. 2 stroke engine on a 24" frame, with 20" wheels and a 44 tooth sprocket. His motor is broken in, and mine isn't fully broken in yet.
his gets going from a dead stop better than mine does (more c.c. = more bottom end torque) but i can catch him once we get going and stay side by side with him at 25-28 mph.
he does weigh more than i do (i am 155 lbs) but even if i ride his 80 c.c. bike, i still get about 25-28 mph top speed out of it.
i think the 20" wheels takes away from some of the top speed because most bikes with 24" or 26" wheels seem to get a little more top speed than what we're getting with the 20" wheels.
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One would have a very difficult time keeping the crank from hitting the ground with a frame that large and wheels that small. Even with a 20" seat post tube would be for a person close to 6' tall. Probably still too large of a frame for 20" wheels and without having crank drag.
Now if you made a very common mistake of thinking wheel size is the same thing as frame size (these frames that use 20" & 24" wheels are generally a lot smaller); one could possibly put 20" wheels on a bike that had 24" wheels.
My desire here is simply to educate so that we're describing things with the correct technical terms.