Originally Posted by
smallwheeler
it only took 81 posts for someone to say the obvious - it's about gearing.
With a 700 vs 20" going the same speed in the same overall gear ratio(this is what we are trying to compare). It seems the 20" takes more energy.
The rider, frame, pedals, crank, chain, frame, seat and seatpost and also the tires, rims, on both bikes are going the same speed. The only difference on the two bikes are the cassette, hubs and spokes are rotating faster on the 20" bike.
The pedal and crank bearings should have exactly the same energy loss--they are rotating at the same RPM on both bikes.
The wheel bearings and cassette to chain mechanical resistance will be higher on the 20" as they are moving faster. The tire to road contact patch will be different since the tires have different amounts of air to be compressed and the wheels are different.
The rider wind resistance should be close to the same as the rider is in close to the same position. Generally this is considered the main resistance we are fighting at 20 MPh---the wind resistance of the rider.
So it seems our conclusion is the faster rotating 20" wheel takes significantly more energy than the 700c. I can fully accept the 20" wheel bearings taking more energy but I don't think that is significant. (significant in this comparison means noticeably slower)
Interesting ...
Rick
I am just trying to think this through....