Originally Posted by
tomdaniels
So now, I want to minimize the length of the contact patch to drop my rolling resistance.
Doesn't work that way. Rolling resistance is created by the energy needed to flex the material of the tyre; it isn't eg drag between the contact patch and ground. So the size of the patch is irrelevant; it's the rate at which material enters and leaves the patch that matters. You'd think this would mean that width is key, but there can be situations when a wider lower pressure tyre (and hence a larger patch) has lower rr; see
http://www.bicicletta.co.za/Download...llustrated.pdf
- very useful paper if you mountain bike, or even ride gravel roads.
This might be useful too -
http://www.schwalbetires.com/tech_in...ing_resistance
Why do wide tires roll better than narrow ones?
The answer to this question lies in tire deflection. Each tire is flattened a little under load. This creates a flat contact area.
At the same tire pressure, a wide and a narrow tire have the same contact area. A wide tire is flattened over its width whereas a narrow tire has a slimmer but longer contact area.
The flattened area can be considered as a counterweight to tire rotation. Because of the longer flattened area of the narrow tire, the wheel loses more of its “roundness” and produces more deformation during rotation. However, in the wide tire, the radial length of the flattened area is shorter, making the tire “rounder” and so it rolls better.
...Wide tires only roll better at the same inflation pressure, but narrow tires can be inflated to higher pressures than wide tires. However, they then obviously give a less comfortable ride.
In addition to this, narrow tires have an advantage over wide ones at higher speeds, as they provide less air resistance.
Above all, a bicycle with narrow tires is much easier to accelerate because the rotating mass of the wheels is lower and the bicycle is much more agile.
At constant speeds of around 20 km/h, the ride is better with wider tires. In practice, the energy saving is even greater than in theory as the elasticity of the tires absorbs road shocks, which would otherwise be transferred to the rider and so saves energy.
I've seen similar stuff from other manufacturers, who seem quite frustrated that most people are buying narrower tyres than is optimal.
On a good road surface the material of the tyre is the main thing to worry about. Schwalbe and Conti now make some very low rr wide tyres, eg the 38mm Marathon Supremes.