Originally Posted by
meanwhile
This is stupid.
Because
1. When aero starts to become important wont be the same, even on the flat, for different types of bike and different tyres
2. It becomes important later going uphill because the other forces - gravity! - are greater. And the guy specified a STEEP hill
You mentioned online calculators, but you obviously don't use them! Here's a reasonable example for a rider on a steep hill at the speed you gave:
[TABLE]
[TR]
[TD="align: left"]Frontal Area[/TD]
[TD="align: right"] 0.50[/TD]
[TD]m[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient Wind Drag[/TD]
[TD="align: right"] 0.50[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Air Density[/TD]
[TD="align: right"] 1.226[/TD]
[TD]kg/m[SUP]3[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Weight[/TD]
[TD="align: right"] 75.0[/TD]
[TD]kg[/TD]
[/TR]
[TR]
[TD="align: left"]Coefficient of Rolling[/TD]
[TD="align: right"] 0.008[/TD]
[TD]dimensionless[/TD]
[/TR]
[TR]
[TD="align: left"]Grade[/TD]
[TD="align: right"] 0.050[/TD]
[TD]decimal[/TD]
[/TR]
[TR]
[TD="align: left"]Wind Resistance[/TD]
[TD="align: right"] 2.5[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Rolling Resistance[/TD]
[TD="align: right"] 5.9[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Slope Force[/TD]
[TD="align: right"] 36.8[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Cadence[/TD]
[TD="align: right"] 100.[/TD]
[TD]rev/min[/TD]
[/TR]
[TR]
[TD="align: left"]Crank Length[/TD]
[TD="align: right"] 170.[/TD]
[TD]mm[/TD]
[/TR]
[TR]
[TD="align: left"]Pedal Speed[/TD]
[TD="align: right"] 1.78[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Average Pedal Force[/TD]
[TD="align: right"] 101.4[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedaling Range[/TD]
[TD="align: right"] 70.[/TD]
[TD]degree[/TD]
[/TR]
[TR]
[TD="align: left"]Effective Pedal Force[/TD]
[TD="align: right"] 260.6[/TD]
[TD]kg m/s[SUP]2[/SUP][/TD]
[/TR]
[TR]
[TD="align: left"]Speed[/TD]
[TD="align: right"] 4.00[/TD]
[TD]m/s[/TD]
[/TR]
[TR]
[TD="align: left"]Power[/TD]
[TD="align: right"] 180.4[/TD]
[TD]watts[/TD]
[/TR]
[/TABLE]
So at the speed you specifed, work against weight will be FIFTEEN TIMES work against air resistance! And this is with only a 5% gradient.
...Bike performance calculators: knowing about them doesn't make you any smarter if you're not smart enough to freaking USE THEM!
4 m/s is 9 mph, not the 11 mph of the faster bike.
When climbing hills, your average rider is going to be, in general, less aero than usual.
But, yes, it all depends.
And even with the example here, the effect with the given rider weight is 7.7% at most, and this only for climbing very step hills.
There are other effects that will make a bigger difference sooner for most types of riding (changing the tires could on most 34lbs bikes will make a bigger effect that will be noticed everywhere, not just on hills).