Using PowerCalc to predict performance due changes in crank arm length.

So I got a hold of a set of 175’s in really good shape for 20$. The difference in the actual cranks and my older cranks is that the new ones have the five arm configuration, so changing rings for fine tuning my gear inch development would take 15 minutes versus impossible.

These are my findings using PoweCalc

Problem: 7% hill on 74 g.i. is a bit tough –

170 = 51.14 pounds @ pedals @ 52 rpm = 08.00 mph. – 291 watts @ pedals

175 = 51.14 pounds @ pedals @ 36 rpm = 11.22 mph. - 425 watts @ pedals!

I do not get it … I will use less pressure on the pedals, yet wattage increases.


Problem: 10% hill @ 5 mph on both cases.

170 = 71.28 pounds @ pedals. 247 watts.

175 = 68.87 pounds @ pedals. 247 watts.

Is Wattage a function of pedal pressure?

In my opinion, it should be …. But PowerCalc seems to disagree.

Who knows this stuff well?