- Fat bike vs Road bike (bad) science
I rode my hill rep loop this am on my On One fat bike. I’ve previously taken my road bike up it.
Road bike (18lb, 23/25mm tyres @ 85psi) 3m 15s; fat bike (35lb, 3.8″ tyres super hard at 20psi) 4m 15s – 31% slower.
My weight is ~80kg, meaning the fat bike and I are around 9% heavier than the road combo, and so the fat bike rolling resistance is 22% greater* – interesting!
*the bad science bit: Assuming the same power. I’ve not got my powercal yet, so I can’t verify this, and I’ve not been riding so much since I did that time a few weeks ago, but my HR was in the same area for the climb, and I’ll re-do it once I have the meter.Posted 4 years agocookeaaSubscriber
Seems like a moderate, reasonable, scientific Approach IMO.
You’ve conducted the same test on two bikes, using the same rider and treating time taken as your measure, you’ve calculated the differences in mass, I’d say Aero is negligible for a climb (discuss) and you say you’ve maintained a similar HR for both (as good a measure of the work done as possible)…
I’d buy that 22% figure, applied to climbing, accepting an appropriate margin for error…
I supposed you could try to verify it by conducting a similar set of tests rolling along on a flat level surface, and coasting down, from a standing start. Both would probably require calculating the difference in frontal area to reconcile the aero differences…Posted 4 years agoigmSubscriber
Better riding position for power / efficiency on one of the bikes?
Huge Wallace-like grin on the fat bike causing aero-drag?
Perhaps try putting the fat bike wheels on the road bike to compensate for the different riding position and see if that affects rolling resistance?
Let us know how you get on with that last one. And if any spoons were harmed.Posted 4 years ago
ton – Member
bit harsh that Al……….
taxi25 – Member
Not sure if the 22% is only rolling resistance. I’d bet the road bike transfers power much better as well.
Despite what mfrs say, I doubt it. It’s a 2.5kg alu fat frame vs a 1kg carbon.
Speed is such that aero is irrelevant IMO (10mph av)
fisha – Member
When you say rolling resistance, are you meaning frictional tyre to Tarmac resistance, or inertial resistance of trying to get a heavier tyre rolling going uphill.
I mean the energy lost to tyre deformation at the contact patch with the road. As the speed is relatively constant the losses due to your latter affect are IMO small, though greater with the fat tyre.
I’m surprised this could be 22% but of course it would be way smaller given the errors involved.Posted 4 years ago
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