Confirmation bias is always a danger if you can't do blind tests, which is what interested me about the fire road climbing results. They went against my preconceived ideas, so can't really be confirmation bias. Although I'll accept that there could be an element of trying a bit harder to minimize what you expect to be a weakness and in the process turning it into a strength. Obviously we'll never know. as I keep saying, this isn't science; just a bit of fun.
29er: Climbing Fire Roads
Big wheels work well on fire roads, it allows for the maximum efficiency gain of 29 over 26. They simply roll more efficiently and that advantage compounds up over long straight lines. I notice the same effect when we use roads to link trails. I'm surprised its even a question really.
On a flat fire road, yes, I can see that rolling resistance (including effect of bumps) will be key. But once you start climbing then you are mainly working to overcome gravity. OK, so a 2lb difference in weight is only about 1% of the total bike+rider weight and there is some evidence that the much quoted "fact" about rotating weight being more important than static weight may be a myth. But still, I'm surprised that the heavier bike was faster uphill.
But once you start climbing then you are mainly working to overcome gravity.
It's a factor but I'm not sure I'd agree with 'mainly'. I guess the experience tends to suggest otherwise, and friction and air resistance are still the main enemies.
Or perhaps the 29er rolling effect benefit becomes more advantageous as the gradient increases.
I don't know if I'm honest.
Air resistance is negligible on a MTB when climbing (unless there's a headwind). Rolling resistance and pedalling efficiency matter far more than bike weight but weight is both easy to measure and easy to feel so that's what everyone obsesses about. And of course in competition, with such close margins between places, fractional gains from weight savings can be the difference between world champion and first loser.
I don't know if I'm honest.
And i don't care, the bike I have now works better than the last one and the next will be better still. I've found what I like, so bollox to the rest of you.
Fireroads are an even enough gradient and surface to maintain a steady speed where acceleration and steering a wheel of greater mass is less of a disadvantage than when negotiating the variable gradient and surface of twisty singletrack. Consider a skateboard wheel versus a tractor wheel. One is easy to accelerate but readily interrupted by even a slightly uneven surface due to a tiny diameter. The other takes some moving from rest but thereafter rolls over anything as the huge diameter allows a very shallow attack angle over obstacles and the greater mass keeps the momentum going. The contrast between 26" and 29" wheels is less marked but the principle remains.
What ever you do, you need to measure the riders power output accurately (strain/speed gauged cranks etc)
Just like Singlespeeds vs gears, people tend to find they go quicker on an SS, this is because i think, if you have a lower gear you are tempted to change down into it, whereas with SS you just HAVE to MTFU!
So, we need a suitable course for 26/29 and enough runs to correlate average(or total) rider power vs speed
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