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Old 07-27-2013, 03:01 AM
Busy Scissors Busy Scissors is offline
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I can't answer the underlying physics of it, but I do know the differences between a 29er and a 26er mountain bike.
The salesman are basically making things up, but it's not their fault. The bike industry needs to find a way to sell more bikes, but innovating the bicycle is exceptionally difficult. So you get these incremental, borderline-bogus, changes like 29ers which the whole industry throws their weight behind. Particularly in the US - some major manufacturers have dropped 26ers from their hardtail range and 29er HTs are now standard.

Most important and unequivocal difference first - 29ers look better if you're a very tall rider who needs a large frame. Riding an xtra-large frame on 26 inch wheels makes you look like a bear riding a child's bike at the circus. Conversely - if you ride a small frame (like a lot of women for example), then 29ers look like clown bikes. Aesthetics are important, let's face it.

For performance differences - the larger wheel size copes a bit better with low-level technical stuff, fast rocky trails. It seems to enable a bit more momentum to be carried through the trail chatter. It's really marginal though. Loads of head to head comparisons have been done in the MTB press and you're talking a difference of a few seconds over several km, with a pro-rider in the seat. 29ers are now common in pro XC racing, where you get these sort of trails. So there is a tiny performance gain, but this is really driven by the industry needing to sell something that looks new.

The other side of the performance issue is that 29er HTs feel a little more cumbersome on tight, technical trails (true, IME), So the dogma is that a 26er HT is a better bet on more difficult trails. 29er full suspension bikes are not really in the discussion - or they shouldn't be. It's v difficult to accommodate the larger frame size without compromising the suspension design, so existing 29er FS bikes are not that good.

There's a another standard that is vying for market supremacy - 650B, which I think corresponds to approx 27.5 inch wheel size. Some major bike lines have been launched with this recently (e.g. Santa Cruz Heckler, orange 5). There you really are in the realms of complete cynical bullshit.

Last edited by Busy Scissors; 07-27-2013 at 03:04 AM.