I have seen more and more reference to the 650b (27.5") mtb wheel size. Whilst I don't see any need for a new standard, does anyone know of any benefit to have a 27.5" wheel over a 26" or 29"?
While I understand there are currently 650b specific frames and wheels I haven't seen forks yet.
Also can someone please make a 650b tag, I don't have the rep yet. Thanks.
You might want to take a look a this question which discusses the advantages of 29" over 26".
650b (or 27.5") falls somewhere in the middle and therefore performance characteristics will be somewhere in the middle of the two. For instance, 650b would be faster than 26" but slower than 29" at same chainring/cog. It would also roll over obstacles easier than a 26" but not as well as a 29". Also, the weight would be somewhere in the middle.
It depends on what type of riding you are doing to determine which is the "better" platform. Also, you should consider how easy it is to find parts in your area for a particular wheel. Since 650b is only starting to gain popularity, it might be difficult for you to find the tires you want, or to find replacement tubes at your local bike store. Also, I'm pretty sure you have to have a completely different frame for all 3 options, as tires aren't really interchangeable at that large of a difference. You could possibly put smaller tires on the frame than it is designed for, if you had disc brakes, but it might look odd, and might have weird handling.
Pinkbike recently did a little opinion piece it. To summarise they thought 29ers were better for open, fast XC; whilst the 26" dominated in downhill, technical sections. 650b (27.5") were considered to be poor in either domain, and not particularly liked by any of the 3 testers.
But remember it's all opinion and it really depends on what you do with a bike.
I know you tagged your question as "mountain bike", but there is also some interest in 650b for road bikes.
Jan Heine of Bicycling Quarterly is keen on wide 650b tyres for comfort without loss of speed.
...we chose 650B because it offers the best handling with wide tires.
The other reason you'd want 650b on a road bike is if you're a smaller rider (say 5ft 5in or less), or you're keen on very low trail. In these situations, slightly smaller wheels fit a smaller frame better, when 700C wheels might result in toe-overlap or uncomfortable geometries. The details are explained here.
The downside is that 650b tyres are harder to find, especially for road bikes.
I'd agree with what Kibbee said that the 650B is essentially "somewhere in the middle" and it really DEPENDS on the type of riding you do.
I did not test the 650 extensively, but being "better" is a very relative term. The 650 essentially is a compromise, so due to that, it is not better than the other platforms.
HOWEVER, in my opinion, 650 is closer to the 26. I measured the overall diameter of a few 650B tires, most are right at 27 (or even slightly under 27). That's only 0.5 inch difference from 27.5, but 2" smaller than a 29er really.
I made my mind up the first time I demo'ed a 29er. I ride mostly XC and wooded trails. The trails have steep drops and tight corners at the bottom, then steep climbs - essentially a lot of switchbacks along a ridge. Throw in a few flat fast sections, and even some techinal areas, these are my local trails. The 29er climbs MUCH better than my 26. It is overall much faster on my trails than a comparable 26. The only thing I would knock the 29er on is really tight twisty technical turns, but honestly it is not nearly as bad as I was lead to believe (or at least imagined in my mind). I still have my 26, but for my local trails the 29er wins hands down.
For my trails, I personally think 29er is better (i.e. faster, smoother).
The only noticeable difference between a smaller and larger diameter wheel is that larger wheels roll over obstacles slightly easier (~5%). Everything else, including speed, is negligible.
Otherwise, the main thing you should consider is if a bike with that wheel diameter will fit you. Bike fit is far more important; it affects not only your comfort, but your performance as well.
If you can't fit a 700c but feel comfortable on a 650b, then perhaps it is for you. 650b's generally have less parts (tires, tubes, etc.) available and at the same price though, so it'd probably be best to just go with 26" or 700c.
Reference for "rollover" ability.
I went from a 26 to a 29, you can go faster and the is more efficient, your wheel takes longer to turn the bigger it is making you produce less work. I would go with the 29, I love mine!
