With Specialized releasing their very first 650b bike, the Stumpjumper FRS Comp Evo, all three of the big boys in cycling have got on board with the latest wheel size craze. With all the hype and claims surrounding new standards in the modern world it can be hard to know if 650b is for you. This is why we've decided to sort the fluff and bring you this handy guide to 650b wheel claims.
Claim One - 650b Bikes Are Lighter
The first claim on our list is only half true. Although 650b bikes do offer weight savings over 29ers - sometimes up to 1kg! - 26ers still dominate in overall bike weight. This is mainly down to the unavoidable fact that larger wheels need more space in the frame which adds weight.
650b Wheels also offer the same problem with larger rims needing more material and weight. Standard 26" wheels are 5% lighter than equivalent 650b wheels but 29ers are a massive 12% heavier!
Comparative Wheel/Tyre Weight Between Wheel Sizes (More Is Worse)
Claim Two - 650b Wheels Are More Efficient
This claim is 100% correct, not only do 650b wheels increase rollover with their larger contact patch but they also reduce the angle of attack by -4°. Although this might not sound massive it is a big difference when on the trail. This rollover does come at a cost to acceleration though, with a larger rim the 650b wheel takes more effort to roll to speed - increasing acceleration times by a minimal 1.5%- although the added advantages eliminates this making them over all more efficient.
Comparative Angle Of Attack Between Wheel Sizes (Shallower Is Better)
When compared to 29ers, 650b also come out top. Although their angle of attack and rollover are slightly lower than what you normally get with a 29er the added acceleration advantage - 29ers are over 3.6% slower to accelerate when compared with 26" wheels - overcomes this creating the most efficient wheel size.
Comparative Acceleration Rates Between Wheel Sizes (More Is Worse)
Claim Three - 650b Bikes Are Perfect For The Vertically Challenged
If you want larger wheels then yes, they are perfect for shorter riders or women - although like most claims on this list, it doesn't hold much weight against the standover clearances of 26" bikes.
29" wheels in the smallest frame sizes and on women's bikes can either create an awkward riding position or require a negative rise stem, this compromises the overall riding enjoyment of the bike. With 650b wheels the frame's standover and geometry can be matched throughout the range, this allows the largest and smallest rider to have the exact same experience when riding a bike.
Not The Friendliest Front End Setup On Emily Batty's Trek Superfly Elite 29er
Claim Four - 650b Wheels Compromise Bike Geometry
Bigger wheels need bigger frames, this is a fact you can't escape from but that doesn't stop bike designers from creating amazing bikes. When 29ers first came out they sucked, this was because many manufacturers just bolted bigger wheels to their proven geometries.
In recent years 29ers have gone from mediocre to impressive, this is mainly due to rethinking the way bike geometry is affected by wheel sizes.
650b have gained from this knowledge as bike designers focus on custom geometries to create the riding feeling demanded. Although certain areas like chainstay length will be affected by larger wheels, the move towards the death of front mechs will create even better bikes - with shorter chainstays than current 26" bikes!
Claim Five - 650b Bikes Offer The Best Of Both Worlds
650b wheels are commonly referred to 27.5" wheels - a false comparison - that has led most people believe that 650b bikes sit right in the middle of 26" and 29ers offering half the benefits of each. This is incorrect, 650b wheels are actually closer to 26" wheels coming in at 584mm without a tyre compared to 559mm for a 26er and 622mm for 29ers.
You might be asking, what does this matter? It matters a lot! This single fact means that 650b is better than the best of both worlds, with the weight and agility nearing that of a 26" bike - when i test rode the latest 650b Giant XTC I found it hard to even notice the agility difference, a nod to Giant's impressive geometry - with the added advantages of 29ers such as improved rollover and increased efficiency with less of the downsides.
Overall, 650b bikes offer the advantages of a 29er without the major downside such as reduced agility and more weight. Whether this is the future of the mountain bike is yet to be seen, I for one think they will become more popular but don't expect the old 26" and his bigger cousin the 29er going away any time soon. Fancy trying out a 650b bike? Why not pop into our stores for a demo ride or get your very own online today.