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A lot of you might will be surprised to see a dropbar 650b bike in our 2014 range (Col du Glandon). Whilst the ‘inbetweener’ wheel size is the current hot trend in the mtb world, we’ve been thinking outside of the box somewhat and have deemed it the ideal basis for an alternative format jack-of-all-trades dropbar bike aimed at both shorter and younger riders. Here’s why...
We already know that the 700c (622mm ETRTO/ISO) wheel diameter frame geometry is generally squeezed with too many compromises made on any frame any smaller than 48cm - the limiting factor being the (relatively large) wheel circumference working with the (relatively small) frame. Manufacturers have to work around issues like wheel/toe overlap which results in some pretty crazy exaggerated angles (like TT-esque steep seat tubes) as they try to make the numbers fit, but not necessarily work. So it goes without saying that a smaller diameter wheel is the answer allowing a little more breathing space in terms of frame design; but viable options are few…
650c (571mm ETRTO/ISO) might be the obvious choice for eeking out that additional clearance when drawing up a frame any smaller than circa 48cm, but the 650c size is not without its shortcomings… Introduced back in 1989, 650c wheels were hailed as the “the toast of triathlon”, the premise being that they were more aerodynamic than the 700c equivalents due to the weight distribution and lower tuck position they enabled with the frame geometry. Needless to say they had a short yet successful tenure in the TT/Triathlon marketplace and by 1993 changes to rules and technology meant that 700c wheels could do the job as well, if not better. As such, 650c tyre choice is very limited (usually only to the very narrow 19-23c range), hasn’t grown whatsoever since the mid 90’s, and neither is it likely to be growing anytime soon - effectively a dormant standard with very limited future scope. I personally wouldn’t ride smaller than a 25c tyre on the road now so why should smaller/younger riders have to suffer?
Traditional 26” (559mm ETRTO/ISO)? Sure, great tyre choice/options (right down to 1” road slicks), well established in the marketplace (spares/replacements everywhere), but a little too small in diameter and disproportionate for the 47cm size of frame we had in mind (and the type of rider)...
Enter stage left 650b with its 584mm ETRTO/ISO diameter, sitting as a nice middle ground between 26” (559mm) and 700c/29” (622mm), and, as you’d expect bringing with it advantages of both. From a frame design perspective it gives us that crucial little bit of breathing space to design a wholly uncompromised frame with sizing/clearance constraints associated with full size 700c wheels. Secondly, they roll just that little bit faster than 26”. To paraphrase a famous character: “They're not too big. They're not too small. They're just right.”
Tyre options for 650b/27.5” (584mm ETRTO/ISO) on the other hand, whilst somewhat limited now, are only going to grow and grow off the back of the increasingly popularity in the mtb market. Given the widespread adoption in the mtb marketplace is goes without saying that 12 months down the line we should have as many options in 650b/27.5” tyres as we currently enjoy with 26”. As is the case with current 26” offerings, narrow diameter slicks will undoubtedly follow the newly-introduced larger volume mtb knobblies – future-proofed, you might say! There are already even a few higher end options readily available like the Panarancer (previously Pacenti) Pari Moto, Soma Xpress, Grand Bois, etc.
Whilst being marketed as the latest and greatest standard to hit the cycle industry it’s important to remember that 650b/27.5” isn’t by any stretch of the imagination a ‘new’ standard. As is often the case, someone else has already been there and done that (similar to Cannondale using the old 25.4mm BMX seatpost standard on their new 2014 Synapse – clever, but ‘new’ only in context of use). In the case of 650b it dates way back to France (early 1950’s) where is was the wheel tyre of choice for Randonneur-style bikes (long distance tourers, where comfort was of the upmost importance mainly due to very poor road surfaces). The ‘650’ part indicates the outside diameter of the the rim and tyre it was designed for, with the ‘B’ letter (there is ‘A’ and ‘C’ also) used to indicate the relative width/height of the tire casing. A 650A, 650B and 650C tire would theoretically all share an outside diameter of 650mm, but since the 650A tire was skinnier than the 650B, the rim of the 650A would be larger to compensate, and thus require a larger diameter tyre. And therein lies the other big plus point for us of the 650b wheel standard – large volume, wide, fast-rolling (now widely proven that wider tyres roll faster – see below) and supremely comfortable tyres.
So, in a somewhat roundabout way, that’s the reason why we designed the Col du Glandon around the 650b wheel/tyre standard.
