Re-Inventing the Wheel.



The bike business is a business like many others, ideas come and ideas go, some good some bad and many are just there to let people know that the company ain’t dead. Every once in a while an idea comes along and just kind of hangs in the periphery, just waiting for their time to come. One such idea is 650b wheels, not that the 650b wheel is a new idea, hell it’s not even an old idea it has been around for decades, but to mountain bike designers and riders it is relatively new. There are some people, and I myself am one, that contend that if we had designed mountain bikes from the ground up in the beginning instead of modifying road bikes and cruisers to go biking in the woods, we would probably have opted for 650b wheels right from the start, however modifying frames led us to the smaller 26 inch wheels that then became the mountain bike standard for so many years.
        A few years ago we made the quantum leap to the 700c wheel, more commonly referred to as the 29er, which has made a huge impact with off roaders. This has made it difficult for the 650b though. Going so long with one choice, the 26, then adding the 29er quite recently has meant some reluctance from mass manufactures to add yet another wheel size and different bike geometry to already swollen product lines. Luckily the fear of being left behind by the competition has won out and we are seeing many choices from frame companies along with tire and rim manufacturers for 650b. This is very good news. And here's why; Choices.
As mentioned before the industry standard 26inch wheel MTB has been around since the start of mountain biking, the 29er or 700c MTB wheel is a relative newcomer and the 650 b is the new kid in town. The important thing to keep in mind here though is to not disregard any of the old wheel sizes just because there is a new one. They all have their place when looking for a new bike.
During this bike season we have seen a lot of new customers, which is very nice, a lot of new MTB’ers have come through the door as well and a good deal of them have opted for the 29er. Now don't get me wrong a 29er is a fantastic machine but it is not for everybody.
Designing frames and frame geometry for big wheels is tough, sure anyone can build a bike to accept big wheels but getting the handling and feel dialed in is a very different matter and it is especially difficult getting it right on mid to small frame sizes. We have seen many, many riders lately that look like they have been swallowed whole by their bike and, while this arrangement is fine for a gentle trail ride, on a more MTB specific trail or good single-track it must be akin to riding a bull elephant with colic.
Before I carry on let me clarify what we actually mean when we talk about these different sizes. Below are the measurements, in millimeters across the wheel, bead to bead. The bead of a rim is about 3mm down from the top of the rim.

26        559mm
650b    584mm
29er     622mm

As you can see the 650 falls about midway between the other two you will also note that the bead seat diameter of the 29er is the same as a standard road 700c so why do we call it a 29er when it is really only a modern 27inch road wheel. Well it is because some bright spark decided to measure the diameter outside to outside with a fully inflated mtb tire on, which gives you a measurement of roughly 29inches. Confused yet?
Anyway, back to the business at hand.  If you are a tallish or leggy person the big wheel option is definitely a choice for you. The frame size will be plenty to accommodate the extra clearance while still maintaining the ride characteristics of a good mtb. All the rules of bottom bracket height and head and seat tube angles still need to be obeyed and they can be with a mid to large frame size. However, if you are, shall we say a little vertically challenged, this is where problems arise. The rules of designing a bike to perform well for the rider tend to get thrown out the window and it all becomes about designing a small enough frame to at least reach the pedals on while the design is sacrificed to fit a big set of wheels. This really does not work. The cut off for a bike designed for the rider instead of the wheels generally falls somewhere around the 5’6” mark. There are exceptions for those with exceedingly long legs in relation to body height but generally speaking this is where sticking with the 26” wheels tends to be the better option.  Now though we have another option 650b.  This is where the slightly smaller size gives us, as frame designers, much more scope to still design the bike for the ultimate ride and handling but still giving the option of bigger wheels.
A Soma "B-Side" Built and ready to roll.
For those wanting to know more about the options available in the 650 or 29er range stop in or fire me an email. There are lots of choices. At the moment some of the best 650b frames tend to be from companies like Soma who offer the B-side. I expect some of the major names to start producing complete 650 bikes in the next year’s product line.
Posted on September 23, 2012 .