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650B - What and Why

by Ed 650Braley • June 01, 2023


Way back in 2006 our friend and 650b aficionado Ed Braley, was a contributor to Bikeman's blog with a series of articles on 650b bikes and 650b conversions.  Ed was an early adopter of the size and you might even say a pioneer in the 650b movement.  Big bike manufacturers had yet to fully embrace the tire size but customer interest was growing as evidenced by the number of visitors to our site to read Ed's articles.  Not long after these articles were published, 650b started to take hold on the mountain bike side of things as a goldilocks size between 26" and 29er and the industry settled on the 27.5 moniker to identify it.  When gravel riding became a "thing" along with renewed interest in bikepacking and general adventure riding, 650b started to take hold on the road side.  The industry played with "Road Plus" and similar names but none of those really ever took hold, thus 650b hangs on as the primary identifier of the size in those applications.  To this day we still get requests to bring back these articles for technical reference and posterity's sake.  So here we go, we're blowing the dust off and publishing them as originally written.  This is Ed's very first installment introducing himself and the wheel size.  Enjoy!    

Originally Published December 20, 2006

Hi, my name is Ed Braley, and Im the author of Bikemans new blog, the 650Blog. I'm wild about bikes, all kinds of bikes, but I have a special passion for a special kind of bike: the fat-tire, all-roads bike, the 650B-wheeled bike. Over the coming weeks and months, the Bikeman 650Blog will introduce you to the world of the 650B-wheeled bicycle. So lets start rolling with an explanation of the 650B wheel.

Trek Pilot Conversion
Trek Pilot Conversion

Not to be confused with the time-trial and women's-specific 650C wheel, the 650B wheel is all about comfort, versatility, and speed over varied terrain. The key to this is all in the tires. A 650B rim with a 38mm tire inflated to 45psi can deliver an astonishingly comfortable ride over rough roads and loose surface materials. And yet, it is surprisingly fast as compared to a similar 700C configuration. This 650x38B setup is about the same diameter as a 700C wheel with a 19mm tire, so although there's a large tire on the 650B rim, the extra weight is located closer to the axle where it is easier to spin-up. And the 650x38B setup rolls better over uneven surfaces than a smaller 26inch road bike setup. The 650B is a nearly perfect, mid-sized wheel option.

Fitting the Tire
Fitting the Tire

The 650B wheel is not new, in fact, it has been very popular in Europe for decades. Master craftsman with names like Rene' Herse, Alex Singer, and Jo Routens, - the "Constructeurs", as they are called, built very lightweight, multi-speed, high-performance, fast-touring 650B-wheeled bicycles with integrated lighting, racks, and baggage systems. And they utilized many innovations before the racing community adopted them.

650B Lotus
650B Lotus

The 650B has seen a revival in the United States in the last two years. Quality 650B rims and tires are in good supply. There are master craftsman - modern Constructeurs, who are now building fully integrated and artistic modern renditions of the classic fast-touring bicycle. These machines utilize today's designs, materials, drivetrain, and braking technologies. There are also a few, new, limited-production 650B-specific framesets being sold today. One of the most exciting aspects of the 650B wheel is that it can be retro-fitted into many existing 700C bicycles. By doing this, a racing or sport-touring bike with limited tire and fender capacity can easily be transformed into a machine suitable for use on all forms of pavement, chipseal, cobblestone, dirt, and gravel roads. It can be ridden on paths, and across fields, or even used on singletrack. A road bike with limited functionality can be made far more versatile with 650B conversion. I've been converting classic road bikes to 650B for over two years now, and I can say that they retain their sharp handling and maneuverability while adding the capability to comfortably carry the rider over the worst roads that anyone is likely to encounter. And yet these 650B-converted bikes retain most of their speed and quick acceleration. Sounds almost too good to be true, doesn't it? But it is true, and there is a growing body of 650B enthusiasts who are discovering this fact.

And it gets better: There is a new bread of high performance 650B bicycle coming into view. We are discovering that many modern high-tech production bikes can be easily converted to high performance 650B-wheeled sport bikes with new, readily available, high quality components. This is a very exciting time for the sport, and an exciting time to begin the 650Blog.

Heron Project
Heron Project

Over the coming weeks and months, the Bikeman 650Blog will introduce you to the world of the 650B-wheeled bicycle. We'll have a 650B photo gallery, which will showcase bikes from the master builders of yesterday and today, as well as examples of 650B production and conversion bikes. We'll show you the bikes: old bikes, new bikes, cool bikes, superbikes! We'll have how-to articles, and ideas and suggestions for creating your own 650B sport bike. We'll do product reviews, and we'll build some 650B machines that utilize those products. There's a lot of ground to cover on 650B-wheeled bicycles, so let's get started! We'll begin by showing you an example of a modern high-tech 650B-enabled sport bike, The 2007 Trek Pilot 2.1 650B conversion created here at Bikeman. We call it "Twenty Two pounds of 650B rocketry". In my next edition of the 650Blog, I'll tell you more about this Trek Pilot 2.1 650B, and just how easy it was to create this fantastic machine.

Ed 650Braley


Final De Barro
Trek Pilot 650B Conversion