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Tech FAQ: What's the big deal with 650b?

  • By Lennard Zinn
  • Published Jun. 26, 2012
  • Updated Oct. 11, 2012 at 4:51 PM EDT

Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
Dear Lennard,
As you are likely aware, the latest hot topic in the mtn bike world is 650b. Opinions range from the “best of both extremes”, the ideal size, to worst of both worlds, marketing ploy by companies that missed out on the 29″ boom.

Kirk Pacenti, the driving force behind the “movement,” notes that the wheel is better suited to trail and AM suspension @ 150 cm and 160 cm than 29″, and still has better roll than 26.”

So far only “microbrew” sized companies have signed up for 2013, now that Fox and RockShox forks will be available, plus more rims and tires every day.

No Trek, no C’dale, no Specialized, no Santa Cruz.

Indeed, now that the initial euphoria starting when Nino Schurter won a WC XC race in March on a prototype Scott Scale has wound down, the backlash has started. One recurring meme is what exactly is the diameter and how does it compare with the other two wheels? When using the generally accepted mtb method of measurement (OD with inflated tire mounted measured in inches) it appears fairly simple and obvious: 27.5 is halfway between 26 and 29. But because tire heights are not uniform the naysayers argue that these denominations are meaningless. Comparing ISO/bsd measurements, generally used for road bikes, is worse than mixing apples with oranges. Kirk Pacenti picked the name 650b instead of 27.5 creating the potential for confusion in consumers at the outset; it seems that there are some in the industry who simply don’t like or want a third wheel size who are intent now on exploiting the confusion, trying to nip the middle wheel off in the bud.

Have you formed any opinions at this juncture?
— Doug

Dear Doug,
Kirk Pacenti did not invent the 650b size or the name for it, and it was natural that he would use the name that already existed for that rim size, especially as 650b mountain bikes have existed for decades. The 650b size has been around for a long time — at least 50 years. It was a popular trekking and tandem size in Europe in the 1960s and 1970s, for instance.

When I was working in Tom Ritchey’s framebuilding shop in 1981, he made some bikes for himself and friends to fit some Nokian Hakkapeliitta 650b tires that Gary Fisher was importing. (At the time, Ritchey was building bikes that Gary Fisher was distributing through his shop in San Anselmo, CA, and they carried the Ritchey logo with “Mountain Bikes,” Fisher’s business name, superimposed over it).

The Hakkapeliitta tires were great compared to the 26-inch mountain bike tires you could find at the time. The Hakkapeliitta casing was supple, the weight was low, and the tread pattern was refined, fast, and quite aggressive, whereas the 26-inch tires of the day were just big square blocks on a heavy carcass. You could even get studded Hakkapeliitta 650b tires, as those were used for bike racing on frozen lakes in Finland, where the tires were made. According to Wikipedia, Nokian adopted the Hakkapeliitta name for its winter tires in 1936. It still uses it.

We used Super Champion 650b tandem rims back then, which were lighter than most 26-inch mountain bike rims of the time.

After all, you should remember that a primary reason 26-inch became the default mountain bike tire size starting in the 1970s and 1980s was simply that import duties on them were cheaper, as the US Customs Dept. charged a higher duty rate on adult bikes than on children’s bikes, and it considered 26-inch to be a children’s-bike tire size.

The sweet fillet-brazed Ritchey 650b bikes Tom was making then were great – light, nimble, and faster-rolling than the Ritchey standard-production 26-inch bikes.

When I left Tom’s employ and came back to Boulder, I took a Ritchey 650b bike with me and rode it for years, including in some cyclocross races as well as all over the Crested Butte area on my honeymoon in 1983. I loved that bike. It always drew lots of looks, because there were no others in Colorado at the time.

I built a number of 650b mountain bikes after I started my own framebuilding business in 1982, and my customers loved them, but when Fisher could no longer get the tires in 1983 or 1984, I quit doing so.

I built my first recent 650b bike in 2008, after Pacenti came out with 650b tires. It was a titanium bike for an ultra-distance rider who does brevets and events like Paris-Brest-Paris on the road and wanted a single mountain bike with which to do the Great Divide race as well as Alaska winter races on the Iditarod trail, plus she wanted to be able to other long-distance dirt rides. She originally wanted a 29er, but due to her short stature and the multi-purpose demands of the bike, I talked her out of that and into the 650b size instead. It worked out ideally for her purposes. She did those races on the bike, and she has three sets of wheels of entirely different rim size for it, which, thanks to disc brakes, can all be used on it. She has the 650b mountain bike wheels and tires (see photo), a 26-inch wheelset with the Alaskan SnowCat rims from All-Weather Sports with super-fat snow tires on it, and a 700C set (yes, this is what a 29-inch wheel uses – the same size as a standard road rim) that she has mounted up with cyclocross tires for fast dirt riding on smoother trails.

I certainly think that there is room and reason for 650b tires and rims to exist as a choice on mountain bikes. I think that it makes a lot more sense for wheels to be proportional to rider height (as they tend to be on kids’ bikes) than to simply jump on whatever happens to be the popular size of the moment.

When I see five-foot-tall women on little tiny 29er frames with giant wagon wheels front and rear, I cringe a bit at the design compromises that had to be made to the frame to allow a short person to ride it and not have toe overlap of the front wheel. Sure, I can understand the interest small riders might have in having a faster-rolling bike that perhaps assists them in riding with more confidence on technical descents as well as on riding whatever is the current fad, but a 650b would be a much more rational choice for short riders intent on graduating from 26-inch.

As for the resistance to 650b, the bike industry has never been one to accept change easily. There is always a backlash to something new. I don’t see that changing anytime soon.
― Lennard

 

Read also: Turner joins the rise of the 650b

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Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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