• Posted Feb 22, 2006

If mountain bike evolution is studied in the future, 2006 will be the benchmark year for 29" wheeled mountain bikes.

Beast of the Burgh, Part III by Michael Browne - Dirt Rag View Other Articles from Michael Browne If mountain bike evolution is studied in the future, 2006 will be the benchmark year for 29" wheeled mountain bikes. Sure, Dirt Rag has been writing about them since issue #82, but we're just a small blip on the radar, hardly pointing to any mainstream acceptance of a trend. But 2006... oh yes my friend, '06 will be the year of the big wheel. Message boards are filled with 29" topic threads, availability of 29" wheel-related products are increasing (a total of 4 suspension forks, we're nearing the dozen count for tires, and we even have companies launched on the 29" wheel platform). I think it's safe to say that any company worth its salt would be silly not to be at least considering the launch of a big-wheeled bike Yet skeptics remain. And I must come forth and proclaim that I am one of them. Oh I'm sure there's a 29" wheeled mountain bike out there that would make me feel at home, make me ride faster, longer and get over bigger obstacles. But I have a couple unique genetic dilemmas that have forced me to accept 29" wheels as only half of a solution. In the past, I've written about the 29/26 combination, or what I called the Beast of the Burgh. Due to my short inseam and penchant for snappy handling over obstacles and quick uphill acceleration, I modified my Vicious Monolith singlespeed into a bike with a 29" front wheel and a 26" rear wheel. I replaced the original suspension-corrected for 80mm 26" rigid fork with a 29" rigid fork with an axle-to-crown length that would minimally affect the original geometry. I ended up with a rideable rig that I found to offer a good balance of attributes of both a 26" and 29" wheeled bike. Some people called it ridiculous, others approached it with intrigue. Some even came to the idea with their own prototypes, having simultaneously developed the idea and furthered it with their own design expertise. John Castellano, of Ibis Ripley and BowTi design fame and founder of Castellano Designs, is one such person. During some recent late afternoon email banter, John mentioned his 50/50 idea. Not to be confused with the newest Crank Brothers pedal offerings, John's mention was in reference to a purpose-built 29/26 creation based on his SilkTi short travel pivotless rear suspension bike, which sparked my interest and inspired the following Q and A session. Dirt Rag: What kind of rider benefits from a 29/26? John Castellano: I built the first 50/50 for my wife as an experiment to see "how small a rider can benefit from a 29 front wheel". She's 5'3" with 30" leg length. It worked better than I thought. She says, "It instantly opens up all kinds of new lines—they just become obvious...26" is so arbitrary--like the 175 cranks used for everyone" So I think the bottom line is: anyone who fits on one can benefit. The 50/50 has great climbing geometry, but with the big wheel, it "rocks" and descends very well too, especially on technical up and down steep sections, as I'm sure you know." Since rider height is the main determinant of CG height, I choose frame sizes (ie wheelbase) for each model based first on height, then on leg length. However, the wheel size options are driven by leg length, for standover reasons. Whereas my smallest SilkTi 29" (15"center to center) fits down to a 31" measured leg length, a SilkTi 50-50 (13" c-c) fits down to a 29.5" leg length. For reference, a SilkTi 26" (13" center to center 26er) fits down to a 29" measured leg length. I'm 5' 9 1/2" and went with the 29, although a 50/50 in my size would be a blast too. Over about 6', everyone should probably be on a 29. So, my 50/50 is ideal for riders about 5'3" up to maybe 6' tops, with at least a 29.5" measured leg length. Dirt Rag: What were the design challenges on SilkTi 50/50? John Castellano: I discovered that the cockpit lengths were about a half inch shorter with a 29" front. This happens because as you lengthen the fork, the bars move closer to the seat. So, I add a 1/2" to the toptube for the SilkTi 29 and the 50/50. This helps with toe overlap issues too. I also use one-degree steeper head angle to compensate for the extra trail from the big wheel. The tall front end also presents a standover challenge, so I squeezed the shortest headtube (3.75") I could with my big tubes (1.75" down tube and 1.5" top tube), and I dropped the rear of the top tube as low as I could. Finally, I believe 10% bigger wheels need 10% longer bars. There aren't many long flatbars out there, so I use the Salsa ProMoto Flatbar which comes 26" wide and has 11deg sweep, which compliments the extra width. I run 25" width and Marisa runs 24". Dirt Rag: What are some drawbacks of retrofitting a 26" frame? John Castellano: You and I both prototyped the 69er the same way with the Surly 1x1 rigid fork. I used it on my Fango designed for 80mm travel. So the main drawback is loss of 80mm of travel. The head angle really needs to be about a degree steeper to lessen trail, and the top tube to be longer for fit and to avoid overlap. The seat tube and head tube should be short as well. Dirt Rag: Some people are looking to retrofit 26" frames rather than buy a purpose-built 29/26. What recommendations do you have? John Castellano: I think the best frame to convert would have a long toptube, with a steep head angle and/or a long fork length. Maybe a 150mm travel North Shore-style "freeride" hardtail. You can also minimize the negative effects of the retrofit with longer handlebars to compensate for the extra trail. Stop by a local bike shop and check one out today! [photo: - The first and only production mountain bike company dedicated solely to the 29er movement] Ride LARGE.

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