Thursday, October 01, 2009

The Conundrum

Every so often the subject of head angle, offset, and trail comes up and trips up the average mountain biker that is just getting into 29"ers, or is thinking a bit deeper about that next big wheeler for the stable. It never ceases to cause mass confusion and statements of "fact" are bandied about that are at best misunderstandings, and at worst, down right fairy tales.
Why is that? Well, part of the blame rests on 26"er geometry and how we as mountain bikers relate to the "known" quantities that represents. Head angles are within a relatively narrow range, offsets are practically locked in, and the handling traits of the segments of mountain biking they represent are codes to live by when buying a new bike. Vast experimentations happened with 26 inch wheels, but that was 25 years ago now. Before a lot of mountain bikers knew about bicycles, or were even born.
When 29"ers became popular enough that Gary Fisher Bikes convinced Fox and Rock Shox to do customized suspension fork offsets for them, the can-o-worms opened up on geometry for wagon wheelers and the old way of codifying handling wasn't working anymore. Call it geometrical chaos. What fork "works" with what head angle. What offset is "best" for trail riding in Fayetteville, Arkansas? What about swapping G2 forks to non-G2 frames? And on and on.
I ended up trying to help solve some of the mess with my fork offset tests that I ran for the better part of 2008. I wrote other posts about the subject as well. Still, I am just one measly voice in the midst of a huge forest. The confusion rages on unabated as more new riders come into the 29"er realm and find out things are "not quite right" with the geometry of big wheels.
Interestingly, the whole of the questions seem to revolve around "what works" and "what doesn't work". At least in a general sense. The term "works" means a lot of different things to different people, unfortunately. My take on it was, and still is that it "all works". You just need to try it "all out" and see which flavor suits you, your riding style, and your trails. Trouble is, most folks balk at experimentation, thinking things through for themselves, and researching. They just want to know "what works".
So, anymore I just have a bit of fun with this. I throw my Blackbuck, pictured above, out as an example. I call it "The Conundrum", the bike that shouldn't work at all, but does, and does so quite well, thank you very much. The numbers, which folks like to read and read in to, are off the charts with the Blackbuck. A huge offset- 51mm- is used. A super steep head angle is the result- 74 degrees- which is a full two degrees steeper than most any 29"er considered to be "twitchy" these days. Even the axle to crown is shorter- 440mm- which is "out there" for 29"ers in that measure. So what you get is a geometry that on paper seems to indicate instability to the point that the bike should be unrideable off road.
Nothing could be further from the truth. It "works".
And I guess that is the best way to leave things. It either will get some folks to think, or just laugh it off as coming from some nutcase and they will go right back to their pontificating and debate.
It's all good. I'll be smiling broadly as I speed through the woods on the bike that shouldn't "work"- but does, all because of the stability of 29 inch wheels. It ain't rocket science folks.

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