Saturday, September 14, 2013

On Wheel Size, Again

About a year ago, I posted results of an amateur experiment that nevertheless showed that, as expected, the overall wheel size and its contact with ground depends largely on what size tire you mount to a rim.
Today's ride at Tolt McDonald tree farm made me think about wheels, or horses for courses, so to speak.

As you see from the map above, there are lots and lots of tight trails at Tolt McDonald. I rode here as my first mountain bike ride in Washington in the winter when trails were muddy and roots and rocks slick.Those conditions were just a hair above my comfort level. Today it was bone dry and I could hit the turns at speed. Each hairpin turn had a tree at its apex (and everywhere around) and the roots of that "apex" tree of course cross the trail. The trick is to lean the bike into the turn and use the roots as a natural bank. If you slow down and hit the root in the middle, your front wheel will likely slip - there is nothing worse than loosing your front wheel in a turn. If you take the turn too wide, you hit the tree.

Today, I was having too much fun on these trails and I practiced a perfect line through each turn while staying on top of tall gear. Yet quite a few times, I had to wrestle the bike (Ibis Mojo 26-er size XL) to "fit" into the tight space. If I rode a 29-er here, I would be hopeless. Yes, it would roll better and I could perhaps lean the bike more due to the larger tire contact and traction, but a wheelbase is a wheelbase and some law of physics says bikes don't shrink much at 8mph.

No other bike color would do here
Don't get me wrong, I love riding my (and other) 29ers. In April, the RM 970 was fantastic on wide open Utah trails and excelled on rocks of Porcupine rim. Last week during the cyclocross race, I could pass much faster guys by taking the inside of grassy turns on my 29er. I guess not because my wheels with big 2.2 tires would be more nimble (actually, a road 700cc rim with a 23c tire is basically a 26-er), but because the tire side knobs had lots of grip. I can also convert my 29er to a commuter or touring bike by using 35c slick tire (more on touring setups in a next blog post).
So again, do I have a need for a 27.5" wheeled bike? I personally think not, even if I had just one bike, 27.5" would be a compromise. For Washington and BC singletrack, I take 26. For everything else, there is a 29er (and a Master Card, of course).

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