The wider rim IMHO and observation makes for a flatter tire surface. I run thinner Mavic rims with 2.1s and get a more rounded tire shape. I also have Sun Rhyno Lites with 2.1 that seem flatter. Flatter gets better traction in loose graveling trail. Rounded seems to hug corners better on hard pack. I'm 220 and ride MTB only. This time of year in the desert SW hard pack is most everything.
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I think its disgusting and terrible how people treat Lance Armstrong, especially after winning 7 Tour de France Titles while on drugs!
I can't even find my bike when I'm on drugs. -Willie N.