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Front tire size (120/60 vs 120/70)
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  1. #1
    Member coov9521's Avatar
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    Default Front tire size (120/60 vs 120/70)

    My bike has stock a 120/60. Can/should I go to 120/70? What's the difference?

  2. #2

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    Yes!! 60 series tires are only good for planting flowers

    Make sure you drop your front forks to keep your geometry the same with the taller tire

  3. #3
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    Quote Originally Posted by coov9521 View Post
    My bike has stock a 120/60. Can/should I go to 120/70? What's the difference?
    120 is the width in millimeters, and the 60 or 70 is the height of the sidewall as a percentage of the width. So, your 120/60 tire has a sidewall height of 72mm (assuming my math is correct). A 120/70 has a sidewall height of 84mm. That is 12mm of difference, so the axle is 6mm higher off the ground with the 70 than the 60 and so is the triple tree, thus throwing the entire geometry of your bike out of whack. Therefore, to expand on what Dave stated, you can use the 70 series, just raise the forks in the triple (lower the triple tree) by 6mm to counteract the 6mm in sidewall height. Or, raise the rear by 6mm, therefore making your bike a total of 6mm higher all over, increasing ground clearance but still affecting handling. Not that any of us would notice it that much.

    In sum, do what Dave said above. 6mm of forks above the top triple is your magic number to return your bike to its original baseline if you install a 70 series tire in lieu of your 60. And watch the clearance on the front fender.

    Of course, all of this is negated if you have your suspension professionally adjusted, and you use a special tire or a slick. But that is a different conversation altogether.
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  4. #4
    Member coov9521's Avatar
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    Damn--I was researching this on the web all last night, and in just two replies got the best explanation! This makes perfect sense. Thanks guys!

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