The treadmill does not work your calves and glutes as much as road running does. So I always tell clients to work with the treadmill on a 1% grade for a week and see how they feel before transitioning to the outdoors. This is only applicable if all you've been doing is treadmill running or if you're recovering from an injury. If you situation is otherwise, just go out and have at 'er, see how it goes.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS