Ok so im gunna build a new dj but im unsure of what frame size i should be riding im 5'10 190
Medium (22" "actual" not "effective" top tube)
Or
Large 22.5"tt
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If you look at Transition Bikes website, for example, they list the "Reach" measurement : Unsecure image, only https images allowed: http://www.sicklines.com/news-images/reach_stack.jpg
I generally like a longer TT with the larger wheels so my foot does not his so much in Xups. 5'10" is big enough for a large frame and you have some weight to throw around as well. I'd go bigger, but it's your bike and I don't know your preferences.