[QUOTE=cjbruin;6416970]At 5'10", 33 inseam...a 56 is probably correct for a road bike...you may want to size down if you're looking at a tri/tt bike.
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If you are looking in the $500 range you are probably going to get a road bike. My advice is to not size down. If you decide that triathlon is not for you or you decide it is for you and you get a dedicated tri bike you can always turn it back into a road bike. If you size down you are going to have a very uncomfortable ride when using it as a road bike. A 56 sounds like it will do you just fine but remember a 56 with one bike manufacturer can end up being a 58 or 54 with another. Good luck and welcome to the sport!