I have to admit I don't remember a need for a 30.8 post before, not saying it hasn't happened. Just not enough to remember. Do you still have your 30.8 post? If so how snug does it fit (and this is some of the answer)? Do you need a longer post then currently? Was it stolen? Did you measure the frame instead of reading off a known post?


On top of all this is that post "sizes" are not actual measured sizes. Typically post are slightly undersized but can be over and even tapered a tad. It's all in the tolerances and production control. Think of the labeled size as clothing sizes, worth understanding but not always a measured truth. So what to do? Like buying clothes a post is really only judged by it's fit. Better shops have a range of old posts that they can use to judge a fit and then order (if not on hand) the one their experience and policies say is best. Andy