I've recently had the opportunity to ride a number of bikes, and am seeing a lot of discrepancy in what should fit vs. what does fit. Is this normal?

I'm 5' 10", 175#, 31-32" inseam. The sizing charts from most companies put me on a medium to large bike with a 19.5"-20.5" (495-520mm) frame.

Yesterday I rode an XL bike, spec'd at 23" frame, 31.9" standover height, and an effective top tube length of 24". This thing felt really good. The top bar lightly contacts my crotch area when standing over it, but the length of the frame really lets me stretch out, and made me feel like I was getting more out of my legs.

Conversely, today I rode a Medium bike, 19.5" frame, 30.5" standover, ETTL of 23.5", and it felt like it was way too small. The shop dude said he was surprised, because if anything he expected me to say the bike was too big. And according to the specs this is the bike I should be on. It just didn't feel right, though. Cramped feeling fore-to-aft, and a feeling that the top tube is so far down there that I might as well be on a mixte or step-thru. Almost enough to give you vertigo...

Looking at spec sheets, and how measurements are done (when shown) I can see that different manufacturers measure things differently. For instance, I note that Breezer and Trek take top tube measurements at completely different points on the bike, so even if they were the "same size" the measurements would not match.

And then there's weight, which no one will talk about, "because there's no standard". Thanks, that helps a lot.

Is it just me, or does this kind of thing happen all the time? I admit I haven't bought a bike in a while, and have never spent this much time researching it, but it seems like these measurements should mean something. Do I just need to ride everything that catches my eye, in every size, till I find what's right?

-- Sam