Cyclocross - Cyclocross Sizing? I'm at a loss.

Hi guys, this is a long, selfish question but any help is appreciated. Who knows, maybe some of the info will help someone else out here. Also, I know this has been asked before, but I have searched and can't find any definitive answer.

I am 5' 10" with about a 31" inseam. I like to ride a 56cm road bike, because I can keep the seat real low and stretch my body out. I also like to be level(ish) with the handlebars.

So now I want a cyclocross bike. Someone one town over is selling a 2005 Kona Jake for $400, which I think is a pretty good deal. He has no clue about bikes as it was not his originally, but he was told by someone that gave it to him that it is 57cm "from center to center." In 2005, Kona's frame sizes did not include a 57cm, just a 56 and 58. So it could be either of those.

But I don't know whether it is worth it to even drive an hour and a half out there to take a test ride. I have heard/read that cyclocross bikes run larger for their size but I don't know why. Is it because of the extra clearance on the ground? If I ride a 56cm road bike, is there any chance that I will fit on this bike with the seat all the way down?

I know that I won't know until I try it, but does anyone out there with any experience know that this is just a mismatch? Also, can someone tell me why cyclocross bikes run so much larger?

Thanks for any help to solve the mystery of buying a used bike.

http://www.cycle-smart.com/coaching/articles/crossbike1.html

Nevermind - but here is a GREAT article on cyclocross cycle setup.

Konas run big. Its PROBABLY a 56. I have a 52 that is Damn near a 54.

Since bikes are sized by seat tube, a 56 cross bike will be closer to a 58 road bike.

Did you wind up buying the Kona Jake?

I'm also 5' 10" 31" inseam and ride a 56" Tricross. I couldn't agree more in the comfort and performance advantages of a low seat that allows stretching of the body and legs, as well as handlebars closer to shoulder level. I tried the 54" and it seemed like a toy in comparison.

My theory is always look at the top tube length, called virtual top tube on non-horizontal (compact) frames. Advertised frame sizes mean almost nothing anymore. In the old days, a 57 meant that the seat tube AND the top tube were both 57. No longer.

My theory is always look at the top tube length, called virtual top tube on non-horizontal (compact) frames. Advertised frame sizes mean almost nothing anymore. In the old days, a 57 meant that the seat tube AND the top tube were both 57. No longer.

Word.

My Steelman has a 55 seat tube, and a 57.5 tt. I'm 6'1, and couldn't imagine anyone shorter than me riding it. Also, some CX bikes have a very high BB making the ST measurement moot. Anyone shorter than me would have a hard time straddling my "55".