Cyclocross - Difference between 48 vs 50cm Redline?

By looking at the specs on Redline's website it seems that the only difference between the 48cm and 50cm bike is the seat tube length. Am I currect in assuming this? It's wierd how they measure their bikes, I have a 50cm Redline right now that has a 50cm seat tube of 50cm c-c and about 55cm c-t but a top tube of only 52.2 and I have a slightly longer stem on there, a 110 because I ride a road bike with a 54cm top tube and 100m stem. Now, I know that people say that when you're sizing a bike it doesn't really matter what the seat tube is as long as the top tube is your size but the whole reason why I got the 50cm is because the 52cm which had a top tube of 53.5cm had a seat tube c-t of like 57cm so I actually couldn't get my seat down low enough. If everything but the seat tube is the same on the 48cm and 50cm I'm actually thinking bout going for a 48cm but the bike shop said it would be too small for me? But how would it be too small with the same size top tube and a c-t seattube of like 53cm? My current road bike has a seat tube length c-t of 50cm but TT of 54cm. Anyone have any comments about this?

Dave

How tall are you? I'm 5'5" and a 48cm Redline Team CX is a perfect fit.

I'm 5'7'

Dave

I've heard "Redlines run big" but I'm not sure what that means. Sounds like your best choice is keeping the 50cm you have. Why are you thinking about getting the 48cm ? Does the 50 feel too big?

I'm not sure you can go by the 2003 geometry that's listed on their website and some of it just seems plain wrong.

I also believe Redlines run big. For example I am 6'2" and my Conquest Tour is a 56cm when I would normally ride a 58cm on most other bikes. As long as the bike fits fine, I guess it doesn't really matter what the size sticker says.

Again, it doesnt matter how tall you are, but what your inseam is. I have always been told that when it comes to cyclox you should go 1 size (frame size) smaller than you would a road bike. I have a 32" inseam and ride a 56cm.

Isn't sizing fun? For whatever reason I'm often between sizes, and I've bought and sold a few bikes trying to get it just right. For me, it's better to go through the trouble of doing the exchange than to try to make a big or small frame by other means.

I say try to find a 48 and do a side-by-side comparison.

Having just spent a lot of time trying to find the right cross bike, let me pass on a couple thoughts. In general bike fit is all about stand over height and top tube length.

I went to a local LBS and was measured for a bike. A system similar to, but a little more complex, than the system used by Zinn. http://www.zinncycles.com/newfitform4.aspx. I took the "bike recommendations" and went shopping. I found myself "fitting" on several sizes, depending on brands. Gunnar, Redline, Bianchi, Ridley. Using the measurements I was "fitted" to a different "sized" bike in every case.

Ended up going for Gunnar steel! Fits Perfect.

Either use the Zinn link for measurements or get measured. I wish I had done so long ago and eliminated a lot of the guess work I have been suffering through.