So..I just picked up a frame set that I originally thought was going to be too small for me since all the bikes I ride now and that fit me are 59cm or 60cm. I'm 6'0 with an inseam of 34. This new bike is an Eddy Merckx Alu Sprint with a carbon fork (Never ridden a bike with anything Carbon on it). Really cool looking and surprisingly very light. It's a 56cm. The guy I bought it off was 6'1 and just replaced it with another bike the same size. Are new bikes different in fitting to vintage/older bikes? I'm really thinking about stripping my Merckx Strada and putting it all on this new bike. SO what's up with that??? I did a quick search but really didn't find too much info.

If by vintage you're talking 80's and 90's, no difference I know of. If you're talking 70's, there might be some difference with some bikes in terms of seat tube size, because sometimes the bottom brackets were a bit lower. This would mean you could straddle a little larger frame than on newer bikes. But a 1997 Merckx should be fitted like any other road bike today.

That is what I'm thinking, but then I remember going to an LBS and looking at the new bikes and they said I should ride a 56cm or 57cm. So....am I to assume that I'm going to have to ride a new bike with a really long seat post??

With a 34" inseam (assuming you are referring to pants size), yes, you are going to have a lot of seatpost showing. You will also have to have a lot of spacers under your stem or be in a very aggressive posture.
They like to sell new bikes with a 3 or 4 inch drop from the saddle to the handlebars because they assume everyone wants to look like Lance.

Vintage bikes (when new) were typically fitted so that there was about 1-2 inches of clearance between the top of the frame and your crotch (and that means 1-2" from a snug fit in your crotch, not 1-2" from anything that might be dangling). With a properly fit vintage bike, there was never any more than a handful of seat post showing. That changed in the mid-eighties, with the introduction of proportional frame sizing. Today, bikes are fit with much more clearance between the frame and the crotch, and much longer seat posts. Part of what's driving that is the theory that on racing bikes, you want the frame as stiff as possible, and smaller frames are stiffer than larger frames. So you get the smallest, stiffest frame you can possibly fit. Of course, that frame sizing theory should not spill over into non-racing bikes.

Here's what Sheldon "The Long & Short Of It" Brown had to say about vintage versus proportional frame sizing in his Revisionist Theory of Bicycle Sizing.

I think there's some amount of misconception about today's sizing. The really small sizing is just a preference that many racer types have, not a method. But if you use the method such as on Colorado Cyclist (the standard method almost everyone else uses), you're not ending up with an excessively small frame at all, but rather just the traditional amount of drop for a road racing bike. Mine is sized that way (it's a custom-made road bike), and I only get minimal clearance with the level top tube (less than an inch without shoes). That would normally put your handlebars probably a couple of inches below the saddle with a standard racing stem setup. I have an extended head tube, so my bars end up about an inch below (unless I use on higher stem, which is what I do most of the time). I don't have a huge amount of seatpost showing either. It's very reasonable. From my personal experience with my own bike (and others before it), the standard "inside leg measurement" times .67 (or .65 for ctr-to-ctr) gives just the right amount of standover. Even the next size up would probably have me resting on the top tube. I consider that to be classic diamond racing frame sizing applicable to bikes from the 80 thru to today.

I wear a 30" inseam and ride 55cm (C-T) traditional road frames, which I consider a perfect fit. With a modern low-profile (Serfas ARC) saddle, the bottom of the decorative fluting on my Campagnolo saddle is just barely covered by the top of the frame's seat cluster/clamp assembly, and I have just over a fistful of post showing. The bike looks right and feels right.

Well, I called my friend at the LBS and he thinks that the new Merckx I just got should fit me fine. I'm going to put some wheels,crankset and a seat and see how it "fits". If it fits, I'm going to kick myself since I just passed on a complete Orbea for a song that I thought was too small at 57cm. Just can't think it's weird!!

You need to check top tube/ virtual top tube lengths, too, particularly on frames with a sloping top tube. Modern relationships between the ST & TT lengths aren't always the same as they were on the "vintage" diamond frame.

Also are the frames sized (measured) c-c or c-t on the ST? Old [small diameter] TTs only add a little over 1cm from one to the other. Many modern TTs have a much larger diameter.

Not sure how you can fit on a 56 at 6 feet. I am 6' with a 34 inseam, and ride a 59 (c-c) frame, for example.

That's why I started this thread. All my bikes are 59cm or 60cm C-t-C. It just that the guy I bought the bike in question from ,was also my height and the guys at the LBS (who I trust) also said that it should be a good fit. My LBS has never tried to sell me a bike. In fact, they have given me a bunch of "old" stuff they don't have a use for. They also know that I'm into older bikes. Hence I trust what they have to say about 56cm Merckx fitting me, but till I build it and ride it, I'll be as skeptical as one can be.

This helps me explain to a new entrant a lot about why that 49cm Cervelo tri-bike fits him a lot like my 54cm Centurion Ironman.

And also why I'm 5'6 w/long legs and ride this 60cm Centurion Carbon. First, the measurements are off because of the frame construction and Second, the "boys" are a little more intimate w/the TT, but I'm having no problems whatsoever.

Nice bike!! If you can live with the top tube reach, I guess as long as the seat goes down far enough, you can "fit" on a larger frame, but as long as the boys are OK when you stand over the bike, go for it. When I say I ride a 59cm frame, here is my seatpost and stem height:

I think the issue is more complicated than most folks are pointing out here. Let me use two bikes I have as a example. My 1972 Bottecchia is 58.5cm C-C. My 2002 Bianchi is 54.5cm C-C. That appears to be a huge difference yet both bikes fit me. To begin with, the Bottecchia is "square", that is 58.5 ST/58.5 TT. The Bianchi is proportional - 54.5 ST/57.0 TT so although the frame on Bianchi is much smaller, the top tube length is only a little shorter. Even that is a bit of an illusion - the bars on the Bottecchia are the classic 'U' shape and the normal riding possition is either on the forward extension of the bars or in the drops on the long flat sections where your hands fit nicely. The bars on the Bianchi have that "anatomic" bend. The two positions that I mentioned as normal for the Bottecchia are unusable on the Bianchi. Instead, you reach forward and ride the hoods of the Ergo levers or, if in the drops, you reach forward to the flat part of the bend in the bar. The horizontal section of the drops where I would ride on the Bottecchia is too short to fit my hands on the Bianchi. Because of having to reach forward, that slight 1.5cm difference in top tube length is cancelled out and you have effectively the same riding position.

If I were to get the next size down Bottecchia, 21" or 53.3cm, it would also have a short 53.3cm top tube which would be much too short. If I put the handlebar and Ergo levers from the Bianchi on my Bottecchia the reach would be too long (unless I got a shorter stem obviously). So essentially you have to look at the modern frame as a package - top tube length, stem, handlebars, integrated brake/shifters, seat post, saddle - to arrive at an appropriate reach and then see what you get for a frame size. And typically it will be shorter than a traditional frame for the same reach.

Assuming the bikes you're talking about are later (mid 80's- early 90's?) then I would bet they use fairly modern dimensions. I'm 5'10" with a 30" inseam and a 56cm might be slightly large for me, depending on the top tube length if you consider that the 54.5cm Bianchi is just right. So if you are 2 inches taller than me with 4 inch longer legs (yeah, I'm shaped like Fred Flinstone) than your upper body is 2 inches shorter than mine but your arms are probably longer. Depending on just how long your arms are compared to mine, you might have the same or up to an inch or so more reach than me or 0-2.5cm more. So in a frame with modern demensions, a 57-59cm top tube should be about right. So that 56cm (if measured C-C) might just work. Try it an see.

I'm 5'11 (~32" inseam; well that's the size for all my pants...), and if I straddle my 54cm 84 Trek, there is nothing left for the crotch. Which reminds me, I need to finish my Trek and ride it. ;-) .

Well guys,
I'm in the process of changing all the components, except for headset, BB, and crankset, from the Strada to the Alu Sprint. I bought a 130mm stem to keep the reach the same length as on the Strada. Also, I bought a new Veloce BB and crankset. We'll see how I feel upon it by next weekend. Thanks for all your input.

Since I hate it when people talk about a bike and never post a pic......here is one:

Well, I'd thought I'd resurrect this thread after finding that the Alu Sprint does actually "fit". I've taken it for many rides now and I have no problem except for the crappy seat I had on it, since I traded the B17. It now has a beautiful Pro on it that feels great (thanks barndoor). Also, as I was reading Bicycling Magazine, I came across one of their reviews on the Eddy Merckx CHM. It appears that Merckx frames are so compact that a "the smallest, 38cm, is comparable to most companies' 53cm." Wow! That sure does make me think that the industry is now, either ,changing their way of adverting the size or their way of measuring. Hence, my Merckx fits me good, yet I find it has a bit too much of seat tube sticking out, but so does every other "modern" bike I see being ridden. I guess, if I want a bike that properly fits me to only have a fist full of seat post is by riding my older bikes. Either way, I have no complaints about how the Alu Sprint fits me. It's really a fast, comfortable ride.