Hey guys, I know this probably comes up a lot but maybe not so much in this forum. The reason I ask is because I'm considering buying a vintage steel frame.

Currently my main ride is 2011 Bianchi steel (from the Gran Fondo line). It's a "59", which according to their website comes from the C-T measurement of the seat tube. When I measure it myself, it looks like 59 C-T (top of the seat lug) is just about right. C-C, though, it looks more like a 55. I'm about 6'1, and every time I measure my inseam I come up with a slightly different number (usually 89-91cm). But using the old x0.65 method, I always come up with at least a 57 C-C size.

On my current bike, I have about an inch and a half of clearance when standing over the bike. Since I'm considering buying an old frame, I'm wondering what I should make of this when choosing a frame. Since I'm likely to buy a frame online like on ebay or something, should I use my Bianchi's 55CM C-C measurement as what I want, or should I go with what my inseam size tells me I should do? My standover height appears to be about 35".

EDIT: It just dawned on me: could the slightly oversized tubing of my modern steel bike be the difference? It seems that measuring C-C on two bikes with the same standover height, the one with oversized tubing would yield a smaller measurement while the vintage tubing would yield a larger measurement - even if they seem the same size to the rider. My old Peugeot which I bought without knowing anything about road bikes is definitely too large for me, about 60CM C-C on both the top and seat tubes. I have about 1MM of clearance standing over the top tube, and the reach to the handlebars is truly ridiculous. But it seems like a few centimeters smaller (57CM) would fix this problem.

don't pay attention to your inseam imo. i think most people measure the size C-T as you stated above. if you are going to buy a frame online, you need to ask the seller how he/she measured it or ask for a C-T measurement.

its really about how you want to feel on the bike. a larger frame will allow you to have your bars close to seat height without a goofy stem. a shorter frame will be lighter and more compact (if the top tube is shorter)...

i would measure the crap out of your bianchi and decide what you like and don't like and go from there.

I'm 6' 1" and have average proportions as well. I have always ridden a 58cm c to c frame. Over the part 10 years though, after growing old, I have found that I like a 59cm c to c frame as it seems to fit me better now. I have bikes that range from 56cm to 62cm c to c. The 56cm is too small and the 62cm is too big (but I can still ride it). I have a few 60cm c to c bikes that I ride without any real hassles but I prefer a slightly smaller frame of 58cm to 59 cm as I stated before.

As for stems, I like a 120mm stem length but I also use 130mm length as well.

I like illwafer's idea of measuring your Bianchi and deciding if you like its dimensions and trying to replicate its position with a steel bike - (but start with a 58cm c to c frame).

If its about leaning towards smaller or bigger, I would go for a slightly smaller. If its not too small, they are easier to handle and weigh less. There seems to be a consensus today about slightly (or much) smaller frames to enhance competetive riding. But it all comes down to how the size makes your riding style comfortable.

I'll jump in here with another stupid beginner question about frame sizing. I understand C-C, and how it impacts the reach and orientation to the bars - very well. But how useful is the C-T measurement, when the end of the seat tube and how far it extends above the top tube varies so much among manufacturers? I mean, that measurement probably varies 5cm or more, and it doesn't seem to directly affect anything other than how much exposed seat post you end up with?

KeS

I'm not sure either seat tube height c-c or c-t are important, for me at least. What is really important is being able to create the correct relationships: BB center to saddle in the vertical and horizontal directions, and BB to handlebar relationships in the vertical and horizontal as well. A good frame design is one that allows me to create those relationships with available parts. A frame can stop me if: the seat tube is too steep (can't reasonably get the saddle back far enough), the head tube is too far forward (can't get correct reach with a decent stem length), or the top of the headtube is not in the right place (can't angle or raise a stem up or down enough, with a suitable extension). It comes down to three basic specs: seat tube angle, height from BB to top of the head tube, and horizontal distance from BB to the top of the head tube. Notice top tube alone is not right, nor is seat tube length.

You can get a good cut at your target values by measuring them on a bike that fits well.

For a frame with horizontal top tube, the head tube height requirement comes down to a seat tube length requirement, as does the recommendation for "a fistful of seatpost." The recommendation to "when in doubt go one size larger" is to facilitate a higher head tube top. Top tube length is to ensure adequate BB to head tube horizontal distance, but it's only a valid recommendation if all seat tube angles are the same. Some portion of the top tube is behind the BB and some of it is ahead of it.

https://www.rivbike.com/article/bike_...g_a_frame_size

I'm 6', and have 1 58cm bike and (counting ones "in production") 5 60cm bikes. The only one I can stand over (comfortably) is the 58cm. Don't let standover height be your guide! IMHO the current emphasis on standover height isn't the way to fit a bike. When you come to a stop do you instantly hop off the saddle and plant both feet on the ground? Of course not. One foot down, lean over.

I'm a masher and have found that I like a little more leg extension than typical so a little more seat tube works fine for me. Then I look at top tube length which I like a little shorter than the seat tube with a typical 100-120mm stem.

The trick is to get fitted on a bike how you like it, measure accurately, and compare those measurements to any potential purchase to see if it can be made to fit you with a reasonable amount of seatpost showing and a stem that is neither too long (>130mm) or too short (<90mm).

IMHO 1-2 x a fist for a seatpost, a 100-120mm quill stem, and no more stem rise than extension are the most aesthetically pleasing criteria for a classic geometry, horizontal top tube road bike. I'll look for frames that allow all that to happen.