Classic & Vintage - Vintage sizes versus Contemporary sizes

I'm looking to buy an older frame that I can convert into a fixie. My problem is that I know what fits in contemporary road bike terms (I have a 52cm C'Dale and a 53cm Look) but I'm not sure I understand the vintage sizing: 1) when a vintage bike is described as a X" bike, is that the seat tube or top tube? 2) ones that I have seen advertised seem to have much longer top tubes relative to seat tubes - is that true?

Any help appreciated.

Should be the seat tube length being described, though not all sellers are sophisticated enough to understand this.

In actuality, what has changed more than the relative proportions of bike tube lengths (which were more a function of which company built them than anything else), is the philosophy of bicycle frame fitting. 30 years ago, if you had an inch of standover, and a "fistful" of seatpost showing, that was considered generally accurate frame fitting. Today, three or four fistfuls of seatpost is considered "normal".

As cyclists have become taller over the years, bicycle frames have generally not grown as fast. As USAZorro points out, lots of vintage racing photos depict riders with very little seatpost showing.

There are two generally-accepted ways to measure frame size:
1) center of crankshaft, along the seat tube, to the center of the top tube;
2) center of crankshaft, along the seat tube, to the top of the top tube.

(1), popular in Europe, makes sense when one is figuring out frame geometry and measuring everything center-to-center.
(2), more popular in the US, seems the most practical to me, as it gives the most direct assessment of things like standover height (which can still vary because of BB height) and leg extension.

Having said all of that, I note that top tube lengthi is also extremely important in bicycle sizing, although one can compensate somewhat by changing the handlebar stem reach.

Jazzy, when looking for an old style road frame, part of the equation to be factored is how tall are you and what is your inseam? Do you like your seat above your stem? How much? Do you plan to use drop bars or some other type? Such information will help others make suggestions for frame size. I have a beater Vista 59cm cromoly frame, tange fork, and forged dropouts, if interested. It will need paint.

There are two generally-accepted ways to measure frame size:
1) center of crankshaft, along the seat tube, to the center of the top tube;
2) center of crankshaft, along the seat tube, to the top of the top tube.


...and the Raleigh Standard, my favorite method of sizing:

3) center of bottom bracket/crankshaft, along the seattube, to the top of the seattube lug opening (not including any fancy spearpoint lug extensions)

-Kurt

You should determine whether those sizes of your current bikes are the actual seat tube length or the vertual. Vertual measurments are what the length would be if you bike had a horizontal top tube. Once you figure out the vertual size you can start to gauge what size you need in a vintage frame.

... Vertual measurments are what the length would be if you bike had a horizontal top tube. Once you figure out the vertual size you can start to gauge what size you need in a vintage frame.

Virtual I think is the spelling, I generally agree but do remember that a "traditional" quill stems placed the handlebar differently than the current stem design trends, basically a new lugged steel frame today designed for modern components, even with a horizontal top tube will probably have an extension to the lug to make up the difference. With exceptions noted, on average, top tubes today are shorter and stems longer than in the 60's or 70's. I am not so sure this is a good thing, just different.

Also note that handlebars are wider today, 40cm ctc was very common 30 years ago, 42 for the "big boys" 44cm traditional bars were made but not till the 80's. A guy who rode a 40cm bar in years gone by would be placed on a 42cm or wider bar today.

In the 50's and prior for reference, 36cm or 38cm was common. Some conjecture, some fashion, some validated analysis increased the width.

I won't even discuss crank length and position behind the BB...

My bet though, if you are on a 53cm frame today, you will probably be on a 55 to 57 "traditional" frame.

53cm modern to 54/55cm traditional sounds about right, 57 is a bit of a stretch in my experience. I agree that you need to look into the specs on your LOOK and 'Dale and compare over all reach (top tube + stem with seat to bar drop considered) and center to center seat tube length (for that virtual top tube point). I've got a friend of mine who rode a 56cm traditional Centurion for a short time before being fitted to a 52cm Specailized. The Centurion was just plain too big on him.

Great info - thanks all (sorry for the delay-been slammed at work)

Me: 5'9", 31.5 inseam, like bars an inch or two below saddle

Bikes: '03 'Dale R600: 52cm (ct?), top tube = 53.5cm, stem is 9cm
'05 Look 555: 53cm (virtual), top tube = 54cm, stem is 9cm

The issue of stems seems to be relevant. I was looking around on ebay and for a vintage frame that was described as "53cm", it said the top tube was 57cm! So I'm wondering how this fits with my current bikes. Do I look for a 53cm as described above and risk a too-long reach, or do I go for reach and a real long seat post? Despite what people will tell you, my body is not all that wierd!

I recently purchased a new mountain bike. I bought my last one in 1998, and mountain frame geometry has changed a lot ever since.
So, since my old bike fit me right, I took three measurements from the old frame:
c-t seat tube
effective top tube
standover clearance

With these three measurements, and considering what I was looking for (more standover clearance than my old bike had, for example) I got a pretty good idea of what "modern day" frame size would be good for me.

Maybe you can do the same in reverse to find the right vintage frame.

hope it helps,
JEB

There are two generally-accepted ways to measure frame size:
1) center of crankshaft, along the seat tube, to the center of the top tube;
2) center of crankshaft, along the seat tube, to the top of the top tube.

(1), popular in Europe, makes sense when one is figuring out frame geometry and measuring everything center-to-center.
(2), more popular in the US, seems the most practical to me, as it gives the most direct assessment of things like standover height (which can still vary because of BB height) and leg extension.
Hi John E,

For classic frames, mid-1980s and older, the sizing approach was typically opposite of what you noted. Most European bikes used the center-to-top (C-T) method while most American manufacturers used the center-to-center (C-C) method. (Notice I said most. :) )

I make this point in case someone is measuring a classic frame and starts getting a seat tube length with a 0.5 cm increment. If you get that kind of measurement then try measuring the other method. You should typically get a seat tube length in whole cm increments.

I ride a 53 cm C-T or a 52 cm C-C (which is a tad smaller) in a classic geometry. Here is my 1975 Bianchi Specialissima which is a 53 cm C-T:

http://www.pbase.com/cleavel/image/68369420/original.jpg

My current Look KG481SL is a 52 cm and it seems that I ride a 51 cm "sized" bike in the sloping geometry format. However, the only sloping geometry bike that I've owned to date was a 2001 Bianchi XL Ti which was called a 53 cm. :eek: It had plenty of seatpost showing:

http://www.pbase.com/cleavel/image/42904422/original.jpg

Finally, top tubes have always been measured C-C but these days you always have to look at the virtual top tube length, not the actual. Also, top tube length has typically varied a bit for any given size bike because different manufacturers have different approaches to fit and handling. As noted above, you can adjust for this variation through stem length.

All of this is to say that different people like and fit well on different bikes because no one is "normal." ;)

...Me: 5'9", 31.5 inseam, like bars an inch or two below saddle

Bikes: '03 'Dale R600: 52cm (ct?), top tube = 53.5cm, stem is 9cm
'05 Look 555: 53cm (virtual), top tube = 54cm, stem is 9cm

The issue of stems seems to be relevant. I was looking around on ebay and for a vintage frame that was described as "53cm", it said the top tube was 57cm! So I'm wondering how this fits with my current bikes. Do I look for a 53cm as described above and risk a too-long reach, or do I go for reach and a real long seat post? Despite what people will tell you, my body is not all that wierd!

I am about the same overall height .5" taller, same inseam, your request to keep the bars just 1" below the saddle will push you to a larger frame, extended head tube and or Nitto extended length stem. Otherwise I would suggest a 55cm,ctt up to a 57cm ctt.

A 53cm frame with a long top tube as you describe is probably custom or late 50's to early 60's Italian or British. Remember back then 72 degree seat tube angles were common, providing more set back, many modern frames will be 73.5 or 74 degrees, so a older machine will place you farther behind the BB or with a "mod" no set back post feel even more. My personal fav. is 56cm ctc for a top tube, but can ride 54.5 to 57, with different stems fitted.

So top tube length somewhat depends on where you place your saddle, (and thereby knee) in relationship to the bb, I place mine the same no matter the era, so, part of what I use is the distance from a vertical line through the bb and measure the length forward of that to the steering axis.

I still have to account for the shape of the bars, and brake levers, so the stem length can still vary up to 15mm.

It was my understanding that the classic Italian racing geometry was square or even a bit shorter top tube than the seat tube. Where on the other hand, the British and American approach was longer top tubes.

I have always taken inch size frames to be measured from the bottom bracket centre to the top of the seat lug. When more and more frames began to be specified in centimetres, they always appeared to be measured to centreline of the seat lug. As for th erelative length of the top tube, that's up to the framebuilder.

My Italian steed from 1953 has 53cm ctc seat tube 55.5cm ctc top tube, a top level "production" bike, many other Italian bikes from that era are similar, such as Bianchi. Also, its 72.5 degrees parallel, I was kind of surprised how "contemporary" it is, with tight fitting for the front brake.

I think "classic" geometries for a given nationality have to be more defined. While not absolute, each decade seems to have its own flavor.

The American's especially later such as in the 70's drew from a number of "styles"