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jaytheman

How do I properly measure the frame size on my 73 TdF? I forgot the size and the decal, if there ever was on, is no more. Thanks.

verktyg

At least up until the late 1970s, most European bike frames were measured from the center of the bottom bracket spindle to the top of the seat tube also called C to T or C-T-T.

The Gitane standard frame sizes during that period were:

50cm, 54cm, 57cm, 60cm, 62cm and 64cm (nominal dimensions).

That translated into VERY NOMINAL inch sizes for the US market (and maybe other markets like the UK, Canada, Australia and so on that used "imperial" inch measurements):

20 1/2", 21 1/2", 22 1/2", 23 1/2", 24 1/2" and 25 1/2".

At some point the measurements changed to Center to Center or C-T-C - from the center of the bottom bracket spindle to the center point of the top tube where it goes into the seat tube lug.

Center to Top is a little easier and more accurate measurement to make on most frames (unless there is a seat tube extension above the seat lug).

Your bike has a 54cm frame... but the most important concern is "stand-over height". Straddling the the top tube you should have a safety zone - usually about an inch - between the tube and your personal areas. This is to avoid a collision in case you have to dismount quickly! Shocked

Wind resistance is the biggest force to overcome when cycling.

Bicycle racers have frequently ridden frames up to several sizes smaller than the average cyclist would ride. With the seat up high, riding bent over with your hands "on the drops" can give a more aerodynamic position.

Also, smaller frame sizes tend to be a little stiffer.

My hero, the Great One "in the drops"! Cool

The breakaway pack on the drops with a horse racing them.

Early Lemond in the drops Nevada City, 1976.

Le Blaireau in the drops - hammering.

Le Blaireau in the drops - sprinting.

Two GREATS!

From the mid 1980s, bikes with sloping top tubes became popular. They provide clearance at the rear of the top tube but allow the bars to be much higher.