Frame size

[Jonnybev82]

Hi,

I'm a 53cm frame size in modern bikes but am looking at getting a old steel frame as a project and they all come in inches. so what size would I need??

Thanks
John

 

[The History Man]

Depends if your modern bike has a sloping top tube. Measure from pedal centre to imaginary horizontal top tube centre.

 

[dirttorpedo]

Re:

I'd take a close look at center to center top tube length when looking for a vintage bike because of the changes in bicycle sizing over the years. If you are a 53 cm top tube you're probably looking at a 19 or 20 inch long top tube on a vintage bike. Vintage bikes tended to have less standover (you still need about an inch) compared to modern road bikes. I'm riding a 58 cm (23 inch) 90's vintage frame and road a 24 inch (60 cm frame) 80's vintage bike. My wife is 5"4" and I bought her a 19 inch 80's Trek and it seems to fit her Ok.

 

[non-fixie]

My suggestion would be to check the Internet on bike fitting methods and calculators. There are quite a few. Wat also helps is understanding what kind of fit you're looking for: an aggressive racing fit (often called the 'competitive fit'), a comfortable touring fit (or 'French fit') or something in between (the 'Eddy fit'). Google is your friend here.

FWIW, I'm 6'1" with a 35" inseam, like a French fit and generally ride 62cm frames, measured center-top. In a formula: CT seat tube length = .70 x inseam. Try .67 for a more aggressive fit.

Be aware that on vintage frames the top tubes don't grow as much with the seat tube length as they do on modern designs, so it's generally easier on a vintage bike to ride a larger frame. Try before you buy.

Good luck.

 

[t47b]

Re:

What height are you, what is your inside leg measurement? Maybe someone here will be the same as you and this would be a good starting point for looking for a suitable bike, but a test ride is always best if possible.

 

[Vino]

Re:

21"

 

[Jonnybev82]

Re:

Thanks for all of this. I am 5 foot 7 and have a 30 inside leg. I think a 20 would suit me right from comments and a bit of googling.

 

[keithglos]

British frame size until about 1980 was measured from the centre of the bottom bracket to the top of the seat lug in inches. Continentals measured centre to centre in centimeters. Top tube was centre to centre.

Keith

 

[mattr]

Depends if your modern bike has a sloping top tube. Measure from pedal centre to imaginary horizontal top tube centre.

Sloping top tube bikes are generally measured to the position of the effective top tube. Not the actual top tube.

 

[Vino]

Sloping top tube bikes are generally measured to the position of the effective top tube. Not the actual top tube.

Yup.

Sure, frames have different geometries and top tube lengths and I can change the stem and so on, but I'm usually happiest with the same size - 56cm seat tube - whether that's an actual measurement of an old frame with a horizontal top tube, or a 'virtual' measurement of a modern frame's seat tube with a sloping top tube.

53cm = 20.8661417 inches