frame size

[stalagmike]

I've owned my Triban 3 for over a year now and the other day, for no particular reason I thought I would measure the frame. Can anybody shed any light on why a 63 size frame actually only measures 55 cm from centre of cranks to point where seat post enters the frame? I was expecting this to be 63. 63 is not the top tube length cos that's about 55 too.

 

[ColinJ]

I assume that it has a sloping top tube? The size will be for a 'virtual top tube' - i.e. the length that a horizontal top tube would be. Measure from the centre of the headset horizontally across to the centre of the seatpost and that should be the size that you were expecting.

You must be pretty tall to need a bike of that size - at least 6' 3"? (I am 6' 1" and a 58 cm frame suits me.)

 

[mjr]

Some brands now seem to use a random number generator rather than a measurement

 

[stalagmike]

I assume that it has a sloping top tube? The size will be for a 'virtual top tube' - i.e. the length that a horizontal top tube would be. Measure from the centre of the headset horizontally across to the centre of the seatpost and that should be the size that you were expecting.

You must be pretty tall to need a bike of that size - at least 6' 3"? (I am 6' 1" and a 58 cm frame suits me.)

I am 6' 3" as it goes. So your deduction is bang on. I now get what you mean. So if I'm looking at bikes that have horizontal top tubes (like older racers) then they would probably have to have an actual top tube length of about 58 minimum. Obviously the best way is to try them on for size but just for when window shopping on eBay.

 

[Low Gear Guy]

Some brands now seem to use a random number generator rather than a measurement

You really need to physically try the bike for size before committing yourself.