MTB Frame Measurement

Different manufacturers measure their frames in different ways, this may well mean and 18" from one manufacturer will be a 19.5" or 20" from another MTB's are usually measure in inches, a less common method is stating a size. e.g. small/medium/large

Frame Size

Centre to Top

Denoted in table as CtT

Measurement taken from the centre of the bottom bracket to the top of the seat tube along it's length. Example manufacturers are Rocky Mountain[1] and Kona[2]

Centre to Centre

Denoted in table as CtC

Measurement taken from the centre of the bottom bracket to the centre point of the top tube along the seat tube Example manufacturers are Saracen[3] and Marin[4]

Centre to Top of Top-tube

Denoted in table as CtTT

Measurement taken from the centre of the bottom bracket to the top of the top tube along the seat tube

Other

Denoted in table as O

Some manufacturers used different methods, see their manufacturer page for details. e.g. Klien, Early Kona.

Who does it how ?

Company	Method	Years	Exceptions & Stuff
Kona	CtT	1993->
Kona	O	<-1992	Used top of bottom bracket shell to top of seat-tube
Rocky Mountain	CtT
Marin	CtC
Saracen	CtC
Parkpre	CtT
S-Bike	CtC		might be half inch less
Cannondale	CtTT
Klein	O		A vertical line from centre of bottom bracket to the effective top-tube
Orange	CtT