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Conference noted::bicycle

Title:	Bicycling
Notice:	Bicycling for Fun
Moderator:	JAMIN::WASSER

Created:	Mon Apr 14 1986
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3214
Total number of notes:	31946

1677.0. "Explain frame dimensions please" by GOBACK::FOX () Tue Jul 31 1990 15:15

    The various specifications regarding frame dimensions, how are they
    measured? Some can be taken literally (top tube length: perhaps the
    length of that tube on the top?) Others like trail, head angle, etc,
    are a little more mysterious. Also, what points do the measurements
    begin at end at? Take chainstay length for example, what are the
    beginnin and ending points for that measurement? Feel free to add
    others as well.
    
    Thanks,
    John

T.R Title User Personal
Name Date Lines

1677.1 Here's all I know... RANGER::WASSER John A. Wasser Tue Jul 31 1990 17:56 30

T.R	Title	User	Personal Name	Date	Lines
1677.1	Here's all I know...	RANGER::WASSER	John A. Wasser	`Tue Jul 31 1990 17:56`	30
	Tube lengths: Most tubes would be measured between where the center line of the tube intersects the center lines of the tubes it meets at each end... Just imagine the diameters of the tubes shrinking to zero and measuring where the lines meet. An exception is the seat tube which may be measured from the center of the bottom bracket to the center line of the top tube (as described above) or to the top of the seat tube (a little longer). I don't know how to tell what method is used if it isn't specified. Probably the first method if the size is in centimeters and the second method if it is in inches. Frame angles: Angles of the head tube and seat tube are measured up from horizontal. A 90 degree angle would mean a vertical tube. Stays: I think these would be measured like tubes (since they are). Fork: Trail is the distance between the line on the pavement directly below the center line of the front axle and the point on the pavement that is intersected by the center line of the head tube. Rake is (I think) the distance between the center line of the head tube and the center line of the front axle.

Tube lengths:

	Most tubes would be measured between where the center line of
	the tube intersects the center lines of the tubes it meets at
	each end...  Just imagine the diameters of the tubes shrinking
	to zero and measuring where the lines meet.

	An exception is the seat tube which may be measured from the
	center of the bottom bracket to the center line of the top tube
	(as described above) or to the top of the seat tube (a little
	longer).  I don't know how to tell what method is used if it
	isn't specified.  Probably the first method if the size is in
	centimeters and the second method if it is in inches.

Frame angles:

	Angles of the head tube and seat tube are measured up from 
	horizontal.  A 90 degree angle would mean a vertical tube.

Stays:

	I think these would be measured like tubes (since they are).

Fork:
	Trail is the distance between the line on the pavement directly
	below the center line of the front axle and the point on the 
	pavement that is intersected by the center line of the head tube.

	Rake is (I think) the distance between the center line of the
	head tube and the center line of the front axle.