The Proteus Framebuilding Book - Proteus Bicycles

.frame more responsive and less energy absorbing. These are benefitsto the racers. On the other hand, a less inclined seat tubeis more comfortable although some sacrifice in quick handling andenergy absorption may occur. This would be better for the touristswho may have comfort as their main concern, especially on long rides.The less inclined seat tube may also make the frame more stable.Another consideration for some people is the distance from the noseof the saddle, to a line drawn through the center of the bottombracket, perpendicular to the ground. In very small frames thisdistance will be very short and in very large frames this distancewill be very long. If you believe this distance should always fallwithin certain parameters, then you must make sure you can adjustyour seat to fit those parameters. To accomplish this, you mustknow how far back the top of the seat tube should be behind a linedrawn through the bottom bracket perpendicular to the ground. Sincesaddle position is adjustable, there should be two possible extremesettings for a seat, and therefore also the seat tube. Figure outthe furthest and the closest distances the seat can be behind thebottom bracket. Then make a scale drawing. Measure the angle ofthe seat tube in the furthest back position and then in the furthestfront position. You now have a choice of selecting either extremeangle or any angle in between. Therefore the considerations firmentioned under seat tube angle can be used since you have a choiceofanglesTop tube length - This is the length from the intersectionpoint of the center lines of the top tube and seat tube to the intersectionpoint of the center line of the top tube and head tube.The length of this tube relates to the length of the upper part of6