|2 CF fork questions||tmac13|
Jan 5, 2004 10:48 AM
|My Reynolds CF fork is damaged and needs to be replaced. 2 Questions:
What is fork rake and what will it do for me?
Fork recomendations for a 195lb rider who races about 6 times/year and about 6 centuries
|rake and trail||C-40|
Jan 5, 2004 11:12 AM
|Rake is the perpendicular distance between two parallel lines, one through the center of the hub, and one through the center of the steering tube. Trail is the horizontal distance between the tire contact point on the ground and a line through the steering axis. The more trail, the more stable the bike (slower steering). The less trail, the quicker the steering. Both rake and head tube angle affect the amount of trail. Steepening the head tube angle or increasing rake will decrease trail, reducing stability and quickening the steering. The formula for trail is as follows, where R is the tire radius, and H is the head tube angle. Trail = (R/tan H) (rake/sin H). As an example if R = 33.65cm, H=73, and rake is 4.0cm, trail = 33.65/tan73 4.0/sin73. This calculates to 6.1cm or 2.4 inches.
Changing the rake from 4.0 to 4.5cm yields a trail of 5.58cm or 2.2 inches.
Changing the head tube angle to 74 degrees, with the 4.0 rake yields a trail of 5.49cm or 2.16 inches. Thus, a .5cm increase in rake will have a similar effect to increasing the head tube angle by slightly less than one degree.
The rake you select depends on the head tube angle of your frame and how quickly you want it to steer.
|re: 2 CF fork questions||cyclopathic|
Jan 5, 2004 2:33 PM
|you wanna maintain your current rake, look it up at mfg or call customer line. The ideal trail is 5.6cm gives "neutral" handling, and you get it by using 43-45mm on 73 HTA or 40mm on 74 HTA.
PS here's an article on rake/trail at Tom Kellogg site, take a look http://www.spectrum-cycles.com/612.htm
|re: 2 CF fork questions||Chen2|
Jan 5, 2004 3:52 PM