Professional Rake and Trail Calculator

Enter your variables and it will tell you what your trail is. One final entry is for longer tubes as people often ask what happens if they put it longer tubes...Well, things rotate around the rear axle and everything changes.

White guys in a "B" movie that made zillions ...riding bikes built by a Black guy in LA. Choppers go way, way, back. Hell, the Indians had suicide clutches on Buffalos till we wiped out the rolling thunder. A million buffalos was rolling thunder. A bunch of Harleys isn't. Nature rules till we mess with it...there's always payback though.

Definitions: Your front suspension geometry is defined by the following six variables which are defined as: Offset-- Centerline of top of steering neck to centerline of top of fork tubes. Rake-- The angle in degrees of the steering neck from the vertical. Fork Length-- The distance between the top of the fork tubes to the centerline of the axle. Diameter of the front tire. Diameter of the rear tire. Trail: Distance defined by vertical line from axle to ground and intersect of centerline of steering neck and ground. Raked Triple Trees-- In order to bring trail figures back into line, triple trees with raked steering stems can be used. Expressed in degrees. Usually adjustable in 3, 5, and 7 degrees of rake. Tire Diameter Formula: If you do not know a certain tire diameter use the following formula: Diam Inches = Rim Diam Inches + [ (2 x Aspect Ratio x Section Width) / 25.4] Example: 200/55R18 Tire: 26.7" = 18 + [(2 x 0.55 x 200)/25.4] Professional Rake and Trail Trail Calculator Wheelbase inches Wheelbase. Softail 66.5"; FXR 64.7"; Dyna FXDWG 66.1"; Sportster 60.0". Choppers can be any length. Rear Tire Diameter inches Diameter of rear tire. 16" rear typically 25.30". 18" rear typically 26.60". 17x200 26.1"; 17x180 24.84; 17x170 25.12; 17x160 25.44"; 17x150 25.66". Front Tire Diameter inches Diameter of front tire. 21" front typically 27.60". 19" front typically 26.10". 18" front typically 26.60". 16" front typically 25.30" Beginning Rake Rake degrees Steering Neck Rake. Softail 31 to33 deg. FXRS models 29 deg. FXLR 31 deg. Evo Dyna FXD/DX 28 deg. Evo Dyna FXDL/DWG 32 deg . Evo FLH 28 deg. Sportster 29.6 deg Choppers 36 deg to 45 deg. Triple Clamp Offset inches Distance from center of top of steering neck to centerline of top of fork tubes. Typically 2.45". Beginning Fork Length inches Length from to top of the fork tubes to the centerline of the axle. OEM Harley forks are in the 31 to 32" range. Aftermarket forks are in the 30", 32", 34" or longer range. Triple Tree Rake degrees For standard triple trees enter 0 degrees. Some OEM Harley chassis like the V-Rod and the FXDWG use raked trees. The FXDWG uses 3 degree trees. For chassis that have been raked to 40 degrees or so, and too much trail is present, Raked Triple Trees are necessary. Enter the degrees of rake, typically 3, 5, or 7 degrees. New Fork Length inches Length from to top of the fork tubes to the centerline of the axle. Harley forks are in the 30", 32", 34" or longer range. Enter the new length in inches. Note: Trail cannot be a negative number as this will adversely affect handling unless you are building a shopping cart. Typical trail figures are between 4 and 6 inches. Various Harley models have the following trail figures: FXR 4.22". Softail 5.0" to 5.8". FLH models 6.16". Dyna Models 4.1" to 5.1". Sportster 4.6". Fork Angle in degrees Trail in inches Rear axle centerline to centerline top of fork tubes, inches Rear axle centerline to front axle centerline, inches Top of fork tube centerline to ground, inches New Geometry Figures From New Fork length New Fork Angle in degrees New Steering Neck Angle in degrees Trail in inches Wheelbase in inches Rear axle centerline to top of forks centerline, inches Rear axle centerline to front axle, inches Top of fork tube centerline to ground, inches