gen_510.1.gif
gen_488.1.gif
gen_1464.1.gif
gen_1809.1.gif
gen_489.1.gif
gen_1442.1.gif
gen_1991.1.gif
gen_2480.1.gif
gen_1984.1.gif
gen_1812.1.gif
gen_1999.1.gif
gen_760.1.gif
gen_2102.1.gif
gen_837.1.gif
gen_662.1.gif
gen_2722.1.gif
gen_1553.1.gif
gen_1995.1.gif
gen_2088.1.gif
gen_2490.1.gif
gen_700.1.gif
gen_3186.1.gif
e-mail me

Changing your Rake & Trail on your Bagger



Rake & Trail Our Solution



e know you were day dreaming about sex when the triangles were floating about the blackboard, or for those of you who were already warped, you were doodling motorcycles while the teacher droned on about sins, cosines, tangents. Now all these years later when you finally got the money to build your dream bike, all you can do is thumb through pictures of other people's projects, searching for that "look" blissfully unaware of what all that trigonometry was for. We're going to show you how to do the calculations. We're going to present some data for you to study, and leave the decisions up to you. It might explain why shopping carts weren't meant to go 200 mph. You may download a copy of your very own Rake & Trail Calculator on the page titled: "Rake & Trail Calculator". Play with it (put in all range of numbers from realistic to the absurd),this is how you will learn & understand. It may not help getting you laid at the bar, but it will impress your friends way more than eating a live frog.

Your front suspension geometry is defined by the following six variables which are defined as:



OFFSET:
Centerline of the top steering neck (Stem) to the centerline of the top of the fork tubes.



RAKE Of The STEERING HEAD:
The angle in degrees of the steering neck (head) from the vertical cord (measured in degrees from a line 90 degrees to the ground). Rake is the angle of the forks off vertical and trail is the amount that the front wheel is being pulled down the road, yes, the front wheel is being PULLED not pushed. A good example of trail is the wheels on a shopping cart. The wheel axle is behind the pivot point. This causes the wheel to follow the pivot point no matter where it is going. If the wheel axle were directly under the pivot, you would not be able to keep in a straight line.


TRAIL:
The distance defined by the vertical line (distance between an imaginary line drawn through) centerline of the axle and the steering head/neck to ground intersection.

Trail is what gives us our handling characteristics of our motorcycle. The more trail we have the better our bike handles in a straight line at the cost of low speed turning ability. The less trail we have gives us very responsive low speed handling at the penalty of twitchy higher speed response. Let us think about different ways to change rake and trail. Most Harley® riders make changes in their bikes rake without realizing it. One of the most common modifications to our bikes is to lower the rear end. As the rear of the bike goes down the steering head angle steepens increasing the rake and trail. A change in wheel overall diameter: from a 16” stock FL to a 18” tire will increase the steering head angle thus increasing the rake and trail. The same for decreased wheel diameter from 21 to a 19 will lower the front axle, lessening the steering head angle reducing rake and trail. Increasing fork tube length will increase rake and trail, but a front end lowering kit by itself will decrease it. Stock HD® front ends come with various rakes from 26 to 33 degrees. A good handling bike for highway use will have 2 to 4 inch trail.

FORK LENGTH:
The distance between the top of the fork tubes to the centerline of the axle.

DIAMETER:
The diameter of the front tire. If you do not know, go to my Metzler Tire Guide (link)

RAKED TRIPLE TREES:
In order to bring trail figures back into line, triple trees with raked steering stems can be used. Usually adjustable in 3, 5, 7 degrees of rake.




HOW TO MEASURE CORRECT TRAIL ON YOUR OWN BIKE:
Raise the bike to an upright position, using a tape measure, hold the tape straight down from the front axle to the floor. Put a mark on the floor at that point. Then place the tape parallel to the steering neck, following the angle of the steering neck all the way up to the floor. Put a mark here also. Now measure the distance between the two marks and you have your trail measurement. It should read between 2 and 4 inches. Note: If your bike is equipped with a rear suspension, have someone sit on the seat when you make the measurements to simulate your actual riding condition.



TOO LITTLE OR NEGATIVE TRAIL:
With too little or negative trail (steering axle mark behind the front axle mark), the bike will handle with unbelievable ease at low speeds, but will be completely out of balance at high speed. It will easily develop a fatal high-speed wobble. EXTREMELY DANGEROUS!

NORMAL TRAIL:
Normal trail is somewhere between 2 and 4 inches. The bike will handle easily at both high and low speeds. Flowing smoothly through curves without swaying or wobbling. If you use a very fat rear tire, you should keep the trail as close to 4 inches as possible.



An Example of what Harley Could Do if it wanted: 2001 T-Sport
• Rake/Trail: 28 degrees / 4.1 in.
• Front brake: 2, four-piston dual-action calipers, 12-in. discs
• Rear brake: Four-piston, dual-action caliper, 12-in. disc
• wheelbase: 63.1 in.
• Front suspension: Cartridge-type, 39mm stanchions, 6.1 in. travel, adjustable for spring preload, compression, and rebound damping
• Rear suspension: 2 dampers, 4.3 in. travel, adjustable for preload and rebound



TOO MUCH TRAIL:
If the trail is more than 4 inches, the bike will handle sluggishly at high speeds. It will seem almost too steady. You will have trouble balancing the bike at lower speeds or on winding roads. It will feel generally sluggish and clumsy.

ALL TOURING 1980 ~ CURRENT
• Rake / Trail: 26 degrees / 6.2" in.
• Front Brake: 2, 4-piston fixed, 11.81" x 0.20" disk (larger disk for the 2008 models)
• Rear Brake : 1, 4-piston fixed, 11.81" x 0.20" disk (larger disk for the 2008 models)
• Wheelbase : 63.5"
• Rear Suspension: 2 dampers, air-adjustably (the absolute worst and cheapest way to raise {adjust} the shock)




STOCK LATE MODEL FL (BAGGERS):
This is how the Factory achieves its steering.



MOTORCYCLE METAL'S SOLUTION:
26 degrees of rake, 4" of trail. Put some performance in that lazy sled. Big motor? Do something with it.

What it looks like with 13" Penske shocks