How do I figure out a 5 degree rake angle on Harley?

Question

I have a 1989 Softail and the stock rake is 0 degrees. I want to add 5 degree raked trees but at the same time keep the bike at its current height. How do I figure out where a 5 degree rake will put the forks so that I can determine the proper length fork tubes? Is there a formula that I need to use? Thanks.

Answer 1

Actually, your stock Harley's rake is 32 degrees.
What you want to do by installing raked triple trees on a stock frame is not good, as it will reduce you trail (what makes you bike track straight at speed).
Where raked triple trees come in handy is if you increase the rake of your frame, the trail increases, making it track straight, but more resistant to turning. The 5 degree trees will bring the trail back closer to stock.
To figure trail, set your bike up right and straight, with the forks straight ahead.
Get a straight edge, and figure the line through the steering neck (not the forks!) to where it intersects the ground.
Then figure a straight line vertically through your front axle.
The difference where these two lines are on the ground are your trail, approx 3-3 1/2 inches.

Answer 2

A Formula!!??

"We dont NEED No Stinkin'...Formula!"

We got the Internet,,We can Cheat!!

http://www.csgnetwork.com/righttricalc.html

Ok,,
To use that for what You wanna do,,
You've gotta "find the Triangle" on your bike.

It's Fork Angle/Rake...easy to see on the picture
The Horizontal Line is AXLE.
The Vertical Side of the Triangle ,,is straight down from Top of Fork

If You look at it for a minute,,easy to figure out how to.

What You want to do is Figure your Existing set-up,,
Plug all the figures in to the calculator to determine current Height.

Also,,realize that the Calculator will give an Odd looking "short" number for HEIGHT.
Remember that the Triangle is only measuring to Axle,not all the way to the ground.

When you Compare calculation results(however Short those numbers seem)
the Difference is ACTUAL the Change in height of the Bike.
......................................................
The calculator only needs 2 Known Figures,and it'll give you the rest.

You will have to do some measuring on your bike
#1 Fork Length
#2 Distance from Axle to an imaginary line running Straight Down from Top of Fork Tube ( Use a string with a weight as a 'plumb bob line")

Plug those figures into the Calculator.
The Results will tell you the Unknowns.
#1 the Current RAKE angle
#2 the Current HEIGHT

ReRun the Caculator using
>Known Fork Length
and
>The RAKE angle that was displayed--MINUS 5*Degrees
(i know you're adding 5*,,the thing is measuring angles from opposite direction so you must Subtract)

The results of That calculation will show the "New Height",,the difference between the 2 Calc Runs is how much Bike's Height will change.

Run the Calc a 3rd time
>Use the ORIGINAL Height as one factor
>use the -5* Rake Figure from the 2nd Run

That will tell You how much Longer the Forks need to be,,simply compare that number to the Original to see how much to Add to the length To Maintain Original Height

*** For Example,,,a 2" change in Height requires MORE than a 2" change in fork length,,,because of the fork being an Angle

It's Not Too tuff.....
You're measuring some things you Can,,and using that to get some Unknowns.
Then Your using the discovered unknowns as "new knowns" to get Other Unknowns.
It's a bit confusing cuz your dealing with both Lengths And Angles


Make sure bike is straight up & wheel straight forward when you measure.
Try to be as accurate as you can,,,but "close enough" will work fine.
Your gonna get fork extensions in probably 1" increments,,,
I dunno anybody that sells 2 13/64" extended forks,,ya know?
If You get close on your measurements,,it will put you more than close enough to chose the right size forks from what's actually available.

Hope that helps

Answer 3

You can buy a one inch lower kick stand and also the springs inside the fork tubes... You can also buy lowered rear shocks..When you put the triple tree on you'll find out how much your gonna have to lower it...

Answer 4

Sit down with a piece of paper and a protractor...it has degrees on it. Draw yourself a image and work the protractor until it fits your needs.