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A few notes about rake and trail ....

I have received quite a few emails from people that are trying to understand the concepts of rake and trail. The steering ability is critical to owning a safe bike and some serious thought should go into the design and maintenance of the steering components. Mini choppers are especially prone to problems, as most triple-tree designs being used with the 40+ degree rake necks produce a trail that is way too long. This can result in a bike that handles very poorly at low speeds. 

Steering problems involve the design and geometry of the front end. You will often hear the terms "Rake" and "Trail" when reading about bike steering and every builder and rider should understand how these factors affect steering.

The rake is the angle of your steering neck compared to a line perpendicular to the frame. Most choppers have a rake between 34 and 45 degrees. The trail is the distance between a line drawn through the steering neck and a line drawn vertically through the front hub at the axle. I have read various articles on the Internet that indicate trail should be between 2-4 inches and other sites that prescribe 4-6 inches of trail (pic 1). 

As an example, a Harley Davidson FXR has about 4" while an FLH has just over 6".

The common thread is that there may not be a magic trail number, but very long or very short trails, and especially negative trail, is always bad. The problems with trail arise when the rake is set at extreme angles, such as 45 degrees or more. This is a cool look, but it creates a very long trail (pic 2). This is usually overcome by adding some offset in the triple trees. The offset increases the rake, but greatly reduces trail. Unfortunately,  raked triple trees are sometimes used as an easy way to gain rake angle on a stick bike, rather than cutting the neck and reattaching it at a new angle. 


This can be very dangerous as it reduces the trail and can quickly lead to a  negative trail situation. The pictures at left show the rake and trail relationship in a standard-type bike (pic 1), a seriously raked chopper (pic 2), and a chopper with rake corrected in the triple-tree offsets (pic 3) and another corrected by adding some forward distance in the front wheel attachment point (pic 4, like that used in a springer front end).

 If you feel you have an over long trail, you might consider making some homemade offset trees for your mini chopper. To do this, you can try notching the rear of the holes on the top of your tree and notching the front of the holes on the bottom. Then you can offset your fork tubes a couple of degrees. 

You can also try adding a piece that moves your front wheel forward slightly, as in the last picture. This is similar to what you can expect when using a springer front end. Check this page to see how a springer works. 

Getting the trail correct may take some trial-and-error, but the better control you will have will be worth the effort. 

This info should help you better understand these important principles. There are also links at the bottom to other sites that can offer much more information, such as how to measure your trail, how to calculate your trail, and other important stuff.

             Just Remember - Keep it Safe! 

 

For More Info - Check out these great links 

A great page devoted to Rake and Trail

Measuring trail on your bike

Trail Calculator

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