Could someone explain ' trail demension " I have a rough understanding of what it all means, but am interested in hearing it explained thoroughly....OLDFENDERGUY or perhaps others out there with chopped sportys maybe can explain it.....I have been ridin for about thirty years, and have always been interested in choppers...and have heard the term used alot. thanks !

 

I'll be interested in this one, too. I know just enough about it to confuse myself!

Teek

 

Maybe the description of 'rake and trail' on the following webpage will give you a better idea of what it means.

Normally, the trail dimension on a motorcycle is set to anywhere from 2 to 4 inches to give the bike proper handling and stability at operating speeds.

The problem comes when people decide to add rake to their bike by only adding additional rake to the neck (which will increase the trail), or only adding rake to the tree (which will decrease the trail).

The trail is meant to be a positive figure, but if you go to an extreme which gives you more than 5" or so you will have handling problems. If you increase the tree angle to an extreme you can actually end up with a negative trail, which is very bad.

In simple terms, you really need to add additional rake to both the neck and the tree. The increase at the tree decreases the trail and the increase at the neck increases the trail, so by adding to both you will end up with a canceling effect, meaning the overall trail will remain at approximately 4" on the Sportsters.

But you don't need to worry about any of this if you add a 'kit' that that manufactured by AME or Seeger. The front end is engineered so additional rake is added to both the neck and tree, and you retain the stock trail.

http://www.hylandmotorshop.com/tips9rake.htm

 

Ok, cool! So that means rake is measured as the angle of the steering neck and NOT the forks. So I guess it's possible to be a "cheapskate" and get, say, a 5 degree tree, lower the rear end a little, and get some taller fork springs to keep the bike level, and still be within the 2"-4" recommended trail dimension? I can't speak for sgt joseph, but I would only be interested in kicking out the front maybe a couple of inches, no more than 4",to increase wheelbase, theoretically improving ride quality at cruising speed. And does an increase in wheelbase help the ride quality noticeably? Would slow speed handling characteristics change much? I know the turning radius would be increased simply due to the longer wheelbase, along with lowering the frame. I'll define turning radius as what thewidth of a U-turn while scraping at full lock. Not that I can DO that, I just want the biketo be able to easily make a U-turn on a typical two-way residential sidestreet. This modwould be waaaaayyyyy down the road for me, though (hell, I have to get a Sporty first!). I'll check out those sites and see what I can come up with.

Teek

 

Thanks bro ! very informative.

 

I understand the rake in the tree changes. But how do they change the rake in the neck without welding?


With a 9 degree kit what is the trail do you know?

 

you don't. the rake angle for the neck is set when the frame is built.

 

The trail must be affected, unless I am missing something.

 

You don't have to do anything to the neck, but if you lower the rear, and go with longer forks in front, it would be likecutting and reweldingthe neck.

 

Good question, and it is somewhat confusing..

The way the front end is engineered there is an offset which actually changes the steering head angle. This gives the same overall effect as cutting the frame and increasing the neck angle, which is necessary to offset the increase the additional rake in the tree.

Kind of hard to see this offset which changes the steering head angle, but below is a picture I took with the kit installed on my 1200C.

Another good thing is that by not needing to actually cut the frame, you could aways reinstall the stock frontend at a later date to put the bike back in 'stock condition'.

Here is another little 'blurb' from the AME site:

"A tried and tested system now for nearly 20 years in Europe, the AMEbolt-on Chopper Kit is a safe and affordable system that lets you transform your bike into a custom chopper in 1 day, using your stock frame. The AME system actually changes the steering head angle on your frame without cutting or welding. This is not simply a raked triple tree, but a patented set of triple trees, bearings, fork tubes and offset components that provide the correct geometry.
The most important aspect of a chopper is the trail dimension, A bike which simply relies on a raked or adjustable tree cannot achieve more then 5 or 6 deg of additional rake before the trail becomes so small that the bikes handling becomes dangerous. The AME bolt-on system eliminates the guess work by providing your chopper with the same trail as the stock motorcycle."