Trail Calculator link

[AussieHard]

http://www.rbracing-rsr.com/rakeandtrail.html


Thought this was an interesting little program and might be of use to people.



Front Tire inches Diameter of front tire.

Rake degrees Steering Neck Rake:

Triple Clamp Offset inches Distance from center of top of steering neck to centerline of top of fork tubes.

Fork Length inches Length from to top of the fork tubes to the centerline of the axle.

Triple Tree Rake degrees

Anyone know the stock figures?

 

[XSLeo]

I plugged in the stock XS650 specs.
Tire size 26.1
Rake 27 Degrees
Offset 1.938 inches
Fork length 29.5 inches
Tree rake 0.0
The calculator gives a trail of 4.47 inches. The book says 3.9 inches.
It don't match.
I measured the fork length from two sets I have setting here. I measured the offset right from the trees. I used their tire size figure for a 19 inch tire. The frame rake is from the book.

 

[XSLeo]

I did some juggling of the figures. I measure from the center of the stem to the lead edge of the fork tubes instead of the centers I get 2.45 inches instead of 1.938. I put the 2.45 and get the 3.9 trail. Maybe the book is wrong because the writers used the wrong offset.

 

[mrriggs]

Measure the offset of both the top and bottom tree. I had a set of stock XS750 trees that had nearly -2° of "rake" built in.

What year trees are you measuring? The later model XS650s had 4.5" of trail.

 

[XSLeo]

I have a 75 set of forks leaning up against the wall. I looked at the wrong spec, the 70- 72 has 3.9 inches of trail. The 4.53 spec started in 73.
I guess I used the wrong spec.
Can some one with a 70-72 bike give us the offset of there forks?
The specs for the frame rake is the same early as late. The offset kust be larger to get the 3.9 trail. About 5/8 inch more Id say. Close to the 2.45 I put in to get the 3.9 trail.
I have a set of xs1100 forks. About the same lendth but the offset is about 1.313. This would alter the rake to about 5.1 inches. Not enough to be unsafe but it will feel different, just not sure how.
Straight line stability increase, slower turn in?