Have done this a few times--but have always gotten confused. it always appears at first look, that this modification will bring the front wheel (axle)closer to the frame, rather than farther, but you're actually moving the triple tree rearward, increasing the rake of the front forks,moving the wheel (axle) away from the frame, thereby decreasing trail?
To decrease trail using triple tree's the angle of the forks is changed moving the axle forward THIS DOES NOT CHANGE RAKE. The set up in your diagram does reduce trail a bit but not all that much and does not address the lower tree at all, It works as the lower bearing no longer makes full contact with its race. I owned one bike years ago that this was done to. In the case of the bike I purchased this way I would say it was a waste of time. It also caused the handle bar mounts to hit and dent the fuel tank. The way most modern tree's are made to reduce trail has the hole that you are making into an eccentric adjustable hole machined at an angle changing the angle of the forks. Then the lower tree is made so that the forks line up with the new angle. The lower tree ends up being a lot larger then original as the forks are moved out. As this also drops the front end some, spacers are usually used on the fork tubes to bring the front end back up. Some times this is done at the tubes, other times it is done with longer spacers for the springs taking some of the sag out of the front springs.
In your diagram you will see that the line down the steering head its ahead of the axle of the bike. By moving the front wheel forward you are moving the line from the steering head forward. Moving it forward moves it closer to the line drawn from the axle. The distance between these two points is your trail. So by moving the axle forward you are closer to the point drawn from the axle so your overall trail is less.
Jay G
DMC sidecars
866-638-1793
www.dmcsidecars.com
866-638-1793
Thank you so much. Hadn't considered the handlebars! This is a 620 Ducati Monster with Bingham MK 2--any availability of a new triple tree setup, or a can a machine shop modify? This mod has worked wonderfully on older bikes, and Doug B and I raced on this mod, with no problems--but just don't trust it on this setup
Never done a 620 Monster, have done several other Ducati's as such I have nothing for this bike and have not even looked at a bike so I have no recommendations at all.
Jay G
DMC sidecars
🙂 it's all good. the steering is OK with 3.75" trail. Just have to complete a lot of stuff on the rig. finished the clear coat today--the main thing is to RIDE it, and the miles are piling up--can't wait for fall. Many thanks for your time! Mike
