Quote from Ben Franklin on January 1, 2023, 10:55 pm

For what it is worth, I posted some pics of the LL build, in a separate thread.  I think it may be the build referenced at the beginning of this thread.

You know, it is possible that we measured the near zero trail wrong, but a lot of eyes were on the technique.  A couple of things make me think the actual measured 0.4" of trail may be pretty close to accurate.

1.  Wheel base of the bike starts out at 62" from the factory.  When we finished the build, it was at 66", with the chassis set level with a digital angle finder.  Four inches of wheel base increase might imply a 4" decrease in trail amount, all other things being equal, which they may or may not be.
2. We put a laser through the steering stem to try to spot on a piece of graph paper where the line would hit from @Drone's diagram.  We  then measured axle center line dropped straight to the graph paper.  It showed a small amount of trail, maybe .4" or so.

Now we did not have the wheel on, with the weight of the bike compressing the suspension.  That may introduce some error in the measurement, but probably not a lot.  Maybe another 1/2" or so?

I don't know.  I was pretty surprised at how the rig handled with the theoretically greatly reduced trail.  Chuck tacked everything in position so I could test drive the rig and get the feel of how it handled, prior to finalizing the trail setting.  However, it was so sweet that I had no intention of changing it...

I have read where hack racers like to run close to zero trail, with the idea that they like the steering to be very quick and are not so concerned about being able to relax a little while riding.  I generally won't remove both hands from the bars of anything I ride, however, a few days ago, at about 65mph, I felt the need to zip up my collar.  Zipper was kind of stuck, so I used both hands, with the cruise control on.  I still cannot believe that I can take both hands off the bars without immediately diving into the right ditch, but it does seem possible.

I felt like I learned a lot, going through the LL build process with Chuck Loftkin; I suspect that I am just seeing the tip of the ice-berg, so to speak, but I sure like how my rig handles, now.

Quote from Andrew Baker on January 3, 2023, 4:22 pm

Raising the back end with taller shocks or more preload will reduce trail.

I suspect lowering the forks in the triple tree would too since it is in effect making the rear taller than the front thereby changing the geometry in a similar way.

 

 

Quote from Resonatorchief on January 28, 2023, 8:42 am

Hal at Metalcraft racing in Houston fixed a DMC leading link that had been built with ZERO trail. If you blinked, boom, you were in another lane. It was super twitchy and you could not take your eyes off the road lest you end up rolled in barbed wire and cedar posts with cows stepping over your carcass. I see why sidecar racers would like it, quick immediate turns with minimal effort.

Hal’s link is adjustable. We ran it out to negative trail once. I tried it on some slow back roads. It sucked. It wandered around sort of picking its own line. My bike stock had just under 4” trail so we adjusted the trail to two inches round about 50% of stock. Result was much stiffer steering at low speed but boy howdy when you got up to 70 it was solid and planted as if on rails. We then adjusted it to 60% of stock trail and for me that’s about all I need. With additional 10% reduction of trail, the steering is quicker and noticeable, especially at speed.

So in my very very limited experience, (3 rigs, maybe 35,000 hack piloting miles)  the closer to ZERO trail you get and beyond, the bike will become less and less controllable the faster you go. Personally, I think reducing stock trail by half would be a good start. But hey, I’m no expert. Each to his own. America, Land of the Free… .

My philosophy on owning Sidecars: You better be Rich or better be able to do all the work yourself. Those that pilot hacks know what I mean. $$$$$