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I guess I am guilty of calling it as I feel it... and the history is quite long as to how I've come up with this peeve.

To make a long story short, the "steering scrub" term comes from watching a lot of tire left bhind on concrete when pedalling away from a previous commute parking space. Over time, I saw a lot of rubber staining the walkways where I did a hard left and I started working on Ackerman compenation correction on my beloved Actionbent trike.

More recently, I noticed our '06 Road had the same symptoms. She doesn't get too many miles so I've left it be.

I had hoped that at least the 700 had better Ackerman follow-through (<- not technical that I know of). But it only took 1 turn to know it wasn't optimized. A frame of reference here is an ICE trike that glided through a slow turn without any "grind" of the rubber. You can almost see it "walking out" (pushing) if you look at the ground at the outside tire in a sharp turn.

As I like saving money... and have no reason to spend more on tires than is neccesary so I felt this needs to be addressed and it turns out to be -very- easy to do.

Again, from experience with my Actionbent, not only do the tires last a -lot- longer, but the trike doesn't slow down as you make a turn. Perfectly dialed Ackerman should indeed add no resistance short of the lateral forces on the tire. The tires -should- follow their natural arc a little bit (g-force - drift compensation). If not, it is no different than having toe error while cornering.

Again, it is a fine science. Performance cars for various sports use all kinds of commonly known "compromises" to achieve an edge in a specific manouver. Nascar tweaks for speed and stability while F1 dials for cornering stability. Their geometries are significantly different. I'm going for the perfect geometry for every day riding/commuting where long sweeping turns should be efficient (proper Ackerman follow-through) and for having the tires follow their natural arc through technicals on trails. I figure every watt wasted in turns is a watt not used for efficiency.

As for speed demons... I would say it is worth learning about this and knowing what can and cannot be tweaked to improve performance. Soon, we will have the human powered challenge here at PIR. This cource has a lot of long sweeping curves and it is a time trial so efficiency is very important at every position on the track. I'd go so far as to say "remove the tie-rod" for this challenge. This would guarantee perfect follow-through.

We all know Paulo is working to make the most efficient factory possible. Unfortunately, this area is one where performance is dialed to the specific wheelbase. At one time, and I have to assume this is still the case, it was confirmed that Big Cat only makes 2 spindle geometries for all the trikes. This means a 20" spindle and a 16" spindle for all the different wheel-bases. I suspect the 16" wheelbase was based on the Speed... and the longer wheelbase of the 700 was a compromise. Not having ridden a Speed, this is only a guess but when you understand Ackerman compensation, every model with a different wheelbase -should- have a different length tie-rod.

In order to completely dial in the 700, I would have to also work with the tie-rod length (slot the hole or make separate brackets) but the vertical change I am talking about here deals with follow-through (again, not technical) in the attempt to maintain proper toe alignment through the entire turning range.

I probably lost most of you by now but for those still hanging on every word... all 2 of you! ...my favorite testing grounds is a baseball diamond. A hard-pack clay that leaves a really nice track to see what your tires are doing. If the tires plow dirt, you got issues. Start out at the extremes of the diamond and slowly start turning tighter and tighter until you end up at the 15-someodd foot diameter. Now retrace your tread marks and see if they are all nice and defined. This works best with threaded tires and I know I am asking a bit much here from a 700 owner so just watch that tire (usually the outside is the follower) and see if it pushed or if the inside tire pulls.

Again, it is just a challenge. I wanted to share this observation but not to have people go nuts on their machines. Those of you who are purely performance driven can gain from this; those of you who recognize this and like the engineering aspect of our machines will gain some insight. Again, the few ICE trikes I've riden had significantly smoother cornering characteristics. My Actionbent was an extreme case... it had -NO- Ackerman compensation at all! It does now and it has pretty darn near perfect follow-through. I have a baseline.

Fly... I cannot convince you but I guarantee you that Mark is -no- expert.
I can only suggest you try it since you are looking for more efficiency on your trike. What have you got to loose?

And, just to be clear... I took a trike from no Ackerman to perfect Ackerman. In the process I learned about this by a BROL member. It has been the primary means to tweak handling to peoples likings. Just 1/2" movement up or down makes a -huge- difference.