steering trail

Steering geometry is a pretty well studied area, and hapilly few motorcycle or bicycle riders need to give much thought to it (although the advanced riders certainly do) because ... well because the best riders already have, and have worked closely with the engineers and makers to make sure that everything is done right. Its pretty well understood these days (like the last 50 years).

Sadly most of the the eScooter community is entirely ignorant of it and the internet fora are of course rife with fools and idiots who know a few buzz words (or don't) and dismiss this idea as etheric.

This results in the perpetuation of unsafe scooters on the market.

In short, trail is the distance the contact patch is behind the steering axis (just as in a castor wheel on a shopping trolley or office chair) on a Scooter it looks like this:

The angle down is called by some the "rake", this angle helps but trail is the main factor in stability (like a castor wheel).

Now this is a common amount of rake and trail on a modern MTB

yet on many modern and fast scooters the amount of trail is dangerously small, such as this Zero which is almost nil:

In contrast both of my scooters above (the Widewheel and MX60) have quite well designed amounts of trail

... meaning that I can briefly let go of the handle bar to (for instance) hand signal a turn, for instance even at high speeds the steering is quite stable:

While many scooters (such as the zero above) are so inherently unstable people consider "steering dampers" for them.

My Giant MTB for instance has the following spec published on the Giant Website:

although what is called rake here is probably offset, and another meaning of rake is the angle that the forks are raked at (which influences flutter of the wheel or better known as wobbles).

Meanwhile eScooter riders wet themselves instead on top speeds and the "advanced" riders know fancy terms like "steering damper" (which essentially means bolt on fix for shit geometry). So as I said at the start, well understood and a published spec in the bicycle world and in the motorcycle world too ... just not in the advertising mush or reviews (don't start me on how miserable and technically ignorant most reviewers usually are).

For the interested I'll leave you with some good articles to read up on this:

The obvious one is this https://en.wikipedia.org/wiki/Caster which soon leads to an issue of flutter:

One major disadvantage of casters is flutter. A common example of caster flutter is on a supermarket shopping cart, when one caster rapidly swings side-to-side. This oscillation, which is also known as shimmy, occurs naturally at certain speeds, and is similar to speed wobble that occurs in other wheeled vehicles. The speed at which caster flutter occurs is based on the weight borne by the caster and the distance between the wheel axle and steering axis. This distance is known as trailing distance, and increasing this distance can eliminate flutter at moderate speeds. Generally, flutter occurs at high speeds.

which naturally leads into: https://en.wikipedia.org/wiki/Caster_angle#Two-wheeled_vehicles

and finally: https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

If you have not yet chosen a scooter I hope this article has opened your eyes to an important aspect of scooter safety.

Happy and Safe scooting