If you're at-all familiar with the iBOB
lists, you've heard of the latest bike-craze: Low trail geometry
Low-trail geometry is supposed to be the bee's knees when it comes to front-loading a bike via a front rack or basket, as many randonneurs
do. Especially important for randonneuring, this design style supposedly makes a bike more resistant to unintended rider inputs (reaching for a water bottle, turning around to look backwards, etc.) so it holds a line better when a rider is dead tired and wobbly. Low trail design also is said to work well with wider, softer, lower-pressure tires, which may be favorable in a bike equipped for off-road riding.
So just what is low trail? On a bicycle, trail
is defined as the horizontal distance between the steering axis of the front fork and the center of the front tire's contact patch, as measured along the ground. Trail is influenced by three things: head tube angle, fork offset, and wheel size. For a standard 700C road-bicycle wheel, low trail is generally accepted to mean trail measurements of around 40-45mm or less.
There are very few modern production bicycles designed with low-trail geometry around today (note I specified production
, of course one can always get a custom frame built to spec); the most infamous is the Kogswell P/R
, another less-well known model is the Raleigh One-Way
Low trail production bikes seem to have been fairly popular through the 1970s up until the early 1980s. There are known low-trail models from Nishiki (e.g., some years of the International
model), the widely-popular Peugeot
UO-8, and some models of Trek
bicycles. Quite probably there are others as well. Many of these bicycles were originally equipped with lower-pressure 27x1-1/4-inch clincher tires on non-hook bead rims, and it is my theory that (at least in part) these sport-touring bikes were designed with low trail to make the best of the ride and handling on these puffy tires. As hook-bead rims and skinny high-pressure clinchers became the norm, we see the low trail geometry being dropped from the timeline.
I dug through the catalog archives at Vintage-trek.com
and identified what seem to be the low-trail models produced early in the company's history:
Low Trail Treks (models with 73-degree head angles and 5.5-inch fork
offsets in sizes 56cm and up)
Curiously, after 1984 the low-trail geometry drops abruptly from the Trek catalog, even though some of these models persist.
So, if you're curious to try out a low-trail bike, but you're shopping for a used bike
, now you know what to keep an eye out for...