SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

9/10/2007

About Low Trail, and Low Trail Treks

If you're at-all familiar with the iBOB and/or KOG 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 and porteurs 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)

1976 TX300/500/700
1977 TX200/300/500/700
1978 510/710/910
1979 510/710/910
1980 412/414/510/710/910
1981 412/610
1982 311/410/412/610/613/614
1983 400/500/520/600/620/630/640
1984 400/420


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...

Labels:

4 Comments:

Blogger Jim G said...

search ebay for these low-trail Treks

1:21 PM  
Blogger Chad said...

Looks like you found a good one on the bay. I wonder what the closing price will reach because there simply aren't new frames like this, except for custom.

I'm thinking about increasing the rake on my '86 Trek 310. The geometry isn't quite as nice as those, but hopefully is close enough.

Good luck to you!

6:13 PM  
Blogger russell said...

hey all -

Just to add to the list of low-trail candidates....

I'm having an old Fuji Touring Series IV built up as a commuter. According to the Frame Geometry Project, that bike has a head tube angle of 73 degrees and a rake offset of 70mm (!!!) yielding a trail of something like 30mm.

URL for the geometry project is http://home.comcast.net/~pinnah/dirtbag-bikes/geometry-project.html, it's worth a look.

Can't wait to ride the thing, I should be picking it up from the LBS on Saturday.

Thanks!!

7:28 PM  
Blogger parksie555 said...

I have an 84 Trek 400 Series. Bought it new when I was a junior in high school and consider it the best $329 I ever spent. Have replaced a few components over the years due to wear and tear but is still a great around town ride that I ride nearly every day.

8:09 AM  

Post a Comment

<< Home