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Debunking Low Trail

Debunking Low Trail

What is geometric trail?  

Trail is a measurement created by drawing a line along your head angle to the ground, and a perpendicular line from the ground up to the front hub. The difference in degrees between where those two lines intersect is called trail. Basically, it’s a measurement of how far the steering axis intersects the ground ahead of the tire contact patch. Numbers nerds read this next bit: Imagine two bikes with the same 73 degree head angle have two different forks. One has a fork built with 42mm of offset (sometimes referred to as rake, although they are not technically the same thing) and one has a fork with 61mm of offset. The 43mm offset fork would be considered high trail and the 61mm offset, low trail. The numbers actually don’t matter too much, but just so you have a basic idea of what this equates to: The 43mm offset fork has a trail of 59mm, and the 61mm offset fork has a trail of 41mm. That 18mm of difference is what this whole screed is about.

 

How does trail impact the way a bike handles?
First, let’s talk about how not to determine the way a bike handles. Lots of ‘authorities’ on bikes tend to employ ‘scientific’ ‘data’ to ‘prove’ a ‘hypothesis.’ They’ll tell you they rode this vintage bike next to this modern bike, and then a sorta modern bike next to this other vintage bike, etc. Graphs and charts and drawings of 15 different bikes will be presented as ‘evidence’. Footnotes will lend an air of ‘authenticity’ to the findings. They won’t tell you that the bikes are so different in every aspect that although these tests are empirical, the information has no control. They can hardly be called tests.
 
Many factors go into bike handling. One of these whatever is happening in your head. If you think you should be careful in a corner, your handling will suffer. If you think your bike is tracking beautifully through a corner, your handling will improve. If someone tells you a bike ‘tracks on rails’ and you go ride it, it could be a terrible handling bike that you’ve convinced yourself is great. In the bike shop we used to call this the Cannondale syndrome. Of course you are gunna say and think that Lefty fork feels great. It cost 2 times a normal fork, so the cost dictates a positive response. The brain is a powerful instrument of self deception. That’s why there are so many scientific tests that use placebos as a control.
 

 

High trail Rivendell Platypus

High Trail Rivendell Platypus


Low Trail Velo Orange Polyvalent

Low Trail Velo Orange Polyvalent

There are so many aspects that affect how a bike rides but if you had to sum up low trail, across a variety of steels, set ups, and riding conditions, a few general observations can be made:

  • Corners funny without a front load. I ride my bikes with loads all the time, but I also ride them without a load. Just a tube and repair kit and a water bottle. I don’t want to have to run a front load to make the bike handle well. Unloaded low-trail bikes feel like they are going wander off into the bushes to enjoy a bottle of Beaujolais. If you had a car that only cornered well with 4 passengers, would you be ok with that?
  • Feels pretty good with a front load. This really, is the crux of my low trail issue. The bike can feel good, but only if certain factors are in place. It’s like going on a date with someone who only likes Nepalese restaurants that are painted orange. It limits your options
  • Tracks well in a straight line, i.e. the steering self corrects if you wack a pot hole, or the bike feels really stable hands free right off the bat. Self correcting steering is of debatable utility. The bike is trying to self correct even when you don’t want it to, like if you are swerving to get around a pot hole. Many low trail bikes shimmy at a higher speeds. Flexy bikes don’t have to shimmy, and some stiff bikes can shimmy too.  
 

I’ve seen terrible shimmy on supposedly stiff touring bikes. Even with thru axles and oversized tubing. I’ve ridden low trail bikes that felt like they were gunna shimmy right out from under me, and a knee on the top tube wouldn’t break the frequency. Trail, of course, isn’t the only factor at play here. You can get a low trail bike to track straight and not shimmy. Wider tires, longer wheel bases, longer front ends, all help. Stiffness in the frame and wheels helps too. Also, headset choice, bar height, wheel weight, rider ability, and mental state. In short, to nail stability to a fork offset alone is akin to someone saying they can’t get a date because they wear red ties. Maybe, but it’s more likely they can’t get a date because they live in their parent’s basement.

High trail and mid trail bikes handle similarly to each other so I won’t break them out into two sections. Let’s call them high trail bikes for short. You’ll secretly know I am talking about mid trail bikes too.

Here’s a question for you: What kinda bikes need stability at both high and low speeds, use big tires, and have to handle a variety of terrains? Mountain bikes! And the OG ones, before 180mm travel forks, were high trail.  

They were great at dealing with fire roads, single track, and the occasional commute to work. Take a 1993 Bridgestone MB-1. It was a no-frills, but really well made, production mountain bike. Bridgestone had enough forethought to stick fender and rack mounts on it. They’re great commuters now, if you can find one. Cruise around on a MB-1, then throw some racks on it or just a big ass rear rack, or maybe a big ‘ol Wald front basket, with no rack under it. The bike still handles the same. Almost. If you overload the basket or rear rack, the handling gets weird. Not because of the frame geometry, but because the basket and rack are flexing like Arnold Schwarzenegger circa 1967.

When you corner with a flexy rack, the load in the rack wants to keep going in a straight line, while the bike wants to turn. That makes handling feel tipsy, like that time at that wedding with the vodka slide. Also, frame flex comes into play with a big load. The bike feels like it has a hinge in it, somewhere along the top tube and down tube.
 
These attributes are not frame geometry issues, though. With a moderate load, the MB-1 corners, climbs and descends with or without a load with equal aplomb. As a bike should. This is typical of high trail bikes: Rivendells, the Crust Evasion, a Gunnar Sport, 1995 Rockhoppers.

Most bikes built after 1985 have high trail, and for good reason! Consistent handling. Handling only gets weird on high trail bikes when tires get huge and traction starts to ‘overwhelm’ the geometry. Good examples include 29’er mountain bikes and fat bikes. These bikes started life with standard-ish trail numbers, but quickly threw those standards in the waste bin. Manufacturers tried to figure out how to make big, sticky tires not handle like a Ford Fiesta with blown struts, but this article is not about those bikes, so we won’t go there!

Trends change for a reason, but the reason is rarely the one you think it is.  

For example, the trend toward long stems on road (and eventually mountain bikes). Folks today consider the 100mm stem the bench mark for neutral handling on a road bike. But the 100mm + stem did not come out of some ‘ perfect’ bike geometry. It came about because of track bikes with adjustable stems. Back at the turn of the last century, when McKinley was annexing Hawaii, track racers started riding bikes with adjustable stems that could reach out far enough for the tallest of riders. They did this because one frames was used for multiple riders on a team. Larger riders needed longer stems. They would loosen a bolt and pushed the bars out. And just like everyone wanted to be Lance in 2004, everyone in 1899 wanted be a track racer. Norm-core bikes, then and still today, copied the race bikes, not out of any sense of practicality, but because it was hip. The long stem took hold, and people forgot that short stems worked well, and eventually assumed they didn’t work well because no one had them anymore.  Point here is, most folks think long stems exist for a good reason, but really they exist because people blindly follow marketing trends.

Back to trail:

The Crust Evasion has the same problem cycloturing bikes had back then. A short top tube, big tires, and a high trail fork. This leads to pretty awful toe clip overlap, not ideal on tech singletrack!

Low trail bikes came to prominence on French cyclotouring bikes. And it was the dominant design feature from the late 1930’s to the late 70’s. These bikes had a bunch of genuinely interesting and innovative features: tons of aluminum parts (whereas racing bikes used steel for stems, bars, cranks, etc), sealed hubs, integrated lighting, all things we still dig. However, handlebar bending and aluminum manipulation was in its infancy. Compact (short and shallow) handlebars did not exist, at least partially because they could not. So these bikes had long reach handlebars. That put the hoods way out over the front of the bike. Which meant big reach, unless the top tube was shortened, so it was. Lunch is never really free. As the top tube is shortened, the dreaded toe clip overlap became an issue and cyclotouring bikes, with their 38mm tires (which was huge at the time!) and big aluminum fenders, had it especially bad. How to solve it…?

Our guess is that low trail was born, not out of a desire for a better handling bike, but as a solution to toe clip overlap issues.

An example: cyclotouring bikes are intended for trudging up mountain sides with a load. That means the front wheel flops all over the place especially when you’re in the lowest gear on the steep stuff. Toe clip overlap for days! The easy solution: push that front hub out, and do it by increasing the fork offset. They left the head tube angle alone (stock lugs are not ideal for slack head tube angles), and the top tube needed to remain short because of the long reach drop bars, so you gotta solve the problem a different way. Voila, low trail is born.

If low trail was actually a magic bullet to bike handling, Rene Herse (the best known of the Contructeors) would have spec’d it on all their bikes. But the bikes they built without fenders mounts had high trail designs. Even some of the bikes designed for front loads had it too,*gasp!* The people who invented low trail didn’t even use it if they didn’t have to!

The question today is: why is it back? The toe-clip overlap issue was solved over 100 years ago. Lengthen the top tube, shorten the stem, and throw on some short-reach, compact dropbars. Done. High trail bikes handle great with stems as short as 0mm! This, combined with shorter reach handlebars, means you can kick the front end out far enough to solve toe clip overlap, while maintaining good handling at any speed with or without a load.

Don't believe the hype!

Hype and what actually makes sense are two different things. The bike industry is permeated with hype and myth, and just a smattering of facts thrown in. Building a bike on a myth is like building an airplane with bird feathers and wax. As Public Enemy would say: ‘Don’t believe the hype!’