4 ms·

The description of trail could be a lot better, given how important it is. It's effectively the degree to which the front wheel acts as a caster. When you pus

The description of trail could be a lot better, given how important it is. It's effectively the degree to which the front wheel acts as a caster. When you push a shopping cart the caster wheels automatically straighten out and trail behind the steering axis in a straight line. The front wheel is doing the same: when moved forward it resists being steered and wants to go straight. The degree of trail effects how much it wants to go straight. Racing bikes etc. are high-trail bikes because by going straight the steering is stabler at high speeds. High-trail bikes can also be ridden no-hands because the wheel is effectively on autopilot. Any time you need more nimbleness and precision in steering -- perhaps a mountain bike? -- you want to lower the trail. Porteur bikes -- bikes that carry big boxes of flowers over the front wheel say -- also need very low trail because they're already hard to steer due to all that inertia. And with small wheeled bikes it is very difficult to achieve significant trail without a very shallow head tube (steering) angle, so many folding bikes by necessity have a very "live" steering. One of the dumber bike decisions I can think of is Brompton's inclusion of a rake on the front wheel, thus making its steering worse.

loeg 6y ago
Trail on road bikes, racing and not, seems to be universally in the range of 55-60mm (across frame sizes, too). I suppose it depends on what kind of racing you're doing, but some kinds of bicycle racing involve cornering agility / nimbleness, and you want a shorter trail for that.
- petre 6y ago
  Randonneur bikes (also road but with fatter 650Bx42 tires) typically have longer trail (typically in the seventies) because they carry front loads.
  - loeg 6y ago
    Right — I was commenting specifically on "Racing bikes etc. are high-trail bikes because by going straight the steering is stabler at high speeds."
  - et-al 6y ago
    Long meandering post on trail.. after rim brakes vs disc brakes and wheel size, trail is probably the next most contested subject in bikenerdom. SeanLuke provides a good example with the caster. I also recommend reading Dave Molton’s blog (who’s built frames longer than most people here have been writing bloated JS SPAs) for more: Trail, fork rake, and a little bit of history - https://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-and-little-bit-of.html https://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-a... Now porteur bikes and typical randonneuring bikes often have lower trail. People are often focused on the trail numbers, but the simple reason is to position the front load (handlebar bag or stack of newspapers) on or right behind the front axle. Framebuilders do this by increasing the rake (fork offset) to stretch out the front axle, which results in decreased trail. The reason is that you want the weight at the fulcrum to reduce any "inertia" when steering--so the bike remains easy to steer with the additional weight. If you’re not intending on riding your bike with a front load most of the time, then you probably do not want a low trail bike as they are more sensitive to rider input on the handlebars when there is no weight. Also, randonneuring is just an activity, so you can ride any bike with any geometry you want. But in America, especially on the West Coast, there is a bit of bike-cosplay in the randonnerding scene, so folks like to ride bikes built in the old French Constructeur style. Lastly, SeanLuke is probably not familiar with mountain bikes, but modern geometry for XC and enduro bikes is towards slacker headtube angles (resulting in higher trail) for stability when descending. For anyone interested in geometry, I highly recommend browsing Bike Insight's category section: https://bikeinsights.com/categories https://bikeinsights.com/categories
    - SeanLuke 6y ago
      > Lastly, SeanLuke is probably not familiar with mountain bikes, but modern geometry for XC and enduro bikes is towards slacker headtube angles (resulting in higher trail) for stability when descending. I'm certainly not familiar with modern mountain bikes. Very interesting that some have slacker headtubes for downhill, but it definitely makes sense.
teslaberry 6y ago
how true! i own a brompton. strida was worse. i also own a low gravity worksman delivery bike. yours is the best concise exaplanation of trail ive heard. THANK YOU. still, almost all folding bikes have shit steering. lots of trail AND a small front wheel!

loeg 6y ago

Trail on road bikes, racing and not, seems to be universally in the range of 55-60mm (across frame sizes, too). I suppose it depends on what kind of racing you're doing, but some kinds of bicycle racing involve cornering agility / nimbleness, and you want a shorter trail for that.

petre 6y ago
Randonneur bikes (also road but with fatter 650Bx42 tires) typically have longer trail (typically in the seventies) because they carry front loads.
- loeg 6y ago
  Right — I was commenting specifically on "Racing bikes etc. are high-trail bikes because by going straight the steering is stabler at high speeds."
- et-al 6y ago
  Long meandering post on trail.. after rim brakes vs disc brakes and wheel size, trail is probably the next most contested subject in bikenerdom. SeanLuke provides a good example with the caster. I also recommend reading Dave Molton’s blog (who’s built frames longer than most people here have been writing bloated JS SPAs) for more: Trail, fork rake, and a little bit of history - https://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-and-little-bit-of.html https://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-a... Now porteur bikes and typical randonneuring bikes often have lower trail. People are often focused on the trail numbers, but the simple reason is to position the front load (handlebar bag or stack of newspapers) on or right behind the front axle. Framebuilders do this by increasing the rake (fork offset) to stretch out the front axle, which results in decreased trail. The reason is that you want the weight at the fulcrum to reduce any "inertia" when steering--so the bike remains easy to steer with the additional weight. If you’re not intending on riding your bike with a front load most of the time, then you probably do not want a low trail bike as they are more sensitive to rider input on the handlebars when there is no weight. Also, randonneuring is just an activity, so you can ride any bike with any geometry you want. But in America, especially on the West Coast, there is a bit of bike-cosplay in the randonnerding scene, so folks like to ride bikes built in the old French Constructeur style. Lastly, SeanLuke is probably not familiar with mountain bikes, but modern geometry for XC and enduro bikes is towards slacker headtube angles (resulting in higher trail) for stability when descending. For anyone interested in geometry, I highly recommend browsing Bike Insight's category section: https://bikeinsights.com/categories https://bikeinsights.com/categories
  - SeanLuke 6y ago
    > Lastly, SeanLuke is probably not familiar with mountain bikes, but modern geometry for XC and enduro bikes is towards slacker headtube angles (resulting in higher trail) for stability when descending. I'm certainly not familiar with modern mountain bikes. Very interesting that some have slacker headtubes for downhill, but it definitely makes sense.

teslaberry 6y ago

how true! i own a brompton. strida was worse. i also own a low gravity worksman delivery bike. yours is the best concise exaplanation of trail ive heard. THANK YOU. still, almost all folding bikes have shit steering. lots of trail AND a small front wheel!