Tuesday, March 07, 2006

Happy Trails

Do you get and read the Rivendell Reader? You should. There is some great reading in it. There was an article in the last issue about wheel "trail." For years I’ve wondered and didn’t know 1) why bikes naturally stay straight when you ride, 2) whey the turn when you lean, 3) why forks are always angled forward, and 4) why I don’t like riding Dutch Oma Fiets (even though they’re beautiful). It all comes down to trail (related, of course, to tons of other stuff).

Answers: 1) trail, 2) trail, 3) less trail, & 4) not enough trail. Fascinating.

Here’s a diagram of trail.

That’s a motorcycle. Bicycle rake refers to the fork bend and not just the angle. Bicycles don’t have steering “offset.” And bicycles have 1 1/2 inch trail, give or take. But the concept of trail still the same.

Basically, the wheel hits the ground not at the point at which the wheel turns left and right, but rather a little behind it. The point of contact the wheel makes with the ground is trying to follow (hence: trail?) the imaginary point that is the center steering axis. The bend in the bike fork lessens the trail, because too much trail makes low speed maneuvering too hard. Too little (or negative) trail makes the bike very unstable at higher speeds. I find this really cool.

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