Bicycle geometry. A brief look into how it effects your ride.

Bicycle geometry.  A brief look into how it effects your ride.

Ok, since I started blabbering about and ripping on the Jamis Aurora, I felt I needed to explain the geometry of a bike a little more in detail.  So after some work in Photoshop, I’ve got a graphic and some more information to help in a touring bicycle search.

Definitions first…

Head-tube angle- the angle between the floor behind the front wheel and the steering axis.

Trail- the distance between the front wheel’s center on contact point and the point where the extending steering axis line reaches the ground.

Fork Offset (rake)- the distance that the hub preceeds or follows the steering axis.

Let’s look at the graphic to put it all together.

Bicycle Geometry

The shaded green thing is the fork.  Remember, the bigger the trail, the more stability.  Small variations in any of these angles can have a serious impact on your ride.  Larger trail figures will give you more stability, but steering precision is compromised.  Longer wheelbases make turning more difficult than shorter wheelbases.  Your touring bike will have a long wheelbases, so don’t expect precise turning.  Your ideal touring bike should also come with a low bottom bracket, which keeps your weight closer to the ground, making it take less effort to move your body from side to side.

Plug all your specs into this website calculator…check the ACTUAL TRAIL CALCULATOR

http://www.wisil.recumbents.com/wisil/trail.asp

Unless I hear otherwise, use 12.25 as the tire radius, that is for a 700 c tire.