Tuesday, July 8, 2008

The Crustacean Part 2

Trail is the horizontal distance from where the steering axis intersects the ground to where the front wheel touches the ground.
Trail = (wheel radius X the cosine of the HTA - rake) divided by the sine of the HTA. (HTA=Head Tube Angle) 50 to 70 mm of trail is the generally accepted range with 50 being quicker steering and 70 being slower.
Since the wheel radius changes by 8mm, this changed the trail of the front wheel. so in order to get the bicycles to handle similar, you want the trails to match. Since this bicycle isn't for racing and more for leisure I want the bicycle to have more stability.

These are the numbers I'd like to use. Since the trail is higher than the Caad9 the handling is going to be slightly slower, on the way I put it it will have more stability. It's not a race frame.

But just for the fun of it I ran the numbers to match the Caad9. First I changed the rake to match, then in the next I change the Head Tube Angle.
So to match the trail I either have to change the rake to 48.5mm, change the head tube to 74.1, or I'd have to change them both. This begs the question, does it make a differencewhich one you change. In short the more rake you have, the longer the fork blade has to be, so it's more flexible/comfortable. If you want a more ridged front end you change the head tube angle. Many factors to consider, none right or wrong, just different philosophies.
Tommorow I get to pick the tubing and small parts.


dmar836 said...

So what happened to the tall bike?

CurbDestroyer Chronicles said...

Got put on hold. I've been telling Crusty I'm going to build his bike for 9 months now.