Rake and trail -

[Mikej]

Real quick, when a builder talks rake and trail, is it assumed to be the horizontal trail or perpendicular mechanical trail? So a trail of 57 would have a mechanical trail of 55 - but it would be referenced as a 57 trail?

[rnhood]

As I understand it, "rake" is a measurement based purely on the fork design, while "trail" is a horizontal measurement based on intersection points driven by the headtube angle and fork design acting together. Hope this makes sense.

[ColonelJLloyd]

I don't know that it makes much difference. Are the numbers ever more than a couple mm different? I would imagine values are given as the horizontal distance between the tire contact point and the intersection of the center of the steering axis and the ground, whatever you want to call that. That's what you see in a BikeCAD drawing, right?

[adamhell]

http://yojimg.net/bike/web_tools/trailcalc.php

click on "Mechanical Trail" at the bottom right and it links you to the wikipedia page. not to mention, this site is pretty nifty.