Originally Posted by
bashley
Bicycle Trail Calculator. Awesome! Thanks Spoonrobot.
Now, can it also be derived if no offset is given, say, by some other means? It's very spotty with bike manufacturers, a lot them not including that offset spec. What if you know the front-centre measurement and HT angle? Not enough data?
Trail is the distance on the ground between the line of the steering angle and a vertical line from the dropout, which requires the outer diameter of the tire.
So you would derive it by drawing a picture of the above and measuring, measuring the actual bike, or writing a math formula - which is what that website does.