SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.

5/19/2008

Measuring Trail

This photo depicts how I measure a bicycle's trail. First I suspend a plumb bob (use a key tied to a length of string) from the very end of the threaded side of the front-wheel's Q/R skewer. Then I hook a string over/around the fork steerer or stem quill, and stretch it down parallel to the steerer and the upper fork legs to the ground, where it's held against a ruler. Measure the distance between the stretched string and the plumb-bob and you've got a rough trail value. Make sure the bike is positioned on level ground with front wheel straight, and is as vertical as you can make it.

2 Comments:

Blogger blackmountaincycles said...

Jim,
There are several easier methods to measure trail. I've got an excel file that I found somewhere on the internet that I just e-mailed to you. There's some good info on Anvil's website too with the same formula.
http://www.anvilbikes.com/?news_ID=49&catID=3
Mike

7:36 AM  
Anonymous Johan said...

You (blackmountaincycles) are clearly missing the point that to use such calculations, you still would have to measure all the variables in the formula, which most probably would induce larger errors than the simple strings method.

Calculating trail with known variables is very simple, the hard part is to get that information, and the strings method does this in a fairly accurate way.

4:41 PM  

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