Stevan Thomas answered Doc Simont:
> The only way you can measure the trail distance on the wheelbase datum line,
> is if you have a drawing (or a computer drawing) of the entire frame. Once a
> fork is built and out of a bike, the only meaningful measurement is at 90
> degrees, because that's the only one you can physically determine with tools.
> If the theoretical head angle is known, you could mathematically get the
> other measurement, but why? Every frame I drew and built, I measured the fork
> offset at 90 degrees, because that's how I was going to check it for accuracy
> when it was finished.
That is of course correct. A quick calculation also shows that a change of ten mms measured that way for normal bike angles will give a change in trail of about 10.45 to 10.50 mms, to small to be of any consequence.
Nevertheless, what interests me is how much differencies in trail mean, subjectively described by people with greater experience than me.
tailwinds
Olof Stroh
Uppsala Sweden