I'm looking for a new frame and different companies measure their head angles differently, some do it with their bikes stationary e.g. with a fully extended at a certain fork travel and others based on a fork at certain travel with 25% sag. Is there a way of determining what a frame with head angle with fork extended would be with 25% sag and vice versa. Its difficult comparing the head angles as they're all measured differently.
linkage if you can still get hold of it would do it for you, failing that hands on is the best reccomendation, also if you are buying frame only see how your fork lengths stack up to others - and headset stacks!!!
have alook at the published geometry and do some trigonometry.
mikewsmith - where could I obtain this from?
General rule is 30mm/1-inch = 1 degree of change
So a 150mm fork sagged 30mm to 120mm length will change head and seat angles by one degree slacker.
The Cotic geek thing is very useful! For instance if you're looking at bikes with 120mm forks, the difference between sagged 25% and static will be the same as the difference between 120mm and 160mm on the geek thing - 1.8 degrees. My Soul with a 140mm fork is thus 68.6 sagged and 66.8 static. The longer the fork, the bigger the difference between sagged and static.