calculating head angle change due to longer fork

ultrazenith · Mar 7, 2017

I have a 92 frame with a short fork, 380 mm axle to crown, and I have been wondering whether it would be feasible to put a longer one (425 mm) on it. Does this sound mad? The frame has a head angle of 71.5 degrees, according to the brochure of the day.

Edit: according to an online calculator I found, the new head angle would be something like 69.3 degrees with a longer fork and slightly fatter front tyre.

cce · Mar 7, 2017

I seem to recall it's something along the lines of +25mm = -1 degree

if it's a suspension fork, remember that it'll sag a bit when you're on the bike which will take up some of the difference.

Also 380mm sounds VERY short....

mattr · Mar 7, 2017

Don't forget to allow for seat tube angle and the higher bottom bracket.

If you keep saddle/bottom bracket relationship the same with the longer fork, you'll take something like 25mm off the reach.

calculating head angle change due to longer fork

ultrazenith

Senior Retro Guru

cce

mattr

Old School Grand Master

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