How long a fork is safe to fit to a 91 steel frame?

[ultrazenith]

Doing some calculations, it seems the Haro head angle was close to 71.5 degrees, so slackening by 1.8 degrees would take it to 69.7.

Going 24x4" on the front might be interesting. Might be a problem finding a fork, though.

 

[Bullpup]

On One did some 24" fat bikes so they may have the right sized fork. Alternatively will a 3" gazzalodi work?

 

[The History Man]

just put a 29er fork in there and have a blast!

 

[ultrazenith]

I think I've found the right fork for a retro 26+ project: the Surly 1x1 80 mm corrected fork, which has clearance for a 3" tyre and a modest 413 mm axle to crown length.