Measure the one in if it is a direct replacement.
Otherwise it changes with frame size, so we will be guessing.
But measure as it easiest.
Or measure the headtube, it'll be 110/120/130/140/150/as Kona kept to nice round numbers.
Then ad you headset stxk height (guess at 40mm for threaded as you can always cut it shorter.
Give yourself the stack height of the headset top parts to play with.
25mm is probably a approx number there.
The existing forks are threadless. I'd quite like to stick with threadless for simplicity, but I can't seem to find any 1 1/8 threadless rigid forks - do such a thing exist?
Ideally I'd just want to swap them out for rigid non-threaded, but I can't seem to find what I'm looking for (1 1/8th non-threaded, rigid), or maybe I'm looking for the wrong thing.
Adding to what F.C. has advised; the 1993 Cinder Cone is Pre-Suspension corrected geometry. A Threadless Rigid Fork with a shorter Crown to Axle and Canti Bosses will be somewhat trickier to locate.
The bike was designed to give the correct Head Tube angle with a C-A of 390mm, which was the spec for the Project 2 that year - but it will be threaded. I believe that the Project 2 was not made in Threadless, 390mm, Canti. You could use a later pair of 410mm Suspension Corrected Project 2 forks that came in Threadless, but this will make the steering a little more sluggish - but no more labouring the the Rock Shox J3 currently on there.
Great info, thanks. I'm considering doing a drop bar gravel conversion on this, so sluggish steering wouldn't be such a bad thing. Definitely want rid of the J3s, they weight a ton!
Head tube is 15cm so steerer as appropriate. Axel to crown of around 410 please. Don't want to spend massive amounts, just want to get an old Cinder Cone rolling. Thanks!