Tessek461

I'm putting a mountain bike together piece by piece so I can get a better understanding of bicycle mechanics, plus it'll also be cool to say "I built that bike." At this point I'm ready to get some forks, but I have no idea what to get. Do all forks fit all bike frames, or is there a measurement I need to be aware of? The frame I'm building from is nothing fancy, just a 1997 Gary Fish Marlin.

Andrew R Stewart 

Fork fit is a variable issue. Some dimensions are critical, others less so.

First is the fork's steerer and the frame's head tube must be the same family. Youe bike is likely a 1.125" standard. Next is the headset spec. Again your bike is likely a "traditional" head set with the bearing cups outside the head tube, pressed into it. the fork crown race must press fit over the base of the steerer, for a 1.125" headset this dimension is a standard. The securing of the headset adjustment should be via your stem, hence a threadless spec (the steerer has no threads at it's top end). Lastly the fork's steerer must be long enough to go through the head tube, head set amount (called stack height) and leave enough for the stem to fit properly. Different stems have differing amounts of steerer they need to fully clamp.

Next are the more varing aspects. The biggie is the axle to fork crown length. This is dependent on, amongst other factors, the suspension travel. More travel means a longer/taller fork. The taller a fork the more it raises the front end of the frame, making the steering more "chopper" like. The frame was designed with a certain axle to crown length but chnging it won't make the bike wrong, just change the feel of the steering response.

Another factor are the brakes. Canti/linier bosses or disk mounts (and which type of disk mounts). Also the axle securment method needs to be understood. Standard 100mm width drop outs? How about axle diameter?


So the replacement of a fork can be easy to do but challenging to get just so. Andy.