A
Andrew Lee
Guest
I have '93 Stumpjumper FS that has a leaky (oil) Specialized Future Shock air/oil fork. It needs an
overhaul, but I don't think the parts are available anymore, at least that's what I was told when I
asked around locally, so I am thinking of replacing it. The fork is much shorter than current forks
and has 2" (or less) of travel. I measured it at 415 mm long from axle center to crown race seat at
full extension. Newer forks are longer. The Marzocchi MX's are 458 mm long for the 85 mm travel
setup. I think that this would increase the head angle by about 2.3 degrees, which might give the
bike too much trail if the offset is about the same. The pdf on the Marzocchi site didn't have the
offset dimension on the drawing, but so I measured it off the drawing at about 41 mm (does that
sound right if anyone knows?). This looks substantially more than the offset of my Future Shock, so
perhaps the trail actually not be made too long by the longer fork. I don't know a good way to
measure the offset of my fork though - the entire offset looks to be at the crown, with the dropouts
in-line and centered with the sliders. It looks like the offset might only be about 15 mm+/-5 at the
crown (it's kind of hard to judge the center of the steerer with it on the bike), so that would be
good. But I really can't tell the crown is angled to provide additional offset. Anyone here know the
offset of this old fork? ( I'm sure a lot of the shop owners here who were Specialized dealers sold
bunches of these 10 years back.)
Also what is a typical trail dimension for a neutral handling mountain bike? I'm guessing that it's
a bit more than a typical road bike.
overhaul, but I don't think the parts are available anymore, at least that's what I was told when I
asked around locally, so I am thinking of replacing it. The fork is much shorter than current forks
and has 2" (or less) of travel. I measured it at 415 mm long from axle center to crown race seat at
full extension. Newer forks are longer. The Marzocchi MX's are 458 mm long for the 85 mm travel
setup. I think that this would increase the head angle by about 2.3 degrees, which might give the
bike too much trail if the offset is about the same. The pdf on the Marzocchi site didn't have the
offset dimension on the drawing, but so I measured it off the drawing at about 41 mm (does that
sound right if anyone knows?). This looks substantially more than the offset of my Future Shock, so
perhaps the trail actually not be made too long by the longer fork. I don't know a good way to
measure the offset of my fork though - the entire offset looks to be at the crown, with the dropouts
in-line and centered with the sliders. It looks like the offset might only be about 15 mm+/-5 at the
crown (it's kind of hard to judge the center of the steerer with it on the bike), so that would be
good. But I really can't tell the crown is angled to provide additional offset. Anyone here know the
offset of this old fork? ( I'm sure a lot of the shop owners here who were Specialized dealers sold
bunches of these 10 years back.)
Also what is a typical trail dimension for a neutral handling mountain bike? I'm guessing that it's
a bit more than a typical road bike.