Fork question for Specialized expedition sport

Discussion in 'Mountain Bikes' started by Alan McClure, Jun 25, 2003.

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  1. Alan McClure

    Alan McClure Guest

    Alright, I ride a specialized expedition sport. I've owned this bike for almost 2 years now. I
    really like it because it never causes me any trouble, and is light enough (29 pounds) to be just
    fine for recreational use. Anyway, I won't have nearly enough money to purchase a new bike for maybe
    3-4 years, but since I ride every day(that is possible at least without missouri mud), I would like
    to replace one more thing on my bike. It already has had some standard things replaced, like the
    steel handlebar, and the seat post which weighed about as much as a gorilla. So, due to the time I
    spend on my bike, I would also like a better and lighter fork. Anyway, apparently (so I'm told) my
    front fork has about a 68 mm travel or so. The guy at the local bike shop suggested that if I want
    to replace the fork, that I find a good deal on an 68-80mm at the uppermost range travel fork. He
    said anything greater than that would mess up the geometry. It seemed to make sense the way he
    explained it. He said he thought that Manitou made a 80 mm Black, and that Rockshock had a Psylo in
    the 80mm range as well. He also mentioned Marzocchi. Anyway, my question is, when I look around at
    the specs for these forks, they are usually 80-100mm or 100-120mm. I'm not having any luck finding
    anything even on the manufacturer's websites. So, is it even possible to find anything--am I looking
    in the wrong places? Also, how badly would the geometry be "messed up" with an 80-100mm fork, and in
    what way? I really don't know much about the geometry of my bike let alone bikes in general, so I
    can only learn, but since the LBS said that a 80-100mm fork would bring the front of my bike up too
    high probably I wanted to see what you guys/gals say.

    Anyway, any help is appreciated. And thanks to all who helped me with my Hayes brake issue--it is
    now perfect, and I love it.

    Thanks, Alan
     
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  2. David

    David Guest

    "Alan McClure" <[email protected]> wrote in message
    news:[email protected]... Also, how badly would the
    > geometry be "messed up" with an 80-100mm fork, and in what way? I really don't know much about the
    > geometry of my bike let alone bikes in general, so I can only learn, but since the LBS said that a
    > 80-100mm fork would bring the front of my bike up too high probably I wanted to see what you
    > guys/gals say.

    It might bother you. Measure your head angle, and the axle to crown distance. Measure the axle to
    crown distance of the fork you are thinking about buying. If you can calculate the new angle, great.
    If not, you can elevate the front wheel enough to account for the longer fork, and measure the head
    angle again.

    If you don't have the angle checker, your LBS probably does. If you don't measure this stuff, and
    simply take other people's word for it, you may not be pleased with the results.

    Most people seem to like 71 degrees for their XC bike's head angle. You can go as slack as 68.5
    degrees and have it work pretty well in most circumstances, but you might find giving up >1 degree
    to be annoying.

    David.
     
  3. Alan McClure

    Alan McClure Guest

    "David" <[email protected]> wrote in message
    news:[email protected]...
    >
    > "Alan McClure" <[email protected]> wrote in message
    news:[email protected]...
    > Also, how badly would the
    > > geometry be "messed up" with an 80-100mm fork, and in what way? I really don't know much about
    > > the geometry of my bike let alone bikes in general, so I can only learn, but since the LBS said
    > > that a 80-100mm fork would bring the front of my bike up too high probably I wanted to see what
    > > you guys/gals say.
    >
    >
    > Most people seem to like 71 degrees for their XC bike's head angle. You
    can go as
    > slack as 68.5 degrees and have it work pretty well in most circumstances,
    but you might
    > find giving up >1 degree to be annoying.
    >
    > David.
    >
    >

    Well theoretically, if an 80 mm travel fork like this: http://makeashorterlink.com/?J2BC12E05
    changed the geometry by a few degrees, couldn't I counter that change with a with a stem that has
    less of an upward angle. Or am I missing something else too? Anyway, I realized that my current
    travel is 63mm, not 68mm. So, to go to 80mm would be adding approximately 3/4 of an inch rise to the
    front end. Anyway, I should do as you suggest and have things measured, but I'm wondering about the
    stem idea.

    Alan
     
  4. > Well theoretically, if an 80 mm travel fork like this: http://makeashorterlink.com/?J2BC12E05
    > changed the geometry by a few degrees, couldn't I counter that change with
    a
    > with a stem that has less of an upward angle. Or am I missing something else too? Anyway, I
    > realized that my current travel is 63mm, not 68mm.
    So,
    > to go to 80mm would be adding approximately 3/4 of an inch rise to the
    front
    > end. Anyway, I should do as you suggest and have things measured, but I'm wondering about the
    > stem idea.
    >
    > Alan
    >

    The problem with adding a longer travel fork is not only the higher handlebar position, which you
    correctly pointed out would be sorted by a lower rise stem or maybe you could just lose a few
    spacers if there are any, but also, and this is turning out to be the longest sentence in the
    history of AMB, the longer fork will in theory decrease the head angle of the bike. The head angle
    is a major factor in how easily the bike steers, steeper head angle = faster steering, slacker =
    slower. Too steep and the bike will feel twitchy - some folks like this, mainly xc riders, OTOH too
    slack and the bike will be slow to steer but very stable at high speeds which is (one reason) why DH
    bikes have slacker angles. Its a balance thing. I said in theory because you may find that at rest a
    new fork is longer, but actually has more sag than your old fork and so when you are sat on the bike
    the angles all return to normal. In essence I am saying I have no clue whether a new fork will screw
    up your bike or not. HTH!

    Steve E.
     
  5. Ctg

    Ctg Guest

    "Alan McClure" <[email protected]> wrote in message
    news:[email protected]...

    snip

    There are many forks available that are only 80mm or can be set at 80mm. I'd go somewhere else if
    your shop can't think of any that come in that range. Personally I'd go with Manitou or Marzocchi if
    cost is an issue. New Zocchi's are expensive but it's not hard to find deals on older ones. Manitou
    has several inexpensive forks and you can also find deals on older models.

    Chris
     
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