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  1. #1
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    Rockshox -> Carbon fork conversion to save 2.4 pounds

    I have a 1995 Trek 930FS. The original Rockshox Quadra elastomer shocks are getting too soft. Two cranks on the adjuster and they are still soft.

    I am considering putting on a carbon fork to save weight. Most the riding I do with this bike is unpaved roads. I quit the stump-jumping and trauma sports years ago. I can get by with just a bit of absorption.

    A quick look at data at www.nashbar.com shows:
    3.4 pounds for a "typical" fork with shocks (Manitou Minute XC) and
    1 pound for a Nashbar brand carbon MTB shock NS-RMF
    (I don't know the real weight of the Rockshox I have. )

    My questions are:
    1. I may have to cut the steerer tube down (if my 2 spacers are not the right fit). How hard is that?
    2. Carbon forks can be designed to have some flex in them. A designer can layup the fibers so that the curve has some shock absorption built in. The Nashbar fork has a curve to it--it is not the "two carbon cylinders" design. Will I get satisfactory results?
    Thanks for your advice.

  2. #2
    rjw
    rjw is offline
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    Your maths is a bit out, that Nashbar fork is nearer 2lbs.

  3. #3
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    You're right

    ~900g is 2 pounds. Now the benefit is only 1.4 pounds.

    I stopped at the bike shop on the way home. The clerk was skeptical that Sram/Rockshox could supply me with parts. I called Sram and the technician said elastomers are outdated and never did perform well--they were harsh. He said I might be able to recondition the elastomers with petroleum grease to fill them out again.

    It is not good that the company won't even support the product for more than 3 years. That basically says that their product is designed to be obsolete and trashed within a decade. I only use this bike occasionally because I am a road rider. It took me a decade to wear out a chain, so I suppose that is a thousand miles or so.

  4. #4
    Spicy Dumpling
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    According to my math 1995-2006 is 11 years not 3. Elastomers had a shord lifespan and hardened up in cold weather etc. Pretty much not worth the trouble. I don't see why they'd have to hold onto parts for that long. I had one elastomer fork, it was on my first mtb in 2000. I replaced it in 6 months. I'd go for the carbon anyway if you are worried about weight. If not, leave what you have, it's better for the road if the elastomer is hard as a rock.
    If I were to beat you senseless with a tire iron, what color would you bleed?..The Missus

  5. #5
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    thanks for the advice

    Telephone support at Sram said that they discontinue support for their products after three years and dump the old stock en masse' to shops like Hippie Tech. New, lightweight shocks go for $375 or $450. I paid $630 for the bike. Know I know why they call them "shocks" !

  6. #6
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    Quote Originally Posted by snappythomas
    Telephone support at Sram said that they discontinue support for their products after three years and dump the old stock en masse' to shops like Hippie Tech. New, lightweight shocks go for $375 or $450. I paid $630 for the bike. Know I know why they call them "shocks" !
    It's a fork (since it is integral in the steering and front axle of the bicycle, motorcycle, etc), a shock suspends the rear end of a motorcycle, bicycle, etc.

  7. #7
    desert smouth
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    Take out the elastomers. Pour in a cup of a two part epoxy called "JB weld" into each side. Put it back together.

    It should be plenty stiff for your needs. Cost, $5.

  8. #8
    The Gimlet Eye
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    Now the question is: Is your headtube 1" or 1 1/8"?

    The Nashbar NS-RMF is 1 1/8".


  9. #9
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    1 1/8" threadless

  10. #10
    The Gimlet Eye
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    Quote Originally Posted by snappythomas
    My questions are:
    1. I may have to cut the steerer tube down (if my 2 spacers are not the right fit). How hard is that?
    2. Carbon forks can be designed to have some flex in them. A designer can layup the fibers so that the curve has some shock absorption built in. The Nashbar fork has a curve to it--it is not the "two carbon cylinders" design. Will I get satisfactory results?
    1. cutting the tube is as easy as pie.....a decent hacksaw will do the job in a snap. Just remember to measure twice....cut once.

    2. I'll bet the Nashbar fork will be good at absorbing high frequency vibrations (like all carbon forks do) but I wouldn't consider it "shock absorbing". But carbon forks are good enough for Cyclocross, so I'm sure this one will be fine for unpaved roads.
    Last edited by covenant; 08-25-2006 at 12:05 PM.

  11. #11
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    Thank you very much. Intuitively, carbon should be good for damping. It's good for damping electrical currents, too! Have a nice weekend!

  12. #12
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    I would doubt that it is worth putting a carbon fork on a 930. Fit a cromoly fork, it will ride as wellas a carbon one and be a third of the cost. $150 - 200 carbon is a lot of money to spend on a bike of that quality.

  13. #13
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    Personally, If I were set on keeping the bike, I would ditch the rockshox and buy a steel or aluminum fork. I agree with posts above that carbon is a bit of an overkill. If you have the means, I would try to buy a newer, better bike. None of the parts on the bike that you have are made anymore. They all will be tough to find, so whenever anything breaks or wears out, you will be faced with similar issues. Before you go and dump a couple hundred bucks into it, Make sure you've thought things through. If you can tolerate the rockshox fork for a while, That could be money saved for a new ride. Thats my two cents. Ride on!

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