1992 Rockhopper Conversion help.- Mtbr.com
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  1. #1
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    1992 Rockhopper Conversion help.

    I recently bought a 1992 Rockhopper that I want to convert to single speed. I have a SS spacer kit that works on a cassette type rear wheel. Would the easiest way to handle the rear conversion be to swap our the rear wheel for one that uses a cassette? I have a set of Sugino cranks that I'm planning on using with the front chain ring.

  2. #2
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    Does your back wheel not have a cassette on it? If it does you can just take that one apart and reuse the cogs for your conversion. If you're not sure how to do this, take the bike to your LBS. They will have the necessary tool.

  3. #3
    jl
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    Does your '92 have a hub with a cassette freehub and with a cassette cluster, or a threaded hub with a threaded freewheel?

    Traditional Thread-on Freewheels

    If it is a threaded hub, you might be able to use a single-speed freewheel.

    ACS Crossfire Freewheel > Components > Drivetrain > Single Speed Cogs | Jenson USA

    If it is a freehub that would take a cassette, you can use your spacer kit and use one of these

    Surly Single Speed Cog > Components > Drivetrain > Single Speed Cogs | Jenson USA

    You need to make sure that if you are using a threaded cassette, that your chainline matches up fairly closely with your front chain ring. You can adjust your chain ring by installing it on the insider or outside of the crank arms, or you can also get a bottom bracket with differing widths.

    It's all _so_ simple .

    I would not take it to your LBS, do it yourself and you'll know more than you ever wanted out bike parts and alternatives. If you end up with a big problem, take it to your LBS for advice, buy something (like a new chain) or give them some beer.
    We don't need more to be thankful for; we just need to be more thankful.

  4. #4
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    A little googling and it looks like the 90' rockhopper used a 7-speed cassette. Assuming specialized didn't get too stupid and downgrade to a freewheel, the OP's bike should have a cassette. Super easy to put on the singlespeed cog on the cassette, and adjust the rear cog spacers for chainline.

    Only real issue will be chain tension. the OP will need a chain tensioner to do this right.
    "a hundred travel books isn't worth one real trip"

  5. #5
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    Thanks! My only other 7 speed was a Bianchi Axis cyclocross bike from 1986 which was threaded. I thought all 7 speeds were threaded after that. I've built up two frames prior to this. The first was a Reynolds Al Bianchi Axis Cyclocross frame. I built that as as an 8 speed triple. The other was a Giant STP that I built as a 1x9. Is it true that I'll only be able to mount 1.95 tires on the Rockhopper?

  6. #6
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    Quote Originally Posted by bamacrazy View Post
    I thought all 7 speeds were threaded after that.

    Is it true that I'll only be able to mount 1.95 tires on the Rockhopper?
    First time I saw a 7-speed freehub (true 7-speed, not 8-speed freehub with spacer), I was shocked. Who in their right mind would do this? Innovation in the 80's and 90's. Has to start somewhere, and 7-speed cassette was the obvious answer to weak 7-speed freewheels.

    And you can put whatever tires you want on the rims, as long as they fit in the frame and aren't too wide for the rim. I imagine an early 90's rockhopper rim is about 20mm inside width, so you could go up to 2.2 or 2.3 in the rear, and up to 2.4 up front (limited based on weight and tire pressure, more pressure = bigger tire). Frame clearance is probably what'll get you though, probably limited to 2.2" tire in back.
    "a hundred travel books isn't worth one real trip"

  7. #7
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    Your Sugino cranks may be too narrow for the Rockhopper. Check for clearance between chainstay and chainring/crankarm. Also the chainline may be too narrow. You may be able to correct this with a longer bottom bracket spindle.

    Your Rockhopper probably came with 5/110 or 5/94 cranks which will work well for MTB single speed applications. A 5/110 crank would be best if you are planning to use this on the road since larger chainrings are more widely available.

  8. #8
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    It has suntour cranks on it now. I'll use those and save the Sugino double for a future build. Thanks!

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