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  1. #1
    baj
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    Crank extractor stripped: removal/replacement/compatibility questions.

    Hi, this is my first post here. I used to ride quite a lot and am going to get back into it after ~8 years of not riding. I need a little help fixing up my old bike.

    I have a 1990 Cannondale 3.0 14 speed racing bike that I am reconditioning. Low miles, great shape, very so-so Suntour Blaze components but what the heck, I already own it. The trouble is that the drive side crank's extractor threads are stripped. The crank is ok but I want to overhaul the bottom bracket. I have a couple of questions about how to deal with this.

    1. Is there a way (not involving an obscure tool that is expensive and/or hard to find) to remove the crank arm without ruining it? If I can't reuse the crankset...

    2. I would ideally like to reuse my chainrings since they have worn with the chain. What do I need to know about a crankset to know if I can put my old chainrings on it? Can I mix brands of cranksets/chainrings? Do different cranks have different chainring bolt circle diameters? Are different chainrings different thicknesses? Or are all road cranks/chainrings pretty much mix and match? It's not hard to find older cranksets on eBay, but it is hard to find Suntour.

    3. If I figure out how to measure my chain and convince myself that it hasn't worn a whole lot (the bike still has its original front tire so this is a possibility), is it ok to just buy a new crankset with chainrings and put it on wiht the old chain and cogs? If so do I need to know anything besides the crank arm length, square taper, and number of teeth on chainrings? Is there any other measurement/parameter that I need to get right? How much can my chain have "stretched" before this is a bad idea?

    Thanks for any advice you can give!

  2. #2
    ppc
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    Quote Originally Posted by baj
    1. Is there a way (not involving an obscure tool that is expensive and/or hard to find) to remove the crank arm without ruining it? If I can't reuse the crankset...
    Your local bike shop probably has a tool to re-thread the crank extractor hole in the crankarm. This creates a larger diameter threading that a special crank extractor can attach to. If you don't want to depend on your LBS to remove the crankarm, invest in a cheap small 3-jaw gear puller and you'll never have that problem again.

    Quote Originally Posted by baj
    2. I would ideally like to reuse my chainrings since they have worn with the chain. What do I need to know about a crankset to know if I can put my old chainrings on it? Can I mix brands of cranksets/chainrings? Do different cranks have different chainring bolt circle diameters? Are different chainrings different thicknesses? Or are all road cranks/chainrings pretty much mix and match? It's not hard to find older cranksets on eBay, but it is hard to find Suntour.
    Chainrings have standard BCDs usually, unless they're very old. The only incompatibility that comes to my mind is the compact Suntour granny ring standard of the 90s that was a bit smaller than what is done now, i.e. 54mm BCD instead of 56mm iirc. But a bit of filing can adapt a Suntour granny ring on a Shimano standard and vice-versa.

    As for ring thickness, it depends on the width of the chain. A 3-speed chainring won't drive a 8 or 9-speed chain without major chainsuck. A narrow chainring can engage a wide chain without problem though. Again, if you insist on matching things that don't want to match, it's also possible to file the teeth on a wider chainring to accomodate a narrower chain, but it's long and it's really if you're strapped for cash.

    Quote Originally Posted by baj
    3. If I figure out how to measure my chain and convince myself that it hasn't worn a whole lot
    If you don't have the nifty go/no-go chain checker, measure 12 links with an imperial/standard/non-metric ruler between the center of the pins: if you find 12" exactly, your chain hasn't stretched. If you find 12" and 1/16" or under, your chain is okay. If you find 12" and between 1/16" and 1/8", time to replace the chain. If you find more than 1/8" of stretch, chances are some of your sprockets and possibly your rings are toast and need changing too.

    Quote Originally Posted by baj
    (the bike still has its original front tire so this is a possibility), is it ok to just buy a new crankset with chainrings and put it on wiht the old chain and cogs?
    You can, if the chain is still okay, but what will happen is that your chainrings will wear out super-fast to match the pitch of the chain, then in a very short time, will be in the exact condition your old rings were before you changed them. I'd say a sounder investment would be new rings, new chain and new cassette, but of course it all depends on how much you want to spend on your bike.

    Quote Originally Posted by baj
    If so do I need to know anything besides the crank arm length, square taper, and number of teeth on chainrings? Is there any other measurement/parameter that I need to get right? How much can my chain have "stretched" before this is a bad idea?
    You should measure the distance between one of the rings and the seat tube on your old crankset before changing them, then check that the new crankset sits about the same place. Sometimes new cranks have a tendency to sit deeper into the square taper, and/or position the rings more or less inboard by design, and end up screwing up your chainline and becoming a major front derailleur adjustment headache.

    As for stretched chains, frankly, when I change a cassette or the rings, I just change the chain. It's cheap and it lasts longer.

  3. #3
    = cyclist's tan rat_factory's Avatar
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    I had this problem very recently. check this thread: Stripped crankarm dustcap/extractor threads .
    '82 Miyata 310, '87 Scott Boulder, '87 Schwinn Le Tour, '91 Cannondale SM500, '96 Schwinn Clear Creek, '99 Schwinn MesaGS, '05 Rockhopper

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  4. #4
    baj
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    Thanks very much for the help!

    I called a couple of LBSs and the only one who suggested anything besides cutting the crank arm off said maybe I could pry it off. Apparently none of them have the helicoil-like tool, and I don't think the design of the crank spider will work with a gear puller. I could try the prying, but if I can find an inexpensive replacement (something like an early 90's Shimano 600 or similar) I might go for that.

    I bought this bike in 1991 ('90 model) and overhauled the bearings in 1993, except for the bottom bracket because when I tried to remove the crank the thread stripped. I don't remember exactly what happened since it was so long ago, but it looks like all of the threads are gone, so I think the puller was probably in thw whole way. Anyway, I rode the bike occasionally for the next 4 or so years while in college (was doing a lot of mountain biking then) before moving to various places where riding seemed less than attractive, so have been off the bike for a while. I grew up in a place with little traffic and great roads and don't have the stomach for road riding in city traffic.

    Now I live near a great system of bike paths and my wife (who hasn't ridden a bike much since she was a kid) wants to get a bike and start riding. Since the grease in the bottom bracket is 16 years old, I don't want to ride it until I service all of the bearings for fear of damaging the cups/cones.

    I am not sure if this will be the bike that I want to ride regularly with my wife, as she wants a hybrid and some of the places we want to ride are unpaved. But I don't want to part with it, and I don't want to buy a new bike until I'm really sure what I want (performance hybrid? touring? cyclocross?). So I want to make it rideable in the next ~2 weeks. Basically it needs new tires/tubes and new grease everywhere that grease goes; otherwise it's fine except for this crank arm.

    Thanks again for the advice.

  5. #5
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    Blaze was low-end Suntour. I wouldn't be too worried about damaging or replacing any of it. Ride the bike as is for a while, you almost certainly won't do enough damage to the bearings to notice. If you do, you're up for a BB to go with that crankset, minimal extra cost.

  6. #6
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    You could also try removing the crank bolt and then riding on it until the crank arm comes loose.

  7. #7
    baj
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    Quote Originally Posted by gorn
    You could also try removing the crank bolt and then riding on it until the crank arm comes loose.
    I thought that would ruin the arm by enlarging the square hole. Is that not the case?

  8. #8
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    Quote Originally Posted by baj
    I thought that would ruin the arm by enlarging the square hole. Is that not the case?
    The arm is already toast - extractor threads are stripped.

  9. #9
    Dave TRUMPHENT's Avatar
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    I finally removed the chainring crank from a dept store mtb. I had to resort to buying a steering wheel puller, and washers and nuts. Two bolts go through the chainring and are secured by the nuts and washers on the bb side of the crank. After much tightening, time and rapping with big steel mallet, it broke free. I think the force used at the factory to put this thing on contributed to the failure of the bottom bracket.

    I used something similar to this http://www.toolking.com/productinfo.aspx?productid=1248

    At least I don't have to buy a propane torch and melt the crank off.

  10. #10
    Jonnys ilegitimate Father cavernmech's Avatar
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    If the bottom bracket is an older cup and cone style, remove the non-drive side crank. remove the left side adjustable cup lockring and bearing. Pick up a longer crank bolt. Install longer crank bolt in drive side bottom bracket spindle. With the left side BB cup removed you should be able to push the drive side crank so it sits against the right hand fixed cup. While holding the crank against the fixed cup give a few whacks to the long bolt with a hammer. Be careful not to hit the bolt on an angle and it should "push" the spindle from the crank. I have used this method many times over the years and it has yet to fail me. Only works with cup and cone b.b.'s tho.

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