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  1. #51
    What??? Only 2 wheels? jimmuller's Avatar
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    Quote Originally Posted by eschlwc View Post
    ^ i've only had it happen once, and fortunately the interface was good enough to retighten and not loosen again (knock wood.) it was a campagnolo record arm and spindle on a new build.
    In the old days the procedure for installing a crank was to tighten it (specs ran about 22lbs-ft, IIRC), ride maybe 30 miles, then tighten again.
    Real cyclists use toe clips.
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  2. #52
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by jimmuller View Post
    In the old days the procedure for installing a crank was to tighten it (specs ran about 22lbs-ft, IIRC), ride maybe 30 miles, then tighten again.
    +1
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

  3. #53
    rsg
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    Quote Originally Posted by onespeedbiker View Post
    It is common knowledge that once a square taper crank comes loose the chances are 99% it's toasted. The usual suspect is always the crank arm interface. The square taper interface usually has a steel spindle and a aluminum crank arm. When the two come together the spindle retains it's shape because it is harder than the aluminum crank arm. The crank arm interface then expands slightly when it is pressed onto the spindle with something called plastic deformation; this holds the crank on the spindle, but turning the crank puts lateral forces on the interface (rocking it side to side) so a crank bolt is needed to keep the interface strong enough that the rocking forces will not loosen the interface (if you ever have a crank arm stuck on a spindle, just ride it around the block without a crank bolt and it will come off). Because of this, if the crank bolt comes loose, the crank arm will start rocking side to side and unscrew the bolt. By the time you have realized what happened, the crank arm interface will have been permanently rounded it will never hold together tight enough to stop the rocking forces (this damage is rarely visible to the naked eye). The spindle interface however will not be damaged.

    As far as a replacement, I assume your crankest looks like this (from velobase VeloBase.com - Component: Sugino No. 5 / Silstar almost any Japanese square taper JIS crank arm will work as a replacement as they are mostly the same. If you want an exact replacement you're probably looking at some money because the older styles, like yours are getting scarce but any of these will work... left crank arm 170 (sugino,SR,alloy) | eBay

    This was the EXACT information I needed to know! - Thank you.

    Now to find a Sugino crank arm, though the link you provided for a Sugino MS looks close.

    Will post more pictures of what the crank set looks like shortly. The arms do have Sugino's logo on them with no colored lettering.

  4. #54
    billy chuck eschlwc's Avatar
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    Quote Originally Posted by jimmuller View Post
    In the old days the procedure for installing a crank was to tighten it (specs ran about 22lbs-ft, IIRC), ride maybe 30 miles, then tighten again.
    yup. i got lazy and it came back to bite me. it was recently at midnight coming back from a friend's house a little tipsy. one problem led to another. first, the fd cable came loose, so i had to ride it as a single speed. then going uphill in that high gear, the crank came loose. i knew right away. had to walk home in the dark. lesson learned.

  5. #55
    rsg
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    Quote Originally Posted by eschlwc View Post
    ^

    after seeing that, a cheap ($15) cartridge bb from shimano.
    Curious, Where can I get these from?? What is bb?

  6. #56
    billy chuck eschlwc's Avatar
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    ^ shimano makes cartridge bottom brackets like the bb-un26. they're ubiquitous: ebay, amazon, your lbs, etc.

  7. #57
    rsg
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    Quote Originally Posted by eschlwc View Post
    ^ shimano makes cartridge bottom brackets like the bb-un26. they're ubiquitous: ebay, amazon, your lbs, etc.
    Just looked up Sugino Bottom Brackets - ALL of them have square tapers on them! Therefore the one I have is correct & is good!

    Look for yourself if you don't believe me.

    http://www.ebay.com/sch/i.html?_kw=B...t+Sugino+103MM

  8. #58
    rsg
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    Quote Originally Posted by rsg View Post
    Here is the pictures I Have on the crank arm.

    Is this the culprit & is there enough material still here to work with to try a cheap fix??

    Attachment 393167Attachment 393168Attachment 393169Attachment 393170Attachment 393171Attachment 393172Attachment 393173Attachment 393174

    Now compare with mine!

  9. #59
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by rsg View Post
    Curious, Where can I get these from?? What is bb?
    A bottom bracket (bb) is the component that holds (and includes) the spindle. The earlier bottom brackets (like yours) came with a separate spindle, cups and bearings; the newer bb are a sealed cartridge.The older bb can be taken apart, cleaned aand greased, the cartridge type can not. If your spindle spins smoothly than there is no reason to replace your bb. Either will work with your bicycle and crank, however the bottom bracket that is not the problem, your problem is a toasted crank arm so a new bottom bracket will not help.
    Last edited by onespeedbiker; 07-15-14 at 07:12 PM.
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

  10. #60
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by rsg View Post
    This was the EXACT information I needed to know! - Thank you.

    Now to find a Sugino crank arm, though the link you provided for a Sugino MS looks close.

    Will post more pictures of what the crank set looks like shortly. The arms do have Sugino's logo on them with no colored lettering.
    The odds of finding a single left crank arm to match your crankest (both arms with the chainrings is called a crankset) are not good. If you really want a crank arm to match your crankset you will probably need to buy another crankset and even then your probably looking at $40-$50 item.
    Last edited by onespeedbiker; 07-16-14 at 12:00 AM.
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

  11. #61
    What??? Only 2 wheels? jimmuller's Avatar
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    I don't know why you are questioning the BB anyway. If it is a square taper there are only two things that could be wrong. Those things do NOT include wearing out the steel spindle with the aluminum alloy crank arm.

    The possible problems? First, there are two different 4 degree square tapers, ISO and JIS. The ISO spec calls for it to be ever so slightly smaller, i.e. thinner. But since they are tapered the thickness covers a range from inside to outside. The problem with a mismatch between arm and spec can be this: If the hole is ISO and the spindle JIS then the arm may not sit sufficiently far onto the spindle to grip well, not necessarily a fatal flaw but affecting the chainline. If the mismatch goes the other way, JIS hole and ISO spindle, then the arm may go on too far so that before the taper has become fully engaged the inside of the arm hits the point where the taper flares out into the full diameter of the spindle. In this case cranking down the nut or bolt will damage the inside edge of the arm, and you will never get a solid fit. Many spindles were made sufficiently thick and arms sufficiently thin so as to cover both options.

    The second possible problem is that there are some 3 degree tapers, pretty rare though, typically for certain applications like track cranks. The only way to know is to look up the spec for that crank and spindle.

    Someone could have mismatched your arms and spindle before. But it is unlikely. Most likely the arm is deformed from riding with it loose, and now it is toast. Very unlikely the spindle taper has a problem unless someone put a file to it.

    As for finding a single arm, sometimes to do show up on ebay. Or in the For Sale subforum. You have to look.
    Real cyclists use toe clips.
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  12. #62
    Senior Member sk0tt's Avatar
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    I have fixed a crank arm that kept coming loose by wrapping some fairly thick aluminium foil around the spindle before installing the crank arm, it has stayed on so far for around 1000kms.
    Giant doesn’t honour warranties.

  13. #63
    rsg
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    The reason I as seeing if there was a cheap fix was due to the amount I have in the bike already.

    Sure I want to do the job correctly but I just can't spend an arm & a leg doing it if I'm going to get my money back when I sell the bike on. Searching for a new arm now, may have to consider switching both of them so they match. Not what I was hoping for.

  14. #64
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by rsg View Post
    The reason I as seeing if there was a cheap fix was due to the amount I have in the bike already.

    Sure I want to do the job correctly but I just can't spend an arm & a leg doing it if I'm going to get my money back when I sell the bike on. Searching for a new arm now, may have to consider switching both of them so they match. Not what I was hoping for.
    Aluminum foil or locktite may work, there is certainly nothing to lose from giving them a try. The best cheap fix that is certain to work, is to buy a left crank arm that doesn't match the crankset and ride your bike. Then you start looking around for a matching replacement at a reasonable price.
    Last edited by onespeedbiker; 07-16-14 at 12:06 AM.
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

  15. #65
    Ride, Wrench, Swap, Race dddd's Avatar
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    Quote Originally Posted by jimmuller View Post
    The second possible problem is that there are some 3 degree tapers, pretty rare though, typically for certain applications like track cranks. The only way to know is to look up the spec for that crank and spindle..
    I've never heard of or seen an example of a 3-degree taper. Do you know what brand or country that one of these came from?

    When crankarms come loose, typically it is the wider end of the tapered hole in the crankarm that gets chewed, while deeper in the square hole the shape is often still fully square.

    Getting the crankarm secured heavily to the spindle and worked on as far as it will go (by tightening the nut repeatedly after pedaling forces are applied to the pedals) and then securing the nut with Loctite, is, in my opinion, the only hope for keeping the original arm in service. It worked for me during the 2012 CX season after my left crankarm worked loose and fell off during the final lap of the 2nd race of the Sacramento Cyclocross series. I completed the season (in two different series) using that same installation and that crankarm remains on the bike to this day.
    Yes, the square hole was chewed but the damage was pronounced only near the larger end of the hole, just as the OP's arm looks like, yet the crankarm survived many holeshot starts and many barrier jumps as well as the many hill-repeats that I did mid-season for training after the arm had fallen off.

    I would not expect Loctite applied to the spindle flats to do anything beyond lubricating the press-fit during installation. The contact pressure there is very high and there is some twisting going on along the spindle flats, so hardened Loctite would likely just move out of the way of this very forceful motion during hard riding.
    Last edited by dddd; 07-16-14 at 12:20 AM.

  16. #66
    Senior Member gaucho777's Avatar
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    Quote Originally Posted by jimmuller View Post
    I don't know why you are questioning the BB anyway. If it is a square taper there are only two things that could be wrong. Those things do NOT include wearing out the steel spindle with the aluminum alloy crank arm.

    The possible problems? First, there are two different 4 degree square tapers, ISO and JIS. The ISO spec calls for it to be ever so slightly smaller, i.e. thinner. But since they are tapered the thickness covers a range from inside to outside. The problem with a mismatch between arm and spec can be this: If the hole is ISO and the spindle JIS then the arm may not sit sufficiently far onto the spindle to grip well, not necessarily a fatal flaw but affecting the chainline. If the mismatch goes the other way, JIS hole and ISO spindle, then the arm may go on too far so that before the taper has become fully engaged the inside of the arm hits the point where the taper flares out into the full diameter of the spindle. In this case cranking down the nut or bolt will damage the inside edge of the arm, and you will never get a solid fit. Many spindles were made sufficiently thick and arms sufficiently thin so as to cover both options.

    The second possible problem is that there are some 3 degree tapers, pretty rare though, typically for certain applications like track cranks. The only way to know is to look up the spec for that crank and spindle.

    Someone could have mismatched your arms and spindle before. But it is unlikely. Most likely the arm is deformed from riding with it loose, and now it is toast. Very unlikely the spindle taper has a problem unless someone put a file to it.

    As for finding a single arm, sometimes to do show up on ebay. Or in the For Sale subforum. You have to look.
    Excellent post, Jim. And I learned something: I was not aware of 3-degree tapers on track cranks. I was wondering how the heck this thread got to three pages. Glad it did.

    I have a C-record crank that has come loose a few times over the past few years. I know the crank arm interface may be on the way out. I used blue loctite on the crank bolt about a year ago and so far so good. Hoping for the best, but now I keep a 7mm allen key with that bike just in case a mid-ride re-tightening is needed. Glad I have a couple spare C-record cranksets, though not one of the 1st gen versions with the stamped logos. Been looking on & off for a drive-side 1st gen C-record crank with [11] date code in 172.5mm length for years...

  17. #67
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by dddd View Post
    I've never heard of or seen an example of a 3-degree taper. Do you know what brand or country that one of these came from?
    I can not say for sure I have a crank arm with 3 degree, but I have been told it might have. It is a drive side crank I bought on ebay that is presumably made by SR (the photo below looks very similar but there is no SR markings). The square taper is considerably larger than JIS, as you can bottom out a JIS spindle in the crank and it still rattles around. I know it's an early Japanese square taper size that didn't last very long and it may be a 3 degree taper. Strangely enough it has the old JIS symbol on the back.

    sr.jpg220px-JIS.svg.png
    Last edited by onespeedbiker; 07-16-14 at 01:10 AM.
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

  18. #68
    Can'tre Member 3alarmer's Avatar
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    Quote Originally Posted by dddd View Post

    I would not expect Loctite applied to the spindle flats to do anything beyond lubricating the press-fit during installation. The contact pressure there is very high and there is some twisting going on along the spindle flats, so hardened Loctite would likely just move out of the way of this very forceful motion during hard riding.
    ...I imagine some of the bedding compounds that Loctite makes for installation of cartridge bearings
    and crank bearings in IC engines would work for this use. It would be a one time deal, and depending
    on which one you selected, might be difficult to remove the arm without cutting it off.

    Disclaimer: I have never personally done this. Always managed to find another crank.
    Quote Originally Posted by Terrierman View Post
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  19. #69
    Senior Member Wogster's Avatar
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    Quote Originally Posted by onespeedbiker View Post
    It is common knowledge that once a square taper crank comes loose the chances are 99% it's toasted. The usual suspect is always the crank arm interface. The square taper interface usually has a steel spindle and a aluminum crank arm. When the two come together the spindle retains it's shape because it is harder than the aluminum crank arm. The crank arm interface then expands slightly when it is pressed onto the spindle with something called plastic deformation; this holds the crank on the spindle, but turning the crank puts lateral forces on the interface (rocking it side to side) so a crank bolt is needed to keep the interface strong enough that the rocking forces will not loosen the interface (if you ever have a crank arm stuck on a spindle, just ride it around the block without a crank bolt and it will come off). Because of this, if the crank bolt comes loose, the crank arm will start rocking side to side and unscrew the bolt. By the time you have realized what happened, the crank arm interface will have been permanently rounded it will never hold together tight enough to stop the rocking forces (this damage is rarely visible to the naked eye). The spindle interface however will not be damaged.

    As far as a replacement, I assume your crankest looks like this (from velobase VeloBase.com - Component: Sugino No. 5 / Silstar almost any Japanese square taper JIS crank arm will work as a replacement as they are mostly the same. If you want an exact replacement you're probably looking at some money because the older styles, like yours are getting scarce but any of these will work... left crank arm 170 (sugino,SR,alloy) | eBay
    If it comes loose, and you keep riding it, it's toast, a few clicks isn't going to hurt it, and couple of hundred clicks, will. The parts to replace in order are the nut/bolt, which is often cheap steel and where the threads can be easily damaged. If you tighten it, and the arm doesn't wiggle, the arm is probably fine. The BB is unlikely to be damaged, those are hardened steel. For a "nice" bike if the arm is shot, then you probably should consider replacing the chainset to keep everything matching. If your doing that, then it's a good time to overhaul a traditional BB, and inspect the cups and cones, replace the bearing balls, put in new grease. Because you have the cranks off anyway, and it's maybe an hour or so to do it. If it's a cartridge, then you don't worry about those, you run them until they stop working, because it all gets replaced with a new cartridge.

  20. #70
    What??? Only 2 wheels? jimmuller's Avatar
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    I've never heard of or seen an example of a 3-degree taper. Do you know what brand or country that one of these came from?
    First, I've never seen any such taper, only read about them. Don't recall where, possibly a Sheldon Brown article first. That's probably where I read a track reference, but I have no real info to support that.

    So I just checked in Sutherland's. He describes the cranks as 2deg and 3deg. By that definition, they should be described as 4 and 6, not 4 and 3. He gives as an example SR Silver. My recollection, probably flawed, is a reference to some rare brand like Ofmega or similar. He also says that they are considerably larger and the spindle will not fit into a 4deg arm. This supports 1-speed's observations above about his unusual crank.

    Anyway, it is very unlikely the OP has such a beast. But the rest of that post, JIS vs. ISO is a real concern. One possibility I did not describe is that if a JIS arm is put on an ISO spindle the spindle can stick through the hole so far that the nut or bolt will not seat against the arm firmly even if the inside edge of the hole doesn't engage the taper's flare.

    It seems to me that all these possibilities are hard to predict unless you know which arms and spindles you are dealing with. That's why I chose a Campy spindle for the only Campy crank I have, JIS for most everything else, and gotten lucky apparently on the remaining few.
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  21. #71
    Senior Member miamijim's Avatar
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    They all could have the same degree of taper and also have different size openings.

    Same taper, different ID's. This is similar to the difference bewteen ISO/JIS

    Last edited by miamijim; 07-16-14 at 07:06 AM.
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  22. #72
    Ride, Wrench, Swap, Race dddd's Avatar
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    Quote Originally Posted by onespeedbiker View Post
    I can not say for sure I have a crank arm with 3 degree, but I have been told it might have. It is a drive side crank I bought on ebay that is presumably made by SR (the photo below looks very similar but there is no SR markings). The square taper is considerably larger than JIS, as you can bottom out a JIS spindle in the crank and it still rattles around. I know it's an early Japanese square taper size that didn't last very long and it may be a 3 degree taper. Strangely enough it has the old JIS symbol on the back.

    sr.jpg220px-JIS.svg.png
    That's an interesting crank for sure.

    First, it looks like an early Sugino Maxy crank, right down to the pattern of the big ring's cutouts and likely the bolt pattern as well, which I believe copies popular old French cranks, among others. This design was widely copied and frequently turns up in an all-steel version as well as this alloy one.

    Then there's this presumably wider taper angle, which limits the "spreading" forces that can be generated with a given amount of bolt/nut force pushing the crank onto the spindle, but which quickly went the way of the Betamax.

    Combined with a "nutted" spindle, these spreading forces would be much lower yet, which suggests that the maker perhaps had little confidence in the bursting strength of the alloy, and/or that they anticipated the possible improper practice by the owner of frequently re-torqueing the crank nut or bolt.
    I would think think that you'd need Loctite on the bolt/nut threads to keep such a taper from loosening under hard usage.

    So, is this possibly an SR "Silver" crank?

  23. #73
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by dddd View Post
    That's an interesting crank for sure.

    First, it looks like an early Sugino Maxy crank, right down to the pattern of the big ring's cutouts and likely the bolt pattern as well, which I believe copies popular old French cranks, among others. This design was widely copied and frequently turns up in an all-steel version as well as this alloy one.

    Then there's this presumably wider taper angle, which limits the "spreading" forces that can be generated with a given amount of bolt/nut force pushing the crank onto the spindle, but which quickly went the way of the Betamax.

    Combined with a "nutted" spindle, these spreading forces would be much lower yet, which suggests that the maker perhaps had little confidence in the bursting strength of the alloy, and/or that they anticipated the possible improper practice by the owner of frequently re-torqueing the crank nut or bolt.
    I would think think that you'd need Loctite on the bolt/nut threads to keep such a taper from loosening under hard usage.

    So, is this possibly an SR "Silver" crank?
    This is the actual crank. The inside taper measures 9.5mm and the outside 8mm; the depth of the ST is 8.5mm. There are no brand markings except these on the back of the arm..

    crank.jpgIMG_5046.jpg
    Chiunque tenti di scappare a queste regole dovrà mangiare un piatto largo di polenta vecchia di tre settimane e sarà schernito per questo, soprattutto se è straniero

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    The Three Arrows logo indicates that is an early '70s Takagi crank: http://www.disraeligears.co.uk/Site/...rs_page_5.html

  25. #75
    rsg
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    Quote Originally Posted by rsg View Post
    This was the EXACT information I needed to know! - Thank you.

    Now to find a Sugino crank arm, though the link you provided for a Sugino MS looks close.

    Will post more pictures of what the crank set looks like shortly. The arms do have Sugino's logo on them with no colored lettering.
    Here is a picture of the arms with the Sugino logo I have.

    Looking for a replacement left crank arm with this logo. Crank I have is a Sugino No 5 FE-WB from 1982

    Left crank arm 5.jpgright crank arm 1.jpgWhole crank 1.jpg


    Would be VERY MUCH appreciated if someone can do a search with me to help me find these crank arms. Will buy a crank arm set if needed (within reason) to match the one I have.

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