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  1. #1
    Senior Member Reeses's Avatar
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    Sugino 75 track crank problems.

    Hello, I got a used SG75 crank and am having issues with the chainring (SG75).

    When I loosen the chainring bolts, the screws come out but the nuts stay firm in the crank arm and don't budge. What is the problem here? I checked the back of the nuts and they are knurled.

    How do i get them out and avoid this problem in the future?
    Last edited by Reeses; 09-11-12 at 07:45 PM.

  2. #2
    Andrew R Stewart Andrew R Stewart's Avatar
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    The female nuts remove with pressure, the knurling acts as a press fit into the spider. Bad fit and/or corrosion can complicate things. I'm not sure that the nuts are wrong to be so set in the spider that removal requires a bit more "effort". Of course if a experienced wrench took a look a lot would be understood quickly. Typicially a grease and periodic removal, cleaning and reinstallation keeps stuff going for a lot longer then doing nothing. Andy.

  3. #3
    Retro Grouch onespeedbiker's Avatar
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    It's not a problem, it's a feature. I use similar nuts on several of the fixed gear/ track bikes because they hold so well; I especially like the way Sugino 75 chainrings snap into the spider; now those are tight tolerances. Anyway, the knurling is only on the bolt flange (not the outside body like others. Just take a dowel and drive them out, or partially screw in the other half and whack it with a rubber handle..

    sugino.jpg

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    Quote Originally Posted by onespeedbiker View Post
    It's not a problem, it's a feature.
    +1. The knurl and ultra snug fit helps prevent chainring bolts from loosening. It's more important for track than rod, because track cranksets are subject to back and forth torque.

    Loosen the screw (front half) about 2mm, then tap the wrench to pop the nut free. Or you can sometimes leave all the nuts in the ring, and gently tap it off, working around by degrees.
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  5. #5
    Senior Member Reeses's Avatar
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    I see. How would I go about adjusting and centering the chainring with knurled nuts? Do the nuts automatically make it centered?

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    Quote Originally Posted by Reeses View Post
    I see. How would I go about adjusting and centering the chainring with knurled nuts? Do the nuts automatically make it centered?
    Generally they're pretty good to excellent. Not because of the nuts, but because they rest on shoulders (if they do), which very reliably ensure concentricity. In any case you don't correct a problem you don' have, so start by mounting the crank and tightening the bolts, then installing the chain, and taking up all but vestigial slack. Turn the cranks checking the vertical play every 30° or so.

    Odds are it'll be spot on, but if not, (and if there's no shoulder or a sloppy one on the arm), loosen the bolts slightly, and center the ring by tapping it back toward the hub where it's tightest, working around until you get it as good as you can and retighten the bolts to keep it there.
    Last edited by FBinNY; 09-11-12 at 08:40 PM.
    FB
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    Dont see the problem, that's how all the track cranks should be. You really dont want to get the back bolt lost and the design is really perfect. No idea if the new campagnolo track cranks use the same design but the old one was like that, well at least the one i bought zillion of years ago.

    It makes your life easier because in a track sometimes you change the chainrings in a jiffy and you really dont want to waste time putting more pieces you know.

    The other thing is that, there is a lot of road stuff that was fixed as track by cutting the back tabs and people just say yeah... track cranksets when in reality are not and the way to say are those knuckled bolts in the back. Low end stuff use just plain road bolts just in case.

  8. #8
    Retro Grouch onespeedbiker's Avatar
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    Quote Originally Posted by Reeses View Post
    I see. How would I go about adjusting and centering the chainring with knurled nuts? Do the nuts automatically make it centered?
    To add the what FBinNY said. These high end cranks and chainrings are made to exact specifications, much closer than your average chain ring on a crank (similar to Shimano Dura Ace track and Campagnolo Track). As I said before, when you mount the chainring it literally snaps into place; there is no other centering or adjusting necessary as these cranks and chainrings have been designed and manufactured to such a close degree, they are known for very tight tolerances on concentricity and dimensions with virtually no runout; check a nice article from the Peter White Cycles web site http://www.peterwhitecycles.com/fixed.asp
    Last edited by onespeedbiker; 09-11-12 at 10:59 PM.

  9. #9
    Senior Member Reeses's Avatar
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    It's weird because I've had SG75s before and the chainring was never as tight as it is on my current setup.

    I originally wanted to center it because I heard some bad sounds from my drivetrain, a sort of clicking. Turns out my chainline is off, and I don't know why because I have the correct sized BB. My drivetrain setup is: SG75 cranks, chainring, BB; SRAM PC-1 chain; EightInch 14t 3/32 cog.

  10. #10
    slow as I ever was Ex Pres's Avatar
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    Quote Originally Posted by Reeses View Post
    ..... Turns out my chainline is off, and I don't know why because I have the correct sized BB....
    Have you measured the chainline to determine if it is off in front or in the rear? You gotta pull out a ruler.
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    Clicking can come from different places not really from the chain or the crankset, specially with your set up. well it could be the hub cones or something else.

    The other detail, if your chainline is off a few couple of millimeters nothing it will happen and clicks never come from the chain line, grinding sound is. Not all the bikes are the same, who knows what hub you have in there either, so is hard to know how off the chainline is.. if you are off like 4 mms then is ok because all the chains flex and you have some limits. If you are off like 15 mm then makes sense that you should be worried about the chainline. The clicks arent coming from the chain line anyways.

    If you have loose balls hubs the clicking might come from there, specially if you have campagnolo hubs. They tend to click for some reason.

    Good luck.

  12. #12
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by Reeses View Post
    I see. How would I go about adjusting and centering the chainring with knurled nuts? Do the nuts automatically make it centered?
    Yes, the protrusion of the nuts out of the front face of the crankarms will centre the chainrings. Notice when you slide the chainring over the nuts that there's absolutely zero radially? Then the bolts clamp over the nuts to prevent axial play and that's it, the entire assembly is locked together in perfect alignment.

    To center road components for fixed-gear use, you typically have about 1mm of play in components. The holes in the chainrings are much larger than the nuts. The chainrings don't press-fit over the crankarm spider. So you can typically wiggle things a little before tightening down the bolts. That kind of jiggling simply isn't needed with the Sugino75 crank.

    If you have a 1-rpm click, that is, once per rotation, that can be pedals or the crankarm-to-spindle interface. I prefer to put a little drop of oil on each of the square faces of the spindle (split the difference between the grease vs. no-grease philosophies). Then tighten to 30 lb*ft. What torque are you tightening your crank to?

  13. #13
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    Quote Originally Posted by DannoXYZ View Post
    Yes, the protrusion of the nuts out of the front face of the crankarms will centre the chainrings.
    With respect, this isn't right. Chainring bolt fit isn't precise enough to locate the ring, which is why SS systems often need to have the rings centered (made concentric) via the tap it around method.

    But quality track cranksets, have accurately machined shoulders on the spider, and a corresponding precise circle machined on the inner rim of the rings. This is a very precise fit that makes centering not only unnecessary, but impossible. On quality cranks, the bolt's only purpose is to hold the ring to the arm, and transmit torque.

    BTW- many better road cranks are built the same way, and these do a better job of eliminating chainring movement so it's rare that they creak or bolts loosen.
    FB
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    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by FBinNY View Post
    With respect, this isn't right. Chainring bolt fit isn't precise enough to locate the ring, which is why SS systems often need to have the rings centered (made concentric) via the tap it around method.

    But quality track cranksets, have accurately machined shoulders on the spider, and a corresponding precise circle machined on the inner rim of the rings. This is a very precise fit that makes centering not only unnecessary, but impossible. On quality cranks, the bolt's only purpose is to hold the ring to the arm, and transmit torque.
    Yes, I was talking about the Sugino75 system. It's the OD of the nuts from the back side (not the bolts) that actually fits tightly into the chainring's holes.

    I'm not sure there's any shear-loads on the bolts & nuts actually. I've successfully used alloy chainring nuts & bolts on my track-bikes for decades without any problems. Once you have the bolts & nuts tightened to spec, their compression should generate enough friction between the chainring and spider to transmit the forces across without loading the bolts & nuts in shear. The only part experiencing any torque is the spider-arms and the BB-spindle (when there's more force on the left-crankarm than the right).

  15. #15
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    No sense arguing, whether it's the chainring bolts, or the shoulder (Sugino 75 has a well fitted shoulder) the chainring will be very concentric and doesn't need to be (and can't be anyway) centered by the tap it around method.
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  16. #16
    Senior Member Reeses's Avatar
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    Quote Originally Posted by ultraman6970 View Post
    Clicking can come from different places not really from the chain or the crankset, specially with your set up. well it could be the hub cones or something else.

    The other detail, if your chainline is off a few couple of millimeters nothing it will happen and clicks never come from the chain line, grinding sound is. Not all the bikes are the same, who knows what hub you have in there either, so is hard to know how off the chainline is.. if you are off like 4 mms then is ok because all the chains flex and you have some limits. If you are off like 15 mm then makes sense that you should be worried about the chainline. The clicks arent coming from the chain line anyways.

    If you have loose balls hubs the clicking might come from there, specially if you have campagnolo hubs. They tend to click for some reason.

    Good luck.
    My hubs are cartridge bearing.

    Yes it's more of a grinding sound and I can feel it in when I'm pedaling. So if the chainline is not off by a lot it won't affect anything? Could it be my chain then? My SRAM PC-1 has some tight links that I can't get rid of even using the chain tool, I'm suspecting that's the problem

  17. #17
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    Fast question. Did you make sure to remove ALL the chain slack?

    This is the most common mistake. SS and IGH chain must never be under tension other than the tension in the top when under load. Theproper adjustment is minimum, but never zero slack as measured by 1/4" vertical play in the middle of lower loop. Another way to check that the chain (non)tension is correct (fixed gear only) is to hold the rear wheel move the pedals back and forth about 1/4" visibly transferring slack between the lower and upper loop.
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    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

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