All NJS but chain line is off

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  • I use a Dura-Ace 7600 crank on Hatta 109mm bottom bracket, which should give the standard 42mm chain line. I recently measured, and the line is actually 45mm or a bit more. The D-A hubs give a 42mm line. I think this explains why my chain ring is worn on the outside, and might explain a drive train louder than what I have been led to expect from fixed wheel. (I'm the only fixed rider around here, and so have nothing to compare with.) A Shimano rep couldn't help me, and I have been unable to find a 7600 BB, new or used. I am about ready to move on to another crank, one with a dedicated bottom bracket. But first I thought I'd ask if anyone on this site has had the same experience, and found a solution -- other than a Phil Wood BB, costly in itself, and requiring special tools. And in case nothing comes of that, I wonder if anyone has experience with both Sugino 75 and the modern Campagnolo track crank and can compare. Knowledgeable US bike parts dealer Peter White has the highest praise for Sugino's precision, smoothness, and quietness. They appear to make nothing but cranks and rings, and perhaps should be best at getting it right. The Campy is more beautiful, and one site says it has a 131mm Q-factor (a k a stance), considerably narrower than the 75 and 7600's 139mm (though mine is higher). But it's not clear if that measurement is of the modern track crank, or the fluted design from decades ago, when all good cranks gave a narrower Q. With appreciation for any helpful education ...

  • Ran DA7600 cranks for a while, always with a 107mm UN55 (or fifty something at least) bottom bracket. Chainline was fine with DA7600 and other hubs.

  • I've found NJS chains more noisy then more common ones.
    I usually use SRAM cheap and easily available. Longeivty is big less tbh.

  • If you change the BB you can get a cheap and cheerful Shimano UN55 in 107mm which would get you 2mm closer to ideal. However it sounds like something is wrong, that BB and crank combo should give a 42mm chainline.

  • I've found NJS chains more noisy then more common ones.

    +1 for that.

    KMC 510 is my usual and tends to run considerably smoother/quieter than the likes of Izumi.

  • Track Supermarket confirms that your setup should be correct:

    Since Shimano stopped making bottom brackets suitable for use with their square taper track cranks, Hatta R9400 is now the officially recommended BB set to match the Shimano Dura Ace FC-7600 crankset.

  • If you are going to start again, it's hard to beat the complete Dura-Ace transmission on offer here

  • Are your DA hubs 7600 or 7710? Are you sure they're 42?
    Here's why.
    I have had three bikes, two custom, one cinelli, all which used DA7710 cranks and 7600 hubs.
    They ran beautifully so I never even measured them.
    However, the cranks AND hubs actually measured at 43.7mm (ish)
    I only found out when I switched wheels on one of the bikes with hubs that had an 'actual' 42mm chain-line and things got a bit noisier.
    I went through this with the guy at track supermarket and he confirmed also that the DA stuff is never 42 but as long as you use 'all' DA it should work. Hence I suspect the issue has come about because of the change in BB.
    I now use Sugino DD2 on two of my bikes and it has about a 42/43mm chain-line. I use them with one set of DA hubs and one set of DT Swiss hubs.
    Bottom line IMO:
    'perfection' is rarely possible; just use what works and eventually you'll forget all about perfect chain-lines.
    Chain lines can happily be a good few mm out and still run perfectly ok...

  • Well damn, who knew?

  • M_V, the references to the UN55 BB say it's JIS taper. The 7600 crankset is ISO taper. So the narrower -- 107mm vs. 109mm makes sense, though from what I've read -- Velodrome Shop, Sheldon Brown -- the difference should be 4mm -- a 105mm JIS BB. But if 107 worked for you, that's good to know.

    Wildwest, my headline was misleading: my chain is not NJS, but a high-end MKS . Previously I ran the SRAM PC-1 and before that cheaper MKS. It's early to conclude, but the more expensive chain does seem bound for a considerably longer life. Anyway, they're all bushingless, non-NJS chains, I believe, and all sound about the same.

    HarmanMogul, Track Supermarket's Rene has tried to help me, but the Hatta R9400, at least in my case, is not ideal. Maybe I shouldn't be such a perfectionist, but it seems that a chain line is unacceptable if it wears down the side of chain ring. I might consider the 7710 Octalink, but would prefer to stick with square taper. And I'm a bit bothered and reluctant to buy from Shimano again, since they don't see it fit to still make BBs for cranks that are not that old and remain plentifully in use.

    Aniki, I bought the hubs five years ago from Track Supermarket, where they are identified as 7710. Low flange. So I have the reverse of your setup. I have measured the hub chainline repeatedly, and am sure it is 42mm, plus or minus 0.5mm.

    Thank you all for your help. I've all but decided to get the Sugino 75 with dedicated BB, which is actually advertised by the company -- no other seems to bother -- as giving a 42mm chain line.

  • As a coda to this interesting little thread, I only use 3/32" parts. I like to think that modern road chains have had more development, and are certainly more laterally flexible, than the traditional 1/8" chain used by trackies. FWIW, they are also lighter. 'YMMV'!

  • Nice; the 75dd2 are lovely cranks. Not sure if it’s something that would bother you but the BB they come with has silver cups. I run mine with a DA9100 BB which has black cups and is very affordable!

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All NJS but chain line is off

Posted by Avatar for Scott_Bontz @Scott_Bontz