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  1. #1
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    Rohloff 54mm chainline recommendation wrong?

    I've just started using a Rohloff equipped wheel which I bought used & in setting up the bike have started out with the recommended 54mm chainline but it's waaaaaay wrong!

    I could tell eyeballing it before I even mounted the chain. But as confirmation, I took a straightedge & laid it flat against the inside of the chainring & extended it to the rear cog. Did that with both sides of the straight edge to be sure that the measurement wasn't off due to the straight edge not being straight. In both instances I found the gap between the straight edge & cog to be ~8mm.

    Which is huge! Even with the chain on, & sighting along the chain from the front the front inward bias is obvious where the chain passes over the cog.

    Has anyone gone with a longer BB to correct the difference?

    Can anyone else (whether you have the Rohloff or not) think of any negatives in doing so,

    I'm currently using a tapered BB in a 113mm length but I'm considering at least a 118mm as a replacement. Figure split the difference. Sort of. Besides the next step up is a 122mm & that's just a bit too long. The bike I have has a EBB so I'll be able to fine-tune it from there.

    Thanks in advance.

  2. #2
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    Rohloff recommends a 54mm chain line because the cog is 54mm from the center of the hub. If the chain is not lining up, then your chain-ring is not at a 54mm center, or your frame is out of alignment.

    I'd guess your chain-ring is not at 54mm, square taper BB systems vary in chain line.

  3. #3
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    Quote Originally Posted by itsdoable
    Rohloff recommends a 54mm chain line because the cog is 54mm from the center of the hub. If the chain is not lining up, then your chain-ring is not at a 54mm center, or your frame is out of alignment.

    I'd guess your chain-ring is not at 54mm, square taper BB systems vary in chain line.
    Thanks for the reply & ideas.

    I just double-checked the frame for straightness with the simple string test & it looks good. Also, double-checked chainline again to be sure that I hadn't made a mistake earlier & it's now at ~55mm. I just re-installed the drive side crank & it takes a while for it to 'settle' in. I have to re-tighten it periodically after the first few rides & then it'll be good.

    Shortly after I did all that I realized my error. I'm new to SS'ing & now IGHs & have never really had to think too much about chainline. It didn't help that the bike I bought used came with a crankset with a built-in bashguard & other cranksets that I've bought off eBay also had the bashguard.

    Took me awhile but I just realized that chainline for triples is measured to the middle chainring. So ... if I'd installed my chainring(s) on the outer, where the bashguard is, instead of the middle, chainline would've been near perfect since the difference between rings is ~4.75mm. Not quite the 8mm I thought I measured but it confirms that I need a longer BB. Going from 113mm to 118mm is close enough so I'll definitely be ordering the longer BB soon.

    Thanks again.

    EDIT: Made a mistake in the replacement BB length. Should be 122mm. 122-113=9, 9/2=4.5 which is close enough to 4.75mm for me. There goes my Q factor :-). Truthfully, never been an issue for me. In fact, altough it's been awhile, I think I actually prefer slightly wider spacing of the crankarms.

  4. #4
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    Caution;  Merge;  Workers Ahead! Rohloff spec is WRONG, IME.

    Yes, it's wrong, IME. I know this is a really old post, but it comes up on the first page of a Google search for Rohloff Chain Line so I wanted to add this reply. Rohloff is also wrong to recommend using a mountain bike triple to achieve the 54mm (wrong) chainline by using the 3rd outer ring.

    I've measured the Rohloff chainline to be 50mm using various methods.

    Also, many Shimano cranksets I've checked are not 54mm outside ring. Spot checking specs on M361, M590 and M610, all three have a 50mm chainline to the center of the MIDDLE ring. This puts the outer ring at almost 59mm.

    The Shimano M615 double crank has a chainline of 48.8 to the INSIDE of the outer ring. Add 1mm for the 1/2 the thickness of the chainring and you've got 48.9mm to the center of the outer ring. Practically perfect.

    Rohloff needs to update their **** in a world where cranks are mostly 2 piece, not 3, and we can't just go dry fitting different spindle length square taper BB's to tweak.


  5. #5
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    Quote Originally Posted by istomtom View Post
    Rohloff is also wrong to recommend using a mountain bike triple to achieve the 54mm (wrong) chainline by using the 3rd outer ring.
    On Rohloff website : "sprocket sizes 15, 16 and 17 with the Rohloff SPEEDHUB 500/14, will require a chain line of approximately 54mm from the frame center. This needs the use of the outer chain ring from triple crank sets such as standard Shimano".
    Yes, it's an old recommendation. Today there is no more standard. There are crankset with 3 rings, 2 rings, 1 ring. There are large BB for new standard as 148mm rear axle, big tires, boost, fat, road, mtb,..... There are a lot of spindle length. Really, there is no more standard.

    Quote Originally Posted by istomtom View Post
    I've measured the Rohloff chainline to be 50mm using various methods.
    You are wrong. It's more or less 54mm.

    Quote Originally Posted by istomtom View Post
    Also, many Shimano cranksets I've checked are not 54mm outside ring. Spot checking specs on M361, M590 and M610, all three have a 50mm chainline to the center of the MIDDLE ring. This puts the outer ring at almost 59mm.

    The Shimano M615 double crank has a chainline of 48.8 to the INSIDE of the outer ring. Add 1mm for the 1/2 the thickness of the chainring and you've got 48.9mm to the center of the outer ring. Practically perfect.
    There are also Shimano 3x rings FC-2203, FC-2303, ...

    Quote Originally Posted by istomtom View Post
    Rohloff needs to update their **** in a world where cranks are mostly 2 piece, not 3, and we can't just go dry fitting different spindle length square taper BB's to tweak.
    Send them an email.

  6. #6
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    I just measured my Rohloff chainline by measuring the gap between the outer face of the cog and the inside of the frame. Add half the thickness of the cog, and subtract the result from 135/2, and guess what. 54mm.

    I followed their recommendation, and have a single-speed type flat ring, mounted in the outer position on a modern 3 ring Shimano SLX crank, with normal bb spacers, and the chainline is PERFECT.

    Seems like Rohloff know what they are doing.
    Last edited by evrac; 03-07-2016 at 10:23 PM.

  7. #7
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    Bernie Rohloff is, if anything, extremely meticulous and precise. The chain line is 54mm.

    Sometime after the Rohloff speed hubs were introduced, Shimano changed thier chainline "standard" by ~6mm to improve clearance for the new fangled full suspension frames. Rohloff never really updated thier website when this happened, so I'll agree that there's probably something there. But all you really need is the 54mm chainline, because whatever crank you put on, and where ever it falls (due to the loose tolerance of frames, BB's, cranks, spacers, etc...) you just need to line up the chain ring.

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