Chain Tension Problems? Niner Bio-centric?- Mtbr.com
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  1. #1
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    Chain Tension Problems? Niner Bio-centric?

    Yeah, I did a search but the typical fixes did not work. I was installing new (used) Race Face Deus cranks on my SS. When I was done, I noticed a major tight and loose spot in my chain. Put the old Evolve cranks back on, same thing. Changed to a brand new Blackspire chainring, nope. Changed the rear cog (Surly), nope. Tried the chainring tapping thing (loosening bolts etc.) nope. The only things I have not changed are the chain (SRAM 971, only a month old) and the recently installed used EBB (two weeks old).
    Hmm, could that be it? I recently put on a used Niner Bio-centric? It does only have one bolt (not centered) pulling it together...I am running out of ideas, and the change in tension is drastic. Could not find this problem with these ebb's when doing a search...any body have any problems like this? Any other ideas?
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  2. #2
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    I have the same ebb and the same problem. My slack goes from 2cm at the tight spot to 4.5cm (top to bottom) I haven't tried centering the chainring yet I will this weekend and let you know if it doesn't fix it.
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  3. #3
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    Unless the EBB is actually moving during pedalling, I can't see how it would be the problem.

    Suggestion: mark the EBB and bottom bracket shell with a line. Then if it moves it will be obvious.

    The tension changes are much more likely to be the cranks and chainring combination. A perfectly round chainring is not going to improve things if the crank manufacturer has bored the crank bolt holes slightly eccentric. With virtually every bike these days being a derailleur, there is no need for manufacturers to have a high level of accuracy because the derailleur takes up the tension differences.

    If you want proper round chainrings, get a Middleburn Uno crankset, or there's several other equally good SS specific brands out there.
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  4. #4
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    Looks like the problem is the cranks. After swapping them out for another set, using the same chain ring, cog, ebb...there is definitely a difference. It helped to step back, get a good nights sleep and then do the check in the morning (staying up till midnight and swapping things out several times was mind numbing)...there is definitely some variance with both cranksets, but one is much more pronounced than the other. Probably not noticeable with gears (derailleur) but as a SS setup, it is not going to work.
    Glad it was not the EBB...I have another crankset...(I'll just swap over from the FS) but I do not have another EBB.
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