Weight Weenies

Dura Ace 9000/SRM Chainline Issue
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Author:  baldkingpin [ Fri Mar 29, 2013 7:27 pm ]
Post subject:  Dura Ace 9000/SRM Chainline Issue

COMPONENTS: Running DA 9000 and Dura Ace SRM (7900). 12x25 cassette, standard 39/53 rings. Dura Ace 11spd. C24 wheelset. Rear wheel is dished, frame and rear der. hanger aligned. Front and rear derailleurs are set up perfectly (cable routing - yes, I used cool 9000 routing tool :), limits, cable tension, etc.) and shifting is smooth, easy and flawless. This is all on a XL (58cm equiv.) Leopard M1SL with normal-length chain stays.

MY CHAINLINE PROBLEM: My only issue is when in 39x23 or 39x25, I'm getting cassette rub/noise when applying serious race-pace torque on steep gradiant climbs (it's silent when climbing normally, even out of saddle - so I think a minor adjustment should rectify the problem). On the stand, I can see the chainline isn't great in these upper gears and the noise is coming from the chain links rubbing on (releasing from) the cassette teeth as the chain leaves the cassette. I'm sure this is the cause, it's not the chain hitting the spokes or anything else and the noise is present even when I overset the rear derailleur towards the spokes. Conversely, the chainline is pretty good in my 12 tooth sprocket and could handle the chainrings moving towards the frame a bit. I suspect my SRM crankset spacing moves the cranks out a mm or so compared to a standard crankset, thus my problem.

POSSIBLE SOLUTIONS?: I may be able to add a very thin spacer behind the cassette to move it outwards a bit, but I'm traveling at the moment and the only spacers I have don't leave enough thread for the lockring. When I get back home, I'll put a 9000 (non-SRM) crankset on the bike and see if it solves the problem. If so, or even if not, I wonder if there's slightly narrower bb cup (compared to the 9000 cup I'm running), which will move the cranks over a hair and correct the problem. I can't think of any other way to correct the chainline and still use my beloved SRM.

Hope this makes sense. Thanks much for any input!!

EDIT: See my below post re: the issue smooth1978 raised. So much for my being sure about the cause... :oops:

Author:  Weenie [ Fri Mar 29, 2013 7:27 pm ]
Post subject:  Dura Ace 9000/SRM Chainline Issue

Author:  ipenguinking [ Fri Mar 29, 2013 7:58 pm ]
Post subject:  Re: Dura Ace 9000/SRM Chainline Issue

Could this relate to defected cassette discussed in prior threads?

Author:  baldkingpin [ Sun Mar 31, 2013 11:37 pm ]
Post subject:  Re: Dura Ace 9000/SRM Chainline Issue


Thanks, hadn't seen that discussion. Despite my chainline issue (which could certainly be improved upon), I threw on a second also-new 9000 cassette today and it was virtually silent in all cogs, including 23 and 25 when under pressure! I should've put it on dry as a test, but having read through smooth1978's post re: a similar problem with noise in his two largest cogs, I first lubed the front and rear of all of the rivets in both the carbon and aluminum carriers that hold the 5 largest cogs. Let it sit for 6 hours on each side to penetrate. Maybe that did it?! I've now lubed the first cassette and will report back if that cures the noise I originally reported on.

The more I think about it the more I think my noise - a loud crunching - might be due to the issues smooth1978 raised. I can see how my chainline issue could cause some rubbing noise but not as much and not as crunchy and loud as what I heard with the first cassette.

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