Bicycle Mechanics - Nexus Hub, Chain rub
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07-10-12, 11:49 AM
beginner here so be gentle:-) i have a Jamis Explorer 3.0 with the 8 speed nexus hub. recently after climbing a steep hill, standing peddling, the chain started to contact what believe is refered to as the cassette joint on the hub, its a black connector that the cable goes through. the rub can be heard once every revolution but not for the entire revololution. does this mean something is broken or bent? or is it something that needs an adjustment? its almost as if the nut needs to come off the right side of the axel, and then the casette joint rotated out of contact with the chain, but i'm scared ****less to touch that hub or any part of it. thanks in advance.
07-10-12, 01:58 PM
Blind guess is the best you get, here.
Might be a insufficiently tight axle nut .
you are pulling the wheel in the dropouts .
till tire hits the chainstay.
better answers require on site inspection..
I have an Alfine 8 speed hub, which has a similar/identical cassette joint to the Nexus. On one occaision, the cassette joint 'unlocked' iteslf and was loose on the hub. I don't recall if it moved enough to rub on the chain, but it is something you can check.
Now that I think about it, the chain really should not come anywhere near the cassette joint, as the cassette joint should be pointing forward between the top and bottom runs of the chain. I would need to see a picture of the hub and chain to get a better idea of what is going on.
07-10-12, 04:16 PM
Sounds like the cassette joint may not be properly locked in position. if that's so, shifting adjustment will be askew as well, so it should be checked out pronto before any internal damage happens.
It may also be that you have the incorrect anti rotation washers, or they are switched side for side. I used to sell several models with Nexus hubs, and had a whole run of one model of bike that was shipped with the anti rotation washers backwards, resulting in a similar issue as you have. Fortunately, we caught the problem before the bikes were sold.
07-10-12, 07:45 PM
07-11-12, 02:06 AM
Your cassette arm is at the wrong angle. You want it positioned for a smooth cable run with no kinks and kept away from the chain.
Take your wheel off.
Check that the cassette arm is locked in place: there is a rotating bayonet-fit locking ring that closes by hand.
Check that the cassette arm is not bent inwards.
The arm is a bit low so check the anti-rotation washers: try switching them over.
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