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Dura Ace Chain Interference(9 posts)

Dura Ace Chain InterferenceTrooper
Oct 11, 2002 5:00 PM
I just installed new Dura Ace Cranks and when I'm in the 12-39 combination the chain will drag on the inside of the big chain ring. Not constantly but it will sort of snatch occasionally. My setup is as follows, Dura Ace 39-53 cranks, Dura Ace front and rear derailleurs, Ultegra 12-25 cassette, ultegra bottom bracket, and ultegra chain. I've helped the problem by carefully adjusting the rear derailleur, but haven't solved it completely. I didn't have this problem with my old Ultegra cranks. Any suggestions?
Oct 11, 2002 8:10 PM
Don't ride small-small or big-big. You can get the same gear ratio elsewhere, with a more direct chainline. Running in the small ring and the small cog is not ideal, nor is simultaneously running the large ring and large cog.
I made the same experience...Markus_B
Oct 12, 2002 11:39 AM
with my Dura Ace.

I think the only possible solution is a BB with a longer spindle (maybe a XTR BB-M952 with 112,5 mm axle will be enough?).

But I don't ride big-big or small-small to avoid exessive wear, so I don't care about the drag.

(And I'm used to not really have 3 x 9 combinations on my MTB, though there the front derailleur is the reason for noise.)
Spacers.Von Zip
Oct 12, 2002 12:03 PM
.6mm chain ring bolt spacers,(washers) will solve the problem when installed correctly. Erik.
cycling 101...C-40
Oct 12, 2002 2:49 PM
One of the very first lessons in cycling is that the two extreme chain angles are off limits. Neither the big/big or little/little combos should be used.

There is no good reason to use them either, since a duplicate gear is available with the other chainring. You can use them briefly, if necessary, but extensive use is just stupid.
cycling 101...Trooper
Oct 13, 2002 5:44 AM
Of course you shouldn't cross chain. My question was why the chain was dragging when in the 12-39 combination when I was checking my setup. I didn't want this to happen if I inadvertently shifted into this combination on the road. If you didn't know the answer you could have spared me your pompous reply. It turns out that I hadn't pressed the link pin in far enough when I reassembled the chain.
Shimano 9 speed sensitivityNessism
Oct 13, 2002 3:44 PM
Chain line seems to be critical when running Shimano 9 speed parts. It's quite common for the chain to rub on the inside of the big ring when running in a crossover situation if the chainline is inboard of center. You can try to shim the bottom bracket outboard slightly - shim are available for this purpose, or install the chain ring spacers as someone else aluded to. The spacers move the rings apart to a similar distance to that found on 8 speed cranks (which work just fine on 9 speed drivetrains thank you very much). My suggestion is to don't give up. You should be able to run through a full 8 cogs in the back without the rub you are experiencing. Get some shims and start fiddling around.

Shimano 9 speed sensitivityREPO42
Oct 13, 2002 11:52 PM
Actually I agree with all who say don't run that combo. I too have that problem when I put it in the 11 x 39. I only run this combo to make sure derailleurs are shifting properly. I don't think the manufactures intended crossing over like that... Or you can shim everything up, but why would you want to do that? There are websites that will give you an exact sub for that combo you are running. like 53x17 or so... I am guessing, but not crossing would be the best bet.. You will save wear and tear on the chain and derailleurs...One racers opinion
re: Dura Ace Chain Interferencesprokit
Oct 14, 2002 2:53 PM
I agree with above posts that you don't run low/low or small/small. I was installing a new Dura Ace front derailleur and Shimano has a note that you may get chain rub in the two smallest sprockets when running the small chainwheel up front and this is in a double not a triple.