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Old 03-11-05, 10:05 PM   #1
hawk00eyed
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Dura-Ace/Cross-Chaining Question

So i'm getting rub when i cross-chain, which from what i've been reading is natural becuase you're not supposed to cross-chain, but for what.. combinations of cog/chainring am i Supposed to get rubbing for? I have Dura-Ace, which i just got, and so when i'm in the small ring, i get rub with the three smallest cogs. when i'm in the big ring, rub with the biggest cog. Are these "rubbing" combos normal, or do i need to do some adjustments so i do'nt get rubbing for a few of these?
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Old 03-11-05, 10:15 PM   #2
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Yes.
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Old 03-11-05, 10:52 PM   #3
Sheldon Brown
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Quote:
Originally Posted by hawk00eyed
So i'm getting rub when i cross-chain, which from what i've been reading is natural becuase you're not supposed to cross-chain, but for what.. combinations of cog/chainring am i Supposed to get rubbing for? I have Dura-Ace, which i just got, and so when i'm in the small ring, i get rub with the three smallest cogs. when i'm in the big ring, rub with the biggest cog. Are these "rubbing" combos normal, or do i need to do some adjustments so i do'nt get rubbing for a few of these?
You don't say what's rubbing, but I'll guess it's the front derailer. It may be that you have it mounted too high. See my article on Derailer Adjustment http://sheldonbrown.com/derailer-adjustment

If the chain is rubbing on the side of the big ring when you're cross chaining in the small ring, it may be a chainline issue, but this is partly dependent on the length of your bike's chainstays.

Unfortunately, there's a widely believed superstition that holds that short chainstays make a bike faster and more maneuverable in some way, so many racy bikes have unpleasantly short chainstays. This exacerbates all kinds of chainline problems, in addition to giving a harsh ride.

You really should not ride in the small/small combination at any time, even if it doesn't rub.

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Old 03-11-05, 10:59 PM   #4
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Holy Crap! Awesome, Sheldon Brown replied to my post! Thanks, yea its the front derailleur, i'll check out the mount height. Thanks!
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Old 03-11-05, 11:46 PM   #5
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Originally Posted by Sheldon Brown
You really should not ride in the small/small combination at any time, even if it doesn't rub.
Or big-big for that matter. There is a duplicate gear (or at least close enough) availiable in the smaller ring.
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Old 03-12-05, 07:15 AM   #6
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Quote:
Originally Posted by hawk00eyed
So i'm getting rub when i cross-chain, which from what i've been reading is natural becuase you're not supposed to cross-chain, but for what.. combinations of cog/chainring am i Supposed to get rubbing for? I have Dura-Ace, which i just got, and so when i'm in the small ring, i get rub with the three smallest cogs. when i'm in the big ring, rub with the biggest cog. Are these "rubbing" combos normal, or do i need to do some adjustments so i do'nt get rubbing for a few of these?
The front shifter has a trim function for the FD too.
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Old 03-12-05, 10:56 AM   #7
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I have a '98 56cm Trek 5500 with 9-speed Dura-Ace that I can use all gear combinations with no rub on the front derailleur. When in the small to small combination the chain rubs slightly on the side of the big ring. I've never even used the trim function. I wish I could say the same for my Record 10-speed.
I'm not in love with the Trek or the Dura-Ace but it's the most trouble free front-end I've ever seen. It was installed by my LBS, I guess we just got lucky.

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Old 03-12-05, 11:18 AM   #8
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Quote:
Originally Posted by Raiyn
Or big-big for that matter. There is a duplicate gear (or at least close enough) availiable in the smaller ring.
Small/small is generally much worse than big-big. In addition to the angle issue, you've got the sprocket size issue:

The small front ring puts a greater pull on the chain. The small rear sprocket may only be sharing the load among half a dozen teeth, so chain and sprocket wear is greatly accellerated in the small/small combo.

Depending on the chainline setup, big/big can be OK. F'rinstance, my Hetchins is set up with a 50-28 double, and the chainline is set to put the 50 ring in line with the middle of the 12-28 cassette. I use all 9 rear sprockets with the 50, and on most rides I never even touch the front derailer.

However, for unusually tough climbs and/or if I'm really tuckered out, I've got that little 28 tooth chainring held in reserve. I only use that with the 3 or maybe 4 biggest rear sprockets, but when I need it I don't mind the big jump.

See: http://sheldonbrown.com/hetchins

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