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Old 08-07-08, 09:09 AM   #1
mcoomer
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Do cranks break in over time???

I put a new Dura Ace crank on my SL2 when I built it and I can't believe how much noise the chain makes on the chainrings. When the chain line is near perfectly straight for the ring I'm on it is very quiet but if I shift up or down more than a cog or two in the back I can really hear the chain on the rings. I've got just over a hundred miles on the bike and just gave the front der a tweak because it had shifted some but otherwise my drivetrain alignment appears good. I'm running a SRAM 1090R chain but if this continues I think I'll pick up the Shimano CN-7801 and see if that's more quiet.

So, is there a break in period for cranks? I'm wondering if there isn't just a bit of an edge to the chainring teeth that will be smoothed down. Let me know what you think.

Mike
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Old 08-07-08, 09:35 AM   #2
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I noticed the same thing with my new crank that also happens to be a Dura-Ace.

I run single speed, and my chainline couldn't be off by more than 1mm, yet I hear grinding at the rear cog.
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Old 08-07-08, 11:32 AM   #3
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Something wrong with u guy's, 'coz mine is silent, and am not the only one, OK Ultegra, but I can't imagine Shimano top-of-the-line is worse than its second fiddle.

Are u guys those very fussing riders who perhaps keep your chain TOO CLEAN?

A recent post says cogs can wrongly be mounted backwards then another says no. U figure it out.

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Old 08-07-08, 02:10 PM   #4
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OK...did some checking and found that the SRAM 1090R is 5.9mm wide and the Shimano CN-7801 is 6.1mm. Is it possible that this slight difference in size is causing the SRAM chain sideplates to rub on the chainrings a bit more causing the noise?
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Old 08-07-08, 04:37 PM   #5
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Should be no break in required. You may need a different chain. I've heard people have this experience occasionally.

As far as the single speed is concerned, I only get grinding when I've got gunk in my chain.
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Old 08-07-08, 08:14 PM   #6
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Quote:
Originally Posted by mcoomer View Post
I put a new Dura Ace crank on my SL2 when I built it and I can't believe how much noise the chain makes on the chainrings. When the chain line is near perfectly straight for the ring I'm on it is very quiet but if I shift up or down more than a cog or two in the back I can really hear the chain on the rings. I've got just over a hundred miles on the bike and just gave the front der a tweak because it had shifted some but otherwise my drivetrain alignment appears good. I'm running a SRAM 1090R chain but if this continues I think I'll pick up the Shimano CN-7801 and see if that's more quiet.

So, is there a break in period for cranks? I'm wondering if there isn't just a bit of an edge to the chainring teeth that will be smoothed down. Let me know what you think.

Mike
Lots of things in play here ...

First, bike frames keep getting lighter and lighter and, as a result, transmit more noise. Think of a nice violin and then think about how much quieter it would be if all the wood in it were an inch thick. One of the noisiest bikes I have heard lately is the Specialized Transition TT bike. That's a pretty exotic frame and it makes a LOT of noise with very fine DA components.

I'd be surprised if the change of chain does not help a little. There's a reason that people will pay $80 for a nice Campy chain. It just makes the whole drive train smoother (and, quieter). SRAM chains are great, but not specifically designed as part of a Shimano gruppo.

Cranks, of all of a gruppo's components, probably will affect how much noise gets transmitted into the frame (= loudspeaker, for purposes of this discussion). And, again, the lighter the crank, the more noise it's going to transmit (again, consider the violin analogy).

So, concluding, there is significant correlation between the amount of noise a bike makes and how "high end" the frame and components are. You want a really quiet bike? Go for a heavy steel frame 10 speed and lube everything with SynLube.

To answer your specific question about "crank break in" ... It's probably as good as it will ever get after just a few miles (to wear down any sharp edges) and then it just goes down hill from there.
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Old 08-08-08, 01:35 AM   #7
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Also chains and chainrings/cassettes wear together. If you've put on a considerable number of miles before swapping your cranks and rings out the chain may be noisy because it's stretched out.
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Old 08-08-08, 02:00 AM   #8
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Make sure the chainrings aren't on backwards...
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Old 08-08-08, 03:28 AM   #9
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Sometimes the new ramps/pins take a few miles to become totally silent, but other than that, the only "breaking in" in relation to the crank is with the BB cups which do become more free over time.
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Old 08-08-08, 08:07 AM   #10
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Went home last night and did some tweaking. Bike has only about 150 miles on it so I checked cable tension to the derailleurs (tweaked the front der just a bit), loosened the left crank arm and cap and then snugged the cap down, and lubed the drivetrain. I don't know how much of a difference it makes but I think I had the crank arm cap much too tight initially. I just snugged it down when I tightened it this time.

The bike sounded much better this morning. Now if the City of Seattle would just do something about the potholes on Airport Way!
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Old 08-08-08, 11:57 AM   #11
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I've noticed that my drivetrain is always more noisy after a thorough cleaning (i.e. complete immersion of chain/cogs in solvent), but then quiets down after a couple of rides. I suspect it's just the effect of the cogs and chainrings getting coated with lube that eventually quiets things down. Also the rollers in the chain probably move around a bit more and clack against each other when they're clean and there's only a thin film of fresh lube on them, and then quiet down as they fill up with grimy "padding".
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