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What are the symptoms of chainrings needing replacement?

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What are the symptoms of chainrings needing replacement?

Old 05-02-18, 08:24 AM
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masi61
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What are the symptoms of chainrings needing replacement?

I believe that the middle chainring on my Ultegra 6603 triple road crank is due to be replaced. The mileage is about 12,000 miles. It will hang up and delay releasing to the granny ring at times causing slow shifting & chain slap.

I found a replacement 39 tooth ring for the “6604” that sounds like it would work.

But i’m also curious to know: what are some other symptoms that my chainrings are on there way out? Does noise increase when under climbing torque? I lubricate my chain and change it when it is stretched @ 1.0% which helps but I am getting “imprecise” type of noises that don’t sound healthy.

Thanks for any help you can give....
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Old 05-02-18, 09:11 AM
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Looks like shark teeth!

If your changing a crank ring, would budget for a new cassette & chain as well, as chances are they will both need replacing as well, would look at the inner chainring as well, as and replace at the same time, as these are cheap.
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Old 05-02-18, 09:25 AM
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Originally Posted by jimc101 View Post
Looks like shark teeth!

If your changing a crank ring, would budget for a new cassette & chain as well, as chances are they will both need replacing as well, would look at the inner chainring as well, as and replace at the same time, as these are cheap.
Although for how much rings cost....you're not that far away from just buying a whole new crankset. Especially if shopping NOS triples.
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Old 05-02-18, 10:10 AM
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Originally Posted by masi61 View Post
The mileage is about 12,000 miles. It will hang up and delay releasing to the granny ring at times causing slow shifting & chain slap.

I found a replacement 39 tooth ring for the “6604” that sounds like it would work.

12k miles is often well under what you can get from road chainrings (but not impossible under hard use) so it may not be worn. Shimano makes all their chainrings to match as a set with corresponding model numbers so that the shifting ramped teeth match up. Some combinations will make no difference in shifting but some others there can be a very slight delay for the chain to move. Not really a big deal for most and works fine but some find it annoying and you can still get the proper 6603 39t chainring from a few places. (Here's one https://www.ebay.com/p/Shimano-Ulteg...3789241&chn=ps ) But first check that all the chainring bolts are tight and that your shifter cable is working smoothly with no fraying or rust/dirt/gunk clogging it up. Also make sure the derailleur moves freely and is mounted correctly since they can be bumped out of position occasionally.
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Old 05-02-18, 11:48 AM
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I recently replaced a middle chain ring of a triple. The teeth were not worn so as to look like shark teeth but shifting into the middle was slow and clunky. After I removed it for inspection it was apparent the pins that pick up the chain were worn and doing a poor job of picking up the chain. A new chain ring cured the problem and restored the usual crisp shifting.
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Old 05-02-18, 12:36 PM
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Originally Posted by Marcus_Ti View Post
Although for how much rings cost....you're not that far away from just buying a whole new crankset. Especially if shopping NOS triples.
Would agree if it was the outer, but inners are normally cheap (vs outers), as always shopping round/comparing prices is key here
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Old 05-02-18, 01:22 PM
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A couple of "symptoms" that I've observed.
  • Noisy (42T small ring). I think this was by leaving the ring in one orientation for many miles, and a stretched chain. This caused narrowing of teeth on one side of the ring as opposed to the other side.
  • Pulling chain off of the big ring under power (and moderate cross chaining). Very worn teeth.
  • Skipping. I have one triple that I bought used. 30/39/53, I think. Anyway, the middle ring skips very badly, and is unusable. That bike is also hard shifting either up or down from the middle ring. I had blamed derailleur adjustment on it, but also need to put on a chain catcher for the small ring.
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Old 05-02-18, 01:25 PM
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Originally Posted by jimc101 View Post
Would agree if it was the outer, but inners are normally cheap (vs outers), as always shopping round/comparing prices is key here
Usually. But it depends on the crankset. Dura Ace 7703 middle rings are hard to find, and expensive And not really interchangeable with other models.

In theory, shifting is best when one maintains a matched set of rings.
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Old 05-02-18, 04:52 PM
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Rohloff HG/IG Sprocket Checker is marginally effective on chainrings too. By eye the fins get to be thin and asymmetric (shark teeth that were mentioned). The space between the teeth becomes box-like. Outer ring gets only slowly worn out, so you can use its a reference for how the teeth should look like when not worn. In terms of how the operation is affected, the leading tooth or teeth begin to do all work, rather than the work being spread out, accelerating the wear of the teeth and chain.
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Old 05-02-18, 05:31 PM
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Originally Posted by 2_i View Post
Rohloff HG/IG Sprocket Checker is marginally effective on chainrings too. By eye the fins get to be thin and asymmetric (shark teeth that were mentioned). The space between the teeth becomes box-like. Outer ring gets only slowly worn out, so you can use its a reference for how the teeth should look like when not worn. In terms of how the operation is affected, the leading tooth or teeth begin to do all work, rather than the work being spread out, accelerating the wear of the teeth and chain.
What I look at, especially with chain stretch is an elongated notch indicating signs of wear, then looking at the pulling edge of the teeth, on a new ring, it should go almost vertical. On a badly ring, it is sloped, allowing the chain to ride high, which causes lots of problems (increases the diameter of the ring, effectively increasing the spacing between teeth, and thus a shorter chain will eventually pop over the top and skip.
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Old 05-03-18, 06:26 AM
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Originally Posted by Crankycrank View Post
12k miles is often well under what you can get from road chainrings (but not impossible under hard use) so it may not be worn. Shimano makes all their chainrings to match as a set with corresponding model numbers so that the shifting ramped teeth match up. Some combinations will make no difference in shifting but some others there can be a very slight delay for the chain to move. Not really a big deal for most and works fine but some find it annoying and you can still get the proper 6603 39t chainring from a few places. (Here's one https://www.ebay.com/p/Shimano-Ulteg...3789241&chn=ps ) But first check that all the chainring bolts are tight and that your shifter cable is working smoothly with no fraying or rust/dirt/gunk clogging it up. Also make sure the derailleur moves freely and is mounted correctly since they can be bumped out of position occasionally.
This idea that Shimano makes chainrings in matched sets made me remember an odd mechanical re-assembly error I made last year when I had been chasing a creaking sound. So, I had the chainrings completely off the arms for cleaning. I had everything clean but then there was a time crunch since I needed to leave on my group ride in an hour. I inadvertently remounted the big chainring one hole off on the spider such that the little pin that normally lines up with the crank arm (to prevent jams should you throw the chain). Could this mean that my shift points are just misaligned a bit from optimal? I feel like 12,000 should not be replacement time even though I guess I do favor the middle ring.

BTW: I believe that the “6604” Ultegra triple crank should be identical functionally to the original silver “6603” triple crank. The difference I believe is that the “6604” may have that distinctive smoked anodized graphic that came out a year or two following the original.

I plan to service the crankset today and take a closer look at all of this.
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Old 05-03-18, 06:35 AM
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One other comment about the shifting lag time... the delay I am describing is mainly only an issue with group riding (drafting) situations. I’m using my triple drivetrain as a racing triple with a 12-23 tight 9-speed cluster. It is early in the season and my shift points are still there but my fast B group are all really solid and we all have been riding together for a few years so the pace line is approaching racer levels of tight.
i’ve been trying to buck the compact double trend with my version of this racing 3 x 9 drivetrain. I’m going to look at replacing my front housing and cable while I’m at it since my 7703 front shifter has been releasing with a harder click than I remember...
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Old 05-03-18, 01:59 PM
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Yes, the ring orientation relative to each other matters for shifting. The chain should be capable to travel smoothly from one ring onto another. There may be a lag if the chain needs to reset itself.
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