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Recently replaced the cables on this old road bike. When indexing the cable I notice how compressed this derailleur is and the two cogs are almost touching - it certainly doesn't look right to my untrained eye and when compared to my modern bike, but the bike is shifting nice and smoothly after much messing around. Is this something I should correct or be wary of?

Inherited this old bike and I'm trying to improve my bike mechanic skills, so any explanations or advice is immensely appreciated.

Thanks

Derailleur Picture 1 Derailleur Picture 2 Derailleur Picture 3

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    Welcome, I suggest taking the tour. The chain may be too long. How does it look like on the biggest chainring in the front and the biggest sprocket in the back? Commented Mar 8, 2023 at 12:19
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    Can you please take the first photo again, but showing the bike in big-big gear? The cage should be poking forward and tending toward almost straight. Update your question with edit
    – Criggie
    Commented Mar 8, 2023 at 18:42
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    Technically that is the 'highest' gear Commented Mar 9, 2023 at 15:11

4 Answers 4

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There's no issue with it looking like that while in small-small. It's very normal.

The derailleur's total capacity number defines what large/large combination is supported while still allowing the chain to be tensioned in small/small. All rear derailleurs will look like that when the chain is sized to take advantage of their full total capacity, which is common.

There is not a chain length problem based on what's going on in the picture. If the chain were shorter, yes it would be further away from rubbing on itself, but that is inconsequential. Meanwhile, if the large/large tooth counts on the bike are indeed set up to employ the full capacity of the RD, the chain will then be too short, which is bad because it means you might ruin your frame or RD if you accidentally shift into that gear under force.

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Maybe your chain is too long. It’s always hard to tell from photos.

If there is still tension on the chain in the smallest sprocket + smallest chainring combination it’s probably fine. You’d need a chain tool (and a master link) to shorten the chain. You’d have to make sure it’s still long enough for the biggest sprocket + biggest chainring combination.

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  • Master link isn't necessary - just make sure to leave a little bit of the pin in one side of the remaining link when removing a link. It's difficult to put a pin back in place when it's gone all the way out of the link. But I agree with your second sentence - it's probably fine.
    – Rich Moss
    Commented Mar 9, 2023 at 19:20
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    @RichMoss: Putting a normal pin back in might be okay-ish with old, wide chains like that, but lots of people say it’s not a good idea.
    – Michael
    Commented Mar 9, 2023 at 19:32
  • This is a 7-speed. I don't think "master links" were used widely (if at all!) when this system was "the thing".
    – arne
    Commented Mar 10, 2023 at 12:58
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Bike is shifting smoothly? Derailleur almost touches the cassette, but no actual rubbing?

You're fine.

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    Welcome to Bike Exchange. Exchange sites operate a bit differently than a traditional online forum. See how other questions are answered to get a feel for the flow of this site. Also, take the tour (just add /tour to the base URL). This answer duplicates another answer, and does not elaborate on the nuances that are present in the question.
    – Ted Hohl
    Commented Mar 9, 2023 at 2:27
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Is the chain on the smallest chainring, at the front? I doubt that you would use that while cycling.

You have 7 sprockets;

  • 2 chainrings? -- use smallest chainring with 4 largest sprockets, and largest chainring with 4 smallest sprockets.
  • 3 chainrings? -- use smallest chainring with 3 largest sprockets, medium chainring with 3 middle sprockets, and largest chainring with 3 smallest sprockets.

Count number of teeth on all gears, and work out the ratios available, to see why. It also keeps the chain straighter, and quieter :-)

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    You generally want all gear combinations to work. It’s very easy to end up in the big-big or small-small combinations “by accident”, even if it’s just for a second.
    – Michael
    Commented Mar 10, 2023 at 7:01
  • Yes of course, all combinations must 'work' ie don't cause a problem, but OP wasn't complaining that this position doesn't work. My answer point out another reason not to worry about it -- you won't use it.
    – Nick
    Commented Mar 11, 2023 at 1:33
  • If you read the question, it says that if works smoothly but looks odd
    – ojs
    Commented Mar 11, 2023 at 7:31

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