I have a 18 speed bike. There are two chain rings in the front and 9 cogs at the back. I am new to cycling and I wish to know which gear combinations should I avoid to prolong the life of the chain and gears and avoid cross chaining. So can someone help me please. The labels are like this:

(1-9) at the rear with 9 being the smallest (1-2) at the front with 1 being the smallest

can you please write down which combinations i should not use if i am conservative or wish to be on the safe side. thank you

  • To answer your question: Avoid smallest to biggest at both ends. And any others that make extra noise. Those gears are usually redundant - you'll be able to find a similar gear using the other front ring.
    – andy256
    Oct 11, 2015 at 7:00
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    But to not answer your question, I don't bother. I think worry about cross chaining is over done these days. I just ride. The bigger worry is keeping grit out of brakes to avoid expensive and dangerous rim wear.
    – andy256
    Oct 11, 2015 at 7:04
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    @andy256 You mean smallest to smallest and biggest to biggest, not smallest to biggest.
    – Alexander
    Oct 11, 2015 at 7:41
  • @Alexander Yep, that would be it :-)
    – andy256
    Oct 11, 2015 at 9:45
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    If you're "settled in" to a particular speed and likely to be there for several minutes, you might want to check and see if you're on the small front ring and one of the smaller one or two rear cogs, or vice-versa. If so you can probably change rings and find another combo with an equivalent gear ratio. This will reduce chain noise and very slightly reduce wear. It's been 30 years or so, prior to the age of "long cage" rear derailers, since "cross chaining" was a real problem, though (except on intentionally "retro" bikes). Oct 11, 2015 at 12:00

3 Answers 3


Big at the front should generally not be combined with big at the back, for two reasons.

  • It forces the chain to use a non-straight chain path, (hence "cross chaining")

  • The derailleur spring has to stretch out forwards to allow the chain to be mostly on the cogs.

You also want to avoid small front and small rear, for similar but opposite reasons.

  • The chain does the same out-of-line crosschaining, merely in the other direction

  • The derailer has so much extra chain to take up that it ends up folding completely up and the chain can rub on itself passing around the two jockey wheels. At extreme cases the chain can catch itself, and wrap itself around a jockey wheel. This tends to bring pedalling to an abrupt halt.

Chains wear out no matter what you do. Grit from roads, salt, and plain old usage wear a chain. You're recommended to fit a new one every 2000 km, but different brands have different numbers, plus your usage comes into it. If you ignore the chain then it will slowly wear out the rear cassette, and then starts on the front chainrings. A $30 chain a year is cheaper than a new cassette and chain every two years.


Sounds like you have a road bike. If that's the case, the front derailleur usually has little clearance. This will cause some grinding noise (between chain and derailleur) before extreme cross chain occurs, providing that the front derailleur is set up correctly.

Usually: - Front 1 matches with Rear 1-6 - Front 2 matches with Rear 4-9

Chain, chainring and cog wear is not the real problem. Extreme load on cross chain wears the free bearing much faster than any other components.


Read this article and use your common sense. It does matter a lot to change gears in the right way but it won't kill your bike if go wrong by one cog :)

  • Gidday and welcome to bicycles SE. The site is intended to be self-contained, and therefore not dependant on info at another website. Could you edit your answer to summarise the main points of the linked article? I agree with you that crosschaining is not the monster it used to be.
    – Criggie
    Oct 11, 2015 at 21:13

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