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The type of cycling I do means I'm never really presented with mega-steep climbs.

I used an online calculator and worked out I never really use gear ratios below about 39, which on my MTB at the moment is gear 1 at the front and 6 at the back. I was thinking about going for a really large chainring at the front and removing the front mech. If I were to use a 46T chainring, this would give me a minimum gear ratio of 36.5 in the lowest gear, and 112.9 in the highest gear, which is much more appealing for me, as opposed to my current max gear ratio of 88.4.

Currently my bike has a 11-34T cassette at the rear and a 36-22T double chainring at the front.

I want to know if this would be possible. I am prepared to replace the cranks as my bike has a very low end Prowheel crankset on it at the moment. I have read a bit on this site and have seen that potential problems could revolve around the rear derailleur not being able to handle the longer chain I will be needed if I were to do this.

Is this possible? Thanks a lot

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  • Put a 46-34 at the front if the chainstay has enough clearance for the rings. You'll have a much more useful range.
    – Carel
    Aug 9, 2020 at 15:53
  • @Carel how would I need to adjust my front deraileur to make this possible? Or would it just work stragitht away. Also i thought 46-34 were only available for road bikes, or is it cross compatible?
    – Rahul Basi
    Aug 9, 2020 at 20:30
  • The FD is either clamp-on or screw-on and can be moved up and down the seat tube. The rings will have to fit the BCD of the crank, there are many options. Rings are not purpose specific. Or if you want to change the crank anyway...
    – Carel
    Aug 10, 2020 at 7:37
  • The numbers you talk about can't possibly be ratios. Your maximum ratio is 36/11 ~ 3.27. So what exactly do you mean by 88.4?
    – Szabolcs
    Aug 11, 2020 at 13:11

2 Answers 2

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I was thinking about going for a really large chainring at the front and removing the front mech

Don't. I have a bicycle without front derailleur.

If there is no front derailleur, when riding over a bump at high speed, the chain is at danger of falling from the chainring. This has happened to me.

Not only that, but the only way to get the chain back to the chainring is to touch it with your fingers, making your fingers oily and full of chain dirt. This has happened to me too.

With a front derailleur, the chain is unlikely to fall as it acts as a chain guide, and in the unlikely event the chain falls, you just operate the front derailleur to raise the chain over the chainring.

The rear derailleur does not care about the chain length. It only cares about the total needed capacity which is (large_front_chainring - small_front_chainring) + (large_rear_sprocket - small_rear_sprocket).

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  • Thanks a lot for your answer. I reckon I would be able to get away with a chain guide in place of the front mech, and potentially one mounted on the chainstay as well. I think this is what a lot of people have done with 1x setups. Could you explain the 'total needed capacity' bit a little further? Would having a super large front ring affect this then?
    – Rahul Basi
    Aug 9, 2020 at 13:24
  • @RahulBasi As you can see from the formula, total needed capacity reduces when switching to 1x chainring setup, because one of the terms goes to zero. The rear derailleur can handle the reduced capacity need. You just need to make the chain longer if installing a super large front chainring.
    – juhist
    Aug 9, 2020 at 13:31
  • Great, thanks for your help. Hopefully I can fix the chain dropping issue with a couple chain guides. Good to know this is possible!
    – Rahul Basi
    Aug 9, 2020 at 13:33
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    All you need is a good narrow-wide chainring and a clutch derailleur. Chaindrops shouldn't be an issue after that.
    – MaplePanda
    Aug 9, 2020 at 19:36
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    @juhist Which model derailleur do you have? Did you even turn the clutch on? If you find it’s dropping a lot, you can turn up the tension as well.
    – MaplePanda
    Aug 10, 2020 at 18:04
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It is possible to do a 2x to 1x conversion but as stated in other answers you generally need to do something to keep the chain on the chainring. Generally a narrow-wide chainring is used on 1x setups to retain the chain. Leaving the derailleur in can also accomplish this.

Re-using a double crank with a single biases the chainring to one side, ending up with unavoidable cross chaining. I’ve heard special rings that offset the teeth are available.

If you want a chainring larger than your current one you may run into chainring-chainstay clearance issues, especially on a bike designed for small rings such as yours. A significantly larger ring (46 instead of 36 in your case) is very likely to have clearance issues.

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  • Narrow-wide chainring is not sufficient to retain the chain. My 34-tooth chainring in my 1x11 bike without front derailleur is of the narrow-wide type. It fails to retain the chain.
    – juhist
    Aug 10, 2020 at 15:19
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    @juhist works fine on my gravel bike. Presumably on an MTB a clutch derailleur is necessary as well
    – Argenti Apparatus
    Aug 10, 2020 at 15:22
  • My 1x11 bike seems to have Shimano DynaSys rear derailleur too in addition to the narrow-wide chainring. I assume the derailleur is of the clutch type. The chain drops very easily.
    – juhist
    Aug 10, 2020 at 15:24
  • @juhist Something is wrong with your setup. However, thousands of other people use 1x setups just fine. It is not their general feature.
    – Vladimir F Героям слава
    Aug 10, 2020 at 16:33

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