Can I use a single speed crank (like a Shimano Vee) paired with an 7 speed rear derailleur and 10 speed 12-32 rear cassette to make an inexpensive 1x10 gearing, for non-technical trail riding?

Is there something special about the more expensive components that are devoted to 1x gearing?

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    Why even spend money on Shimano Vee when you can get no-brand square taper cranks for cheaper? Those were found on quality bikes much later than 7-speed. – ojs Nov 1 '18 at 18:02
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    with a 7 speed rear derailleur , you will only have 7 of the 10 gears of your 10sp cassette. But yes there are relatively cheap ways to go about it, although i don't think your listed method would be the best route. – Nate W Nov 1 '18 at 18:19
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    @NateW actually 7 speed shifter and derailleur would not index properly on a 10 speed cassette - sprocket spacing is different. – Argenti Apparatus Nov 1 '18 at 19:14
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    @ArgentiApparatus If it is friction shift rather than index it will do just fine. This is what I did for a winter commute bike. – Rider_X Nov 1 '18 at 20:56
  • Very true, my mind automatically thought friction but yes you are correct – Nate W Nov 2 '18 at 17:44

Dedicated 1x systems do have some specific features:

  • 11 or 12 speeds
  • Derailleur able to handle a super ratio cassette (at least 11-40)
  • Narrow-wide chainring
  • Clutch system on the derailleur.

You can definitely cobble together parts to make a 1x10 (or 1x9) system. A Vee crank will most likely be fine. 12-32 cassette is reasonable (11-32 would be OK too). A 7 speed derailleur won't work.

You'll want to consider your overall gear ratio spread vs size of the ratio steps. Trying to run a cassette with a too-wide range means you'll have big jumps between gears, and requires a derailleur that than handle the largest sprocket size. If you settle for a narrower range cassette (sacrificing either high or low ratios, depending on what size chainring you select) gives you more derailleur choices. A narrower range cassette also means the derailleur has to deal with less slack chain when on the small sprockets and hence less chain slap.

The rear derailleur does not care what crank you use, or the chainring size. Just select a crank that fits your bike, gets the correct chain-line and has a bolt pattern and diameter that will take a chainring of the size you want. Narrow-wide chainrings are a good idea for better chain retention.

You need a derailleur compatible with a 10 speed shifter. For Shimano 1x10 you will have to use a 10 speed derailleur because Shimano 10 and 11 speed MTB groups use a different derailleur actuation ratio than 9, 8 and 7 speed groups. The derailleur also needs to be able to handle the largest cassette sprocket

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I'm going through a similar dodgy hack at the moment.

A 7 speed deraillur may have enough physical range to cover the width of an 8 speed cassette, or it may not. Note an 8/9/10 speed cassette are all the same physical total width.

You will require a 10 speed shifter, and the main problem here is whether the cable-pull matches the cable pull of the 7 speed derailleur. Using a friction shifter should work, but that's an aquired skill and its not particularly ergonomic.

It is safer to fit a 10 speed rear derailleur, shifter, 10 speed chain, and cassette all at once and all from the same vintage/groupset.

Additionally, theres "dynasys" which is some Shimano marketting-droid's buzzword for "yet another incompatible system" so make sure your rear shifter and rear mech match, either both or neither.

Regarding the front, you can use pretty much any crank you like that fits the chainring. The chainring will probably work fine too, but if you ride bumpy things then a chainkeeper/guide would be a good idea. As a frugal solution you can use your existing front mech but use the limit screws to lock it into one position, and do away with the left-hand control. This will help keep the chain on the front chainring.

Later, if you wear out the chainring then consider buying a narrow-wide chainring, which should mostly negate the need for a chainguide.

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