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Most of the folding bikes I've seen, which are used for urban commuting/recreation, usually have MTB components except for the big chainring. If they're going to be ridden most of the time on paved roads, why not use road bike components?

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  • ...MTB? Citation needed -- as a long-time Bike Friday fan, I've noticed more in common with recumbents, at least in terms of rims/wheels/&c. Not that there aren't other places where things differ -- your newer high-end folders are moving to belts instead of chain drives, and I don't think I've seen a belt-drive MTB yet. (And the ability to easily build -- and repair -- long chains advantages them in 'bents) Jan 28 '17 at 17:43
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    ...I don't think I've seen internally-geared hubs show up in MTBs either, whereas they're rightly a huge hit in folders (a derailleur is easy to break when throwing a bike around, having the chain exposed more makes more mess, and of course, one can't use a derailleur with a belt drive). Jan 28 '17 at 17:46
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    @Charles those are some good points. But if you consider derailleur folding bikes I think the question is valid. It sounds like the OP was mainly thinking of the drivetrain. And there are plenty of folding bikes with derailleurs, even if a lot of popular good ones use IGHs.
    – Chris H
    Jan 28 '17 at 18:58
  • Something to do with gear range. My folder was 6 speed 14-28 which was too low, even on 20" wheels. MTB components seem to span more rear gears without needing a front mech.
    – Criggie
    Jan 28 '17 at 22:27
  • @Charles the ones I've seen in stores like Dahon, Tern, Giant, Doppelganger have MTB shifters, derailleurs, cassettes, etc.
    – dork
    Jan 29 '17 at 4:39
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Great question!

I think the market drives this -- not necessarily just the folding bike market, but the component market.

Mountain bikes have been the predominant type of bicycle for the past thirty years. This has meant that every manufacturer has a line for very, very inexpensive mountain bike componentry. If you want to build up a bike on the cheap, you use mtb hardware.

Finally, related is that most adolescent-size BSOs are also mountainbikes - which further drives down price on those components with the added benefit that they fit folding bikes better.

tldr: Most folding bikes are not sold by virtue of their component line (unlike road bikes) but on the basis of their folding mechanism. Most buyers will see "Shimano" gears and be happy -- not knowing it's the bottom end plastic Shimano for a BSO mtb.


There is also some physical factors that also play a role, notably the brakes. Most folding bikes have 20" or smaller wheels. Because the wheels are smaller, the tires have to be wider to provide resilience and suspension. The brakes also have to be stronger and "grabbier" because the smaller wheel torques on the brakes more. So you want cantilever or V-brakes for the reach around the fat tire -- or disc-brakes. Final nail in the casket, you have to consider which brake handle styles have the right pull ratio given that folders don't have drops. One of the few folding bikes that has road-style caliper brakes is the Brompton - and it has custom brake levers and has been heavily criticized for its poor braking. One of the few folding bikes with drops and calipers is the Tern Verge X18 below, which is a niche-niche bike. So in general, considering cost and effectiveness, you end up with mtb style brakes and brake levers. Christian Lindig has also mentioned the derailleur but there are some considerations there (long-cage mountain derailleurs don't work on stubby wheels) that complicate a response.

Tern Verge X18

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  • This is a rather interesting theory, but it's kind of hard to prove if this one or one of the other answers are correct. Or maybe it's a combination of all of them.
    – stijn
    Jan 28 '17 at 17:14
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    Sounds accurate to me. Or to put it another way: Why would they NOT use "mountain" components? Jan 28 '17 at 17:25
  • @stijn it's completely compatible with my answer, and has the advantage that RoboKaren is a bit of an expert on folding bikes.
    – Chris H
    Jan 28 '17 at 18:54
  • @ChrisH - But the primary motivation is almost certainly price and availability, not the physical qualities of the components. Jan 28 '17 at 22:07
  • @DanielRHicks I'm inclined to agree, and commend this answer. I would still have written my answer if this is had appeared first, but slightly differently.
    – Chris H
    Jan 28 '17 at 22:11
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Road-bike specific components are designed for weight not strength. MTBs are expected to survive rougher handling. Although folding bikes don't want to be heavy, they need to be tough, often getting knocked over onto drivetrain components, or bumped into doorframes, etc.

Other bikes built for mainly on-road use but not top speeds also share components with MTBs. For example plenty of hybrids use MTB gears even if their wheels have more in common with tourers (at least mine does, some others use road components except the bars)

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    On the other hand, cyclocross racers use road components.
    – ojs
    Jan 28 '17 at 19:56
  • @ojs good point. My limited understanding of cyclocross is that it's a bit gentler on the bike than some other off-road disciplines, and less likely to be taken up by unskilled riders.
    – Chris H
    Jan 28 '17 at 22:10
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Road bikes have short rear derailleurs which are incompatible with a cassette that offers a wide range of gears (like 12T to 30T in 10 steps) - they are designed to offer smaller steps over a narrower range (like 11T to 23T in 10 steps). A strong motivation to use an MTB rear derailleur is to offer a wide range of gears as there is typically only one chainring in the front.

As noted by another answer, a long derailleur is a problem for the small wheels used on folding bikes. As a result you will notice that the chain runs very close to the ground - and will pick up dirt from there.

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  • This backs up your point in a way, but 12-30 isn't a very wide range. Even my 3x8 hybrid came with an 11-32 cassette, modern mountain cassettes are wider still because of the range needed with a 1x setup
    – Chris H
    Jan 28 '17 at 18:51
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    I was using 12-30 just as an example - it could be wider. But it is often too wide already for a short road bike derailleur. Like you are saying, many modern MTBs have a 1x setup and have to use a very long rear derailleur for this. Jan 28 '17 at 19:01
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    12-30 is pretty wide compared to 12-23 that used to be road default until few years ago.
    – ojs
    Jan 28 '17 at 21:24

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