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Folding bikes have typically been built for commuters and are designed to be compact and light weight. In the spirit of discovery, i wanted to ask if anyone has seen or tried to build a gravel focused folding bike that doesn't compromise on portability?

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    There are certainly bikes with S&S couplers (not quick folding but pack to a similar size as a folder with the same size wheels). Would they be of interest? And it's certainly possible to do rough stuff on a good folder - one of my club mates has done the local blue MTB trail on a Brompton
    – Chris H
    Commented Oct 20, 2022 at 8:32
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    I have seen very few drop bar folding bikes, so if that's part of your definition of a gravel bike, I bet it will be hard to find off the shelf. I wonder if Brompton, Tern, or others do frame kits?
    – SamA
    Commented Oct 20, 2022 at 14:37
  • Drop bars tend to not be found on folding bikes because they don't fold up well. One might find bull-horns a better fit, especially if the stem has a quick-release to let everything pack away flatter and better.
    – Criggie ♦
    Commented Oct 21, 2022 at 2:15

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a gravel focused folding bike that doesn't compromise on portability?

All bicycles are a study in compromise.

Here are three examples of the many different approaches to the portability requirement.

Montague
enter image description here
Less portable due to large wheel size but better off road.

Brompton
enter image description here
More portable with smaller wheels

Moulton
enter image description here
Smaller wheels and a frame design that is very strong.

You have to decide what factors are more or less important to you and your situation in order to select the right platform for gravel bike portability.

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  • Moulton make a model called XTB that has fat tyres and would be quite fun as a gravel bike. I think the frame geometry is almost the same as the drop bar models.
    – Noise
    Commented Oct 21, 2022 at 12:37
  • @Noise I also like the Moulton. Alex Moulton put a lot of thought into designing his frame.
    – David D
    Commented Oct 21, 2022 at 13:15
  • sorry but the first one seems to be very flimsy, not for offroad but in general. Have a look at bikefriday.com/product/bike-friday-all-packa
    – EarlGrey
    Commented Oct 21, 2022 at 14:19
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    @EarlGrey I'm not a fan of the Montague. It's only here as an example of a folding bike that has large wheels. Back in the day Fuji made a fairly solid large wheel folding bike.
    – David D
    Commented Oct 21, 2022 at 17:16
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Something like Tern Bicycles' Verge 8i looks like it could be a good, stable and flexible platform for a gravel/bikepacking build: enter image description here

Tire selection might be a limitation with 20" wheels, and the gear range of the Alfine 8 might not be wide/low enough if you have big climbs. But I bet this bike would actually perform quite nicely on dirt roads.

That's just one example of a quality folding bike with clearance for some wider tires, which you could ride on gravel.

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I have a 20" folder, which was retrofitted form 1x6 to 3x8 gears. At the bottom end, it has around 15 gear inches. I've ridden gravel and very light offroad, and it tows a hundred kilo trailer adequately.

In theory it can climb steep grades, but as the ground gets steeper, the handlebars end up aft of the BB axle. This makes pedalling darn-near impossible.

The clamps are not as rigid as a piece of metal or carbon, so there are several additional points where flex enters the system, and you can definitely feel the bars move.

Many folders have clearance for a 45mm+ tyre, but 20" wheels don't have the same "rollover" as a larger 26" or 622 wheel. So lumpy or rutted ground is extra hard.

On the positive side, folders tend to enjoy a short wheelbase which makes for a more agile ride, and the small front wheel allows fast steering inputs.

Every bike is a compromise. A folder has to compromise somewhere, which is often weight, so an otherwise identical bike without the hinges and clamps will be lighter and stiffer. How important is folding to you ?

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    Of course, rollover can be improved by lowering the pressure. My 20" trials bike is much more comfortable on ruts than my 700C gravel bike, the tradeoff for this being abysmally bad rolling resistance on tarmac.
    – leftaroundabout
    Commented Oct 21, 2022 at 17:31

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