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Old 06-12-10, 05:25 PM   #1
Gotte
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20 inch wheel question

I'm tempted to do my next tour on a 20" folder. Am I right in thinking that 20" wheels are less prone to spokes snapping, and easier in gravel/dirt?
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Old 06-12-10, 06:27 PM   #2
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Twenty inch wheels are strong, Some Moulton separable bikes use them such as the APB as does Bike Friday even on their tandems. There are many wide tire choices in the 406 wheel size suitable for gravel roads and trails.
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Old 06-12-10, 07:53 PM   #3
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You may notice that not many 20" folding bikes are made for off-road. Let's figure out why, shall we?

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I'm tempted to do my next tour on a 20" folder. Am I right in thinking that 20" wheels are less prone to spokes snapping, and easier in gravel/dirt?
In terms of wheel strength: theoretically yes, practically no. Any well-made wheel is going to hold up to most touring conditions; any poorly made wheel is more prone to bust a spoke. Plus, any wheel can get damaged in transit.

In terms of gravel and dirt: Smaller wheels generally provide a harsher ride than 26" or 700c. You can easily compensate by using tires that are wider and/or have a lower PSI. You'll have a minor performance penalty, but one that is totally negligible in a touring context.

In addition, the drivetrain on a 20" wheel is going to be much lower to the ground than a 26" or 700c wheel.

Additionally in addition, most folding bikes have non-diamond frames with a big hinge in the middle and very tall handleposts (e.g. Dahon and many others). This has neither the structural strength nor maneuverability associated with, say, a BMX bike. Not a great choice for extensive off-road use.

If you are occasionally hitting gravel and dirt, you'll be fine with a 20" folder; just keep an eye on the drivetrain. If you plan to spend most or all of the time playing in dirt (e.g. Katy Trail), there are a handful of 20" folders and collapsible bikes made for offroad use. Or, I'd look into an S&S coupled bike like the Surly Traveler's Check.
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Old 06-12-10, 08:56 PM   #4
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, and easier in gravel/dirt?
no, not easier to travel in gravel/dirt.
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Old 06-12-10, 10:12 PM   #5
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When Alex Moulton introduced his ATB 20 inch wheel bridge truss design with front and rear suspension in 1988 I bought one. It was a wonderful off pavement machine within its wheels inherent limitations mentioned above.

The tire footprint was small so the wider the tire the better to reduce washouts in loose material. The 20 inch wheels did not roll over obstacles as easily as 26 or 700c wheels but this is manageable with adjusted technique and expectations. The truss design was/is very strong but most single hinge folders without suspension may not be durable enough for loaded off pavement touring. That is only a guess on my part from my lengthy Moulton and Raleigh Twenty experience. I would still give it a try to gauge the possibilities. A folder plus public transport plus touring sounds good to me.
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Old 06-13-10, 02:23 AM   #6
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I've had my Bike Friday New World Tourist for 10 years. I haven't had any spoke or wheel issues, but I rarely had any spoke problems with "regular" bikes. I'm a small rider. I've toured on several unpaved trails including the bumpy C&O Canal and I also used to commute regularly on a route which was mostly an unpaved trail. To be honest, I haven't noticed any difference on those trails due to tire size. I've been using Schwalbe Marathon 20" x 1.5" tires with kevlar for several years and they're great.
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Old 06-13-10, 05:06 AM   #7
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Thanks for that. much appreciated.
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Old 06-13-10, 08:09 AM   #8
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Gotte, 20" wheeled bikes can do a lot of things with some adjustment but it's a simple relation between wheel size and roughness of surface that makes larger wheels better. For a given sized bump the smaller wheel will experience a more abrupt shock that slows you down and greater tendency for the front wheel to dig and slide. I've got a Bike Friday with 2.0 Big Apple on the front and 1.6"Supreme on the rear. The 2.0" is much better when riding through gravel than a 1.5" tire and is better on packed whoopty doo trails than narrow 20" tires but when it comes to wanting something better for crappy surfaces 26" and 700C will provide more secure control. One of my regular routes last summer was a 12mile ride with about 2miles on dirt trail that was packed, loose and gravel. I did it for awhile on an old mtn. bike with 26x 1.5 tires then later with the BF with 1.5"-2.0" tires. It was immediately obvious when hitting the dirt with loose gravel sections that the smaller wheels were skittering over the gravel with twitchy handling compared to the old mtn. bike. I got the folding bike for a reason, storage, and enjoy it's handling attributes. With front panniers and heavy load over the rear wheel it's bizarre how stable it is.
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