Pick a folding bicycle wheel size
 

20" is the sweet spot. Perfect compromise of size & function.

Thanks
Yan

16". I own both a 16 and 20", but honestly the reason to have a folder is to be able to make it small and take it places easily...and a 16" wheel does the best job of meeting both criteria. The real question is why bike manufacturers don't spend money on r&d to develop a 16" that rides spectacularly, has massive non-proprietary upgrade potential, folds ultra compact, is super light weight, and has a reasonable price tag? My Bike Friday pakit meets many of these needs, but the fold could be more compact and the price could be better. Ride, weight and upgrade potential are brilliant.

Tried other folders with 26" and 20" wheels in the past.

I'm most happy with 16"/349 ETRTO:
https://farm2.staticflickr.com/1488/...affceef4_z.jpg
Bike To Work by 1nterceptor, on Flickr
https://farm5.staticflickr.com/4446/...ab9dc569_z.jpg
Office parking 2017 by 1nterceptor, on Flickr

I have 26", 20", and 16" folders. I just received my Downtube Mini 16" folder today,... 16" is the sweet spot for me.

I'd go for 20"

I have a Brompton and a Swift. I feel little difference on smooth pavement between the two. Brompton folds smaller but the 349 only take 1 3/8 tires or smaller, or at least that is what I can find. The Swift doesn't fold as small, although that is more the design than the wheel size. If the Brompton had 20 inch wheels it would be maybe 2 inches longer. The Swift will run 2 inch tires which can help with riding on gravel, potholes and ruts etc. At this point wheelbase and tire choices matter more to me.

2 - 349 wheel bikes, and 1 406, here ... 1 Brompton, 2 Bike Friday ..


The Rohloff hub works well in a 20" wheel with a common 53t chainring..

in a 16" wheel a hub with the 1:1 ratio, more in the middle, like the Alfine 8 or 11 or AW3, is a better choice.






....

I own (or have owned) folders or ridden friends' folders with: 14", 16", 20", 26" wheels. If, and that is a big if, I could only have one size for the rest of my life it would be the 20" for the same reasons Yan stated.

I'm afraid the rest of the bike must come into consideration. There is no sweet spot.

i would choose 16" bikes.
i have a brompton and a dahon curve and bolth are amazing!

my third opition is dahon prrmium bikes. i have a dahon mu sl and its also amazing fast, dispite having 20" wheels

20 inch, because you have the most tire choices, balance durability, speed, weight, and comfort to your wants.

The majority of folding bikes have 20" wheels therefore you have the more choice in bikes, again balancing your wants.

I agree with this because with the right gear range a 20 inch can still keep you moving with traffic (20mph+), tons of tire options, and have not come across a surface yet where I regretted not having the large tires...although on a nice day and nice road I do love my 24x1 tires :)

What is the purpose of the bike and which is more important, portability or ridability?

My foldup bike has 24 inch tires (507mm) that ride very nicely, but the bike is not very portable when packing it up to go onto an airplane without an oversize fee. Works for me but the bike when folded might be too large for some that are more interested in folding the bike frequently while they are using the bike for short commuting distances.

Without knowing the purpose of the bike, you can't really say what is best.

I don't find portability is much of an issue with any of the tire sizes. Storage at work maybe but portability? Bikes in these tire sizes generally all weigh similar, fit on transit and move through buildings/elevators without being unmanageable. I find no difference in packing times or airline issues when flying between my 20 and 24. Same with the train to work. If I brought my bike into my work space then smaller has an advantage. We have a bike rack in the building so no issues there.

20" seems to be a sweet spot for both ride and compact fold.

I'll also go with a 20" wheel, mainly because I'm a Raleigh Twenty addict.

I believe most will pick 20-inch. You can also check out some comparison on Youtube

I wonder how it feels riding a 12" or 14" inch wheel ?

I have 2 26"Montague and Dahon Matrix
2 20" Dahon and Downtube

Mobiky 12.5
They are tools with specific uses.
You have to know where you want to ride
20+"are bulky but smooth
12"max I would go is a mile

EDIT added a Bromton 16". wIth it , nice if the roads are smooth, does not like rough or broken pavement. great fold..
and a Dahon Curve, with plump 16" tires, small frame size and not geared for hills, Better on coarser roads than the B , but small cockpit and only a 3 spd.
So, again, a lot depends on terrain you ride and have to cross with it folded.

In order to get the correct answer you must ask the right question, there are TWO different sizes of 20" wheels: 405 & 451

Now, why there are TWO wheels named 20" is a bit of a mystery but the answer begins with the fact that the metric system is superior.

BTW the answer is: 451

406 has the largest tire selections (including knobbies), and is stable enough for fast group ride with roadies.

My 349's don't have any problems keeping up with roadies:
Or any other type of bike on any size tire. :)

I have/had 14", 18" 20-406, 20-451 and 700c bikes.

It really depends on the individual's use case. (ie. last mile commute; casual riding; part commute by car; city riding; gravel riding; long distance, etc)
14" - best fold and lightest to handle/fold, but can be harsh on bumps and don't roll over things well. Also not fast unless gearing is very specifically catered for it. Not something for very long distances (ie. above 30km) (Crius Smart 3.0).
18" - pretty nice compromise for compact fold, good choice of tires for many types of riding. Decently fast even riding with 700c bikes though of course more effort is needed and it looses out on top end speed.
20-406 - Starts to get big folded, but good range of tires and styles of bikes. A choice between 18" and 20-406 bikes really depends on what the user prefers/thinks matters (ie. fold size vs better rolling, tire choices )
20-451 - More 'speed' orientated. The best of the 20" and under wheeled bikes to match up to 700c bikes in terms of speed. It still looses out in the rolling over of bumps and rougher roads though. Also looses 700c on the top end of gearing, so looses out in sprints and surges, though I find that its not that important if a course is long and individual effort is involved since I will reel most 700c riders in over a 10km stretch. Very lacking in tire options, mainly narrow tires limit the versatility of 451.

Ideally, I'd like 20-451 with tires choices from 1" - 1.75".

I'm trying out a 650b folding bike soon, as it better rolls over gravel/trail routes for my touring needs, though I do think it crosses the line wrt folding size.

If I don't have the habit of riding my small wheeled bike vs roadies every weekend, I'd probably settle for the 20-406.


So I don't really have the answer to this question :D