Thought I'd start a discussion about 24" folding bikes. The market seems to be dominated by 20" and 16", but 24" could be a good compromise between size and performance that's most similar to 700c.

Anyone have experience with a 24" folder?

For me, its the opposite, 24" folder is a bad choice because:
- this size of wheel is not common and for ETRTO507 mainly for BMX, there are not that much good tires. Ultra limited choice of tires for ETRTO520 and ETRTO540.
- it doesn't provide the benefit of ETRTO622 wheels, i.e. the widest choice of tires and the best tires available having the latest technology improvements.
- but it has the drawbacks of bigger wheels = increased folded size, increased weight.

Unless it's the Helix Ultralight
It's a 24" (technically a 23") and is really compact when folded. However, it does take up some space because of the wheel size.
I wonder how a 20" Helix would ride because it would make sense from a marketing standpoint.
I'm really happy with my Helix, but you have to make concessions because of the unusual size, like the ones mentioned above.
I'll write a post about my Helix experience.

There are a few 24s. Dahon and Tern have done a couple and still catalog one or two in various markets. The current Helix, mentioned up thread. The Airnimal, a well-known yet rare series of semi-fold, semi-take apart bikes from the UK. For the most part, the market agrees with Jipe.

To compare comparable things, an ETRTO406 Helix with the same kind of wheels in ETRTO406 (same hub, same type of rims but in ETRTO406, same type of spokes but shorter) and lightweight ETRTO406 tires (there are several) would weight less than the current lightweight ETRTO507 Helix.

But to do that the frame should modified otherwise the bottom bracket will be too close to the ground.

Here is my Dahon Glide with 24 inch wheel. The ability to fold and save space is useful but this comes with a weight penalty. I think 24 wheels make more sense on non folding frames.

The issue of the availability of several type of tires remain:
- 24"/ETRTO507, BMX size, mainly wide tires, no road tires.
- 24"/ETRTO520, very few tires, mainly road tires. This size is (was) used for road bikes for smaller riders for instance by Terry and by Airnimal.
- 24"/ETRTO540 I don't know any recent bike using this wheel size?

The lack of tire availability is really a question for the industry as a whole, as the folder market is too small to exert enough influence to make a change.

I have a 20" folder (Zizzo Liberte) and a 20" 451 folder (Bike Friday Pocket Rocket). When ridden side by side, the compromises of 20" wheels are pretty clear. And while the Bike Friday rides 90% like a 700c bike, when I get on my 700c bike, the differences are there.

The question for the industry as a whole is, why the obsession with 700c? Anyone riding a 700c bike and with an inseam of 30" or less is riding a compromise of odd geometries and toe overlap. Mini velos and 20" folders are fairly popular in countries short on average stature for this very reason. I rode a 650c road bike for years, and it provided many of the rolling benefits of 700c with none of the 700c/small frame drawbacks.

It's within this context that I ask this question. Helix has shown - the precious few that actually got their bike - that nice rolling 24" folders can be made. It could be the Goldilocks size - rolls well and folds ok.

It's encouraging that ebike makers - faced with new packaging challenges - aren't as dogmatic (700c or bust!!!) as the rest of the industry with respect to wheel size. 20" wheels are popular for electric cargo bikes, and 24" and 26" options are also widely available too. Perhaps the ebike market - one of the fastest growing in the industry - will spur Schwalbe, Continental, and others to provide a greater variety of quality tire sizes that folder makers can then choose from.

The reason why eBike have ETRTO584 wheels instead of ETRTO622 is that these eBike have wide tires and even very wide tires like 62mm wide. Such a wide tire on a ETRTO622/700c rim will end up with a very big diameter wheel (basically, a 62mm wide tire is about 62mm high) too big for many cyclists.

The choice ETRTO406 for the wheel size for cargo comes from either the box in front of the cyclist (long john type of cargo with an ETRTO406 front wheel) or a long, low rear rack (long tail type of cargo with an ETRTO406 rear wheel). These bikes have also wide (and strong, made for heavy load) tires also up to 62mm wide.

There are also a few ETRTO507 cargo bikes but its not a trend at all and these cargo bike have also wide tires.

All this won't help for road bikes with small wheels because these would need fast relatively narrow road tires.

I had 2 frames of the same children race bike. I built the 20" (406) bike without problem other than the need for 28c front tyres the next size up which I have is 24" and I looked at rims and tyres.... there is nothing because the market for 24" is very small and budget orientated (cheaper kid bike that dumb in a garden in the rain). Yes, there are few MTB like orbea laufey but nothing for road.

There is a British fitter/custom bike builder who was saying that one of his custom affected with dwarfism rode a 24" wheel bike which was compromised due to wheel/tyre availability; they built a custom bike around 650B because there are loads of gravel and MTB tyres.
Note that many manufacturers offer their XS and XXS bike in 650b only.

In my case, I think I move the kid toward 650b bike rather than 24" when the 20" are to small.

the focus for 700C of road is down to the UCI; they setup the rules on equipment and the mass manufacturers who only aim is the make money will make whatever sells bike. If the UCI says you have to rave of roller blade wheels, you will many bike with roller blade wheels on the market.
Then, there the the XC scene, used to be 26" then 27.5" and XC rider found the 700c rims with big XC tyres (29") roll better over irregular terrain and are therefor faster. So, the market in MTB is shifting towards 29".
In gravel, fast "smooth" terrain works well with 700C and on rougher terrain, old XC setup (650B) works better because of the frame limitation But, if you look at "adventure-gravel" several new models are design for 55-622/29x2.2 or 65-584.

Out of interest, I rode 42-584 and 42-622 back to back and I must say unless you are on a small frame or require faster acceleration, I cannot understand why someone would ride 650b with small tyres; it is less comfortable, compromised (BB is low).

In New York, there's a healthy mix of non-cargo 20" ebikes with fat tires and 20" ebikes with not so fat tires, i.e., 2.5" or less. Fat-tired 20" ebike are significantly heavier, which can pose a challenge for someone that needs to haul their bike up a flight of stairs (or 2) or fit it into a confined space of an apartment or bike parking storage area. Outside of New York and similarly dense urban areas, the not-so-fat tired 20" ebikes will appeal to anyone needing to fold their bike and place it in the trunk of their car or otherwise maneuver it while not under power.

And as urban areas continue to build out bike infrastructure, the demand for 20" ebikes of all varieties will continue to grow, and considerably faster than the non-ebike market.

Personally, I just purchased a folder that takes 20" wheels up to 2.4", so I'm happy that the BMX and ebike markets are incentivizing tire makers to continually serve this market.

There are enough excellent wide touring tires in ETRTO406 like the very efficient with very good puncture protection Continental Contact Urban (in 32x406, 42x406 and 50x406) and the high puncture protection but still fast Continental eContact Plus (in 50x406, 55x406 and 62x406) to not be obliged to use BMX tire, with for most of them low puncture protection, for city riding.

Schwalbe has also good wide ETRTO406 tires like the Big Apple, Big Ben, Big Ben Plus and Supermoto X.

My Dahon Glide has 50-507 Schwalbe Big Apple tires that fit the use (urban) of the bike well. I understand tire selection is limited which makes sense given the limited market for these but why would you want a performance bike with 24 inch tires? There are plenty of options in other sizes. This can be related to both the UCI requirements and manufacturers. The latter want to keep things as simple as possible (lazy), hence the poor selection of some bikes in North-America. They want to focus on the performance market, larger and more important here, to the detriment of urban cyclists for instance. Urban cyclists are focused on utility. They probably don't upgrade or change their bikes often which in turn limits sales. Offering bikes in 700, 29, 650b sizes also creates larger and heavier bikes, another less interesting feature for urban users. Lastly, this leaves shorter cyclists with having to ride bikes larger than they need. Tall riders don`t often realize this but shorter people have less options. Smaller wheels are one way around this. BTW, what is the average height of Tours de France riders? I found 5'8''. That`t not very tall. In my opinion, tire size is based in large part on use. MTB, Road, urban bikes, travel bikes all have different needs. One is better than the other only if it really meets the needs of the rider. In other words, 24 inch tires are a compromise which the industry doesn't know what to do with. This size would certainly be something that urban cyclist would find easier to live with.

Who would be interested in a 24" wheeled performance bike? Anyone under 5'-5" tall. 20" wheeled mini velos are growing in popularity in Asia precisely for this reason despite the speed penalties that 20" wheels suffer. A 24" wheeled performance bike would close that performance gap and still set the rider up with a bike with good geometry.

Some bike manufacturers had the same idea like Terry for race bike for women and Kerautret (who was using ETRTO571/26"race size) but they face the problem of the lack of top performances tires in anything else than ETRTO622/700c.

My 20 inch 406 (Big Apple) tires on my urban minivelo.

I also use Big Apple in 55x406.

For 50x406, the Continental Contact Urban are the fastest and nevertheless are long lasting with an excellent puncture protection. Their only weak point is their thin sidewall, better not to use them offroad on trails with sharp stones.

I have an Airnimal Joey, built it up in 2006. That is a 24 inch bike. I built it up with 507 wheels, 520 was the other option.

A folding bike is a compromise. The designer either prioritizes rideability or portability. More portable means less likely to ride really well. The Airnimal Joey rides quite well, almost as well as one of my touring bikes or road bike, but is not very portable. If you want maximum portability, buy a Brompton. I prioritized rideability, I bought a 24 inch folder.

I can put my Joey into an S&S case for non-oversize airline travel, but that is the smallest case I can pack it into. And I have to spend almost as much time to pack the bike in that case as I would spend packing my S&S bike in that case. I have only flown with it once using that case. So, if you want a bike to take on a plane, maybe buying an S&S coupled bike or a Ritchey Break Away is a real consideration instead?

It still is more portable than a full size bike, but if I wanted a bike that I could ride to work on, then fold it up and put under my desk at work, the Airnimal is way too big for that. I think most people that want a folding bike would be better served with a 20 inch folder, or if portability is a big priority, 16 inch.

A couple photos of my Joey at this link:
Folders in the wild - post your photos

Why did I buy the Airnimal? I had a job that had a lot of travel, I was thinking it would be nice to have a bike that I could take on airplanes. And at that time, most airlines gave you two free checked bags so I could take it on a plane for free. That was why I bought the frame and built it up.

But, soon after that, the free luggage ended. And my job changed to one with a lot less travel. The bike no longer had a purpose. So, I have not ridden it much at all. Have not rode it at all this year, not sure if I rode it last year or not.

The trip where I took the photos at the above link was a van supported ACA trip. The Airnimal Joey performed as well as one of my touring bikes or my road bike would have, so it was not a disadvantage to have taken it. But, as I noted above, an S&S coupled bike or a Ritchey Breakaway could have served that role just as well.

I just installed the Contact Urban tires on another minivelo (20x 175). I read good reviews also.

Let me know if the Airnimal is ever for sale. Thanks

With a road bike like this Airnimal Joey, the key element for performances is the tires.

But there are no high performances road tires in ETRTO507.

I am pretty sure that a folding road bike like a Tyrell FSX with 20"/ETRTO406 wheels and top road tires like the Schwalbe Pro One 28x406 will perform better even if it has 18% smaller wheels because it can have much better tires than the Joey with its ETRTO507 wheels.

I have a Change Bike 650b which I have been quite satisfied with.
Long term review here.
Change Bike 650B

My conclusion having tried many folding bikes is that its a compromise of pack size vs 'full sized bike performance'.
A larger wheel size has better rollover and less rotational losses, wider tires also mean better damping on rough surfaces.
All these come at the cost of pack size.
In the end, each user has to decide on his/her use case which will determine what is the better wheel sized bike.

AFAIK, there are not many 24" options.
Airnimal and Helix being the notable ones.
The Change Bike has an older version in 26" wheels.






You are too modest, I think the Airnimal with the better rollover will be faster than a 20".

It's fine, I ride my minivelo with the kids on 32-406 urban contact. As long as it is not guppy mud, it works on stone/gravel I more worried for the rims than the tyres

I agree; it is all about tyres. If you fit excellent 20" tyres vs 24" budget tyres, the 20" will be faster with equivalent gearing (GI). The fix to GIs is bigger chainrings.
When I built my minivelo, I looked at what hill climb people road (light 700c with and 34T chainring). The mini velo (aluminium) has the same weight as many hill climb carbon bike and as Jipe said can be fitted with super fast Schwalbe Pro One. I have no problem to keep up with amateur group ride. The bike is geared too low to keep up with faster rider but, it is the case of increasing the range with a 58 or 60T ring rather than the current 50T.

I used to ride with Kojak 35-406 with a RR in the mid 20 and when for contact urban with ~16W RR. Despite the weight gain of 300g, the saving in W made the bike so much faster; 3 to 4kph faster on an average "base" ride.
Ultimately, what count is how many Watt the rider produces and how much of these go to the wheel. With a RR ~10W for the Schwalbe Pro One VS RR~25 to 30 for budget tyres, that's 30 to 40W loss as it makes difference.

The problem with ETRTO507/24"is that there is no tire with a low RR comparable to a high performance road tire like the Schwalbe Pro-one.

In ETRTO502/24" there is a Schwalbe One which is a training road tire not bad but definitely not at the level of the Pro-one.

The current range of Schwalbe is a little bit confusing, the current generation of One replaces the Durano while the Pro-one replaces the original One that was the highest performances road tire of Schwalbe