The Folding Society

Fixed Gear Airnimal

AirnimalMy search for the ideal fixed gear bike has taken me over a year. Online articles and reviews like the ones at the Folding Society were very useful, so I am keen to repay the favour and provide details of my quest for a folding fix.

I only got into cycling in July 2005 when I bought a Dahon Speed Pro. I wanted to go fast and my wife would not allow a non-folded bike into the flat. I really liked the Dahon and fell in love with the feeling of riding a nimble small-wheeled bike. However, I had many problems with the bike, I do not want to put people off Dahons, but I basically wore out two frames in 9 months. The main hinge on the cross tube wore out on the first bike, the bike was replaced, but then the same hinge wore out, the joint where the stem folds broke and the Pantour suspension hub broke so that the axle was locked in the most depressed state. I don't want to put people off as I not heard of anyone else having these problems with a Speed Pro, it must be that I have a very intensive riding style that wore out the bikes (I don't understand what I am doing though). I only mention this as it had a big influence on my choice of bike. Also, I was never able to getting into the ideal riding position on the Dahon, I would have liked to have the handle bars about 15 cm lower and 8 cm further forward and to have the saddle about 4 cm higher. I am 195 cm (6' 4") and really like a stupidly aggressive riding position.

Over the first winter riding the Dahon I wore gloves that meant that I couldn't easily change gear. I also noticed that there were all of these couriers that were constantly passing me on single speed/fixed bikes. I started riding single speed (i.e. not changing gear) and got hooked. I realised with practice you can accelerate away from traffic light quicker than with gears and there is such a freedom that comes without always having to think about when to change gear. I could see the next logical step was to go fixed, I tried a few fixed bikes and really liked the extra control and real connection with the road (I did nearly kill myself though the first few times I tried).

I test-rode many 700C and 650C bikes including some very expensive all carbon bikes with all the trimmings, but after the Dahon, they felt like knives cutting into the road that didn't want to turn so I decided to search for something else.

There are two things that are quite important when looking for a folding fixed gear. First, having either track ends (rear facing dropouts) or at least horizontal dropouts, but not vertical dropouts, this is to be able to adjust the chain tension (very important on a fixed). Second, is a unified rear triangle so that when the bike folds or any rear suspension moves, the distance between the bottom bracket and the rear axle does not change. You can get around the first issue by changing the dropouts (a very serious undertaking) or by using an eccentric bottom bracket or eccentric hub (eccentric means that the axle can rotate around the mounting). Some people say that you can find a 'magic gear'; the two cogs that fit perfectly into your frame so the chain is tight even with vertical dropouts, but I have had to re-tighten my chain 3 times in 3 months as the chain has stretched so I would not recommend the magic gear solution. The only way that I know of to get around not having a unified rear triangle is to undo the rear axle each time you fold the bike.

Looking at the folding bikes commonly available, I decided that I would dismiss bikes with both vertical dropouts and a non-unified rear triangle i.e. Bromptons and Birdys. Also, after my experience with the Dahon, I decided to rule all of them out as they all have the same kind of hinge in the cross tube. This left the following bikes:

Moulton - some AM frames have a unified rear triangle and horizontal dropouts
Bike Friday Pocket Rocket - without a unified rear triangle, but available as a custom build with track ends
Swift Folder - with track ends and a unified rear triangle
Airnimal Chameleon - with a unified rear triangle, but vertical dropouts

I test rode some Moultons at the Moulton workshop in Bradford Upon Avon which were great bikes, but I found the suspension so soft that I was too disconnected from the road. I can imagine that there could be nothing better for a long distance ride, but most of my rides are between 5-10 miles. Also the high price, relatively heavy frame and the inability to fold easily put me off.

I really liked the fixed Bike Fridays I saw online, but the idea of having to re-set the chain tension every time I folded the bike seemed like too much hassle.

I was really set on getting a Swift Folder, all the reviews I found said the frame was light, stiff and responsive. Peter Reich, who custom builds Swifts in New York, was very helpful and I got as far as ordering a bike, but then there was a serious delay with shipping and in that time I test rode a Chameleon and loved it. I had not had a chance to ride a swift and Peter suggested that the delay would be so long that I should probably look for another bike (I think this was specific to my order so don't let this put you off).

I originally dismissed the Chameleon as I thought the bike would be too big and it would take too long to fold. However, I moved to a new flat where the space for keeping bikes is bigger. I test rode one just on a whim and fell in love with the handling, it felt as nimble as the 20" bikes I was used to, but much quicker and stiffer.

Side Views

Rob at Ben Hayward Cycles, Cambridge was very helpful with choosing the parts and building the bike. At first we considered an eccentric bottom bracket as this would mean that the chain tension would not have to be set each time I took the wheel off to fix a puncture etc. However, the bearings on an eccentric bottom bracket are smaller than on a regular bottom bracket and are prone to wear out quite easily. Then I was able to have a look at a wheel built up with a White Industries ENO hub and decided it was a really impressive way to create fixed gear. You can see in the photo how chain tension is adjusted by rotating the wheel axle around the bolts that attaches the wheel to the dropout. I have found it very easy to set the chain tension, it is actually easier to put this wheel on than it was to mess around with the derailleur on the Dahon when replacing the wheel. All you have to do is tighten the bolts almost all the way, then take a spanner (I have a tiny adjustable one in my bag) and rotate the hub around the bolts until the chain is at the correct tension. Then tighten the bolts completely, whilst still holding onto the spanner to make sure the wheel doesn't move.

ENO hub

The chain ring is 53t which is the second largest commonly available in 1/8" (track) size. I needed to have a big chain wheel because the 24" wheels are smaller than the more common 700C the 53/16 set up gives 74.5 gear inches. If I had gone with a 20" bike I would have real difficulty finding a chain ring big enough, probably having to use a weaker 3/32" road chain or getting one custom built. After my experience with the Dahon, I went with 3-cross 32 spoke wheels and a steel steerer for extra strength.

Complete specs as follows:

Chain Line

Frame: Airnimal Chameleon Aluminium
Fork: Carbon forks/steel steerer
Headset: Crane Creek S2
Bottom Bracket: Race Face XC Taperlock steel 110mm
Cranks: Dura-Ace Track
Chain Ring: 53t Dura-Ace Track
Fixed Cog: 16t Dura-Ace 1/8" Free Cog: 16t Shimano
Chain: Sram nickel plated 1/8"
Front Hub: White Industries RacerX
Rear Hub: White Industries ENO eccentric hub
Rims: Airnimal 32h 24"
Tyres: Schwalbe Stelvio
Brake: Ultegra
Brake Lever: Crane Creek 200TT
Handlebar: Profile Airwing
Stem: Deda
Saddle: Specialised Alias 143
Seatpin: Race Face XY 400mm
Mudguards: SKS Quick Release Race Blades
Original Pedals: MKS AR-2 Quick Release with Powergrips
Current Pedals: Crank Brothers Egg Beaters C

Weight: 9.2 kg / 20lb
Price: £1480 inc. MKS pedals and mudguards

This bike is so fast and accurate, it goes wherever I want it to go and always feels steady and safe. On average, the bike is about 2-5 mph faster than the Dahon - the difference between 30 minutes and 24 minutes to do the 5.6 miles from Brick Lane to Imperial College, London. I regularly hit 35 mph going through underpasses and the bike could go faster, I am only limited by being able to pedal at about 160 rpm. I could change the gearing of the bike to go faster, but with practice I could probably do better than 160 rpm. - I have heard stories about people getting close to 300 rpm.

The suspension is great, a lot stiffer than on a Moulton or a mountain bike. It gives a lot of feedback from the road, but with the carbon fork, the ride is quite comfortable.

There is some debate about if the smaller wheels are an advantage when riding fixed. They are lighter than 700C wheels so you think that they should accelerate faster, but they have to rotate quicker so I think it is a much of a muchness. All I know is that my Chameleon is certainly more nimble that a 700C bike and it is by far the fastest thing I have ridden.

Strong FrameOverall I am really pleased with the frame, I have had to make a small modification with the elastomer (see below). Also, the joint where the seat post attaches to the cross bar creaks from time to time. I currently have the saddle 2 cm lower than the maximum position marked on the seat pin and I can get rid of the squeaking by putting the saddle lower, but then that wouldn't be as aggressive/fun. I have a theory that (at least when I ride a bike in my clearly abusive way) there is lots of stress on junctions where metal meets hard, (i.e. the hinges on the Dahons I broke and the seat post hinge on the Chameleon). If you compare the amount of engineering that goes into headsets, bottom brackets and the joints on most folding bikes, maybe it is not surprising that those folding bikes are breakable. The Chameleon eliminates a hard metal junction at the back of the bike by using the suspension hinge as the main folding hinge. This means the junction is soft rubber pressing against metal. The hinge used on the Chameleon is far bigger and beefy than hinges I have seen on other folding bikes and I believe the suspension also removes quite a bit of stress from the seat post joint. The contact area of the seat post joint is twice the size of most joints on folding bikes. There is also no folding joint at the front of the bike, instead the Chameleon becomes smaller by removing the front wheel. In comparison, both the Swift and the Bike Friday Pocket Rocket have three hard metal junctions with quick releases (seat post, rear triangle and steerer). Overall, considering that I can still make the over-engineered Chameleon squeak a bit from my riding (I have no idea how I do it though) I am very pleased that I went with the frame with only one metal/metal junction.

The MKS quick release pedals that I originally had, were a nice idea, but I have never had to get the bike small enough that I have taken them off. They are tapered which improves ground clearance when cornering. However, there is a bit of play in the joint such that they can move around in the housing which is not ideal (see what I was saying about joints where metal meets metal). I think I noticed this more because when riding fixed I often have to pull back on the pedals and I can feel the pedals wiggling in the mountings. Also the bearings in one of the pedals have started to catch a little, so I changed only a few days ago to the egg beaters. It is still early days with these pedals and it is the first time I have used cleats and I keep seem to be falling over, but I hope I will get better with practice.

I had powergrips on the MKS pedals, they give more connection with the pedals than straps and clips, almost as much connection as cleats, but you can wear any shoes you like with them. - A really great invention. However, with intensive use, they can really cut into soft shoes which was getting a bit painful.

SKS quick release mudguards are useful as the front wheel and mudguard need to be removed to fold the bike. Putting the front mudguard back on can be a bit of a hassle and every time it manages to slip down and start rubbing against the wheel, but then after a bit of adjustment it is fine. The rear one is not ideal either, I still get mud sprayed all over by back so I might add a little extension to it.

I also built a compass mount from a reflector mounting, cable ties and super glue. Handlebar mounted compasses are surprisingly rare and I don't really need to go as far as having GPS. I use tiny LED lights mounted to the stem (one on each side) that leave more space on the handle bars for my hands; having the bars so low means that I often want put my hands pretty much either side of the stem as this allows a more upright position.


In three months of riding the bike I have made a few modifications:

I have added the left brake lever housing. This means I have somewhere to put my left thumb and also makes the bike more stable when I turn it upside down to fix a flat.

I have lowered the stem on the steerer by 8 cm giving a much more aggressive (and slightly scary) riding position. This had the surprising effect of making it a lot easier to start from standing still, somehow the power goes to the pedals better (not sure why though).

I found that after a few weeks, the elastomer compressed by about 2.5 mm (the manual says this is normal). This meant that the frame geometry changed slightly which changed the feel of the bike and I didn't like it. Also, when I lifted the bike, the rear triangle would fall back slightly which was annoying. I went to my local friendly acrylic machinists and got a little yellow disk made that spaces out the elastomer slightly (for only 5). The spacer is slightly too big (they only go down to 3 mm in yellow acrylic) so it puts a bit of stress on the catch that holds the frame together, but it has made the ride quite a bit firmer and I like it. It also raises the bottom bracket slightly which improves ground clearance for cornering.


I have only folded the bike 3 times in as many months, once to go into a friends house, once to go on a very crowded train and once when I got a puncture in the rain I hoped on a bus home. Every time it was really great to be able to fold the bike (especially when I was not in the mood to be fixing a flat on a cold, dark and rainy night with muddy hands). However, I now realise that because I fold the bike so infrequently it would probably have been not much hassle to get the Bike Friday which would require me to release the chain tension each time I folded the bike. This would also mean that I would have more options for hubs and wheel rims etc. and produced a lighter, more foldable bike. However, there is the issue of the metal junctions in the frame that I mentioned above and the feel of the Chameleon is just about perfect for me so I have no regrets at all.


I am not quite satisfied with the handle bars. They are comfortable and can get me into an aerodynamic position, but they are a little too wide to do some of the traffic acrobatics necessary to go fast in London. I would like a sub 35 cm bull horn, but I think they would have to be a custom build. I could be fine with just a 28 cm flat bar with bar ends, but then I would not have the round corners that give more hand positions.

I would like to get rid of the top of the steerer that is perilously close to my crotch when I am standing on the pedals.

I am keen to look at wheels, I am getting better at city riding on a fixed and often spend long periods cruising through traffic at over 20 mph so I think better wheel aerodynamics could make a difference. HED and Velocity make some interesting 24" wheels, but the unconventional size does restrict my choice of manufactures. I still want to keep the wheels very strong and with quick acceleration, but more importantly I have to get some extra cash first.

In case you haven't guessed, I think this is a really great bike.

Back View

for your daily dose of bike porn:
check out bikes 757, 793, 897, 1251, 1452, 1566, 1608, 1851, 2164, 2337, 2790, 2772, 3028, 4261, 4355

great tutorial on how to ride fixed:

custom built fixed bike fridays:

a fixed swift:

UK fixed gear road racing:

NYC couriers using track bikes on the road:

great reference site about fixed gear bikes:

Andrew Stewart - near Brick Lane, London, UK - January 2007
email: minty at minty-ai dot net

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