In the summertime, and Fall/Autumn, and Spring, my normal, two-wheeled bicycle works perfectly well.

But then there's Winter. What is normally friendly, non-slippery asphalt and grainy forest paths suddenly have turned into slippery death traps. Any route I pick is now like a lethal obstacle course where I put my life on the line. One mistake and CRACK! There goes my skull. Or rib. Or any part of my body. While typing this, I have just come back from one such terrifying bicycle trip, and it was anything but enjoyable. Scared to death almost every single meter, I was forced to move extremely slowly, sometimes even walking with the bicycle by the side, constantly on guard and ready to engage "operation save my own life and body parts when the whole thing just falls to the side".

Even when they have "sanded" the roads, many places look basically like a pure-ice slope down to Icy Hell. I've had "near-death" encounters like this many times in the past, and I never forget how scary it feels, so I'm very much trying to avoid it happening again.

I can't help but think how great it would be if, instead of one wheel in the middle in the front and in the back, it had two wheels, to the left and right, both in the front and in the back. Spaced apart quite a bit. This, at least according to my understanding of physics, would almost make it impossible for it to turn over while I'm riding it, no matter how slippery and hostile the surface is.

It would also have the added benefit of making it much more doable to have somebody ride in the back in non-winter time, because the weight is distributed better and the two wheels provide enough support for another person, or higher load (such as lots of groceries).

I know that there are those "fatwheel" (I think it's called? Fatbike?) bicycles now, but that doesn't help in this scenario. It doesn't matter how thick the wheels are -- they have to be two ones that are placed apart, no?

Short of some amateur-built "crazy inventor" contraption, I've never seen a four-wheel bicycle in the wild or for sale anywhere. Why is this? Why not enable me to move around in the winter? Is there a good reason for why this is not done that I have not considered? And it's not like it would not work in the summer as well, so you wouldn't need two different bicycles. And if one wheel is punctured, maybe it could offer a way to continue on home with just the three other ones. I see only benefits, myself.

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    Two wheels: bi-cycle, three wheels: tricycle like in tadpole and four wheels: quadri-cycle (they exist)
    – Carel
    Commented Jan 1, 2022 at 16:05
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    Biking since my youth, 12km to school (one way) since fifth grade, and since not much less biking, I've learned one thing: Slipping once per winter is perfectly ok and expected. There is no reason to be scared to death. When you slip on ice, you are falling on ice, and thus don't get much abrasions. Also, your bike escapes from under you sideways, causing you to fall on your shoulder, hip, and thigh, a rather large contact area. Finally, you are wearing winter cloths which help to cushion your fall and which take the brunt of abrasion. It's really slip, ****, scramble up, fetch bike, continue. Commented Jan 1, 2022 at 16:33
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    Bicycles have two wheels by definition. Commented Jan 1, 2022 at 16:35
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    Time to invest in studded tires. Commented Jan 1, 2022 at 16:36
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    ‘impossible to turn over’ Nope, if that were the case then rollover crashes in cars would never happen either. To be ‘impossible to flip’, you have to have your center-of-gravity on the road surface, or at least very close to it. But, that aside, falling off a bike is really not as dangerous as you might think unless you’re going pretty fast. Most of the danger of cycling is being hit by other vehicles moving much faster than you. Commented Jan 3, 2022 at 3:09

10 Answers 10


Why do they not sell bicycles with four wheels?

They do sell vehicles with four bicycle wheels.

As Carel said,

  • Two wheels is by definition a bicycle
  • Three wheels is a tricycle
  • four wheels is a quadricycle

Google "quadricycle bikes" and you can find a variety of small companies that make them.
Here is one example:
VierBike Sport Standard
enter image description here
This reference is intended only as one example. I have no idea how good this product is.

There are several market related reasons products like this are not more popular.
The bottom line is that there are not more of them because there is limited demand.

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    In Europe these four-wheelers are commonly used as rental cycles used by tourists and guests in seaside towns. They range from single to six-seaters and are quite heavy and cumbersome. Nothing one would use for daily commutes.
    – Carel
    Commented Jan 2, 2022 at 18:51
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    @Carel seconding this, lived in Ostend, Belgium a few years - they had a whole place renting these out, and the biggest one was this monstrous thing where there was one person steering at the front and this weird table like thing in the back for 8 people, each seat rigged with pedals and everything. I think the whole point was that the people in the back could drink beer and look around or something. Commented Jan 3, 2022 at 12:23
  • 2
    The problem with these as transport is that they're too wide for most bike infrastructure and usually too slow for roads with traffic. If you did get up to a decent speed and hit some ice on normal tyres, you might not fall over, but you wouldn't stop either - not great on a bend with a wall
    – Chris H
    Commented Jan 3, 2022 at 18:39
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    There's a tad bit of irony in saying that the correct term is quadricycle and then give an example that the manufacturer refers to as a 'bike'.
    – JimmyJames
    Commented Jan 3, 2022 at 20:13
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    @htmlcoderexe A "Konferenzrad", something like this. It is indeed an event-like thing that became quite a nuisance in Berlin in recent years to the point that the call to regulate them was made. And yes, beer is as important as the pedals. Commented Jan 4, 2022 at 4:04

Trikes, particularly recumbent trikes, are relatively common and provide the kind of stability you're talking about--although they (and quads) are prone to flip in turns if you don't know how to corner. My impression is that whatever marginal advantage a quad might have over a trike is not worth the disadvantages.

Riding a trike or quad on a flat tire would not be viable.

Trikes and quads are considerably more complex, heavier, more expensive, and harder to manage when you're not riding them. Rolling resistance, mechanical resistance, and aerodynamics are all poorer, so you will go slower, or work harder to go the same speed.

I have owned recumbent trikes. They're a lot of fun, but they do have their drawbacks.

  • 1
    Riding a bike on a flat tyre is even less viable. Been there, done that.
    – Vikki
    Commented Jan 2, 2022 at 15:47
  • Depending which wheel it is, riding on with a flat on a trike is easy to just doable, (if it is the driven wheel it is the hardest and depends on the kind of tire.) In Quads it seems that it is no problem at all, often the people in Quad velomobiles mention only noticing a flat when steering a difficult bend.
    – Willeke
    Commented Jan 2, 2022 at 21:30
  • While it is possible to tip a trike (and likely a quad) in a bend, it is much easier to go down with a bike. In 5 years of riding a normal trike (delta) I have had once that one wheel left the ground. No risk in flipping yet.
    – Willeke
    Commented Jan 2, 2022 at 21:32
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    @Willeke I think the point is that "4-wheels = won't tip" is just as invalid as "4-wheel-drive = I can stop". Sure, it's more difficult to tip a trike/quad, but the mentality of "I'm invulnerable" needs to be stopped.
    – FreeMan
    Commented Jan 3, 2022 at 19:11
  • @Willeke, there are two kinds of trike: those with 2 wheels at the back and those with 2 wheels in front. The traditional style, with 2 back wheels, is very easy to tip, and in most jurisdictions that configuration is banned for motorized vehicles (far too many deaths). Commented Nov 3, 2022 at 14:23

The main downside to a quad wheel is keeping all wheels on the ground.

The surfaces we ride on are not flat, so there's always a situation where one wheel would be off the ground or at least lower ground-pressure.

If the bike has one powered wheel, then it can get hung up with the powered wheel off the ground. This can be reduced by adding a locking differential or a live axle. Both add weight, and the axle will cause tyre scrubbing in turns because both rear wheels are locked together.

This bike would also need ackerman steering, because the front wheels turn at different speeds when cornering. Without this, the front wheels scrub too.

So you need to carry a lot more weight in terms of frame material and extra components, and suffer twice the rolling resistance. Quads are very much not aero either because of all the extra mass.

The places where Quads work well is when you have additional wattage, from a motor, and/or perhaps you're carrying so much mass that the additional bike weight is required.

I've seen a quad bike used to hold a solar panel/roof which worked for an expedition bike.

In your case, there's either modifying your bike as a winter ride, or realising that the colder places like Canada and Scotland and Finland have distinct riding seasons. It is okay to not-ride in winter.

You might look at options like studded tyres (for ice) or winter tyres (ice and snow.)
Fatbikes are acceptable at floating "over" snow but generally that means an additional bike, and they're no better on ice.
I've heard of tyre chains for disk brake bikes but have never seen them.
Another valid solution is to change your route over winter - could be that the road is a bad place to be, so take a back-road or a trail/track. Going out of your way for a longer route is its own reward :)

enter image description here
from this listing and it costs quite a bit more than I've ever spent on a bike.

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    Surely lack-of-aero comes from additional surface area, not additional mass? ("slow to accelerate", OTOH, would come from the additional mass :) ) Commented Jan 2, 2022 at 3:59
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    You actually see quite a few three a four wheeled downhill "bikes" around here, independent suspension and disks all around. Of course, they're downhill rigs so weight isn't much of an issue and they're gravity driven so the drivetrain isn't a big issue but they're pretty good at keeping all their wheels on the ground and steering. Commented Jan 2, 2022 at 4:46
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    You don't need a differential with two powered back wheels, just two freewheels, which is very light. Then the slower wheel (or the one with grip) automatically gets power.
    – Davidmh
    Commented Jan 2, 2022 at 8:44
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    It is true that you need Ackerman steering for the front wheels to prevent scrubbing, but that is not because they turn at different speeds; that is not a problem since the two front wheels rotate independently, anyway. The reason you need Ackerman steering is because the inner wheel needs to have a greater angle with respect to the "forward" direction compared to the outer wheel in order for both wheels to be tangent to the paths that they trace out, respectively. However, when it comes to the back wheels, a naive construction will make them rotate with the same speed, which is a problem. Commented Jan 4, 2022 at 13:14
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    @ChrisH The Red Bull Soapbox Races have been running for a few years now, and the level of engineering that's gone into some of them is outrageous. If you've not seen this yet, I totally recommend it. It's equal parts great engineering, great driving, and utter hilarity.
    – Graham
    Commented Jan 5, 2022 at 10:58

In addition to all the other answers: A trike or quad won’t fall over on slippery surfaces, but you can still lose traction causing you to crash or go off the road.

Unless you are going very slowly your forward speed is much more dangerous than the meter or so your center of gravity is above the ground. The mere act of falling off the bike is relatively harmless, unless you have bad luck or low bone density.

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    An important addition, imho. I wrote a comment in that same vein, but I agree that it's probably better to have this as an answer, simply because comments get deleted while answers remain. Thank you. Commented Jan 2, 2022 at 11:56
  • 1
    Also worth noting that friction does not depend on the size of the contact area, and that a heavier bike requires more force to accelerate. Adding more tires makes you no less likely to slip, nor does adding weight to the bike. And when you can't control the bike, the heavier vehicle is more dangerous for anything/anyone else you might hit. Commented Jan 4, 2022 at 15:26
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    I disagree that forward speed is more dangerous. Forward speed of 25 km/h is about 7 meters per second. A cyclist falling with head at 1.8 meter height from the ground, is like a rigid rod with one end on ground falling: the head will hit the ground not with energy m*g*h but with 1.5*m*g*h. To get speed of head crashing to ground, you calculate sqrt(2*1.5*9.81*1.8) = 7.28 and the unit is meters per second. The height of head from ground is more significant than forward speed!
    – juhist
    Commented Nov 3, 2022 at 17:41
  • ...now of course, if you crash, you can in worst case get effects from both forward speed and height of head from ground. But of these two, height of head from ground is more significant, unless the cyclist is going downhill.
    – juhist
    Commented Nov 3, 2022 at 17:42

Look into the winter road below (image credit), similar (little worse) than that I need to deal with:

Winter road

A bicycle with wide, knobbed MTB tires can take the car spur on the right. It is not a very nice ride but it would work on lower gear. In my case, my electric engine will help me to pull through if not too far. But a tricycle would need to dig a thick snow right between the spurs. A quadricycle would have a problem that the left spur is much less developed than the right spur. To span over the thicker layer of snow between the spurs, both also need additional ground clearance. So you need a well cleaned winter road for using such a "bicycles".

The problem you describe can be easier addressed via using appropriate tires: wide knobbed MTB tires (mines are 2.35") hold on the road well just on snow, and studded tires should be used when there is a notable amount of ice on the road.

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    On the plus side: if you fall on this snowmobile trail, you fall softly (deep snow may have saved my life when I was sent flying in a traffic accident once).
    – gerrit
    Commented Jan 4, 2022 at 9:06

They exist. And no, you won't fall to your death. Chances are simply very slim. Side wheels on bike

Adult training wheels fitted to an adult-sized frame

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    I don't really think that's what the question is talking about, independent of the fact that training wheels are a bad idea in almost all cases.
    – DavidW
    Commented Jan 2, 2022 at 18:05
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    Bikes with training wheels are not available in adult sizes. Was this a good faith attempt to answer the question?
    – Weiwen Ng
    Commented Jan 2, 2022 at 18:09
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    @WeiwenNg: In fact, they do exist. Also with very stable brackets, as they are intended for physically disabled people who can ride a bike but have (very) poor balance skills.
    – Carel
    Commented Jan 2, 2022 at 18:45
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    @WeiwenNg image of adult sized training wheels added to answer now. I think this started as a funny answer but the core of truth is totally valid.
    – Criggie
    Commented Jan 5, 2022 at 10:07
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    @Criggie I'm now imagining someone attaching those wheels to a carbon or even light aluminium frame and crushing the tubes. The clamps look best suited to gas-pipe BSOs
    – Chris H
    Commented Jan 5, 2022 at 10:53

There is a Velomobile on 4 wheels.
The QuattroVelo.
And it can come with a child seat in the back.

I have heard about two seater velomobiles which have the second person behind the first but could only find pictures and websites with them side by side, making quite a big item which will likely not fit on the bike infrastructure where you live.

As all the sites and videos I could find so far are basically selling sites I do not give links, but an online search should find them for you.

For those who wonder, velomobiles are cycles, most do not have an e-assist build in. But they are expensive, hardly found second hand (outside the Netherlands and Germany) and even then still not cheap.

  • More on velomobiles in this question and its answers.
    – gerrit
    Commented Jan 4, 2022 at 9:07

I have owned and ridden bikes with two, three, and four wheels all year round, including it in the winter in Stockholm. Here is my experience.

The problems a two wheeler face are:

  • Hidden lumps of ice or mud under the snow, that might throw you off
  • Edges of the road hidden, you can easily end up in the mud
  • Patches of low traction, often uphill
  • Exposure to the elements, both for the rider and the machine

Two velomobiles

Upgrading to a three-wheeled velomobile (in yellow) greatly helped with the first problem, allowing me to go much faster on broad paths with good visibility. The two front brakes add redundancy to control too.

I can notice when I go off track when one of the side wheels hits it, and often correct before anything bad happens.

Having a full fairing protects the mechanism from ice and salt, so it requires much less maintenance (but does make it more cumbersome). And it protects the driver, which is very nice.

The last point is the only problem: on steep hills, if the back powered wheel looses traction, I have to climb of and push. Much more annoying than on a two-wheeler.


The next step up is a four-wheeled velomobile, a Quattrevelo, pictured after commuting through the snow. The stability is even better, so lumps are barely noticeable. In fact, it was originally designed for Human Powered Vehicle racing to help cornering at higher speeds than trikes.

Both back wheels share power through a double freewheel. That avoids the need of a differential, and it means that, whenever one looses traction, the other gets power, so either of them needs to grip at any given time. That doubles the chances to get traction, and in my experience, after a full winter commuting, at no point have I had both loose grip, even crossing icy patches uphill. This also guarantees a better grip when sliding off the side of the road, since at least one will be firmly inside the tarmac.

In a comment, @HelloGoodbye asked if it would make them click all the time. The answer is, when going straight, both freewheels are almost engaged, so there is no strong clicking, but there is a rumbling when steering under power. I could only notice that once I changed to summer tyres, the studs masked the sound.

Cockpit view

A particularly nice thing of that design is the amount of protection it offers. That is the cockpit view one commute through a blizzard, -5C, snowfall, and I was in a t-shirt.

Problems other people have pointed out:

  • Flats are worse: no, I have three wheels to spare, so I might take some time to even notice it, and cargo space for repair kit. Plus, I can change tyres without removing the wheel, since they are attached on one side only.
  • It is hard to keep all four wheels on a plane: the four wheels have individual suspension.
  • If the back wheel(s) looses traction, it makes it unstable: that is true, but the same happens on a two-wheeler. What I think happened in the video is that both one of the front and the back wheel lost traction, making the machine turn. But with trikes, I have two wheels at the front biting on the snow, so double the grip and control. Having experienced going downhill on slippery slopes, velomobiles are much more controllable. Black ice is a real concern, though, but not more than any other bike.

On the downsides, both velomobiles have a lower clearance, so snow barriers created by snow plowers crossing the path can be problematic. And when snow gets too deep, getting off and pushing is less comfortable than on an two-wheeler.

Also, the chassis greatly limits the width of the tyre that can be installed, so no floating over deep snow.

And lastly, it is hard to see right in front of you, so one has to keep track of potential obstacles a bit further away.


Local laws usually don't allow 4 wheel vehicles to be classified as bicycles, so that is the main reason you don't see them except at the beach and as rentals in larger parks. Equipping them for the road would require a windshield, safety equipment- on and on until it is too expensive to buy for use on the street.

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    Welcome to the site - could you expand on what locality you're referencing? Different regions have different laws, here in New Zealand the road rules specify a maximum length and width (but not height)
    – Criggie
    Commented Jan 2, 2022 at 2:47
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    Seconding what Criggie said: In Germany everything that is pedal driven and does not include a motor is called a bicycle (Fahrrad). That starts at the usual bike, and ends with big vehicles for a dozen people or two, complete with table, roof, and a beer faucet, where the riders can enjoy a beer while pedaling. Only the driver has to keep away from alcohol due to road laws, but the entire contraption is legally a bicycle. Commented Jan 2, 2022 at 10:18
  • @cmaster-reinstatemonica that point holds fairly broadly in Europe, but of course the "bi--" in bicycle doesn't make much sense with more wheels, and isn't a component of the German word. The lack of a single, standard, logical name probably doesn't help in searching
    – Chris H
    Commented Jan 4, 2022 at 13:01
  • Yeah, I guess there are quite a few other countries with similar rules. Which makes sense: After all, the pedal driven part causes all these vehicles to cruise at similar speeds, forces them to relatively slow acceleration and slow uphill speeds, while allowing them to be very significantly faster on downhill roads. It only makes sense to put them all into the same class of vehicles. Commented Jan 4, 2022 at 13:56

While other answers have pointed out some 4-wheel "bikes", TrikExplor make an off-road quad recumbent which can even be 4 wheel drive and have electric assistance.

Stick some fat studded tyres on that and it will be very capable indeed.

Parking won't be easy and I suspect the cost is bank-breaking given that they're built to order.

  • Cost is still less than a new car and certainly less than a new high spec car.
    – Willeke
    Commented Jan 22, 2022 at 12:16

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