Why do they not sell bicycles with four wheels?

Question

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.

Answer 1

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

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.

Answer 2

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.

Answer 3

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 :)

_{from this listing and it costs quite a bit more than I've ever spent on a bike.}

Answer 4

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.

Answer 5

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

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.

Answer 6

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

Answer 7

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.

Answer 8

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

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.

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.

Answer 9

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.

Answer 10

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.