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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 ...
23
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 ...
18
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 ...
11
That’s called a deep-section rim. The ones you have pictured are probably about 30 mm, but in extreme cases they can be 80 mm or so.
You don’t need to worry about the brakes though. The brake track is in the same spot on all rims of a given diameter, give or take a couple mm.
10
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 ...
8
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 ...
7
Mavic has different families for their hubs, so 'CrossRide' is not accurate enough to give an answer, as it changes over years and entry level hubs may not be the same as the higher end ones.
If you look at the specifications of your hub and see that it is ID360 or ITS-4: you can just replace the freehub body without having to unmount the rear hub.
https://...
6
They exist. And no, you won't fall to your death. Chances are simply very slim.
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The jargon for that is a "deep section rim" vs a "shallow section" or sometimes a "box-section rim"
The taller the side's profile, the better the aerodynamics in the forward direction. The ultimate case is a disk wheel where there are no visible spokes and the whole wheel is one solid-sided shape.
Conversely, the side-wind ...
4
I'm not familiar with Mavic's offerings, so I shall not contradict Renaud's answer. I will offer a possible alternative: some third party manufacturers like Sunrace make 12s MTB cassettes that fit on Hyperglide freehub bodies. These cassettes will only start at 11t because the HG freehub's diameter is physically too large to take a 10t cassette. Hence, this ...
3
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 ...
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Until the Topstone Carbon, it was a mountain only thing. Now it's most of the nicer mountain bikes plus Topstone Carbon.
Note that there are two different generations of Ai offset; 142 and 148/Boost bikes use different offset values. The old version of the true stand/dish stick adapter tool doesn't work with 148, which is one potential source of confusion. ...
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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.
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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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