Does this mean my wheel is too small or something?

A lot of times when I’m outside, if I do a sharp turn, the lowest pedal might bang onto the ground and jerk me back up. I think my wheel is somewhere around 10"-15" tall, and I’m beginning to think it’s a little small… is it?

How much the crank bangs on the ground depends both on crank length and wheel size… I do it on the 24" occasionally.

The smallest unicycle I know of that isn’t purely for novelty value was a 16"… in which case I don’t think it’s really meant for fast cornering. I’m not sure what 16" unicycles are aimed at… I think 20" is the smallest practical size.

Generally the only thing you can do is don’t lean as much…


A fifteen inch is reeaally small. How tall are you? If you’re smaller than 5’5", then you should get a 20 inch. If you’re any taller, get a 24 or above.

My son’s unicycle is a 12" and it is still slightly too large. My daughters is a 16" and fits her perfectly. My oldest son’s is 16" and although it fits him fine he could probably do with an 18". I think a 20" would still be too big for him.

So, as far as my kids are concerned a 20" is the LARGEST practical size.

For the curious the kids are:
2 (almost 3), 5, and 6 (almost 7)

No way!

Can your almost 3 year old really ride his unicycle? If so, can he mount it, or do you help him with that?

I am considering getting my 2 year old daughter a Uni for her birthday or Christmas(4 days apart) How is your 2 year old doing on the 12 inch? Is he able to ride at all?

Can your almost 3 year old really ride his unicycle? If so, can he mount it, or do you help him with that?

[B]He hasn’t yet had the opportunity to practice. The Sun 12" that sells has a frame that makes it too large for him to reach the pedals. Also the cranks are too long. I’m having a smaller frame made and it is not yet complete. I’m also probably going to have to have some shorter (50mm) cranks made. He has spent a small amount of time in the saddle of the original 12" with me holding him on it.

Based on how my other two learned I believe that he’ll be riding soon. Just need to get the new frame finished and he’ll be all set.[/B]

Interesting. Are you building it or having someone else do it for you? How much is it going to cost to make one? Also how long do you think he will fit it once it is made? Are you going to make it so it will be able to grow with him?

Do you mean a 20" unicycle, or wheel? I’m clueless O_o


Unicycles are traditionally described by their wheel size. So a 20 inch unicycle is a unicycle with a 20 inch diameter wheel; a 24 has a 24 inch diameter wheel, and so on.

In case you’re not sure of the terms, diameter is the measurement right across the wheel in a straight line (like a CD has a diameter of 115mm or 4.5 inches). Radius is the distance from the centre to the edge (so radius is half the diameter); and circumference is the measurement all the way round the outside of the wheel.

So, as a general rule, when you read any posts referring to the size of a unicycle, they will be talking about the diameter of the wheel.

The exception is giraffes - chain driven tall unicycles. These usually have a 20 or 24 inch wheel, but they are described as “5 foot” or “6 foot” giraffes (and so on) which is the approximate height of the seat from the ground.

The popular wheel sizes are:

16 inch - normally only used by small children, people who aren’t very tall, or people looking for a novelty. I am aware of no practical advantages to the 16 except that it is suitable for small people.

20 inch - a standard beginner’s size. 20s are good for use in small spaces (on stage, among crowds, and so on) and are very manoeuvreable and easy to mount, idle, reverse and hop.

24 inch - also a good beginner’s size. A 24 will roll over bumpier ground than a 20, and will tend to be faster. (A 24 with a fat tyre might have a real diameter of 26 iches, but it’s still called a 24!)

26 inch - normally used “off road” for MUni.

28/29 (also 700c, which is a metric size: approximately 700 mm which is 27.5 inches) - used for distance work and speed.

36 (also called a Coker, as The Coker Tyre Company makes the only tyres in this size) used for frightening children and small dogs, squashing squirrels, and covering huge distances very fast.

There are other sizes available, though. 12 inch unicycles are not unknown. I guess if you looked around, or made a special effort to get one made, you could also have a 14, 18 or 22 inch wheel. UK riders might still be able to get 27 inch wheels.

So, what size is yours? There are two ways to find out: measure it, or read the tyre.

To measure it, just stretch a tape across the wheel and measure its greatest width. So the tape should pass from the outer edge of the tyre across the centre of the hub, and right to the far side of the tyre, keeping the tape perfectly straight.

Alternatively, stand the uni against a wall and slide two cardboard boxes (or similar) up to the wheel like ‘bookends’ and then measure the distance between the boxes.

To read the tyre, look on the side for something like:

20 x 1.95
24 x 2.3
16 x 1.75

The first number is the diameter (wheel size) and the second number relates to the cross section of the tyre. A 2.3 is fatter and bouncier than a 1.75, for example.

Sometimes on older wheels, the tyre size will be written with the second number as a fraction. For example, bicycle wheels in the UK were often 27 x 1 3/8, or 27 x 1 1/4.

So, by one of these methods, you should be able to find out the size of your wheel. You will then be able to tell us whether you have a 16 inch unicycle, a 20 inch unicycle, or whatever other size.

So, why do your pedals hit the floor?

It could be a small wheel. (Anything smaller than 20 is considered “small”)

Could be the cranks are too long for the wheel?

In case you’re not sure, the cranks are the long metal things which have the pedals attached to them.

On modern unicycles, the cranks are usually measured in millimetres (US = millimeters?) and typical sizes are:
175mm Mainly for serious off road use
170mm Mainly for serious off road use
150mm Popular general purpose size
140mm Popular general purpose size
127mm Popular general purpose size
125mm Popular general purpose size
110mm Popular on 20 inch unis.
102mm Mainly for speed freaks.
89mm Mainly for freaks.

On modern unicycles, the crank length is often stamped on the back. look for a number like 125 or 127. That’s the length in mm.

On older unicycles, the cranks may be imperial sizes - often about 5 inches or 6 inches. (125mm or 150 mm approx.)

If you can’t find a size stamped on the cranks, then you can measure, but it’s a little bit fiddly. You’ll need a straight rule rather than a tape. Measure from the centre of the axle (hub) to the centre of the pedal spindle. (US = center. ;0) )

No need to be accurate to the last millimetre. Just get an idea of what the measurement is.

Now, it is possible that your cranks are the wrong size for your unicycle, but it is unlikely unless the unicycle is a strange size. Basically, if the cranks are too long, then the pedals will hit the floor too often; if the cranks are too short, the uni will be harder to control.

There are no absolute rules, but here’s some guidance:

A typical 20 inch wheeled unicycle comes from the shop with 125 mm (5 inch) cranks.

A typical 24 inch uni will come from the shop with either 125 or 150 mm cranks. (5 or 6 inches.)

Most people would agree that 170mm (almost 7 inch) cranks are too long for a 20 inch uni.

I ride a 20 with 110 mm (just over 4 inches) cranks, but this was an upgrade. I can get the pedals to hit the floor if I try hard. ;0)

So if your uni is a 16, any cranks longer than 5 inches/125 mm might be part of the problem.

It is possible to change the cranks, assuming they are a standard fitting. However, if your wheel is smaller than 20 inches, you will almost certainly want to move up to a 20 or bigger. Look on ebay and there are usually several for sale.

Hope that helps.


Dang, I don’t even think my wheel is foot in diameter… WAAAHHH!!! :frowning:

Oh, nevermind, just measured it… it looks a lot smaller than it is. It’s really a 16"…

I am having it built by someone else. I asked the builder if he could do it VERY inexpensively and he agreed to make it for ~$25.

I don’t know how long it will fit him but once he outgrows the custom frame we still have the stock frame. Using that frame with the 12" wheel he should be able to keep using it until he’s about 7 or 8. Of course by then the wheel will be too small for normal use. Since we already have two 16" unicycles I suspect that by the time my youngest son outgrows his 12" my oldest son will be on a 20" and we can “upsize” the youngest to a 16".


Smutty schoolboy laughter all round.:smiley:

More constructively… :o …

If you have a 16, that’s great, because you have sooooooo much to look forward to. A 20 is a massive 25% bigger! A 24 is a massive 50% bigger.

And bigger means faster…

For a cheap 20, look on ebay, or you could check to see if your frame has clearance for a 20 inch wheel (you will need 2 inches extra clearance in the length of the forks, not 4 - think about it:) ) and see if you can get a 20 inch wheel from

Local bike shops often sell budget 20s too.

Or splash out big bucks and get a really good one from or :wink: