Wheel Sizes Explained | Kids Bikes, Mountain Bikes, & Unicycles

remember the good old days when there

was just one standard wheel size when 26

wheel was ruled the roost and there was

no debate about what's faster or bare so

what about all those other wheel sizes

where did they come from and why have

they elbowed 26 out of the way let's

have a look at a lot of them and try to

decipher what they're all for the most

accurate way to measure a wheel is down

to its ET RTO or iso measurement for

example a 29 inch wheelers an ISO of 622

millimeters and a 27.5 inch wheel has an

ISO of 584 millimeters this measurement

is the diameter of the rimmon is the

best way to identify what wheel size you

actually have


traditionally 20-inch wheels have been

for BMX bikes and that sport dates right

back into the late 70s so there's been

an incredible amount of development

happen in that sport over time the wheel

size never really differed though and

became a defining point of the BMX bike

itself small enough to throw around and

strong enough to take some of the

craziest tricks known to man in man in

bike in the 20-inch wheel has

importantly found its feet in the kids

category and you'll find a whole load of

kids bikes with 20-inch wheels some of

them even getting full suspension frames

the choice of kids bikes really is

awesome and it means that MTB has a much

younger entry room which is obviously

great for the future of the sport at one

time BMXers and road riders might

migrate to try an MTB once they were

tall enough but now it's a sport that

tiny riders are excelling her like

20-inch wheels

24-inch started off in BMX bikes they

started in the cruiser class and became

a sort of comfortable BMX size if that's

the thing

but for marring bikes it has a couple of

important uses firstly it fills in the

void between 20 inch and 26 inch and

also like the newest selection of

20-inch bikes 24 inch kids bikes have a

lot to offer giving kids the chance to

really rip it up on the trails secondly

and more famously the 24-inch wheel is a

size of choice for a generation of

street trials riders who have been

inspired by Danny MacAskill and fabio

Whitmer I actually introduced the first

24-inch street trials bike way back in

2003 then inspired bikes who sponsored

Danny MacAskill started to adopt the

size a little later and a whole legend

was born

you're welcome YouTube

the pioneers of mountain biking had to

find something that worked and 26 inch

wheels to fit the bill

well when man in biking was in its

infancy there was no specific components

that were designed to go off-road and

that 26 inch wheel had to come from

somewhere that source was the American

cruiser bikes that were then transformed

into the clunkers or first mountain

bikes for nearly 30 years 26 inch wheels

with a standard and pretty much only

option form an invoice nowadays you'll

only find them on dirt jump bikes and

youth models isn't it a shame oh man


believe it or not 27.5 or 650b wheels

are actually 26 inch bare with me there

have been a number of different 26 inch

wheel standards over the years and 650b

wheels are originally called twenty six

by one and a half so it wasn't so much a

new wheel size but a reapplication of a

previous one after 29 inch wheels were

introduced in a mountain biking many

people thought that the gap between 26

and 29 was just too big

we have curt percent II to thank for the

push to bring 650b wheels into mountain

biking thanks Kirk Kirk felt that there

was a compromise to be found between 26

and 29 inch and so found the 650b wheel

size and renamed it twenty seven point

five thanks again Kirk it's become such

a popular wheel size that you'll even

see a number of gravel bikes and Road

plus bikes sporting 27.5 inch wheels

Kurt's got a lot of answer for


the 29er wheel size has caused its fair

share of controversy they originated

from road bikes and maybe that's the

reason the major differences between

700cc road wheels and 29 inch mountain

bike wheels is the internal rim whip and

of course the application MTB wheels are

built to be more robust and have wider

rims to suit wider tires they both have

an ISO measurement of 6 to 2 which is

the diameter of the rim it had a fairly

slow start in mountain biking but it

soon gained momentum and now based on

the fact that most downhill bikes are

available in 29 errs they really have

proven their mettle there's often a joke

around that 29 inch wheels are like

wagon wheels then you see a 29er

up against a 36 inch wheel bike and your

perspective changes pretty quickly we've

only really seen one brand offering 36

inch wheel bicycles and mostly for the

likes of Shaquille O'Neal who is over 7

feet tall in researching this however we

found that 36 inch wheels are very

popular in another wheeled sport

unicycles if I'm right side from GCN

tried to ride one once so well oh sorry

I just have to reset quickly riding

should give it another go take 2 okay

all right I'm going for it right in so

before we talk about highlights of your

trip then so what who can you can you

kind of distill down 22 but hey wheel

size is a useful thing to know about but

one thing all these different wheel

sizes prove is there no matter what bike

you have and what wheel size it has in

it you can ride it legitimately knowing

that as many years of design development

and testing behind it so it's all smiles

thanks for watching and hopefully you'll

understand and appreciate just why the

wheels on your bike are exactly the size

they are from now on

for more on GM BN then click just here

for a tech show playlist and just here

for my Rob Warren of random tandem ride

which was a lot of fun hit the globe to

subscribe to GM BN and give us a thumbs

up like or see you next time thanks for