## Bike Tires 101 : The basics of bike tire sizing

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hi there welcome to my quack Community

College my name is Nathan today we're

going to talk about bike tire sizing

when it comes to finding the right size

tire for your bike it can be a bit

confusing usually you can just look at

the old tire and get the same size and

be totally fine but occasionally the old

tire might not be available and even if

it is you might look at the wrong number

and when you try to throw the new tire

on the wheel you'll have some troubles

and like the rest of the bike industry

standards have changed over the years

not to mention the strange mixture of

millimeters and inches you'll find when

you're looking for new bike parts so a

little understanding goes a long way

first off let's talk about the most

common wheel sizes out there now when we

talk about these wheel sizes we're

talking about the outside diameter of

the wheel with the tire fully inflated

in reality of these common measurements

or approximations we'll talk more about

that in a second but here are some of

the most common sizes you'll run into

700c is the most common size road wheels

it's not 700 centimeters in diameter at

700 millimeters the SI is a holdover

from an old French Standard where they

used a B or C to denote the width of the

tire for some reason the C stuck around

we're not sure why that's just the bike

industry for you 26 inch wheels are the

old standard for mountain bikes 27.5

inch wheels as a new standard for

mountain bike you'll also see this

occasionally written as 650 B and lastly

for the most common sizes 29 inch wheels

are another common size you'll see for

mountain biking days

you'll see other sizes out there as well

like 12 16 or 20 inch wheels for kids

bikes 24 inch wheels for youth mountain

bikes and 650 c inch wheels for smaller

road bikes I call these common sizes

because that's the way most people will

refer to the wheel or tire size and most

of the time you can rely on the common

size when looking for a new tire for

example a road tire may be labeled as

700 C by 23 where 23 is the width and

millimeters or a mountain bike tire may

be labeled as 27 point five by two point

one where the two point one is the width

in inches however you will occasionally

run into some problems if you rely just

on the common sizing for example older

bikes that are say 30 years older will

have a 26 inch wheels but they'll be

labeled as 26 by one and 3/8 remember

what I said about standards changing 26

by 1 and 3/8 inch wheels have a

different internal diameter than regular

26 inch wheels so if you get a 26 inch

wheel with a different width when you go

to throw it on your rim you're going to

run into some problems the more reliable

measurement is the ISO measurement ISO

stands for international standards

organization and they adopted the ET RTO

measurement ET RT o stands for European

tire and rim technical organization

sometimes you'll see it labeled as iso

and sometimes you'll see it labeled as

ET RTO just know they're the same thing

whatever you choose to call it this

number is much more exact and reliable

it will always be written as a two-digit

number and a three-digit number

separated by a hyphen the bigger number

is the inside diameter of the tire in

millimeters where the bead seats to the

rim the smaller number is the width of

the tire in millimeters the units of

bikes and mountain bikes so if you use

the ISO measurement there's little room

for error

if you're replacing an old tire just

look for the ISO measurement it's

usually printed into the sidewall rubber

right Megan for the common sizing if you

have a brand new wheel or an old wheel

without a tire on it just look for a

label with the ISO measurement on it on

the rim that's the external diameter but

it should match the internal diameter on

the ISO measurement of the tire most

rims will accept a range of tire width

just make sure you don't go too wide or

too narrow for the type of bike you have

we might run into some issues with

getting the tire to seat to the rim or

rubbing against the frame of your bike

so there the basics of tire sizing if

you have any questions please feel free

to contact bike wagon customer service

and look at your point in the right

direction thanks for watching ride well

my friends

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