# 700c wheels...

#### Maz

##### Legendary Member
Does the 700 mean 700mm in diameter? Is this a standard size wheel on a road bike?

Regards,
Maz.

#### Smokin Joe

##### Legendary Member
The diameter of a 700c wheel is actually 622mm. I think the 700 refers to the approximate diameter when a tyre is fitted, and it is the standard size roadbike wheel.

#### TheDoctor

##### I've seen things you people wouldn't believe
Moderator
Smokin Joe said:
The diameter of a 700c wheel is actually 622mm. I think the 700 refers to the approximate diameter when a tyre is fitted, and it is the standard size roadbike wheel.
Bang on.

There used to be 700A and 700B - I think the letter related to the width of the rim.

OP

#### Maz

##### Legendary Member
Thank you very much.

#### andy_wrx

##### Über Member
Smokin Joe said:
The diameter of a 700c wheel is actually 622mm. I think the 700 refers to the approximate diameter when a tyre is fitted, and it is the standard size roadbike wheel.
I agree you're right, it just doesn't make a lot of sense, not today at any rate

622 is the wheel diameter (to the tyre bead seat, not rim-to-rim), so a 700 wheel including tyre would need a tyre (700 - 622) = 78, /2 as it's twice the tyre 'height' => 39

So it would be a '700' wheel with a 39mm tyre.

Perhaps that was a standard tyre size in 1910 or whenever they invented this system, but today we're all running racers round on 700/23 (= 688) or tourers on 700/28 or 32 (= 678 or 686)

#### HJ

##### Cycling in Scotland
For a fuller explanation there is alway Sheldon Brown, although it maybe more that you really want to know.