Retrobike Forum Index

It is currently Fri Mar 31, 2017 1:52 am

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 5 posts ] 
Author Message
 Post subject: 700c wheel diameter
PostPosted: Fri Dec 14, 2012 12:55 am 
Old School Grand Master
User avatar

Joined: Fri May 01, 2009 7:11 pm
Posts: 8499
Location: Fircombe.
What is the diameter of a 700c wheel including a 38mm ish tyre?
What about 650b?
Ta,


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 14, 2012 1:49 am 
National & North West AEC
National & North West AEC
User avatar

Joined: Mon Nov 03, 2008 12:43 am
Posts: 8151
Location: Macclesfield Forest
A 700c with a 38mm tyre will measure up at 27 inches or perhaps a little under. More like ~ 680-690mm rather than the 700mm that the size would suggest.

For mountain bikes the following is true when using a normal mountain bike tyre measured from edge to edge.
Also included the actual outer rim diameter too.

"26 inch" = 26 inches - outer rim diameter = 559mm
"650b" = 27.5 inches - outer rim diamater = 584mm
"29er" = 29 inches - outer rim diameter = 622mm

29er rims are the same diameter as those used for 700c wheels, it's just the tyre sizes that make for a different diameter.
The volume and side-wall height of the tyre make up part of the wheel diameter so there is quite alot of variation.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 14, 2012 10:35 am 
Retro Guru
User avatar

Joined: Thu May 08, 2008 4:18 pm
Posts: 2348
To be strictly (and admittedly boringly) accurate, those numbers are actually the bead seat diameters -- the diameter of the bit of the rim where the tyre beads sit in use -- rather than the rim outer diameter, which is a little bit bigger.

26in is the outside diameter of a 2.1in cruiser tyre as used on the original clunkers, which is where the name comes from. Most "26in" tyres in common use are nowhere near 26in in diameter -- I have some 26x2.4in ones that are over 27in :)

Similarly, 650B tyres aren't always 27.5in, which is a number chosen because it's halfway between 26 and 29 rather than having any particular bearing in reality. As Paul's numbers show, 650B isn't halfway between 26 and 29 -- put a 2.2in tyre on all three rim sizes and the 650B is closer to 26 than 29.

29in wheels are often quite close to 29in, though ;)


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 14, 2012 1:20 pm 
MacRetro rider
MacRetro rider

Joined: Fri Feb 09, 2007 4:16 pm
Posts: 8713
Quote:
What is the diameter of a 700c wheel including a 38mm ish tyre?


As near as damit 700mm which when divided by 25.4mm (1 inch) is 27.5 inches. Fit say 44mm wide tyres and you hit near on 28 inches exactly.


Top
 Profile  
 
 Post subject:
PostPosted: Fri Dec 14, 2012 6:59 pm 
Old School Grand Master
User avatar

Joined: Fri May 01, 2009 7:11 pm
Posts: 8499
Location: Fircombe.
Thanks y'all!

It's all a lot clearer now, :? , especially the bit about 650b wheels being bigger than 700s...
:lol:


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 15 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

About Us

Follow Retrobike

Other cool stuff

All content © 2005-2015 Retrobike unless otherwise stated.
Cookies Policy.
bikedeals - the best bike deals in one place
FatCOGS - Fat Chance Owner's Group

Powered by phpBB® Forum Software © phpBB Group