Retrobike Forum Index

It is currently Sun Dec 11, 2016 1:21 am

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 3 posts ] 
Author Message
PostPosted: Mon Feb 02, 2009 8:41 am 
Retro Guru
User avatar

Joined: Sun Nov 04, 2007 3:40 am
Posts: 269
Location: Melbourne, Australia
Obtained a mystery frame the other day, and was wondering if there is a 'rule of thumb' measurement from the dropouts to the brake mounting holes on the fork or seatstays to determine correct wheel size? I'm figuring that chainstay length would vary with wheelbase, so that wouldn't work. This might just be my first road bike since 1982, if I decide to build it up, so I am a little rusty regards this area. Back then it was strictly 28", none of this Metric stuff....
Thanks,
Pete.


Top
 Profile  
 
PostPosted: Mon Feb 02, 2009 10:23 am 
Old School Grand Master
User avatar

Joined: Wed Feb 20, 2008 12:21 pm
Posts: 5785
Location: Lost in Translation
ozpete wrote:
Obtained a mystery frame the other day, and was wondering if there is a 'rule of thumb' measurement from the dropouts to the brake mounting holes on the fork or seatstays to determine correct wheel size?

Dropout to brake mount will give you a good idea of the intended wheel size, but often more than one wheel size will work, depending on the drop of the brake calipers you fit.

In a nutshell:

(dropout centre to brake bolt hole dimension) equals (rim radius plus brake reach)

You can use the tyre bead seat diameter to estimate the effective rim radius - that's 630mm diameter (315mm radius) for 27", 622mm (311mm) for 700C, 584mm (292mm) for 650B, 571mm (285mm) for 650C, 559mm (280mm) for 26". Most modern road brakes have a maximum reach of about 47-49mm, but longer models are available.

Most road bikes built in the last 20 years use 700c wheels and either 47mm or 57mm reach brakes.

Once you've measured, try a wheel in the frame. If there's clearance for the tyres you want to run, and the rim is within range of the brake hole, you're good to go.

Frames built for 650C can often be used with 26" (559mm) rims. Frames built for 27" can usually be used with 700C. Frames built for 700C can be used with 650B if the brake calipers are replaced with long-reach models.


Top
 Profile  
 
 Post subject:
PostPosted: Thu Feb 05, 2009 9:25 am 
Retro Guru
User avatar

Joined: Sun Nov 04, 2007 3:40 am
Posts: 269
Location: Melbourne, Australia
Thanks for that, I'm off to the shed with a measuring tape to do me some maths!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Bing [Bot], Mr.Toad, mr_gumby and 32 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