1 inch fork - what does 26.4 mm refer to ?

Two questions please:

When talking about a 1 inch fork what does 26.4 mm refer to - is it the diameter of the fork crown or the inside diameter of the crown race (I assume the two have to be different to ensure a press fit) ?

If the fork crown needs to be machined should a crown race cutter cut it down to 26.4 mm?

On 10/14/2012 1:58 PM, Rik O'Shea wrote:

Two questions please:

When talking about a 1 inch fork what does 26.4 mm refer to - is it the diameter of the fork crown or the inside diameter of the crown race (I assume the two have to be different to ensure a press fit) ?

If the fork crown needs to be machined should a crown race cutter cut it down to 26.4 mm?


Right, two different formats:
30.0mm cups with 27.1mm crown race
30.2mm cups with 26.4mm crown race

Any competent LBS which commonly services bicycles will have
the various cutters.
http://www.yellowjersey.org/camill.jpg

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Sun, 14 Oct 2012 11:58:49 -0700 (PDT), "Rik O'Shea"
wrote:


Two questions please:

When talking about a 1 inch fork what does 26.4 mm refer to - is it the diameter of the fork crown or the inside diameter of the crown race (I assume the two have to be different to ensure a press fit) ?

If the fork crown needs to be machined should a crown race cutter cut it down to 26.4 mm?

I believe that you are referring to the diameter of the "bearing
seat", a very short cylindrical portion of the fork crown where the
lower Crown Bearing (which has a 26.4mm I.D.) fits.

Yes. The crown race cutter will cut it to size but remember that there
are two sizes of cutters (actually more then two) 26.4 and 30.015 for
1" threaded and 1-1/8" unthreaded.

--
Cheers,
John B.

On Sunday, October 14, 2012 12:58:49 PM UTC-6, Rik O'Shea wrote:
Two questions please:



When talking about a 1 inch fork what does 26.4 mm refer to - is it the diameter of the fork crown or the inside diameter of the crown race (I assume the two have to be different to ensure a press fit) ?



If the fork crown needs to be machined should a crown race cutter cut it down to 26.4 mm?

That is the crown race. Most modern forks have a 26.4 race. Whenever you order a 1 inch headset, it will likely have this measurements. Japanese bikes used to have a 27 mm crown race. So, when you were buying a headset for a Japanese bike, you needed to specify the 27 mm crown.

Second question, answer is yes. or go to ebay, and buy a 27 mm headset for very little money and you won't have to grind anything.