Originally Posted by
dezork
Thanks for the reply Dan!
If I bought a 26.4mm ISO headset to fit my new steerer tube, would I have to replace the JIS pressed frame races?
Also... I assume having a bike shop cut new threads in my steerer tube is going to cost more than 20 bucks (the cost of a correct-height tube)?
Edit: I noticed that the ISO standard cup outer diameter is 30.2, while the JIS is 30.0. So ISO cups won't fit my frame? Sheldon Brown's site claims that both JIS and ISO have the same threads per inch on the headtube- so why doesn't my threaded race thread on?
The same bike shop that would be equipped to thread the steerer would probably have a reamer to make the ISO cups fit.
As for the top cup not threading on, probably just a matter of having the thread chased with a die. This will be done in course of extending the threads.
Yeah, it will cost you a few bucks to have it done, but the alternatives are, buying the tools and doing it yourself, a heavy investment for a one time use, or paying somebody that has the tools and knows how to use them to do it for you.
Another option is to get a conversion headset. Tange and others, make headsets with ISO cups and JIS crown races and vice versa.