Mixed ISO/JIS headset
08-05-09 | 11:09 AM
#1
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From: Washington County, Vermont, USA
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Mixed ISO/JIS headset
How common is it to run into a frame with that takes 30.2 mm ISO headset cups, but with an (original) fork that takes a 27.0 JIS fork-crown race? My mid-80s Miyata 912 is like that, and so I think is a Lotus Unique of comparable age that I'm working on now. Can you buy mixed headsets or do you have to get one of each and mix the parts yourself? Alternatively, how much of a production is is to have the fork-crown race re-sized to the ISO 26.4? I'd hate to ask a shop to do that and have them screw it up. (I'm spitting out all those dimensions from memory--hope they're correct.)
08-05-09 | 11:40 AM
#2
Cat 6
Joined: Dec 2007
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From: Mountain Brook, AL
They do exist. The ebay seller I bought my headset from had ISO, JIS, and mixed headsets available. Cheapo YST, but for $13 shipped hard to beat.
And shops can resize crowns. If they have the tool it's supposedly an easy job - but i have no first hand experience.
And shops can resize crowns. If they have the tool it's supposedly an easy job - but i have no first hand experience.
Last edited by Ex Pres; 08-05-09 at 01:26 PM.
08-05-09 | 11:53 AM
#3
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From: SF
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Crown race sizing is very easily done by any local frame builder/repair guy/girl or a well stocked bike shop
08-05-09 | 01:03 PM
#5
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From: Chattanooga
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You can carefully work the interior circumference of the ISO fork crown race with a Dremel and a fine, large diameter, circular stone to open it up .2 mm all around. Everything else should be a match.
Work, test; work, test. No hurry; no problem.
I wouldn't do this with a high class piece but with a cheaper or used set, it's fine.
Work, test; work, test. No hurry; no problem.
I wouldn't do this with a high class piece but with a cheaper or used set, it's fine.
Last edited by afilado; 08-05-09 at 01:10 PM. Reason: add text
10-21-13 | 07:40 AM
#6
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From: Washington County, Vermont, USA
Bikes: 1973-4 Gitane Tour de France, early 1970's Lejeune, 1970 Italvega Super Speciale, 2010 Surly Long Haul Trucker 26
When I just now Googled "mixed ISO/JIS headset," I was amused to find that the first hit was my own post from a few years ago. I'd forgotten about it. I guess mixed headsets are pretty common, because I just ran into another one on a 1984 Lotus Classique--26.4 cups, 27.0 crown race. That's my third one so far. Sort of a pain, but I was able to order a new Tange Levin crown race in the right size for under $10. Someday I'll remember to measure before I order the headset.
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10-21-13 | 11:15 AM
#7
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From: Tampa, Florida
Don't think of JIS headsets as being 27.0 fork race headsets. Think of them as being 30.0mm frame cup headsets.
JIS headsets may all have 27.0mm fork races but non-JIS headsets have them as well.
Back in my shop days 30.2mm frame cup headsets could be ordered with either 27.0 or 26.4 fork races.
JIS headsets may all have 27.0mm fork races but non-JIS headsets have them as well.
Back in my shop days 30.2mm frame cup headsets could be ordered with either 27.0 or 26.4 fork races.
