JIS threaded headset

Having difficulty sourcing a JIS 1″ threaded headset. Possible to get on import but many are just regular ISO headsets with 30.2mm cups (instead of 30mm) with the crown race swapped for the JIS 27mm size (to replace the ISO 26mm). eg here

Couple of Q's if anyone can offer any advice? I have a couple of old 27mm crown races already so could I just get the regular ISO headset (available easily in this country and at a reasonable price) and swap the 26.4mm crown race that comes with it for one of my own 27mm ones? Will the slightly wider JIS crown race sit ok with the bearings of the ISO headset? I assume the extra 0.6mm is in the hole and doesn't affect the outside diameter of the race?

If the above works has anyone had any experience of fitting a 30.2mm ISO headset cup into a head tube that is meant to have a 30mm JIS cup? Any warnings? Will I trash / crack the frame? I'm thinking of freezing the cups before fitting them to make this easier.

Its on a very old steel Dawes frame that is slightly worn anyway on the head tube anyway so might have wider tolerance already. I expected it to be standard ISO fitting but looks like it's JIS (which I've found out is likley because of it's age). Luckily the ISO Tange Levin I got for it fitted another bike.

I'm aware I could get the head tube / fork milled but would rather avoid if if possible and go the easy route of getting a regular ISO headset with my own crown race if possible.

Anone got any advice or had experience of this?

Hope this helps.

Bit cryptic? Not sure. Any hints?

Edit: Their heads are too small for their bodies?

I had this issue with my Koga Miyata. I tried to look around for a quick fix but most advise is don't mix and match the parts and it is not worth damaging frame or bearings. In the end I spent the extra on a JIS Dura Ace headset. it's not worth messing about for the sake of a few quid IMO in the end I was glad I did anyway as ended up with a much better functioning and looking part.

Google JLS, enlightenment shall ensue

Thanks guys. I think your Koga frame is a bit nicer than the 50 year old Dawes (salvaged from scrap) I'm trying to sort out and probably more worthwhile spending the money on the Dura Ace for your bike. Aren't the Koga frames Alloy? I was hoping someone would chip in and say I'd be fine with the extra 0.2mm on an old worn steel frame.

Might be cheaper to get the head tube reamed in the long run. Then use 27mm crown race with ISO headset.. which I'm still assuming will sit ok?

Read lots of mixed opinions in the last few days. Some people saying they've fitted ISO into JIS and been fine (mostly steel frames) and other stories of cracked head tubes (on alloy frames).

• oh I see.. proof I'm getting old.. never heard of JLS. I was trying to work out what clothing company advert its was :)
  

Mine is a 1979 steel frame. Not sure about getting it reamed I was given the advice that it would be better to get the correct size.
If you use the search function on here you might find a previous post with some info.

good luck with build!

Thanks. Thinking more about it I agree I think I'd feel happier getting the right size instead of getting someone to ream the head tube... retain the integrity of the frame and keep it proper thickness, even though it's only a couple of mm.

Having said that I removed the cups this afternoon to double check measurements and managed to press the lower cup back in by hand, so it's a very loose JIS 30mm fit. It's snug enough once it's in there (esp if I add a dab of loctite when fitting finally) but doesn't require a press to get it in. Can't help feeling a 30.2mm cup would go in.

Anyone know...

• Anywhere that sells the Dura Ace JIS headset in the UK?
  
• What the stack height of the Dura Ace headset is? (Need something the same or less than the Tange Levin 33.4mm)
  

You could try http://cgi.ebay.co.uk/TANGE-SEIKI-HEADSET-1-INCH-THREADED-27-0-NEW_W0QQitemZ290417620286QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item439e3d353e
Much cheaper than I got my dura ace and that is including the shipping!

Thanks.

I sent them a message earlier to get them to confirm that the cups are 30mm and they're not just selling an ISO (30.2mm cup) headset with 27mm crown race like most people are and calling it JIS. No reply yet though.

JIS headsets are looking really difficult to find. Lots of searches turn up plenty of results but few places actually have any in stock any more.

why not just get an ISO headset and get the headtube reamed and crown race seat cut...?

i hate JLS with a passion
cunts...

why not just get an ISO headset and get the headtube reamed and crown race seat cut...?

If that ebay JIS headset is really JIS then it's cheaper than the Tange Levin that I bought in this country.

I considered the reaming / milling thinking it might be worth it if I was going to get through numerous headsets (cheaper in the long run), but the frame it's going on doesn't get loads of use, so it might be the only time I ever replace the headset for quite a few years. Not worth paying twice for alterations and more expensive headset if that ebay JIS one is ok.

If it's not true JIS then with the apparent lack of JIS headsets around, yes I will be getting the work done and go ISO.

found one...

http://www.tokyofixedgear.com/productdetails.asp?productid=00303

ouch