ISO, JIS crown race compatibility
 

26.4 vs 27.0 crown races on 1" threaded forks. Are they interchangeable between headsets?

The new fork I bought needs a JIS crown race, but the headset I plan on buying is supplied with an ISO. I don't have anything now to test.
I was under the impression that after the correct size is seated on the fork, that they could be used interchangeably. My LBS is telling me otherwise.

Any experience?

I'm not exactly sure what you're asking.

But let's start with nomenclature. ISO does not specify a crown race diameter. It is a thread form standard and that's about it. The 27.0mm is in fact the JIS spec, but the 26.4 is what was previously the Campagnolo standard, but nowadays more often called either the Professional or the "Modern European" standard.

Now as to interchageability: If your crown race seat is milled to 27.0, you can have it milled to the Professional standard if that's what you want to use. But once your fork's crown race seat has been milled to the Professional standard, there's no way a JIS crown race will ever fit again. You can't cut it bigger.

The other thing to know about the Professional and JIS standards is that they specify different cup skirt ODs. Press-fit cups are interference fit. Professional spec is 30.2mm, JIS is 30.0mm. The ID of the head tube bore has to be 0.1mm less than that for the interference fit. So a head tube milled to Professional spec won't hold JIS cups tightly; they'll slip in and out by hand, in fact. A head tube milled to JIS spec will make for a too-tight fit of Professional cups, and it might actually stretch to accommodate them (seen it.)

Unless you're asking about mixing the parts from the exact same model headset, the experience other people have mixing headset parts isn't going to tell you much. The shape of the crown race is not universal and not only goes to match the shape of where the bearings ride but the dust seals.

I think if you had (for instance) a Tange CD model headset and substituted 27.0 CD crown race for a 26.4 CD crown race it would likely work perfectly. But if you use a Tange race with a Shimano headset the result is completely unpredictable.

Wasn't sure on the nomenclature, so I just called it ISO. I'm wondering if a fork with a 27.0 race installed will work with a headset that was supplied with a 26.4 race. To further complicate things, the frame needs 32.7 cups for one piece cranks / BMX.

The headset I'm buying is a Tange BMX headset (supplied with a 26.4 race). There are 27.0 Tange crown races available. I'm wondering if that will work with the headset.

I know this is a lot to ask. But I figured it wouldn't hurt to.

Of course it doesn't hurt to ask. Are you trying to use the crown race from one headset with the cups from another headset? Might work, might not, as Kontact said; headset parts even from the same manufacturer are not usually compatible unless they are the same model, only made to a different dimensional standard.

The mishmash of dimensions on a headset comes about because neither the crown race nor the cup skirts nor the threading cares at all what the others are. You can theoretically mix and match them any way you like. MOST of the time, BMX headsets have 26.4mm crown races, but not necessarily.

Be aware that the BMX cup skirt standard is bigger than either of the other aforementioned standards and incompatible. (At least Sheldon Brown got that one right, unlike his ISO headset dimensions. He missed that one.)

The answer to your question is yes, they will interchange.

JIS is more of a cup diameter thing... 30.0mm diameter frame cups.

Really surprised me when the crown race on my Gitane TdF turned out to be 27mm when I changed out the Stronglight B10 headset on the bike to an all aluminum A9, about a month ago..... which leads me to think that the 27mm crown race spec can occur on BSC threaded headsets too...
I had to switch crown races with another A9 headset I had in my stash to make things work out on the Gitane....

100% correct.

https://i.imgur.com/pNLjVlZ.jpg

I have a Motobecane that has the crown race at 27mm and the rest of it is French standard.

A JIS 27.0mm crown race will not seat securely on an ISO 26.4mm crown race seat, and an ISO 26.4mm crown race will not seat (and may in fact split if forced) on a JIS 27.0mm crown race seat.

But some headset manufacturers (e.g. Tange, Hatta, perhaps others) make the same model headset in both ISO and JIS dimensions, and sometimes the crown races can be purchased separately.

Another option if your frame/fork is milled to JIS dimensions, is to have it re-milled to ISO dimensions, and simply use an ISO headset.

Yes, that can happen:

http://www.os2.dhs.org/~john/headset-fit.jpg
Source: Sutherland's 4th Edition

Or mill the crown race seat to more standard 26.4mm diameter.

A 27.0 mm JIS crown race will be too loose on a 26.4 ISO* crown race seat. An ISO crown race won't even fit on a JIS crown race seat.

Some people are of the opinion that you can use 30.2 mm ISO cups in a headtube sized for 30.0 mm cups. My experience is that you shouldn't do it. Before I knew there was a difference, I installed ISO cups in my daughter's '81 Fuji that was originally equipped with JIS. It took a lot of force to get those cups installed, and it was difficult to keep them straight during the installation.

On the other hand, some bike had mixed headsets from the factory. I have two that have ISO cups and JIS crown race or vice versa. In those cases, it's perfectly OK to mix a JIS crown race with ISO cups. Tange even supplies them that way, if requested. I've purchased Tange Levin and Tange Passage mixed-spec headsets.


* I don't know offhand if the 26.4/30.2 headset standard is officially codified by the International Organization for Standardization (ISO), but in common parlance, it's an "ISO headset".

Go here. They have exactly what you need, and a few models to pick from. Nice head sets with the big cup (32.5) diameter. And they will send both 26.4 and 27.00 crown races for a $1.99 upcharge. Good product, good prices, Fast shipping.

Porkchop BMX 1" Threaded Headsets Old School BMX Bicycle Products

I got this one. Nice aluminum, cartridge bearings, nice dust seal on top...




http://cdn3.bigcommerce.com/s-d9og6f...0.1280.JPG?c=2

Like the OP I swapped a fork into an OPC frame with large head tube. Because it was a "Velo Cheapo" contest bike I mixed the headset parts rather than buy new. I tried but could not get it adjusted properly. I assumed it was because the because the "diameters" of the bearing surfaces were significantly mismatched between the two donor sets. What SquidPuppet shared ^ looks like a much better way to go.

An approach I have used is to stick to Tange headsets, then buy several to match the fork crown, the steerer, headtube and stack (mostly to get the stack I need - I had a bike made for a Chris King grip-nut threaded that drove me nuts). So far I have had very good luck jockeying Tange headsets of three different models. Mix and match seems to work just fine. (Yes, that bike's headset is dying now and I am limping along with bigger balls for a little while longer. But it has 8k miles; just about what a $30 Tange is good for.)

Edit: a little off topic but if you really need super low stack, the cheap Tanges at $8 are it. The lower races are really low but have no seals at all - use mini fenders and lots of marine grease or an inner tube sleeve slipped over the cup - and their hardware on top is very low also; great to mix with the better sets to reduce their stack.

Ben

[MENTION=416665]Lovenutz[/MENTION] - If the fork is not original to the frame (impression I'm getting) you may need to consider stem quill diameter too. A BMX headset may not accept a 22.2mm quill.

Provided your steer tube is long enough. The aluminum headset squidpuppet suggests needs 41mm of stack, which is on the tall end of things. If that's too tall for the steer tube, the Tange "Passage" headset only needs 32mm of stack, and is less than half the price of the aluminum model.

http://cdn3.bigcommerce.com/s-d9og6f...84.380.500.JPG

Tange SE-32 MINI BMX / ROAD BIKE headset - 1" threaded - CHROME

This forum is amazing! Thank you all.

I was planning on buying a Tange/Tioaga "Bear Trap" or the MX-2 and buying a 27.0 Tange crown race separate. I probably still will, and hope they will work together. It sounds like there is a good chance it will.

I know that the race has to seat on the fork. I could mill it down, but I'd have to find a bike shop to do it. The LBS I usually go to doesn't have the tool.

The steerer is uncut and is really long, so a taller stack might be better.

[MENTION=362748]SquidPuppet[/MENTION] That is perfect! And I love the price. I'll probably get this too as back up. Was this what you used on your Varsity cruiser?

Yes, in black.

This other place has a bunch too. Black and or silver. They come with 27.00 crown races.

lowrider bike Head Sets, beach cruiser bike Head Sets, fixie bike Head Sets. - top lowrider

I used one of these on my brown bike. $8.99 LOL

Available for 22.2 or 21.1 stem.




https://www.pedalroom.com/p/caramel-coaster-21856_7.jpg

That one won't work Mr. Thompson. He needs the Old, Old, Old school cups for OLD electroforged Schwinns and some old BMX bikes. Cup skirt OD of 32.5mm.

I had one of these on my 650b-converted Univega FrankenRover; it's a great headset- especially for the price.

Keep in mind though, there is a weird nomenclature-thing about old BMX & 32.5mm headset dimensions... I forget exactly how it goes (I only had to deal with it once, in the case of the above-mentioned Univega & I've since forgotten the details), but it had to do with two different, advertised dimensions that actually turned out to be exactly the same; the confusion was caused by some holdover slang from the early days of BMX.

Edit:

Oh yeah- totally agree. Some of them were still 21.1mm.

It's not, and common parlance is frankly inaccurate. It's unfortunate that Sheldon Brown's web site mistakenly gives the "Professional" standard dimensions as so-called "ISO" when that is quite simply wrong. As with BB spindle tapers, it simply creates a falsely simple dichotomy when the reality is far more complicated.

According to Sutherland's, the ONLY ISO specs for headsets are the threading ("ISO 965/1, 60° modified to H/6 truncation at root") and possibly the cup skirt OD (30.0mm). Period.

Here's where it gets complicated. Deal with it:

The BSC and French standards were also ONLY a thread standard, not comprehensive dimensional ones.
The Professional/Campagnolo standard was ONLY a dimensional standard, not a thread one.
The JIS (and Austrian) are the ONLY standards that specify both threading and dimensions.
Cup skirt and crown race diameter "standards" are generally trends rather than actual mandated standards, so don't expect consistency.
There's much more to the story than just that. Sutherland's lists no fewer than twelve "standards" in the 25mm to 26mm (including 1") steerer tube size range. If you need to know more, let me know.

Let me throw one more thing about "standards" out there: Most standards are "standard" by way of common usage. Others are standard by way of some organization or corporation that defined the standard. Unfortunately there is no "standard" use of the term "standard" that will tell you which is which. Not only that, but "common usage" standards will have common exceptions. "Organization" standards are voluntary. Which means neither are totally reliable guides as to what you will find on any given bicycle. At best, they are starting points or guidelines.

Allow me to reiterate that if you are dealing with C&V bikes, you need to break out of the false JIS/ISO dichotomy. If you're stuck in that you will end up banging your head against the wall when the door is right there.

Common parlance is often inaccurate to some degree, but for better or worse, it's the lingua franca. If someone's talking about an "ISO headset" without further clarification, I expect that they're referring to 30.2/26.4/24tpi, whether or not there's an official ISO spec. It might irk me personally that we're misspeaking, but hey, the listener knows what the speaker's talking about, and that's the ultimate goal of communication.

I'm always trying to learn about inaccuracies and correct them when I can -- and I appreciate your input for that -- but it's important to balance that with an awareness of common nomenclature. If we're too pedantic, we'll miss out on a lot of communication.

I agree with that to a great extent. But it's only the lingua franca in the echo chamber that the internet has become, and unfortunately largely because of Sheldon Brown's publishing of inaccurate information. Credit where it's due: the vast majority of what he published is accurate and useful. God bless him for for that. But his inaccuracies persist. IMO his inaccuracy and oversimplification of the headset "standard" situation seems to me to have created far more confusion than clarity. Better IMO to acknowledge the complexity and deal with it than to try to stuff the past headset world into two neat boxes.

Before sheldonbrowndotcom, literally nobody talked about ISO headsets because there was no such thing. Technically, that's still true. JIS, sure, that means something. But otherwise there were British and Italian and American and what have you. And we dealt with the dimensions and threads as they existed. In the current age of S.H.I.S. I am frankly baffled at the seeming desire to reduce the past's lack of standardization to a overly simple but inaccurate dichotomy. Especially when talking about C&V bikes.

I don’t know why this needs to be so complicated...

JIS 30.0 cups
British/ISO or whatever 30.2 cups