Soma Grand Radonnuer - ISO or JIS Headset

[John Hawrylak]

For those who have a Soma Grand Randonneur, is the headset ISO or JIS??  The Soma webpage lists only a 26.4mm crown race, which would be ISO.

I remember a screw up on the headset race diameters when they first came.   

Considering a 55cm frame and I have a 1" VO needle bearing ISO headset, which would seem to fit.

TIA

John Hawrylak

Woodstown NJ

[Karl Sanchez]

Your headset should work, presuming you get one of the the v2 frames.

[satanas]

I had a v1, but can't recall whether it was JIS or not out if the box. I fitted a Stronglight Delta headset, and would have just machined the frame and fork if necessary, a quick job if one has access to the neessary tools; I've done it many times.

Later,
Stephen

[John Roberts]

Gosh I always think of bottom brackets using those acronyms... I'll tell you, your instincts are probably right. I'm using the IRD "Needle Blastr" headset on my v2. 

[WMdeR]

Dear John,

V1 came set up for a 27.0 (Surprise! The Tange factory skipped the final milling step on the super-stout dog-leg forks!) vs 26.4. Good shops milled them down to 26.4 to install a needle-bearing headset. V2 and later (i.e if it has a reasonably pretty fork) had that boo-boo fixed. If you have one of the raked-out Wolverine forks, then you'll have to measure....

Best Regards,

Will

[Mark Bulgier]

A caution about machining forks down to 26.4 when they came as 27.0:

Will mentioned using a Wolverine fork -- aren't those welded?

Almost all welded forks (unicrown and 5-piece) have a separate ring for the headset race, that is welded only at the bottom.  The thin bit that extends up from the welded base should not be milled down to 26.4, because that leaves it too thin (0.5 mm).  The thin bit is not attached to the steerer, only to the thicker base where it is welded, and it can break off there, at the transition from thin to thick.  It may work for years, or indefinitely, but it is less reliable and lots of them have failed that way.

Rarely, adapter rings have been brazed to the steerer, on an otherwise-welded fork, but that's pretty much only seen on high-end or custom forks.  Here's a picture of a welded fork with a brazed crown-race adapter.  (Read the builder's comment for why he does it that way.  I used to do them that way too, on the few custom welded forks I made)

Outside of those rarities, the only unicrowns with a brazed ring for the headset are the fully fillet-brazed, or the occasional brazed-lugged-unicrown like on some early StumpJumpers, Bianchi Grizzlies and a few others:

You can usually tell by looking -- even if painted over or chromed, the little fillet at the top from brazing should be visible.  If not brazed, I recommend leaving it at 27.0 and getting a crown race to match.

The problem of 26.4 size on a welded ring can be mitigated somewhat by using a cutter that leaves a large radius at that inside 90° corner, where the thin cylinder meets the thick welded bit. Headset races always have clearance for that fillet, or at least I've never seen a headset that didn't.  The Campagnolo cutter and clones thereof had a 45° chamfer at the transition, not as good as a curved fillet, but better than nothing.  The chamfer still has a sharp transition from the thin part to the 45° angled part, so there's still a stress-riser where the thin bit might tend to break.

Sorry, I have never seen a Wolverine fork in the flesh, maybe they deal with this some other way.  This warning is more about generic welded forks.

Mark Bulgier

Seattle WA

[Philip Kim]

depends, if you have an earlier version i believer is 27.0, and the later versions were 26.4. i think you can tell because the 26.4 forks have a more elegant fork bend than the 27.0 forks.

[WMdeR]

Dear Mark,

I was imprecise when I wrote. The V1 fork used the Wolverine fork blades, brazed into a wide 1" steerer fork crown, with a 1" threaded steerer, and a pretty distinctive (read: ugly) dog-leg bend. It was fine to turn down with shop tools.V2 had a narrower crown, got milled to ISO at the factory (should still be chased and faced by your favorite well-equipped shop), and had a lower and more-elegant-to-my-eye rake. They also made some adjustments to the fit of the bike. If only they'd fixed the hugely overbuilt seatstays and ditched the rear rack eyelets too....

Best Regards,

Will

William M. deRosset

Fort Collins, CO

[Mark Bulgier]

Ah got it. Sorry, I'm pretty ignorant on Soma models.  Got nothing against 'em, they seem like a cool company, I just never paid attention.

-Mark

WMdeR wrote:

Dear Mark,

I was imprecise when I wrote. The V1 fork used the Wolverine fork blades, brazed into a wide 1" steerer fork crown, with a 1" threaded steerer, and a pretty distinctive (read: ugly) dog-leg bend. It was fine to turn down with shop tools.V2 had a narrower crown, got milled to ISO at the factory (should still be chased and faced by your favorite well-equipped shop), and had a lower and more-elegant-to-my-eye rake. They also made some adjustments to the fit of the bike. If only they'd fixed the hugely overbuilt seatstays and ditched the rear rack eyelets too....

Best Regards,

Will

William M. deRosset

Fort Collins, CO