Hello,

I'm looking at a frame from an online seller that has (as measured by the seller) a 130mm headtube with a 170mm steerer on the fork and no headset included with the frame. Stack height should be 40mm.

I'd like to use the Velo Orange Gran Cru headset with cartridge bearings that has a 41mm stack height according to Velo Orange. Are these close enough to risk purchasing at the same time? Or should I verify the frame/fork dimensions first? How sensitive are threaded headsets to +/- a couple millimeters?

My other option would be a Tange Seiki falcon that has cartidge bearings and ~35mm stack height.

Thanks!

I’d probably wait until I had the frame in my hands.

A steerer too long is better than too short, but a millimetre or two short is usually OK, you just need to make sure the lock nut has engaged enough threads.

You can always add a spacer if your steerer is too long, or even cut it down if it’s more than a few millimetres. If it’s wildly too long, you’ll need to make sure you’ve got enough thread for the top race.

Another thing to check is if the VO headset has a keyed washer, and if the steerer tube has a slot for one. You can always file off the tab if there isn’t a slot in the steerer, but still something to consider.

I'd echo everything P!N20 writes, but after you take your own measurements and THEN if you are still looking for a 40mm SH unit, you might be in slightly better luck if Sutherland's published SH specs are correct: the Falcon FL250S is just over that with 40.1 so might be just fine.
That said I really like and have had excellent luck with the (much easier to find) Tange Levin which for the stock model has an even shorter SH -37.8- that you can easily compensate for with some washers or a thin spacer and I rarely have any trouble servicing them so the sealed bearings (in the Falcons) are not a big selling point, for me.
Here' a screengrab of just the Tange HS specs from Sutherland, the last column is the combined (full) stack heights, as they measured the actual samples (rather than the mfgs, claimed specs), or so they tell us...



My old copy of Sutherlands does not have any of the VO units, nor do they show the Tange Passage model, which has an even lower SH than the std. Levin, and cheaper too, but it has lower quality races than any of the Levins (AFAIK) so keeping that one well-lubed is more critical

Get the horse first, worry about the cart after. Get the headset figured out AFTER, as they say above.

1-You don't know how much the crown race you choose will take up above the fork crown. That race can vary in thickness, (generally not much.)
2-The headset cups will raise the bearings above and below the head tube.
3-Per your info, you have 40mm to fill with the crown race, bottom bearings/cup and top bearings/cup.

My initial guess is you'll need a spacer, and I suggest making sure you have a keyed spacer (or two) on hand, and maybe a couple 2mm 1" spacers.
In a best case scenario, you simply buy a standard headset and it all works. Often does.