Originally Posted by
chaadster
I just put the calipers on my stock Nano headset, and it looks like 35.5mm (25.5 upper cup to locknot top, and 10mm for lower cup).
You're going to need to stay pretty close, obviously, because you'll need to have enough purchase on the steerer threads with the locknut. Of course you know that, probably, so I guess I'd say 1.5mm either way because there is a spacer washer you can remove and substitute with a little thread locker to drop height of a taller unit a bit if needed. I'm no pro, though, so verify that!
HTH...and yeah, the stock HS is a POS; not even sealed! Let us know if you find a good JIS unit. I've been wanting to replace mine, but really wanted a blue one, and could only find one for $200; I'd be happy with black at this point.
Chaadster,
Thanks for the measurement data, it's much appreciated. One of the headsets I linked to had 30.6mm stack height, with 30mm outer diameter, and 27mm crown race, weighs 100grams and sells for around $25, so I'll probably go with that one and let you know it works out.
Quick question though is it possible that the listed stack hieght of 30.6mm is too short? I don't think that would be a problem as I know a stack hieght can be too long/tall but am not sure that the opposite could pose any issues...