How minimum is the minimum stack height on a 1'' threaded headset?

I've got a '93 Specialized Rockhopper with steerer tube @ 120.9mm and head tube @ 86.4mm, so 120.9 - 86.4 = 34.5mm.

I've got an option with a Tange Seiki Levin JIS headset, which apparently has a 33.3mm stack height.

...but would bad things happen stretching the definition of minimum to another option with a 37.6mm stack height?

All advice gratefully received. Thanks in advance.

The headset with a higher stack might not have enough exposed threads for the locknut

alcjphil is absolutely right. An easy way to see this is to loosen and remove just the top locknut and measure how much thread is visible. Now take away 4mm of that thread.

The one caveat has to do with the number and thickness of the spacer(s)/washer(s). If someone added additional spacers/washers to your existing headset, you have to take that into account.

John

Tange MA-60 is just a tad under 32mm stack:
Source: Barnett Manual

That table is an absolute gold mine. Many thanks John, much appreciated

I suppose I ought to post the second page as well:
Source: Barnett Manual

Thanks again John. I've had a quick look into the Barnett Manual, since I hadn't actually heard of it before. Looks to be a fantastic resource.

At the risk of repeating something you may already know...

Tange-Seiki have both a "Levin" and a "Levin CDS".

The Levin CDS - the one to which I think you are referring - is pretty useful as a replacement for some mountain bikes and hybrids of that vintage.

I'll add here that not too long ago, I replaced the original headset on my 1995 Trek 730 Multitrack.

The original was a Tange-Seiki Passage, which has an even smaller stack height than the Levin CDS. The original setup had one extra washer in the stack, though, and leaving that out was enough to get the Levin CDS to work.

I'll have to wait to see how it holds up over the long run, but my impression of the Levin CDS was very positive. Felt like quality stuff; looks great on the bike; reasonably priced.

Many thanks for the update John. The CDS seems perfect for what I need so an order has been placed. The other benefit is there is actually stock available. Getting hold of components in the UK is like finding hen’s teeth at the moment.