This is a somewhat specific question, and I haven't yet found an answer in the forums.

I am buying parts to build a touring wheelset. Instead of spending tons of money on hubs, I thought I'd put that towards rims and tires, and as people seem to really like the XT hubs for touring, I'd go for that.

I was going to get older hubs on ebay, probably, and thus have a few decades worth of parts to choose from. My question: are there notable and important differences between certain years/periods of xt / shimano touring-ish hubs? Certain good years, or years to be avoided?

Other details: Trek '83 720 frame, 100mm front (I think), 126 rear (to spread to 130). Medium weight touring, 32f 36r spoke count desired. Freehub also seems like a good idea; rim brakes.

I went through this last spring, and I was surprised to have trouble finding used XT hubs. Perhaps I just looked during a dry spell, but there was nothing on eBay that was even remotely attractive. I ended up buying a new XT rear hub and was similarly surprised by how expensive it was, and that even for new XT it was fairly hard to find the non-disc version. I wanted non-disc because, as far as I understand, that adds a little more dish, which I wanted to avoid because I don't foresee ever wanting to use the wheels with disc brakes.

Again, maybe it was just a dry spell (I could certainly imagine that the highest demand for such hubs is in the spring), so I'll be curious to see what you find.

Good luck!

Recent models have aluminium axles. These are wider diameter than steel and are stiffer and lighter BUT something has to get smaller to accomodate the wider axle. They use smaller bearings. They may use thinner freehub bodies but I cant find any data on that, only reports of bursting freehubs that never used to happen.
I cant tell you the Shimano part no of the alu-axle versions or when they were introduced but it was a few years ago. Basically the current XT is not the same hub as the old XT.

Mid 1980's Shimano XT hubs came in 130mm width. But they changed to 135mm at some point. I would guess early 90's.

a Shimano 105 hub is 130mm. Take a look <here>.

I believe that the M770 was the first aluminum axle version. I have M756 and M760 on my touring bikes. I have never seen 130mm XT hubs, although SteveD (above) said they existed.

When I built up another touring bike this past spring, I noticed that Surly was using the M770 hubs on their LHT but according to their catalog on their Big Dummy (a heavy duty cargo bike) they used an older steel axle M756 XT hub. For that reason, I used a steel axle hub on the touring bike that I was building, as I wanted cargo bike capabilities for my touring bike. (Surly has changed parts again, they now use a Deore on the latest version of the Big Dummy.)

When you buy spokes, measure the hub because they made subtle changes over the years and if you use the dimensions off of the internet, they might be from a different version of the hub.

All the varieties of older XT hubs are listed here:
https://mombat.org/Shimano.htm
The old 6 and 7 speed 130 mm hubs were beautifully made but I do not think you can get replacement cogs without paying quite a lot.

get a 105/ultegra road hub.

same hub, different hub shell.

Better spacing for your particular frame.

Do you know how much of a downgrade you get when you go down from 105 to Tiagra for a rear hub?

apparently the bearing surfaces are lower quality... not sure if the bearings themselves are lower quality? The tiagra is also heavier.

Not really sure about the specifics, sorry, but since i like building wheels to last until the rim surfaces wear through, id probably spring for the 105 on this component. For the brifters and FD, tiagra is great stuff, and not really a downgrade at all.

Check out what Sheldon Brown@ Harris cyclery says about the Tiagra Hubs.

https://sheldonbrown.com/harris/hubs.html#road

I have been using a 36-hole front and 40-hole rear XT hubs from I think 1990. Simply bomb proof. I would love to find another set.

I would probably get new LX hubs if it were up to me. They have served well, and are very cheap if you just find an every day sale. In theory second relacings should follow the original pattern, and there are a number of different ways of going about lacing. So I would prefer to find the whole old wheel just to follow the pattern. I don't think the failures in the shell are a recent phenom, they have been addressed in the boutique hubs for a long time.

Thanks for all your comments.

I finally realized the 130mm spacing is the first and most important limitation, as that's based on the frame itself (after spreading). If I'm doing the old XT hub route, according to the site previously mentioned, 1993 I think was the last year they did 130mm. So there was a good 5-ish year period before that that were 7 speed hyperglide (and uniglide?) compatible, I think at least. So there's that, and you can find some of these on ebay.

So then I started looking at cassettes - there's the sram-730 with 12-32, and even a megarange that goes up to 34 teeth at the top. Oh, and there's lots of xx-28 in seven speeds - all of which, I think, would work. So there still seem to be a decent amount of 7 speed floating around.

But all this got me thinking, will it go with my rear derailleur? Someone switched out a lot of the original stuff, and the rear derailleur is a Super Record campy - the newer variety, rather than the initial SR. People on the forums say it'll only accept up to 28 teeth, and even then it's finicky. The front is the original Sugino cranks, 28-45-50 (but with a NR derailleur).

Anyway, a bit of a mess, and probably beyond the scope of my original question. Everyone was nice enough to respond, so I thought I'd go ahead and fill in the details.

btw The bike came with the original maillard helicomatic hubs now laced to skinny, black, nameless rims. I was originally quite against using the Maillards based on Sheldon Brown's opinion of them. . . . hmm. And I still can't get over that the bike came with a carbon seatpost and a Salsa Stem, among other oddities. Weird.