I've restored a couple of vintage tourers and am now interested in purchasing an LHT or Saga frameset to build. Even though the vintage touring bike geometries were very similar to the road bike's compared to todays, they used the equivalent to MTB components. The current thinking seems to be to use MTB gearing ratios and derailers. I can understand keeping the gearing low, but why is MTB stuff superior to road stuff on a touring bike. Is it just tougher?

As far as I know, it's primarily about getting the gearing down low enough for where many tourists prefer their gearing to be.

With a "road triple" you have chain rings of 50-39-30 and with a current 10-speed rear cassette you'll have something like a 12-27 in the rear.

With a "mountain bike" drive train you can get a triple with (for example) 46-34-24, or 44-32-22 and a 9-speed rear cassette of 11-32, 11-34, or even recently 12-36.

The road triple w/a road cassette in the rear gets you a low of 30 gear inches; the MTB drive drain gets you down to less than 20 gear inches. Big difference.

Take a look at the way that Bruce Gordon spec's his loaded touring bikes:
https://www.bgcycles.com/faq.html

Or Co-Motion Americano:
https://www.co-motion.com/single_bikes/americano.html

Nothing says you have to do a MTB drive-train -- plenty of people seem to survive with the higher gears. My own light touring bike is a mix-and-match -- a road triple in front (50-39-30) with a 9-speed MTB cassette in the rear (12-34). You can also do what Cannondale does on one of their bikes -- mix a "road" triple with an IRD wide-range 10-speed derailleur. But if you want low, low gears and are building a bike from scratch a MTB drive train will get you there faster.

The other common MTB component brought over to touring bikes is rear hubs with 135mm spacing. Supposedly helps create stronger wheels than a standard road hub.

All true. I will add, however, that some road triples can be fitted with a 24 tooth inner ring, if the inner bolt circle diameter (BCD) is 74mm. Shimano, in a effort to screw up every thing, has introduced a 94mm BCD crank. The smallest inner ring for that crank is 30 teeth. Shimano has done this because, as everyone knows, only strong, young, fit racer dudes ride bikes in places where it's flat

Mountain bike cranks used to be able to take as low as an 18 tooth inner...until Shimano decided that strong, young, fit racer dudes ride bikes in places where it's flat

Now the trend is towards 2x9 systems because only strong, young, fit racer dudes ride bikes in places where it's flat

All ranting...well, most ranting...aside, mountain bike stuff makes sense because it allows for lower gears both front and rear.

Ya know, I try not to worry about that sort of thing.

Except for a couple of rather obscure specs and standards that I assiduously ignore I could care less whether someone in a marketing department decided that I have "road" cranks and an "MTB" cassette.

I say just figure out the gearing that suits your touring style, and use whatever compatible components will achieve that gearing. I see no particular reason to worry about anything else.

As to tougher, it seems to me you can get crap MTB and very rugged road parts. Shimano also makes a handful of very expensive high-end lightweight parts -- both road and MTB. I wouldn't use that on a touring bike though, too pricey and too likely to sacrifice a tiny bit of robustness in favor of reducing weight.

How someone wants their gearing set up will depend on the type of touring they plan to do. For lightly loaded fast tours, road gears should be fine.
For me, I plan to do self contained fully loaded touring towing a trailer, so I want pretty low gears, which are most easily achieved by using MTB components. As a 60+ rider, I no longer qualify as a "young, fit, racer dude" so I have to make my setup work for ME. You need to evaluate the type of touring you want to do, and use what works for you.

it's really a mix of road and mtb gear. for the derailleurs, you won't see rapid rise style rear derailleurs or any of the weird top swing front derailleurs ... so it's really the typical road style high normal rear, bottom swing front, but with the range to do an 11-34 rear and a triple in the front. this stuff just happens to be labeled as mtb gear. for shifters, it's almost always road style--either sti or barends ... or maybe thumbies or downtube shifters. 135 mm rear hubs are also popular.

Why not just stay with a mountain bike? I have a mid 90's mtb that I'm considering to use on a Canadian tour begining May of 2011. Is there a issue of fitting panniers on a mtb? I will replace it's front fork with shock to a rigid version if I stay with the mtb, but that is the only major revision I plan. There will be gravel roads on this tour and it seems to me a mtb will be the way to go. Any thougts.

There can be an issue about heel strike. I run 10.5 to 11 feet on a 6'1" frame that doesn't seem to be a heel strike fiesta, and I used to tour on MTBs with special MTB paniers (smaller, sorta the alpinist pack vibe vs backpacker gear was the trend when I bought them). At that time most MTBs had rack mounts on them but suspension did bypass that to some extent. You would just have to give it a try. There are ways of moving the load back, but they aren't all that clean.

As far as the gravel road thing goes, MTBs aren't really special as far a roaded terrain goes. People drove bikes with big tires, gears, etc... offroad from the very beginning. If anything 700c will float more, and 26" wheel touring bikes will be indistinguishablefrom MTB where the rubber hits the road. You don't need 2" plus tires for that kind of thing for the most part, 1.5" tires will do most anything. The real advantage to MTBS is cost and availability. Use what you have, or can buy for next to nothing. But there is a "proper" touring bike for anything you can imagine, short of snow and 4" tires in the desert.

Check out the Riv site to see slide shows of people riding their touring bikes (and some MTB like bikes) on gravel roads.

https://www.rivbike.com//

Just a historical note. There once was a time when MTBs, as we know them, didn't exist. In order to create multi geared bikes with large capacity derailleurs, the first builders had to adapt touring gear for their early MTBs. Mountain bike and touring components have always been similar and interchangeable. Touring bikes went out of fashion in the nineties at the same time MTBs became dominent, so there are a lot of MTB components available.

Thanks all for the information. It's starting to make a little more sense to me. Wider rear spacing of 135mm provides less dish therefore stronger wheel. Lower gearing options with a MTB crank.

I have a road bike capable of light touring but I'd like to build one for heavy touring so I've looked at a lot of photos of builds and the usual suspects seem to be some sort of Deore RD, low range cassette, either a road or MTB crankset probably depending on whether the rider is really going to carry a heavy load or are going to commute with a lighter load and occasionally take a loaded trip, front D doesn't seem to matter as long as it can reach a triple, 135mm rear spacing seems to make sense I suppose. Cantilever brakes are traditional on touring bikes, but I read an article in Adventure Cycling about the advantages of linear pulls. strong rims with lots of spokes. Except for the shifters, sounds pretty much like your average hardtail to me except for the longer chainstay for stability and heel clearance.

The main advantage of 135mm spacing is greater availability of replacement parts with the use of 26" wheels for touring off the edge.

keep in mind that shimano Deore was originally a touring-specific group. this was 1982, pre-MTB... these days, the modern equivalent is "MTB" stuff. 135 builds a stronger wheel, and long cage derailleurs are capable of handling larger gear ranges (bigger rear sprockets). if you have a friction shifting bike, oyu can mix and match whatever you want... I tend to use road FD, and MT RD, for example...

My parts lists that I used to build up a couple touring bikes is below.

I used "road" crankset with MTB cassette on the one I built up five years ago and liked it enough that I used an identical setup for the second one that I built up about a month ago. The outer (52T) and middle (42T) chainrings on the Sram eight speed cassette (11/12/14/16/18/21/26/32) are almost exactly one and a half step gearing which is fantastic once you figure it out and get used to it. The inner chainring (24t) is limited to steep hills only and is rarely used.

***

LHT - 2004 Sage Green 58cm for 700C wheels.
Mavic A719 rims.
XT hubs, M752 Rear and M760 Front.
Wheelsmith DB-14 spokes (36).
Hutchinson Globetrotter 700X37 tires 87psig.
Zefal 45mm fenders.
Generic (Nashbar) cantilever brakes.
Generic cross interupter brake levers.
Cane Creek brake levers.
Eight speed BS64 bar end shifters.
Generic stem.
3ttt drop bars.
Generic computer.
Garmin Etrex Legend handlebar mount.
Cane Creek C2 headset.
Vintage Suntour Le Tech front deraileur - high normal.
Campy Mirage triple, 52T, 42T and 24T (generic 24T ring swapped for original 30T).
Ritchey clipless V4 pedals.
Generic seatpost.
Brooks Conquest seat.
XT rear deraileur M739.
SRAM eight speed cassette 11-32.

***

Thorn 2009 Sherpa black frame and fork
XT 760 hubs
Salsa Gordo rims, 26 inch, 36 spoke
Wheelsmith DB-14 spokes
Zefal rim tape
Planet Bike Hard Core fenders
Nashbar cantilever brakes, conventional straddle yoke and straddle cable
Tektro R200A brake levers
Nashbar cyclocross bar top brake levers
3ttt Prima 220 handlebars
Origin8 stem, 90mm, 17 degrees
Headset mixture of FSA and Cane Creek components
Shimano BS64 eight speed bar end shifters
Vintage Suntour LeTech high normal front deraileur
Shimano XT M739 rear deraileur
Sram 11-32 eight speed cassette, 11/12/14/16/18/21/26/32
Campagnolo Veloce crankset 52/42/24, the 24t is a no-name brand substituted for the original 30t
Campagnolo bottom bracket 111mm
Ritchey MTB V4 clipless pedals
Generic seatpost
Salsa seatpost clamp
Brooks Conquest saddle
SI90 bicycle computer
Garmin Legend GPS for when I am not sure where I am going

Should this go to the top? Looks like one to cause some thought. Thanks LHT. A related thought provoker. How about a 29er wheel frame to start with? Wing Nut

I have no experience with 29 wheels. I toured last summer on a rails to trails route and while on that trip I decided I wanted a fatter tire than the 37mm wide tires that fit on my 700c LHT (with fenders, which limited tire size options) and decided to build up a 26 inch touring bike. On expendable items like tires, I prefer to use a size that gives a lot of options and there are more tire options for 26 inch wheels than for 29er wheels.