Don't overlook Cannondale. My 88 feels feather light even with a steel fork and wire bead Mythos tires, very rigid too. Hell even the Brooks saddle didn't weigh it down much. For steel though, my 990
was the best MTB I ever owned. It was LIGHT, fire engine red lugged True temper, and Deore XT. I may be stupid for selling it, but it truly was more bike than I needed. The Red C'dale made the loss
bearable. I have a 22" Puch in red also, lugged and may get bull moosed.,,,,BD

Got some numbers but no pics, all the weight talk got me motivated.

The Ross, not sure what model, with some ice and snow on it weighed in at about 35Lbs. A beast complete with bullmoose bars, but should make a fun urban road curb bumper.

Nishiki Bravo, sloping top tube, 14.5" frame, hi-ten steel, 31Lbs.

DiamondBack Outlook, hi-ten steel, 20" frame, minimal slope on the top tube, 32Lbs

GaryFisher Marlin, medium to minimal slope top tube, 16.75" frame, 25Lbs with a full rear rack mounted on it. Feels a lot lighter than it weighs. I really like this bike. Tubing is a cro-mo of some sort, too dark to read the text on the frame.

GT Outpost, 4130 steel, about an 18"-20" frame, 30Lbs.

I couldn't get to the Timberlin which is racked on back and fendered, probably in the 25-30Lb range naked.

Hope this helps some. If I decided to unload most of these I'd keep the Timberlin and the GF Marlin, the rest could go and probably slowly will come sunny weather.

Ps, I'd maybe use one of these in an offroad triathlon but probably not for a legitimate MTB race. But for a weekend brush or trail fun ride then sure if it wasn't too rocky.

Most any old mountain bike that isn't total bottom of the line will take a serious beating. My suggestion though is to put on a suspension fork with lockout, because you'd really have a much better time with it off road and can lock it out for on road.

As a beater and hauler, I have a Shogun Prarie Breaker III. Lugged steel, butted Tange tubing, vertical D/os. Looking at the bike, it's from a fairly early point in MTB design; it really looks like a 26" wheeled touring bike (more so since I've set it up with drops). Triple bottle cage mounts on the frame, that sort of thing. Works great as a hauler; I really haven't ridden it off road, as I a) put slicks on it and b) own a Surly Karate Monkey, which is set up for off road. But I like the Shogun a lot, and even though it was given to me for free I'd have a tough time getting rid of it; equipped with fender it is just too darn practical.

Even with very lightweight wheels and without the Brooks, my Bridgestone MB2 weighs 26 pounds. I don't know how you'd get a steel-framed MTB much lighter than that.

I do. But not all these solutions are what people might want:

-go with a single ring up front
-go single speed or even fixed
-I like good old MTB wheelsets, but modern ones can be much lighter
-small, light tires (this changes everything, often)
-even high-end bikes used to often have steel stems and/or bars. Change them out.
-cranks (this one takes a lot of money for not much improvement)

A rigid frame made of good tubing can certainly be set up to weigh a few pounds under 26, if that is your thing. I have a couple that come in way under that.

jim

Those are modern lightweight wheels and the tires are 1.3's. The front is a 28 spoker with an Ultegra hub. The bars are aluminum Ritchie/Nitto bullmoose. All of the large bolts on the bike are titanium. There are steel bikes with lighter frames like the MB-0 but they have a reputation for breaking. My digital bike scale is highly accurate. I'm finding that most bikes weigh more than claimed.