My bike ( http://bike4u.ru/modules.php?name=Pages&go=page&pid=2 ) was intended for mountain expeditions. For the last years it has been tested in the mountains of Tian-Shan, Altai, Sayans and Baykal Region. A larger part of luggage I put in a frame custom bag without using carrier. Other things move in a backpack. It's very convenient:
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On some terrains where it was impossible to ride I had to hook it onto my backpack, and I usually carry my front wheel in my hand as a stick.
http://www.bike4u.ru/project/pic/120904/DSCN3784.JPG
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In mountains I replace only other tyres and pedals (Wellgo 95B), cassette 11-32, neopren cover on a saddle. The complete bike set for expeditions does not exceed 9.5 kg (16-20 kg with luggage in a frame)!

Bottle Cage Bolts: replaced by plastic caps - 2
Bottom Bracket: НОРЕ Ti - 68/111 (М36 Italian tuned Sychuzhkin) - 162
Brake Levers: shifters units Shimano XT (tuned cable adjusters) -
Brakes (Rear): XT 99’ сeramic (with Ti bolts) - 227
Brakes (Front): XTR BR-M951 сeramic (with Ti bolts) - 198
Brake Cables: Jagwire Teflon / XTR housings & caps - 69
Cassette: Shimano Ultegra tuned 11-27 with Al lockring - 219
Chain: Shimano CN-7700 (108 links with PowerLink lock) - 271
Crankset: Truvativ Stylo Team 00’ square (bolts: Ti self-extracting, Al/Ti ring) - 652
Derlr (Front) XTR FD-M951 (with Al shim under 31.8, Ti/Al bolts) - 130
Derlr (Rear) XTR RD-M960-SGS (Al bolts, w/o rubber cover) - 199
Fork: RockShox SID XC 99’ 80 mm travel 1.1’steerer 180mm (inc star nut & Ti canti studs w/o rubber covers) - 1286
Frame: 19,5’ Igevsk custom hend made Titanium 3-2.5 - 1380
Grips: Velo Pork (w/o caps) - 30
Handlebar: 3TTT O2 CC PRO (560mm 11° with plastic caps) - 139
Headset: Ritchey Fuzzy Logic1’ tuned to 1.1’ (inc. top cap ВВВ, Ti bolt) - 102
Headset Spacer: 5mm plastic Cane Creek - 3
Pedals: Koski (optimized) - 310
Quick Releases: DT Swiss (tuned аxleTi, R - 130mm) - 81
Seat Binder: Kalloy Alloy (Ti bolt tuned 28,2mm) - 19
Seat: Selle Italia SLR - 142
Seatpost: Titanium custom MTI (Igevsk) 320mm/27,3mm - 158
Shifters: Units Shimano XT (tuned cable adjusters, Ti bolts) with the shift cables polished stainless and XTR housings & caps - 467
Stem: PRO Shorty MTB 60mm 35° (Ti bolts + shim 1.1’) - 118
Tire (Front): Maxxis Fly Weight 330 26х1.95 - 325
Tire (Rear): Maxxis Fly Weight 330 26х1.95 - 327
Tubes: Maxxis Fly Weight 0.45mm 1.75’-2.125’ - 190
Wheelset (Front): (630)
--Rim: SUN CR17A TCC 32 - 421
--Spokes: Ritchey (DT Revolution) (1.8/1,5/1,8 ) 2X - 130
--Nipples: DT Aluminium 1.8/12 mm - 11
--Front Hub: Totenkopf Elite 68 (AC micro) - 68
Wheelset (Rear): (806)
--Rim: Bontrager Mustang Ceramic ASYM 32 - 428
--Spokes: Ritchey (DT Revolution) (1.8/1,5/1,8 ) 3X - 131
--Nipples: DT Aluminium 1.8/12 mm - 11
--Rear Hub: DT Swiss Hügi 240 (130mm) - 236
Misc Option: Rims tapes, Chain Guard OROCAL tape - 12

TOTALS: 8654 gr (19.78 oz)

The lightest complete set here is submitted. I use it only in Moscow country region. Photo here: http://www.bike4u.ru/images/content/kletka_bike.jpg
Picture is not updated! In a new easiest 19 lb complete set, other stem, other cassette, other wheel and tyres, there is no computer, brake amplifier, bar ends, on a fork there are no rubber covers (boots).

Nice bikes, cool pictures and interesting expeditions! Guess it really pays to have a WW bike in those kind of situations...

The joy from autonomy (our routes in one thousand miles frequently hundreds miles wild without a civilization) that costs ! We in direct sense carry all on ourselves. Weight is minimize not only bikes, but on other equipment (tents,sleeping bags and another), rational meal. All only most qualitative least volumetric and universal in use! Second use of my bike marathon race.
On long trips the vibrating comfort is very important. Titanium in this sense it is much better than aluminium. Earlier I used telescopic RockShox seatpost. Now titanium bent seatpost at smaller weight extinguishes vibrating more effective.
About durability. Behind ten thousand real such run on this bicycle all Revolution spokes are whole! The puncture of tubes Maxxis FlyWeight 0.45mm happens at me on the average of time on 800 kilometers! My weight of 70 kgs. The cargo happens from 8 up to 20 kgs.
My original system of packing of a cargo is very important! Here a custom bike of my friend:
http://bike4u.ru/modules.php?name=Pages&go=page&pid=36
It weight 11 kgs, but in a bag (0.55 kgs) in it frames (21’) are located 35-40 litres!