'94, erm '92..., well '93 Rocky Mountain Cirrus rebuild

[foxb13]

Update May. 2, 2021: new specs/pictures p. 5-6

Dear RBers,

My first rebuild. For the impatient, the before/after pictures, with technical data below.





Frame: Rocky Mountain Cirrus, 21.5" size

Fork: Rock Shox Mag 21, 1 1/8" (200mm) threaded steerer/crown, 60mm "long travel" kit

Headset: Shimano Deore XT HP-M736
Stem: 1st gen. Syncros Cattleprod, 120mm 0° rise, Syncros Monoshim 25.4mm shim
Handlebar: Syncros Flatbar, 5° bend
Grips: ODI Attack
Barends: None

Brakes: Shimano Deore XT BR-M734
Brake Pads: (update Nov. 10, 2018 ) Shimano Deore XT M System
Brake Cables: Shimano SLR MT-092
Cantilever cable hangers: (update May. 2, 2021) Shimano A/73 (front), Shimano B/82 (rear)
Brake Levers: Shimano Deore XT ST-M092 Servo Wave SLR Plus

Shifters: Shimano Deore XT ST-M092 Rapidfire
Front Derailleur: Shimano Deore XT FD-M735, 34.9mm
Rear Derailleur: Shimano Deore XT RD-M735-SS (Short Cage)
Derailleur Cables: Shimano SIS
Cassette: Shimano Deore XT CS-HG90, 7-speed 11-28 teeth
Chain: Shimano Deore XT CN-HG91, 104 links
Cranks: Shimano Deore XT FC-M730, 175mm
Crank Bolts: Shimano Crank Arm Fixing Bolts
Chainrings: Shimano SG C-24/36/46
Chainring bolts: Shimano Double Gear (M8 x 8.5) and Inner Gear (M8 x 13.5) Fixing Bolts
Bottom Bracket: Shimano Deore XT BB-UN71, 68 x 127.5mm English thread
Pedals: onZa High Output BPD-1401, stainless steel spindle

Hub Skewers: (update Nov. 10, 2019) Pulstar Mombo (front), Shimano Deore XT (rear)
Rims: Wolber AT 400 Titanium Light, 32 holes
Hubs: (update Nov. 10, 2019) Pulstar Mombo (front), Shimano Deore XT FH-M732 (rear), 32 holes
Nipples: DT Swiss, brass standard, 2.0 x 12mm
Spokes: (update Nov. 10, 2019) DT Swiss Competition, double-butted 14/15g, straightpull 273mm front, 265/263mm (drive side) rear
Tyres: (update Apr. 29, 2019) Panaracer Smoke/Dart Classic, 26 x 2.10
Tubes: Vary with flats...

Saddle: (update Nov. 10, 2019) Selle Italia Flite Transalp
Seatpost: 2nd gen. Syncros Propost 30.4 x 330mm
Seatpost Binder: Shimano Deore XT SQ-M730

Weight: (update Nov. 10, 2019) 12.5kg, including pedals

PS: As English is not my mother tongue, don't hesitate to correct my sentences, vocabulary, spelling, grammar, etc.

 

[foxb13]

It all started with a classified on eBay Germany in the summer of 2017. The bike was plainly advertised as '94 classic/cult MTB from Canadian manufacturer Rocky Mountain. I was dreaming of the Cirrus since I first saw it in a '91 or '92 issue of French MTB magazine Vélo Vert, IIRC. I thus quickly made the deal with the vendor, a cool German guy who was able to tell me more. The bike was bought new in 1994 by his father in a LBS in Vancouver, where he was a student BITD. He eventually came back home with the bike that evolved as a commuter over the years before lying unused in the cellar (dry conditions, fortunately) for the last 15 years. 10 hours and 1000km later (local pickup in Germany), it was mine.

 

[foxb13]

Bike S/N is YA1Z429, meaning it was built in 1992. As @RockiMtn's Cirrus [1], the color scheme however differs from the bike presented in the '92 Rocky Mountain catalogue. It is rumored that this finish was available as a frame set only [2]. This is further emphasized on my bike by some of the still original components: the derailleurs, crankset and front wheel.



The front derailleur is Deore DX whereas '92 Cirrus came standard with Deore XT drivetrain.


While matching the specs, the Deore XT front hub is stamped with Shimano date code RB, indicating it was manufactured in February 1993.


Additionally, the front rim is Wolber AT 400, as on several '93 Rocky Mountain bikes vs. AT 18 on '92 Cirrus.

All this suggests that the bike was probably assembled in 1993.

 

[foxb13]

The other components were replaced over the years (fork, cockpit, rear wheel, brakes, tires, middle chainring, pedals, seat clamp, skewers) or are simply missing (saddle, *cough* seatpost *cough*, outer chainring).

 

[foxb13]

Albeit not perfect, the frame is still in great shape overall: no cracks, dents or bad scratches. I thus opted to leave it as is, with it's imperfect harmonies. No tedious decals stripping nor frame polishing that would have over-restored the bike.




Just a little bit metal cleaner to deoxidize everything did wonders, IMHO:

 

[Minifreak]

Great project, look forward to seeing it come together.

I did one myself a few years back, see if I can find the thread to give you some inspiration

 

[Minifreak]

viewtopic.php?f=6&t=323398&hilit=Rocky+Mountain

 

[foxb13]

Thanks @Minifreak. I initially planned to rebuild the bike as advertised in '92 Rocky Mountain catalogue and started collecting the required components. By chance, a NOS "noodless" 1st gen. Syncros Cattleprod stem, exactly as pictured in the catalogue, was quickly located in Germany.

A NOS Shimano Deore XT SQ-M730 quick release, FD-M735 front derailleur, SG C-46 outer chainring, as well as NIB HP-M736 head set and CN-HG91 chain followed shortly.









But the still original front wheel from 1993 eventually convinced me to depart from the strict '92 specs, allowing me to pick up parts in the '93 Rocky Mountain range of components, despite the Cirrus no more being made this year. To start with, I had to find a matching 32-hole Wolber AT 400 rim for the rear wheel. This didn't take that much before I source a NOS one in Germany.

 

[foxb13]

"with dedicated Rockshox geometry" as can be read in the '92 Rocky Mountain catalogue, the choice for the front was obvious. Well, more or less. Indeed, the Cirrus was spec'd with a Mag 30, though I seem to discern damping adjuster knobs at the top of the upper tubes on the bike pictured in the catalogue. As well as on the Mag 20 of the '92 Cirrus pictured below.



OK, OK, the stem, shifters and crankset are also different than in the '92 Rocky Mountain catalogue. Not speaking about the added bar ends While he no more holds photos of how the bike looked like when his father bought it new, the previous owner seemed to remember that it sported a Rock Shox Quadra fork. For sure, the light grey/silver color of the Quadra was probably pleasantly matching the raw aluminum finish of the frame. But I was less than impressed by the performances of the Quadra when it debuted in 1993. So thanks, but no thanks. But this at least learned me two things. Firstly, some compromises were done on the original build of the bike: lower grade Deore DX front derailleur and elastomer-sprung fork vs. XT derailleur and air/oil fork as standard. Secondly, the bike was delivered with a fork from (at least) 1993. This year, besides the Quadra, the only other option available from Rock Shox was the newly-introduced and well-acclaimed Mag 21 hydraulic fork (the Mag 10 debuted production in 1994). Presented as "the ultimate downhill formula" in the '92 Rocky Mountain catalogue, my Cirrus thus deserves nothing but a '93 Mag 21 for the front. And I precisely just found one, still in working condition and holding air, but with wrong brace, incorrectly sized steerer and missing the canti bosses and the tiny screws of the damping adjuster knobs

 

[foxb13]

Notorious for its lateral flex, the Mag 21 will probably benefit being paired with a "suspension" hub. This quickly ruled out Shimano as the Parallax series wasn't yet on the market. And led me to interesting readings for days. Ringlé, Bullseye and Pulstar were famous names BITD. Ringlé hubs were apparently prone to flange cracking. Bullseye rear hub didn't accomodate for a Shimano HG cassette. And finding original Pulstars with the right bearings and freewheel was tricky. Not to mention that I already own another bike with Pulstar hubs. Mavic Gao Dakar/531/577 were great choices too but, again, didn't suit a Shimano HG cassette. Then, all of a sudden, I stumbled across this NOS Syncros hub I didn't even knew the existence before.




I've later discovered that this Syncros Hardcore hub was in fact introduced in 1994, so slightly off by one year from my plans. In retrospect, I even could have gone with a Shimano Parallax hub that was marketed the same year! But in the end, I find the Syncros hub more cool, with the possibility to adjust the preload as the bearings wear, even though it seems it wasn't that great of a suspension hub, despite its 15mm axle [1]. Probably in an effort to work around this, Syncros introduced in 1996 the Hardcore DH hub with stiffer heat treated nickel cro-moly axle (vs. ceramic coated Zicral for the Hardcore hub) and titanium axle bolts. Since the Hardcore hub shares the same "cabriolet design" with the Hardcore DH hub, it can easily converts to the titanium axle bolts for increased system rigidity (2.5 times over quick release).

Update Nov. 10, 2019: Syncros Hardcore hub now replaced with a more 1993er Pulstar Mombo front suspension hub (p. 5).

No fancy with the rear, on par with the original specs: Deore XT FH-M732 freehub and CS-HG90 7-speed 12-28T cassette.




And so were the skewers.



Update Nov. 10, 2019: Front skewer now replaced by the integrated Pulstar Mombo front suspension hub one (p. 5).