CHUMBA URSA Major Review: The Celestial Bear

I spent several months with the URSA Major and tested it in a myriad of landscapes, from the deserts of Utah to Colorado’s rugged and snowy San Juan Mountains. Much of that time was spent unloaded, ripping along high desert singletrack around Durango, CO. When the snow would fall, I’d don pogies and ride trails to work. I was even able to enlist the URSA Major on some ice climbing and ski missions. Accessing long ice climbs and backcountry skiing via fatbike on snowy access roads felt like the perfect mode of travel. We’d easily roll past stuck vehicles, snow shoers, and skiers who were all attempting similar climbs. But snow isn’t the only place this bike shines; the desert seems to be its second home. Naturally, some testing was needed out in Utah’s sandy southeast, and a three-day bikepacking trip outside of Moab and a bikepacking/canyoneering trip in Grand Escalante provided the perfect opportunities to put the URSA Major through its paces.

Before going much further, I’d like to say hats off to CHUMBA for continuing to charge ahead in the ever-competitive market of adventure bicycles, all while building their frames here in the USA. Surely it would be much cheaper to send operations overseas, but they remain committed to staying close to the design process, which ultimately provides the ability to tweak designs more quickly, resulting in a more refined build.

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• Highlights
• Frame: titanium
• Seatpost: 31.6mm
• Bottom Bracket: Threaded 100mm
• Rear hub: 197x12mm (rear) or 190 QR
• Max tire: 26×5″ / 29×3″
• Price: $1,795 (frame) / $4,950

The Bike

The URSA Major gets its namesake from the celestial constellation, Latin for “The Great Bear.” Just looking at this bike – in all of its shiny titanium glory – it doesn’t take much imagination to understand how it earned its name.

The URSA Major Ti was undoubtedly designed with adventure in mind, as evidenced by its vast array of bottle and rack mounts, oversized tubing, and build kit. The overall construction seems to be intentional and well built. The Ti tubes are beautifully welded, especially around the cable and bottle mounts. Speaking of which, this rig has mounts for four bottles, two of which are on the bottom of the frame. The particular URSA Major that I demoed has been passed around and ridden all over the place, and its Ti tubes have been marred by strap wear (as seen in the photos). Although, with some elbow grease and buffing compound, Ti usually shines right back up. I like to think of myself as a “function over form” kind of guy, but I do enjoy a bit of aesthetic appeal. I’d be somewhat disappointed if the costly Ti frame I purchased had worn/peeling vinyls, like on this particular URSA Major. The Ti has a couple of spots where designs are laser etched into the frame, but I would enjoy seeing more permanent designs rather than vinyls. A well crafted headtube badge would boost the aesthetic factor as well.

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I was pleased to see that this Ti frame comes with an English threaded 100mm Paragon Machine Works bottom bracket. Threaded – as opposed to PressFit – bottom brackets are typically less creaky and arguably easier to maintain, especially while touring in inclement weather. As with most of CHUMBA’s bikes, the URSA Major Ti comes equipped with sliding dropouts (machined by Lynskey with Paragon Machine Works inserts), something this reviewer simply adores. Sliding dropouts have a variety of benefits, and the Paragons seem to work superbly. They allow for adjustment of effective chainstay length, which, according to CHUMBA, means the frame can accommodate either a 4” tire at 435mm or a 4.8” tire at 455mm. I ran 4.8” tires on 82mm rims with the inserts slammed nearly all the way forward in the dropouts, albeit without much mud/snow clearance.

As with any sliding dropout system, it offers the ability to convert to a single-speed drivetrain in case of failure. The Paragon system uses an easily adjustable tensioning system that keeps the wheel from unexpectedly sliding forward. Much like Salsa’s Alternator dropouts, Paragon’s inserts are easily swapped to accommodate various axle and hub sizes. The bike industry is constantly hopping on the next axle/hub standard bandwagon, so being able to change hub and axle sizes on a costly Ti frame is a must in this day and age. My build came with 150x15mm & 197x12mm Industry Nine Torch hubs laced to 82mm Dirt Thumper Carbon hoops. I think they were trying to spoil me, and spoil me they did. The lightweight, high engagement wheelset combined with the MRP carbon fork and Ti frame made for a light yet burly build that yearns to tear up singletrack. I think it’s important to note that I was riding a top of the line build, and riding this same frame coupled with lower end components (especially wheels) won’t result in the exact experience I had.

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These days, bike builders need to find every edge they can to stand out from the crowd. As it happens, I have a couple of suggestions to do just that. First, as Benedict Wheeler pointed out in his NAHBS coverage, it’s time for bike builders to start designing and building their own forks. Besides the MRP Carbon fork my rig was spec’d with, CHUMBA offers the Surly Ice Cream Truck fork as a build option. For bikepacking, I’d take the weight penalty of this steel fork over the Carbon MRP just because of its wealth of bottle mounts. A Ti fork would be extra special and help set Chumba apart, although it would surely be obscenely expensive. At the very least, a steel fork could be manufactured so as not to use a competitor’s non-color-matched part. Secondly, it would be neat to see the chainstay length customized to each of the frame sizes, something many brands are starting to do. Most builders opt not to pair each size with its own corresponding chainstay length because it’s expensive and most consumers don’t notice the difference. But, the extra effort would ensure each size frame is optimized and has the same handling characteristics.

For those of you with sticker shock, note that the chromoly version of this bike is significantly cheaper. But, to be quite frank, titanium is better. This wonderful material is 40% lighter than steel and has many positive ride quality attributes. It’s much more resistant to crash damage than carbon, the strength to weight ratio is higher than aluminum, and has the best vibration damping compared to chromoly, carbon, and aluminum. Ti is for life.

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Build Kit

• FRAME URSA Major Titanium Fat-bike (Made in USA)
• FORK MRP Fat Fork Carbon 150×15
• HEADSET Cane Creek 110 Series ZS44/EC44 Tapered
• STEM Thomson X4
• HANDLEBAR Thomson Flat 31.8mmx730mm, 12° sweep
• BRAKES Shimano Deore XT, 180mm
• SHIFTER Shimano Deore XT 11spd
• BRAKE LEVERS Shimano Deore XT
• REAR DERAILLEUR Shimano Deore XT
• CRANKS & CHAINRINGS RaceFace Turbine
• BOTTOM BRACKET English threaded 100mm Paragon Machine Works Bottom Bracket
• CASSETTE Shimano XT
• CHAIN It’s a chain…
• FRONT Industry Nine Fat Torch 150 x 15mm
• REAR Industry Nine Fat Torch 197mm
• RIMS Dirt Thumper Carbon
• TIRES Maxxis Colossus 4.8”
• SEATPOST Thomson Elite 31.6mm x 410mm, no-offset
• SADDLE Ergon SMC3
• WATER BOTTLE MOUNTS 2 inside main triangle, 2 below frame

The Ride

At first glance, the URSA Major may not appear to be an industry leader in fat bike geometry. But, digging further, it has some unique geometries and qualities that distinguish it from the competition. When comparing chainstay length and head and seat tube angles, for instance, this rig is similar to the Salsa Mukluk and Surly Wednesday. Short chainstays like this, especially when slammed all the way forward in the dropout, make the rig nimble and snappy. Although, to clear larger tires while leaving room for mud/snow clearance, the sliding dropouts need to be pulled all the way back, rendering the effective chainstay length to 455mm and simultaneously lengthening the wheelbase. Obviously, these adjustments will result in slight changes of the handling characteristics.

Where the URSA Major differs is the bottom bracket height, wheelbase, and standover height. CHUMBA designed the bottom bracket to be fairly high in order to clear obstacles. This certainly helped me avoid pedal strikes when I was pedaling through technical rock gardens on Durango’s more challenging singletrack. The low standover height gives plenty of clearance to riders’ precious bits when stepping off the pedals in boulder-strewn terrain and deep snow alike. Although, the shorter standover height translates to less frame space for packing. The small frame triangle leaves enough space for a full four-liter bladder that fits snugly into Wanderlust’s Divide frame bag. Luckily, the underside of the frame can accommodate an Anything Cage and bag along with an extra bottle to create more storage space.

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As for climbing, the URSA Major thrives with an aggressive rider. The bike seems to climb much better with some speed. When climbing slow and steep terrain, the front wheel tends to wander. With some weight on the handlebars, from either rider positioning or a loaded handlebar bag, the front wheel tracks a bit straighter. The rear wheel seemed to stick to the ground, even when I was standing up and cranking on loose ascents. Even more impressive was its traction when climbing on snow. I wouldn’t dare get out of the saddle in the snow on most fat bikes, but I found the URSA Major “held on” as long as I didn’t get too far forward. I was impressed by how the bike responded to short sprints; the power seemed to transfer straight to the back wheel with minimal tire slippage (on dry ground, of course). Titanium’s lateral stiffness was surely to thank for the power transfer, and the short chainstays coupled with the seat tube angle kept the tire under the center of gravity. The fresh Maxxis Colossus 4.8s surely helped as well.

Overall, the bike seemed to enjoy being loaded down. Its relatively steep 69° head tube angle means quick and responsive turning optimized for slower riding, which bodes well for both bikepackers and snow riders alike. The reach is relatively short, making for what felt like a compact cockpit. This left me sitting upright with more weight on my tush than my hands. When I was out of the saddle, my knees would often come in contact with my feed bags. If this were my personal rig, I’d employ a longer stem and possibly even a seatpost with a bit of setback. In fairness, I was on a medium sized frame, and at 5’10” I likely would have fit better on a large.

When I was peeking at the numbers before receiving the bike, I wondered how the high bottom bracket would translate to the ride quality. I worried the bike would feel unstable at speed and awkward in the corners. However, with its relatively long wheelbase, the URSA Major felt stable, even well planted, on all except the chunkiest of descents. The progressive angles, light wheelset, and carbon fork kept the front wheel light. This made for a playful bike when descending. The bike’s natural tendency is to pick through technical sections by hopping from one obstacle to the next rather than plowing right through. I’d love to pop a Bluto (which would slack the head tube angle to 67.5°) and a dropper on this rig to see what it’s really capable of. That said, I never felt like suspension was actually necessary. All things considered, I’d even go as far to say that this might be one of the most fun rigid bikes I’ve ridden.

Sure, there are other fat bikes on the market with similar angles, but there aren’t many that are built out of titanium, have threaded BBs, are made in the USA, and have similar geometry.

Here’s a quick comparison of a few other well-known fat bikes, the Salsa MukLuk, Surly Wednesday, Specialized Fatboy, and Chumba Ursa Major.

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• Size tested Medium
• Rider height/weight 5’10” / 155lbs
• Model Tested CHUMBA Ursa Major Backcountry Titanium
• Place of Manufacture USA
• Price (frame) $1,795.00 (on sale from $2,295.00)
• Price (full build) $4,950.00
• Manufacturer’s Details Chumba USA