Review: Chumba Cycles Ursa

Chumba Cycles USA is a company with a 20 year heritage, known in prior years for national championship winning downhill racing designs produced by Ted Tanouye and his crew. These days, Chumba USA is a rider driven company focused on building durable steel or titanium USA manufactured bicycle frames. They use innovative designs that are tested in races, such as the 2,745 mile long, self-supported Tour Divide. The Chumba Ursa is one of the few steel framed 29-plus bikes welded in the USA. It is obviously designed for carrying a load with rear rack mounts, Anything Cage mount, and stout tubing utilized in specific locations. The tubing support cut outs include a star in the yoke at the top of the seat stay, and a CHUMBA cut out of the yoke where the seat stay and chain stay come together on the non-driveside. The cut outs are a very nice touch that give the impression that this bike is well thought out. All of the finishing details make you wonder if everything that could have been improved has already been considered. Here are the specs of the Ursa frame as listed on Chumba’s website: Frame Features:

• Oversized 44mm Headtube for tapered or straight steerer tubes
• 29 x 3.0″ mid-fat wheelsize
• ISCG-05
• 150 x 12 Thru-Axle Rear
• 31.6 Seatpost Size
• CHUMBA USA Select Steel Frame (Oversized True Temper and Double Butted 4130 tubes)
• PMW stainless steel sliding dropouts w/ replaceable hanger and dropout inserts
• DH spec’d chainline
• 83mm bottom bracket
• Room for three bottles on all frame sizes
• Mounts for Anything Cage
• Brazed on rear rack mounts
• Loads of tire clearance (room for mud and snow to go, fits wider 3.0″ tire casings with ease.)

When I initially saw this bike revealed on the Bikepackers Magazine Chumba First Look Article and subsequently, on the Chumba USA website, I was intrigued to find a plus-sized, bikepacking-oriented bicycle that was designed for my intended applications. The stainless steel adjustable Paragon Machine Works slider dropouts are probably the most well-respected dropout-based chain-tensioning system in the industry for single speed setup. This particular implementation of the PMW dropout system is consistent and reliable, provides the ability to regularly run a simplistic, lightweight single speed setup. It also allows for a geared setup (such as the 2×10 drivetrain on this test rig’s build kit) with the versatility of being converted to a single speed in the event that the rear derailleur becomes inoperable in the backcountry. Since I have an affinity for simplicity, reliability, durability, single speeding, and long-distance off-road cycling, I was pleased to see the designers at Chumba had chosen a PMW design with a 150 x 12mm thru-axle. The 150mm wide rear hub seemed unusual at first. On a regular 29er, a need for such a wide hub would be unnecessary. Due to the increased tire width, Chumba USA designed a combination of a wide (150mm) rear end and wider (83mm) bottom bracket to allow for a chain line that would provide adequate clearance for a 2×10 drivetrain without rub against the 3.0 rear tire. As seen in the pictures below, the hub flange width on the Hope Pro 2 Evo 150mm hubs aren’t much wider, at 53mm, than that of a 135mm or 142mm hub, which have 50mm and  51.5mm hub flange widths. Since the hub flanges aren’t spaced out much more, the rear wheel has about the same dish and stiffness as the other aforementioned hubs. For this flange width on a wider overall hub shell, Hope designed the 150mm rear Pro Evo 2 Hub with lots of space between the disc side flange and the disc brake mount as can be seen in the photo below. The BOOST 148 standard implements a 148mm width with wider flange spacing, which has been adopted by Hope because a “small change in the width of rear hub flanges made a massive difference to the rigidity of rear 29er wheels”. The BOOST 148 rear hub uses 57.5mm flange width while utilizing the same dropout type as a 142 x 12mm hub. During the design of the Ursa, the BOOST 148 rear hub standard was not available, but I could see it being useful for future revisions to the design of this frame to keep the chain line virtually identical while allowing for increased stiffness of the 29 inch rear wheel. It goes to show that Chumba  was indeed innovative in their design and ahead of their time to utilize the wider 150mm rear hub to increase clearance for the wider 29 plus tires before there was ever a BOOST 148 standard in place. Here are some pictures of the clearance for the rear tire on the Ursa with the dropout sliders almost all the way forward. The build configuration used for this review was the Ursa XT, equipped with an MRP Rock Solid fork. This configuration comes with a Shimano 2 x 10 XT drivetrain and XT hydraulic disc brakes, as well as a Thomson stem, seatpost, and carbon bar. For the wheelset, Chumba USA chose Hope Pro Evo 2 hubs laced to Surly Rabbit Hole rims with Maxxis Chronicle 29 x 3.0 tires setup tubeless with an Orange Seal midfat tubeless kit.  A Raceface crankset, saddle, and grips rounded out the build. Chumba unapologeticly uses oversized, USA True Temper and 4130 cromoly. They clearly take their fabrication process very seriously and it’s shown as they describe the production process in detail on their website’s Tech Page.  Chumba lists a few of their production “guiding principles” on their site that definitely help to explain why I observed this increased stiffness in the ride quality of the Ursa:

• Bent double-butted down tube to strengthen the steering junction by supporting the head tube from impacts on the trail more horizontally than a straight tube would, while keeping the main triangle light.
• Oversized chainstays to ensure everything you put into the bike gets transferred onto the trail and is stable loaded down. Bends and profiles are chosen per model, but they are all oversized.
• Oversized main triangle tubes to miter stronger around one another and provide predictable tracking through technical terrain.
• Stainless steel dropouts dramatically increase frame strength at the dropout and will remain rust free.

The oversized tubing in these specific locations would lead most to assume that Chumba USA frames are exceedingly durable. While this is highly probable, Chumba prefers to ensure customers that probability is not enough. They stand behind their products by offering a 3-year warranty on all of their frames and a lifetime crash replacement program. During the first ride on the Ursa, I quickly noticed how stiff the bike felt for a steel framed bike. It seemed to be overbuilt and not as supple as most steel 29er hardtails I had become familiar with. When taking the Ursa on shorter rides I noticed how stiff the fork and frame were on downhills over rougher terrain. Although the longer wheelbase gave extra stability and confidence, I kept feeling like I had to ride the brakes whenever rough sections came up or I would experience a surprisingly higher degree of jolting and harshness than I expected for a 29-plus rig.  Though the longer, rocky downhills were more jarring than I had anticipated, the stiff frame and fork combination provided a solid platform for efficient climbing, making pretty quick work of the uphills and with the bigger tires, a lack of traction was a thing of the past. No matter what the terrain, the Ursa felt efficient, even with the larger tires. Getting it up to speed took a little more effort than a 29er initially, but it was definitely less noticeable than when I had moved from 26-inch wheels to a 29er. The momentum the Ursa maintained once it was up to speed was tremendous. The 29 x 3.0 Maxxis Chronicle tires also have much better rollover and compliance than a normal 29er. What I didn’t expect however, was how efficiently the tires rolled on pavement and smooth hardpack. I rarely found situations where the Chronicle tires broke loose on the climbs. They did loose traction on more technical sections with 10% grades or higher, where the tires would hook up better when the bike was slightly leaned to one side or the other. On sections of trail with sand or cobbles this bike remained very efficient with the increased tire width. Realizing this ability of the 29-plus tires, I actually aimed for the sandy side of the trail in many places as the 29 x 3.0 tires rolled very quickly over this type of terrain. To me, the combination of fast rolling but compliant tires, a stable, longer wheel base, and more neutral frame geometry felt just about right for a long distance bikepacking rig.

Geometry can be an important consideration to many riders who have grown accustomed to a certain slackness or lack thereof. I tend to be most familiar and prefer a XC racing geo bike for riding my local trail network, but while taking a beating on longer endurance races or rides, my mind tends to wonder if a slightly slacker geometry may be more beneficial for the longer hauls. The geometry on the medium Ursa has a 69 degree headtube angle, which is less than 2 degrees slacker than the 29er I regularly ride, yet is just over 4mm longer in the reach at 426mm. With a shorter stem than what I typically rock, the geo on the Ursa left me slightly more upright and definitely more comfortable over the long haul. After the dozens of moments lifting the loaded bike up and over rock steps during the hike-a-bike sections up Mount Woodson, I was especially thankful for this design.

The next day I would undoubtedly have had a sore lower back if I were riding all day with XC race geometry. As it was, I remained very comfortable and pretty relaxed the following day, being able to sit a little more upright than I do on my 29er. The longer wheelbase definitely helped as well, adding stability that allowed me to stay loose and somewhat relaxed as well on the descents and the flats when I would normally tend to tense up after the strenuous ride and hike-a-bike from the day before. Once I attached and loaded up the supplied Chumba USA branded, ZULU bikepacking bags (made by Wanderlust Gear), the Ursa really came into its own.  Immediately, I noticed how the ride felt markedly different. It was now more supple, yet it remained feeling very predictive, sturdy, and efficient. Whether they were full of commuting gear or gear for overnight trips, it was apparent that the ride had improved. Downhill braking took a little more forethought when fully loaded, as would be expected for any loaded rig. Only when loaded, was it apparent that the Chronicle 29 x 3.0 tires didn’t grip as well when braking on straight sections of hardpack trail. Only the center section of tread would make contact, but when leaning and braking, they seemed to hook up really well with the trail in most conditions. Speaking of the ZULU bikebacking bags, I found them to be high quality, easy to attach, and quick to pack up. Without having any prior experience with the bags, I attached them 1 hour before taking off on an overnight bikepacking trip and didn’t have to readjust the bags at all the whole day. The front roll, named the Sawtooth Handlebar Bag System was my favorite bag of the bag set. It had solid, yet simple attachments, more than enough capacity for most trips, and it looked really good. The multicam camouflage seems to blend the handlebar bag with the removable zippered pocket nicely and definitely gives it a cool look, but the actual function of the front pocket was phenomenal. I used it to hold arm and leg warmers, food, pump, and other items I wanted quick access to. It was very easy to access while on the bike and I ended up becoming very fond of using it instead of the pair of Rattlesnake Stem Bags which are the type of bags where I usually tend to put stuff that I want immediate access to. I used the ZULU Frame Bag to hold my tools, heavier items, and hydration bladder, along with some clothing that I wanted to have quick access to. While the frame bag blocked the water bottle cage mounts inside the frame triangle, I still had an attachment point for a water bottle cage on the bottom of the downtube. Although I am not a fan of getting trail junk thrown up on my water bottle in this location, I wanted to use a water bottle for drink mixes instead of having to thoroughly clean my hydration bladder afterwards. I utilized a method I have seen others use recently where a plastic bag is placed over the water bottle top and secured with a rubber band. This method worked really well. At times when I wanted to drink from the bottle with drink mix instead of the hydration bladder, I moved it to one of the stem bags. The ZULU Seat Bag was another great addition to this bikepacking rig. I found that it had plenty of room for me to stuff my 20F down sleeping bag into as well as a SOL lightweight tarp. On top of the seat bag, it had a shock cord that held my sandals securely during a bikepacking trip, although I lost one sandal somewhere along my commute home from work one week. The combination of the multicam bags and the very durable, desert tan colored powder coat finish on the frame gives a very unique tactical look. It continually made me wonder if the team at Chumba USA intended to give riders a feeling that the Ursa was made to execute specific, rider extraction missions in the backcountry. I like the look. It’s not flashy and depending on what you choose to wear as a rider, it doesn’t necessarily look all that tactical. After enjoying the simplicity of numerous 1 x 10 and 1 x 11 drivetrain systems so frequently in recent years, I also wondered about the 2 x 10 drivetrain that Chumba had chosen for this build. For many shorter, non-bikepacking rides, I found myself riding solely in the 36 tooth chainring and forgetting I even had a front derailleur to make use of, until I hit those crazy steep or long climbs that pushed me to realize the limits of my fitness. I figured that if I built this bike for myself, there would be no way I would use a 2 x 10 system, I would use a 1 x 10 or 1 x 11 with a wide range cassette and force myself to get stronger like I had in years past when racing single speed endurance races. When loaded up with gear for bikepacking trips however, I quickly sang the praises of a front derailleur once again. A friend and I decided to set out on an overnight bikepacking trip, each of us riding a 29-plus bike, so we attached the bags, loaded them up with our bikepacking gear, and set off. We rode a route that had many short, steep climbs that were challenging to say the least. Many had loose over hardpack sections of trail while others had sharp rock gardens. Our route had us heading up and over Mount Woodson in San Diego, one of the highest peaks around – with a brutal climb full of steep fireroad and many rocky hike-a-bike sections as well. My friend was riding a Surly Krampus with a 1 x 10 drivetrain, using a 30-tooth chainring, while I was on the Chumba Ursa with a 2 x 10 drivetrain using 26 and 36 tooth chainrings. I normally ride with a 1 x 10 drivetrain using a 32 tooth chainring that normally seems to be great for most rides. I was so very glad to be equipped with a 2 x 10 drivetrain on this ride and it was very apparent that my friend, though very fit and capable, would have preferred to be equipped with the same instead of his 1 x 10. Great drivetrain choice Chumba USA. I liked the lighter weight of the carbon MRP Rock Solid fork, especially when having to heft the rig over rocks on sections requiring us to hike-a-bike. I would love to ride this setup with a steel fork to see if there would be any increase in compliance and comfort while not giving up the efficient, predictable, and stable handling a rigid fork would provide. One aspect that didn’t get tested in this review is the rack mounts that Chumba USA has included on the Ursa frame. While I almost always like having more capabilities and not using them, rather than not have a capability and wishing it was available, I can’t say that I would regularly make use of the rack mounts. The option for the Surly Krampus fork with the Ursa frame would provide the rider with front rack mounts as well to provide for an ultimate, front and rear rack touring rig. The Krampus fork is also equipped with Anything Cage mounts on each leg and would probably be preferable over the MRP Rock Solid carbon fork because I have utilized these mounts regularly on another bike over the years. I have had rack mounts on a fork that I have used for 5 years and have intended to use a front rack from time to time, but with the bikepacking bags we have available to us now, I do not see myself ever using the rack mounts, whether front or rear, unless I was doing more of a bicycle touring style ride where I intended to travel on wider, less technical trails and had intention to carry very heavy loads.  If that was the case, I am not sure that I would be utilizing the larger plus sized tires that makes this bike so unique, but it depends upon the anticipated terrain I suppose. Although the bike wasn’t the lightest, nor the most flickable rig I have thrown a leg over, there were some flowy sections of trail that it allowed me to rail with confidence, even when loaded down. The bike went where I wanted it to go. It felt faster and more nimble than I would have expected a fully loaded bike to feel. It was probably because of the stiff frame and fork combined with the increased traction of the 3.0 wide tires, but regardless of what exactly it was, I felt in control and comfortable enough to throw it around a little – go into turns a little bit hot, and for a few brief moments, forget that I was on a loaded bike. I did catch a little bit of air on that flowy section a half dozen times or so even with loaded bikepacking bags as we descended back down Mount Woodson, which left me stoked as we made our way back home. While I would likely prefer a supple and svelte steel frame with a more compliant fork for normal, shorter weekly rides without extra bags or gear, the design that Chumba USA has developed for the Ursa is remarkable in my experience for bikepacking with loaded bags on longer rides. The Chumba Ursa is available in small, medium, and large. For the frame only option, you will be paying $1,195. Framesets run between $1,295, for the frame with a Surly Krampus steel fork, up to $1,999 for the frame with a Manitou Magnum 29-plus suspension fork.  The Ursa XT build kit starts at $3,495 with a steel fork, or $3,795 as tested for this review with the MRP Rock Solid carbon fork. Chumbausa.com