Why the Obed MMR Gravel Bike Can Fit 2.25″ MTB Tires
We are all bike geeks here at Obed. That’s the whole reason we started building bikes. Our goal has always been to design gravel bikes with the features, specs, geometry, and ride quality we want for our dream rides. Now, our dreams are getting bigger, and they require tires that are wider and knobbier than ever.
The Obed MMR represents the next evolution of Obed gravel bikes. The biggest headline is that it is the first Obed gravel bike that officially clears gravel and mountain bike tires up to 2.25” (57mm) wide. This was a spec we wanted from the beginning of the design process. Let’s dive into why increased tire clearance was essential for our latest gravel adventure bike.
Extra-Wide Gravel & MTB Tires Are Often Faster
In the world of gravel racing, tires are everything. It’s no exaggeration to say that tire choice is the single most important component for a gravel bike because it has the biggest influence on how a gravel bike performs and feels.
When extra-wide (50mm and above) gravel tires started coming to market, we got pretty excited. When racers and bikepackers started hacking their gravel bikes with XC mountain bike tires, we knew the gravel world was ready for bikes capable of going ultra-wide. So for the last couple of years, we pooled all of our energy and resources into creating an Obed gravel bike ready for the future.
Tire choice is a complicated topic. To explain why we focused so much on wide tires, let’s focus on two key tire performance characteristics: rolling resistance and puncture resistance.
If you’re a racer or just interested in maximizing your performance, a tire with low rolling resistance makes a huge difference in your speed. Fast tires reduce rolling resistance by using more supple casings that reduce hysteresis, which is the energy loss that occurs when a tire flexes as it rolls or hits bumps. This means you use fewer watts to go the same speed.
The downside to a more supple tire casing is that they’re usually thinner and easier to puncture than a tougher casing. There’s nothing slower than a flat tire, so a gravel tire needs to have enough puncture resistance to survive hitting rough or sharp stones. This often comes at the expense of suppleness.
The goal of any good gravel tire is to strike a good balance between suppleness/speed and toughness/puncture protection.
Extra-wide gravel and XC MTB tires potentially give you the best of both worlds. By increasing tire width, you increase tire volume. This has a lot of benefits (which we’ll point out below), but when it comes to performance, increased tire volume increases puncture resistance because it allows riders to run lower tire pressures. Lower tire pressures reduce casing tension, which makes a tire casing harder to puncture or cut (imagine trying to poke a pencil through a loose piece of paper versus a piece of paper pulled tight). Because they work at lower pressures, an extra-wide tire allows you to also get away with using a more supple (and thus faster rolling) tire casing than you can with a narrower tire.
Bike geeks who follow independent tire testers like bicyclerollingresistance.com noticed this years ago. In some cases, 2.2” - 2.25" XC mountain bike tires have actually tested faster than narrower gravel-specific counterparts. That’s why we’ve seen a surge of gravel racers stuffing the largest tires they can fit in their frames.
Through testing and experience, it’s become increasingly clear to us and gravel riders around the world that extra-wide tires offer the best performance for most gravel riding and racing conditions. In general, the rougher the terrain or course gets, the faster a wide tire will be. As a result, ample tire clearance has become essential to modern gravel bike design.
More Comfort, Traction, and Confidence
Besides more speed and puncture protection, wide tires have plenty of other benefits when riding off-road, too.
Because they provide more tire volume and work at lower tire pressures, extra-wide tires are more comfortable, provide more traction, and increase confidence on rough terrain. This is great for people who are taking on endurance gravel events, bikepacking, or riding backcountry roads and singletrack trails.
Even if your local terrain isn’t an off-road gnar-fest, comfort, traction, and confidence are all good things to have. More comfort lets you ride longer and more often. More traction increases your safety margin when cornering and braking on loose surfaces. More confidence makes it easier for riders of any level to explore new terrain and enjoy the riding experience in new places.
When Narrower Tires Are Still the Right Choice
Despite all the hype around ultra-wide tires on gravel bikes, we should be clear that going extra-wide isn’t the best choice for every riding situation.
If you’ve experimented with 50+ mm gravel tires or 2.2” MTB tires on your gravel bike, then you’ve likely noticed that they do feel a bit sluggish on pavement. While extra-wide and high-volume tires run at lower tire pressures feel amazing over the chatter, bumps, and vibration you get on rough gravel roads, they can feel heavy, inefficient, bouncy, and "squirmy" on smoother and more consistent surfaces.
If you’re riding a lot of pavement or hard-packed dirt roads, then tires that are slighter narrower might be a better option. Narrower gravel tires at higher tire pressures will be lighter, feel more efficient, and corner better when they suit the surface, and even be a bit more aerodynamic too. Ultimately, you’ll need to do some research and experimentation to figure out what the ideal tire width is for your riding needs. In some cases, a narrower gravel tire in the 40-45mm range might be perfect for your terrain or riding goals.
It’s important to keep in mind that the extra-wide tire trend is largely being driven by riders taking on ultra-rough gravel events—for example, UNBOUND Gravel and the Big Sugar Classic in the US. These courses are notoriously rough, and ultra-wide tires provide a significant performance, comfort, and traction advantage. If the gravel you ride regularly doesn’t feature sharp flint rock or baseball-sized chunder (e.g., SBT GRVL or Sea Otter Gravel), then maybe you don’t need to worry about using the widest tire possible.
Our Dream Adventure Bike: Designing the Obed MMR
When designing a gravel bike to do it all, it’s important to remember that it’s easy to use a narrower tire on a frame with ample clearance, but it’s impossible to squeeze a wider tire into a frame with limited clearance. That’s why extracting as much tire clearance as possible on the MMR was our top priority. It gives you the most options!
This is harder than it might seem. There are a lot of parts of the bike fighting for space, especially at the rear end. We had to figure out how to also make space for the crank arms and chainring(s), without compromising the Q-factor or chainline of a standard gravel crankset. We also wanted to maintain a short chainstay length for optimal handling. Most importantly, we didn’t want to compromise on stiffness, compliance, or ride quality. This meant avoiding solutions other brands have employed, like thin carbon plates or extremely elevated or dropped chainstays to increase space.
This is a tough (but fun!) puzzle to figure out, and it required a lot of engineering, prototyping, and testing. Fortunately, our lead engineer, Brad DeVaney, is one of the most talented and experienced in the industry, and we work with some of the best carbon factories in the world to design and build our frames. After what felt like an eternity, we finally arrived at the bike we all had dreamed of: the MMR.
Not only did our final MMR test mules ride amazingly well and feel bombproof, but they also provided ample clearance for 2.25” (57mm) tires, plus some clever features like downtube storage and suspension-corrected geometry. We named it “MMR” for the rough minimum maintenance roads we expect to encounter, now that we've unleashed the most capable gravel bike we’ve ever created.
The MMR truly is our ultimate do-it-all gravel adventure bike. It's built to handle a high-octane gravel race, a long cross-country bikepacking tour, and everything in between. And the MMR is only the beginning. We plan to use everything we’ve learned building our latest adventure bike to bring more dream bikes to life. So stay tuned!