650b Vs 700c Wheels for Gravel Bikes: Which is Best?

For years, 700c has been the default wheel size for gravel bikes, touring bikes, mountain bikes, and adventure bikes. Recently, there has been a resurgence in the popularity of a smaller wheel size called 650b. Many manufacturers are introducing bikes designed around 650b wheels. Some cyclists are swapping their 700c wheels for 650b. Many gravel frames can accommodate both wheel sizes. After some extensive research and testing, I’ve put together this list of pros and cons of 650b vs 700c wheels to help you decide which wheel size is best for your riding style.

In this guide, we’ll cover traction, wheel strength, ride quality, maneuverability, weight, cost, tire options, and more. I’ll also talk about a few compatibility issues to consider when converting from 700c to 650b. I’ve ridden both wheel sizes pretty extensively over the past few years while mountain biking and bikepacking. In this guide, I’ll share my experience.

What is the Difference Between 650b and 700c Wheels?

The difference between 650b and 700c is the rim diameter. 650b are smaller rims.

650b wheels measure 584 mm in diameter. 700c wheels measure 622 mm in diameter. 650B wheels are 38mm (about 1.5”) smaller than 700c.

650b wheels are sometimes referred to as 27.5 inch wheels in mountain biking. Both are exactly the same. The terms are interchangeable.

700c wheels are sometimes called 29er or 28 inch. All three have the same outside diameter of 622 mm. 700c usually refers to road bike wheels with narrow rims. The term 29er is used to refer to 700c mountain bike wheels. These come with wider rims that are made to accommodate off-road tires. 28 inch is a vintage term that is still used in some parts of the world.

For whatever reason, the bike industry decided to measure road bike components in millimeters and off-road components in inches.

Both 650b and 700c come from a French sizing system. The number represents the approximate diameter of the wheel and tire in millimeters. The letter represents the width.

Why 650b Gravel Wheels? Tire Volume and Diameter

The main reason riders choose 650b gravel wheels over 700c is the ability to run wider tire sizes. Running smaller rims allows you to mount larger tires on the same frame. This is possible because the seat stays and chainstays and the fork blades widen toward the hubs. Smaller wheels offer more tire clearance because the tires sit at a wider part of the frame. This gives you wider tire size options.

For example, most gravel, touring, and cyclocross bike frames limit the maximum tire width to 700c x 40-45 mm. By swapping the wheels to 650b you can often fit 47-53 mm wide tires (up to about 2.1”). An extra 5 mm of tire width makes a major difference in terms of comfort and off-road handling.

You may be thinking, won’t running smaller wheels change the bike’s geometry and gearing? The answer is yes but not as much as you might think.

650b wheels are only 38 mm (about 1.5 inches) smaller in diameter than 700c wheels. That means the bike will sit 19 mm (.75 inch) lower assuming you run tires with the same height.

However, you will probably run larger tires when you switch to 650b. The geometry remains more or less the same because the larger tires make up for most of the difference in wheel size. In other words, a 700c rim with a skinnier tire and a 650b wheel with a bigger tire will have around the same outer diameter including the tire.

More specifically, many riders find that 650b wheels fitted with 42-47 mm wide tires measure about the same in diameter as 700c wheels fitted with 28-30 mm wide tires.

Of course, in practice, there is usually a slight difference in total diameter. For example, 700c x 40 mm tires measure about 2 cm (.75″) larger than 650b x 47 mm tires.

Because the wheels have a similar diameter when including the tires, the bottom bracket height, frame geometry, and gearing also stay about the same. With proper tire selection, there are very few issues, compatibility wise. I’ll talk more in-depth about compatibility later on.

650b Vs 700c Wheels for Gravel Bikes

Both 650b and 700c are great wheel size choices for gravel bikes, mountain bikes, road bikes, and touring bikes. In this section, I list all of the pros and cons of each wheel size to help you make an informed decision.

650b Wheels Pros

• 650b wheels offer better traction/grip- Wider, higher volume 650b tires make a larger contact patch with the ground than narrow 700c tires. This increases traction. This is important when riding on potentially slippery surfaces like loose dirt and gravel as well as snow and ice. Increased traction allows you to accelerate, corner, and brake harder without worrying about your tires slipping out from under you. You can also let some air out and run 650b tires at a lower pressure. This makes the tire softer so even more tread contacts the ground, which gives you even more traction when you need it.
• 650b wheels are stronger- 650b wheels are smaller in diameter than 700c wheels so they use shorter spokes. This makes the wheels structurally stronger. The small wheels can take more of a beating without breaking spokes, cracking, or flexing. This comes in handy while gravel riding or mountain biking. 650B wheels can also handle heavier loads without failing. This is important for bicycle tourists who carry a full load or heavier riders. Spoke count also plays an important role in wheel strength.
• 650b wheels offer a smoother and more comfortable ride- High volume tires are generally run at lower tire pressures. This makes them softer. Softer tires absorb shocks and vibrations from the road. They give you a bit of cushioning so the ride isn’t quite so harsh. This reduces fatigue while riding on rough surfaces.
• Increased maneuverability- The smaller size of the wheels makes the steering faster and more responsive. This comes in handy while navigating technical terrain or single track. Smaller 650b wheels also make the bike easier to manhandle. The bike is just a bit less cumbersome.
• Lower gearing- All else being equal, the smaller wheel circumference of 650b wheels effectively lowers your gearing across the gear range. You get an extra-low gear for climbing when you swap from 700c to 650b. This really comes in handy while touring fully loaded. If you don’t want lower gearing, you can correct this by installing a chainring with a couple more teeth or a cassette with slightly higher gearing.
• Better geometry for shorter riders- On small-framed bikes, 650b wheels often fit the frame geometry better than 700c. They create a more comfortable and natural riding position. The smaller wheels also slightly lower the top tube to decrease the standover height. This makes the bike easier to mount and dismount. The height cutoff is around 5’5” (165 cm). 700c wheels are just too large for small frames. Some manufacturers don’t even offer 700c wheels on their small bikes.
• You can run 650b tires at lower air pressure- This is possible because you don’t have to worry about pinch flats as much with higher volume tires. The benefit of riding at a lower is increased traction and a more comfortable ride. Low pressure also gives the bike some flotation when riding on a loose surface. You can often run wide tires as low as 22 psi.
• Faster acceleration- Because 650b wheels are lighter and more aerodynamic than 700c wheels, you can spin them up to speed faster. This comes in handy if you do a lot of stop-and-go city riding. It doesn’t take quite as long to get to speed after a stop. It takes less energy as well. For this reason, 650b wheels are a great choice for commuting. 650B wheels also accelerate faster when coasting down hills.
• Lighter wheel- The smaller 650b wheels use less material than larger 700c wheels. This reduces the weight of your bike. Of course, your tire selection also plays a major role. Wide off-road tires weigh more than narrow road tires.
• Swapping to 650b wheels can make your bike multi-use- Some modern 700c road bikes have a max tire width of just 25mm. There isn’t even room to install fenders. By swapping your wheels out for 650b, you increased your tire clearance to 35-38mm. There is also room for fenders. Now you can ride your road bike on gravel roads and in the rain. If the bike uses disc brakes, you can easily swap out your wheels to suit the riding conditions. On a dry day, you can install your 700c wheels. During the winter, swap them out for your 650b wheels. You could even mount studded snow tires on one set of wheels. It’s like having 2 bikes in one.
• Toe overlap is less of an issue with 650b wheels- Smaller wheels are less likely to hit your toes when you turn the handlebars. This is particularly true for small-framed bikes.
• You can fit larger bikepacking bags– If you’re touring or bikepacking with your bike, luggage capacity is important. Smaller wheels allow more clearance for seat packs and handlebar bags. The bags are less likely to hit the tires. The frame triangle may also be larger. This allows you to fit a larger frame bag. For more info on luggage, check out my bikepacking bag vs panniers guide.
• Easier to pack the bike for transport or shipping- If you plan to fly with your bike or transport it in your car, 650b wheels make it slightly smaller and easier to pack. A couple of inches can make a big difference when you’re trying to pack up your bike.

650b Wheel Cons

• 650b wheels don’t maintain speed as well as larger 700c wheels, making them less efficient- The smaller 650b wheels lose momentum faster when you stop pedaling. There are a couple of potential reasons for this. First, smaller wheels have more rolling resistance because the tires deform more at the contact patch. Because smaller wheels must make more rotations to carry you the same distance as bigger wheels, there is more frictional loss in the bearings and chain. This makes the bike a little bit less efficient and causes you to ride at a slightly slower average speed. You have to pedal more to cover the same amount of ground. You can’t coast quite as far when you stop pedaling. On a long tour, you’ll end up spending more time in the saddle and burning more energy.
• 650b wheels don’t roll over obstacles as well, resulting in a rougher ride- Smaller wheels have a harder time rolling over obstacles like potholes, rocks, roots, branches, etc. due to the smaller diameter. For example, when you hit a pothole, a 650b wheel can fall in further because it’s smaller. When you roll over a large rock, the smaller diameter wheel doesn’t have as much leverage to lift itself over so it can get hung up. The angle of attack is higher. This makes the ride a bit rougher and less comfortable. You’ll feel each bump more. It also makes riding technical terrain more challenging because the smaller wheels can get hung up more easily. They don’t glide over like larger wheels can.
• 650b spare parts are harder to find in the developing world- Even though 650b is growing in popularity, you’ll have trouble finding spares in much of the world. Bike shops in developing countries usually don’t carry 650b rims, tires, or inner tube