For years, 700c has been the default wheel size for gravel bikes, touring bikes, mountain bikes, and cyclocross bikes. Recently, there has been a resurgence in the popularity of an old French wheel size called 650b. Many manufacturers are introducing bikes designed around 650b wheels. Some cyclists are swapping their 700c wheels for 650b. This guide lists the pros and cons of 650b vs 700c wheels to help you decide which size is best for your style of riding. I’ll also talk about a few compatibility issues to consider when converting from 700c to 650b.
What is the Difference Between 650b and 700c Wheels?
The difference between 650b and 700c is the diameter of the 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 diameter of 622 mm. 700c usually refers to road bike wheels with narrow rims. The term 29er is used for 700c wheels 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 cycling industry decided to measure road bike components in millimeters and off-road components in inches.
Why 650b? A Note About 650b and 700c Tire Volume and Diameter
The main reason riders choose 650b wheels over 700c is the ability to run wider, higher volume tires. Running smaller wheels allows you to mount larger tires on the same frame because the seat stays and chainstays, as well as the fork blades, widen as they head toward the hubs. Smaller wheels offer more tire clearance because the tires sit at a wider part of the frame.
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 skinny road tire and a 650b wheel with a big off-road tire has around the same total 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 tire measure about 2 cm (.75″) larger than 650b x 47 mm tires.
Because the total diameter including the tire stays about the same, 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
Both 650b and 700c are great wheel size choices for gravel bikes, mountain 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. We’ll compare traction, strength, comfort, maneuverability, frame geometry, and much more.
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 air 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 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.
- 650b wheels offer a smoother and more comfortable ride- High volume tires are generally run at lower air pressure. 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 terrain.
- Increased maneuverability- Smaller wheels make the steering faster and more responsive. This comes in handy while navigating technical terrain or tight trails. 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 loose surfaces. 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- 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. 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 larger wheels, there is more frictional loss in the bearings and chain. This makes the bike a 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 wheel doesn’t have as much leverage to lift itself over so it can get hung up. 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 tubes. If you destroy a wheel and need a spare while you’re cycling from Cairo to Cape Town, you may have to fly to another country to buy what you need or wait weeks and pay customs fees to have parts shipped in. If you’re touring in the developing world and you’re concerned about parts availability in your destination, 650b is probably the worst wheel size. Even in the developing world, you can have trouble finding spares in a small town bike shop or department store. On the bright side, globalization is making it easier to get spares, wherever you are.
- Fewer tire options- 650b wheels are nowhere near as popular as 700c or 29er. Because there is less demand, manufacturers offer fewer tire options. This can be a bit limiting. Some popular tires don’t come in 650b versions. Most 650b tires tend to be on the wider side. Hopefully, this will change in the future as this wheel size becomes more common.
- The bottom bracket height, gearing, and geometry change when you switch to 650b- When you swap out 700c wheels for 650b, the wheel diameter changes in most cases. Almost always, the 650b wheels are smaller, even if you’re running big tires. This lowers the bottom bracket height about .5-1 inch in most cases. This increases the likelihood of pedal strike. Smaller wheels also lower the gearing. If your gearing was already low, it could be too low when you switch to 650b. The smaller wheel also changes the bike’s steering geometry.
- Frame options are more limited- If you walk into a bike shop today, you’ll see way more 700c bikes than 650b bikes. 700c is still the standard for road bikes, gravel bikes, and touring bikes. Most mountain bikes are 29ers which is the same diameter with wider rims. You’ll probably only spot a few 650b touring bikes and gravel bikes on the showroom floor. Having said this, 650b is growing in popularity quickly. Another thing to keep in mind is that most (but not all) 700c bikes are compatible with 650b if you want to buy new wheels.
- Switching to 650b changes the steering geometry, which can make the bike feel twitchy- Wheel diameter affects your bike’s trail. Trail is the distance between where your steering axes touches the ground and where your front tire touches the ground. Switching to smaller 650b wheels decreases trail by around 3-6 mm depending on the tires you’re running and the frame and fork. A lower trail number makes the bike steer quicker. In some cases, the steering can feel twitchy. This may make you feel unstable because the bike becomes harder to control. It reacts faster when you turn the handlebars. For example, it may be harder to avoid a rut or rock in the trail. Usually, this twitchy feeling goes away after you grow accustomed to the bike. You may have to ride for a few hours to get used to your new wheel size. For more info, check out this great guide about trail from Bike Insights.
- 700c wheels have less rolling resistance, making them more efficient- There are several reasons for this. First, 700c wheels don’t lose as much speed when they hit a bump or obstacle because they roll over more easily. Next, the hubs and chain introduce less friction into the system because the larger wheel doesn’t need to revolve as quickly. The more narrow tires tend not to deform as much at the contact patch as well. Due to their mass, 700c also have more inertia so they gather more momentum. Once you get your wheels up to speed, they want to keep rolling. When you stop pedaling, you won’t slow down as quickly. On flat sections, it takes less energy to maintain your speed. This increases efficiency. You can ride further using the same amount of energy.
- 700c wheels have better rollover capability- Because 700c wheels have a larger circumference, they can more easily roll over potholes, bumps, branches, roots, and other obstacles on the road or trail. When you hit a hole, a larger diameter wheel can’t fall as far into the hole. It just rolls over. Larger wheels have more leverage to pull themselves over bumps as well. This allows you to navigate technical terrain more easily. You can glide over most obstacles without losing speed or getting shaken around too much.
- Spare 700c parts are easier to find- 700c wheels have been the standard on road bikes for decades. In the developed world, spare tires, tubes, and rims are available at every bike shop. Even though 26 inch parts are still the most common in much of the developing world, 700c is catching up. In most countries, you can find spares without an issue. You may have to travel to a capital city in some cases. 650b spare parts, on the other hand, are harder to find. If you’re touring in a remote region and your rim cracks, you might not be able to find a new one. 650b has only been popular for a few years. Small bike shops might not stock the parts that you need. For this reason, 700c is the better choice for touring and bikepacking.
- More tire options- Because 700c wheels are so common, bike tire manufacturers offer a wide range of tire options. You can find pretty much every style of tire in a 700c version from 18 mm road slicks to 3+ inch mountain bike tires. Some popular 700c tires are not offered in a 650b version yet. One thing to remember is that wider 700c tires are usually marketed as 29er. They have the same diameter.
- 700c wheels allow you to cover more distance in less time- Because the wheels have less rolling resistance once they are at speed, it takes less energy to keep them rolling. This allows you to cruise along at a higher average speed with 700c wheels. This is great for long-distance touring and riding on-road.
- More frame options- Most modern frames are designed for 700c wheels these days. There are almost too many frame options to choose from. Most 700c frames are also compatible with 650b wheels but you’ll want to make sure before you buy if you plan to switch. More on that later.
- Smoother ride- Assuming you’re using the same width of tires, 700c wheels offer a better ride quality than 650b. The larger circumference wheels glide over obstacles without getting hung up.
- More stable- Some riders find that larger wheels increase stability because they steer a bit slower. You don’t get that twitchy feeling that you get with smaller wheels. Larger wheels also increase trail (the distance between where the steering axis and front wheel touch the ground) which makes the bike feel more stable.
700c Wheel Cons
- You are limited to more narrow tires- The frame clearance limits your maximum tire width and height. Because 700c wheels are larger, there is less clearance for high volume tires. This is due to the way bikes are built. The fork arms and the seat and chainstays become more narrow as they move away from the hubs. On many gravel and touring frames, the max tire width you can fit is 42 mm. Less if you use fenders. With 650b wheels, you can often fit tires up to 47 mm on the same frame. The extra 5 mm makes a big difference when riding off-road. Of course, there are frames available that are designed for 3+ inch 29er tires if you want to stick with the 700c size.
- Less traction- Narrow, low volume tires make a smaller contact patch with the ground. While riding on loose or slippery surfaces like gravel or ice, you won’t get as much grip as you would with wider, higher volume tires. This means you can’t brake, corner, or accelerate quite as hard without your tires trying to slip out from under you. You also can’t run narrow tires at as low of air pressure as wide tires. Firmer tires get less traction.
- 700c wheels are weaker- Because 700c wheels are larger in diameter and use longer spokes than 650b wheels, they are structurally weaker. Longer spokes can bend and break more easily. Larger rims can twist under stress. Assuming all else is equal, 700c wheels can’t handle quite as heavy of loads as 650b without cracking or flexing. You will probably experience more broken spokes as well. One way to slightly increase wheel strength is to use Presta valves instead of Schrader valves. Of course, wheels that were properly built with quality components are plenty strong no matter the size.
- Slower acceleration- Because 700c wheels are larger and heavier than 650b wheels, it takes more energy to get them rolling. The taller wheels also create more air resistance. You can’t spin them up quite as fast when you start from a stop. This slows you down if you do a lot of stop-and-go city riding. When coasting down a hill, it takes more time to get up to speed.
- Less comfortable ride- Hard, narrow 700c tires don’t absorb shocks and vibrations as well as softer high volume 650b tires. This can make the ride feel a bit rougher. Bumps and vibrations transmit through the wheels into your hands and body. Of course, this entirely depends on the tires you’re using and the pressure you’re running them at.
- Heavier- The larger 700c wheels and tires take more materials to build. This adds weight to your bike.
- 700c wheels are less maneuverable- Large wheels steer slower than smaller wheels. It may be slightly harder to navigate tight technical terrain with 700c wheels.
- 700c wheels are too big for some riders- For smaller riders, big 700c tires make the bike feel too big and cumbersome. People under 5’6” might feel more comfortable riding smaller 650b wheels with big tires. Some manufacturers don’t even offer 700c wheels on their smaller frames because they throw off the frame geometry.
- Toe overlap- With some frame geometries, your toe can rub against the front wheel when making a turn. This issue mostly affects 700c bikes with small frames.
- Higher gearing– Assuming you’re using the same chainring and cassette, a bike with 700c wheels will have higher gearing across the range than a bike with 650b wheels. The larger circumference wheels increase the gearing. This makes it harder to climb steep hills or ride fully loaded. If your gearing is too high, the solution is to install a smaller chainring or rear cog.
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Compatibility Issues When Converting Your Bike From 700c to 650b
Most 700c or 29er gravel, touring, and mountain bikes can be converted to 650b without any issues. In fact, some manufacturers, like Salsa and Kona, even advertise this option on their marketing material. They design some of their frames to be dual wheel size capable. The problem is that not all frames offer this flexibility.
700c x 37-40mm tires are the most common for gravel riding, bicycle touring, and cyclocross. When compared to a 650b x 47mm wide tire, there will be a slight difference in diameter. It turns out that the difference will be around 1 inch (2.54 cm) give or take with most tires. This means that the bike will sit around 1/2 inch lower.
The difference in wheel diameter slightly changes the bike’s steering geometry, bottom bracket height, and gearing. Most riders will feel the difference but will get used to it in after riding a few miles. The problem is that, even though the difference is minimal, there are a few compatibility issues you can run into. You’ll want to check the following before committing.
Rim Brake Reach
The main issue that you’ll run into when switching from 700c to 650b is brake reach if you’re using rim brakes. If you’re using disc brakes, you won’t face this issue and you can skip this section.
Because the rim radius of 650b wheels is 19 mm smaller than 700c wheels, the brakes have to reach that much further to grip the rims. They also need to reach around the larger tires that you’re likely to install. This means you will need to replace your rim brake calipers with a pair with a longer reach. The exact reach you’ll need depends on your frame and fork. To help you measure brake reach, check out this guide from Sheldon Brown.
Basically, you’ll need about 19 mm more reach than your current brake calipers. Usually, u-brakes and centerpull calipers have long enough reach. It is also possible to build a bracket to move your existing brake calipers if you’re comfortable with DIY.
Bottom Bracket Height
Another issue you may encounter when converting from 700c to 650b the bottom bracket being too low. Assuming the tire height is the same, your bottom bracket will be 19 mm lower after you swap out your wheels. Your 650b tires will probably be a bit taller and more voluminous so the difference may be a bit less than this.
If your bottom bracket is too low, you’ll experience pedal strike while leaning into a turn or riding over a bump. This usually isn’t a problem on modern bikes because bottom brakets are plenty high.
Having said this, you should take some measurements before making the switch. For reference, the average bottom bracket height for mountain bikes is around 335 mm. Touring bike bottom brackets height is usually around 270mm.
If you find that your bottom bracket will be lower than 260 mm after converting to 650b, you may want to reconsider. Alternatively, you could install some shorter cranks to reduce the likelihood of pedal strike.
Some road bikes have seat and chainstays or forks that are too narrow to accommodate wider 650b tires. This usually isn’t a problem because the stays and fork arms widen as they approach the hubs. The smaller diameter 650b tires have more space because they sit slightly closer to the hubs. Having said this, tt’s worth checking if your bike has particularly small tire clearance, like some road bikes.
The minimum distance from your tire and bike frame should be about 3 mm. Ideally a bit more. Any less than that and you risk tire rub if the tire deforms or your rim goes out of true. Your wheels can also get clogged up by mud if you don’t have enough clearance. Before converting to 650b, you’ll want to check for clearance at the fork crown, brake calipers, seat stays, chainstays, and fenders (if you’re using them).
You can measure tire clearance with a pair of calipers. To help you out, check out this guide to tire clearance from renehersecycles.com.
A Note About Bicycle Tires
The major differences between 700c and 650b wheel performance are determined by the tires that you choose. If you were to run the same tires and tire pressure on both wheel sizes, the ride quality and traction will be about the same. The only difference will be in the handling, gearing, and geometry changes caused by the different wheel diameter. These are mostly negative changes.
The main benefit that 650b wheels offer is the ability to run wider, higher volume tires at lower air pressure. As mentioned above, these offer better traction and better bump absorption. Some cyclists run their tire pressure as low as 22 psi to achieve greater traction.
Before converting between 700c and 650b, consider measuring the diameter of the tires you plan to use. This will give you an idea of how the geometry of the bike will change.
Another Popular Wheel Size to Consider: 26 Inch
26 inch wheels were the standard mountain bike wheel size for decades. Over the past 15 years or so, they have fallen out of favor as cyclists made the switch to 29er or 700c wheels for off-road riding.
26” wheels measure 559 mm in diameter. This is 63 mm (2.5”) smaller in diameter than a 700c wheel and 25 mm (1”) smaller than a 650b wheel.
The main benefit of that 26 inch wheels offer over 700c and 650b is parts availability. Because 26” was the standard for so long, spare tubes, tires, rims, etc are easy to find pretty much everywhere on earth. This is particularly true in the developing world. For this reason, many expedition bicycle tourists still use 26” wheels.
In addition, 26” wheels are stronger due to the smaller diameter and shorter spoke length. Because they are smaller, they are also lighter due to the fact that they take less metal to make. Parts are generally cheaper as well.
There are a few major drawbacks. 26” wheels don’t roll over obstacles as well as larger 700c or 650b wheels because they have a smaller circumference. They also don’t maintain speed as well as larger wheels because they have more rolling resistance. They lose momentum faster when you stop pedaling. There are also fewer tire and frame options because 26” has fallen out of favor
On some frames it is possible to convert from 700c to 26” or vice versa. If you’re trying to size up or down, you’d probably be better off going with 650b wheels, which fall between the two in terms of size. The size difference between 700c and 26” is too great for most frames. You probably could switch from 650b to 26” if you wanted to.
For more info, check out my 26 Inch Vs 700c Wheel Pros and Cons List.
A Bit of History of 650b and 700c
Over the years, a wide range of wheel sizes have been used in cycling. As the sport evolved, different countries developed their own sizing systems. Both 700c and 650b are french sizes. The number indicates the approximate diameter of the wheel, including the tire. The letter indicates the width. Tires have either no letter (the most narrow), or an A, B, or C (the widest).
700c won out and became the most popular road bike wheel size. The 650b size was common in France during the early 20th century but waned in popularity as 26” mountain bikes took over during the later part of the century.
In 2007, the first 650b mountain bike hit the scene. Now the size is making a comeback in bicycle touring, mountain biking, bikepacking, and gravel riding. If you walk around a modern bike shop, you’ll see at least a few 650b bikes. Popularity seems to be growing.
Final Thoughts about 650b vs 700c Bike Wheels
When it comes to choosing a wheel size for your bike, you’ll want to consider what kind of surfaces you ride, where in the world you ride, your bike frame, as well as your height. If you mostly ride on gravel roads, 650b is an excellent choice. Running tires that measure just 5 mm wider can really improve grip and increase ride quality. If you stick to pavement most of the time, you’ll probably be better off with 700c wheels for their superior rollover capability and efficiency.
Personally, I like the feel of smaller wheels. Even though I’m a taller rider, smaller wheels make the bike feel a bit more manageable and less cumbersome. Having said that, I prefer 700c wheels for touring due to the increased parts availability around the world as well as the efficiency. Whichever wheel size you choose, I hope this guide has help make the decision a little bit easier.
Where do you stand on the 650b vs 700c debate? Have you converted your bike? Share your tips and experience in the comments below!
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