Updated: Aug 1
With the invention of the gravel bike, we saw a lot of new technology come to cycling. We had different sized wheels, flared and new handlebar designs, and even new suspension systems to take the edge off the gravel roads. It's an exciting time for cycling, but it can feel a bit overwhelming when picking your bike.
A question I get asked all the time is about wheel sizes. The main question is, what wheel size is better, 650b or 700c? In this article, I want to tell you everything you need to know about these two different sizes, so you know what to choose when it comes to picking that new bike or wheelset.
Both 650b and 700c wheels work better for different situations and have advantages and disadvantages when it comes to your riding. The best way to explain each wheel size is to tell you about each and then where they are best suited.
650b is the smaller-sized wheel of the two. It shares pretty much the same size as 27.5 mountain bike tires. It's one of the most popular choices of mountain bike riders, and only in the past decade has become big in the gravel cycling world. What makes it good for your gravel bike though?
When it comes to gravel wheels, you want a strong wheel that will be capable of all riding, including mountain biking. 650b wheels are very strong because of the shorter spokes and larger tires. They can take a huge hit and absorb it all.
The 650b wheel being smaller makes it much better at accelerating compared to the 700c wheel. This is because it is slightly lighter, smaller, and takes less effort to spin up to higher speeds. This makes it an ideal wheelset when it comes to short courses with a lot of short sharp corners or loose terrain.
The 650b wheels being smaller makes them much easier to throw around and much more agile. This makes them excellent wheels for technical courses and rides where you need control rather than speed. Being able to turn faster does make a huge difference on trails and makes the bike feel very nimble.
Gravel bikes typically come with larger tires to suit gravel riding off-road. Using 650b wheels, you can actually fit larger tires in a frame because of the smaller wheel size. You will see a lot of gravel bikes with 650b wheel on tires as large as 50c and even some using 27.5" mountain bike tires, which is huge tire width. This gives you a huge amount of choice when it comes to off-road tires and also gives the bike amazing ability when it comes to off-road riding.
Lower tire pressure
When you use 650b wheels, you normally use larger tires. Using larger tires means you can run lower pressure in your tires. This means you get extra comfort and grip from the wheels, but your rolling resistance does increase.
Although the 650b wheel provided amazing acceleration, it does come at the price of top speed. The smaller wheels make it harder to hold the wheel at a higher speed than a 700c wheel. This is very noticeable when it comes to long descents as you can easily get out geared and have to work to stay quick.
Although you have a huge amount of options when it comes to smaller off-road tires, because of all the mountain bike tires, you are hugely limited on-road tires. The 650b wheels are wider and because of this, riding road tires that sit well is more challenging. Typically the smallest you can go is around 38c, which does give you more rolling resistance on the road.
Using smaller wheels does change the bike trail and can make it feel very twitchy compared to a bike with 700c wheels. A lot of gravel bikes can work with both, but it's very noticeable when you change down a wheel size.
700c wheels are the larger wheel size of our two contenders and are the wheel sizes you will typically see on road bikes, gravel bikes, and even cyclocross bikes. It's pretty much identical in diameter to the mountain bike's 29" wheelset. It's probably the most common size you will find on a gravel bike frame, but is it better?
One of the best things about a 700c wheel is its ability to hold a top speed. With the wheel being bigger, it takes less effort to hold at a higher speed, and this makes the bike much faster when working at high speeds. You will also find for the same gearing, you will be able to descend at faster speeds.
When you buy a gravel bike with 700c wheels, you will find the tires are normally thinner and roughly around 35c-40c. This is because they need to be smaller to fit inside a frame with adequate clearance. You will find that using smaller tires gives less surface area to be caught by the wind, making them slightly more aerodynamic.
700c wheels have a huge amount of options when it comes to tire choices. You have all the options of the 29" mountain bike tires, the options of all the road tires at 700c, and also all the options of 700c gravel tires. It makes the bike much more adaptable to all different kinds of riding and means you just have much more choice.
Rim Depth Options
When it comes to 700c gravel wheels, we are now seeing many new wheels hit the market with aerodynamic profiles. Unlike 650b wheels, we are seeing 40mm and 50mm deep options now on gravel wheels, and this can hugely improve speed on flat courses and also massively improve the strength of a wheel.
Roll Over Ability
Although smaller wheels are more agile, larger wheels like 700c have a much better ability at rolling over objects. When it comes to objects like tree roots and larger rocks, the 700c wheel can tackle it much better than a smaller 650b wheel which would be better at going around.
Lower Rolling Resistance
Using a smaller diameter tire compared to a high volume tire, you typically get less rolling resistance. Less rolling resistance makes it easier to go faster and the work much easier. Wider tires do offer better grip for technical terrain but do make you slower on the roads.
Using a larger wheel that can weigh more does make your acceleration slower. It's harder to get the wheel moving, but it is easier to maintain speed when it's rolling.
The larger the wheel, the less agile it is going to be. On very technical terrain, you will find it harder to throw the front wheel around so much. If you are planning on very technical gravel riding and lots of challenging trails with rough terrain, the 650b could be a better option.
Less Tire Clearance
With 700c wheels being larger, they do sit deeper into the same frame, so you find that you have to use smaller tires compared to 650b wheels. On a lot of frames, the max tire width can typically be 40c on a 700c wheel or 50c on a 650b wheel.
Which is best for you?
Picking the right wheel size for you comes down to multiple factors, which we could speak about for hours, but I personally think it comes down to one single thing, and that's the riding that you plan to do.
If you plan to do lots of technical off-road riding, then 650b will be the better wheelset for you. It can use larger tires. It is much more agile and much stronger. Alongside all this, you get better acceleration which really helps up those short loose terrain climbs and when coming out of very technical sections. 650b wheels are great for gravel riders who want to go on mountain bike trails too.
Road and Light Gravel
If you're getting a gravel bike for mainly road riding and just the occasional light gravel ride, then 700c wheels are the best choice for you. They are better at higher speeds, wear smaller tires, and you have many more options for aerodynamic rim profiles. 700c wheels are great for gravel riders who want to be on the road a lot as well.
Whatever wheels you pick, you're going to be able to do all different types of riding. Getting the right wheel size for you will make it easier and give you much more ability on the bike. Modern gravel bikes will give you the option for both wheel sizes, and sometimes you are able to pick when you first buy. Thanks for reading!