What Is A 700c Wheel? Everything You Need To Know
A quick look at your bike’s geometry specs will reveal enough numbers to make your head spin. The humble wheel is no exception.
Of all your bike’s components, the wheels and tires may be the most important. They are, after all, the link between you and the tarmac.
Whether you’ve just bought your first bike, or have been riding for ages, you may be wondering: What is 700c wheel size?
In this article, we’ll be getting to grips with:
- What Is A 700c Wheel?
- A History Of “C”
- Is 700c The Same As 29 Inch Mountain Bike Wheels?
- Are 700c Wheels Standard For Mountain Bikes Too?
- How Did 29 Inch Wheels Get So Popular?
- Putting It All Together
Ready for the lowdown on 700c wheel size?
Let’s dive in!
What Is A 700c Wheel?
700c wheels are the modern industry standard size for road bikes.
“700” refers to the approximate outer diameter of the tire (in millimeters) when mounted on the wheel. The “c” means almost nothing anymore – but we’ll get to that later.
“700” is actually a bit of a misnomer when discussing wheels. This is because the more accurate term for a 700c wheel is 622 mm.
622 mm is your bead seat diameter (BSD for short), which is the diameter of the wheel from the shelf of the rim that your tire seats into.
Why is 622 mm the more accurate measurement?
Well, that would be because it never changes. The International Organization for Standardization (ISO) maintains various standards across a variety of industries for the purpose of creating internationally recognized standards.
ISO stepped into the cycling world and maintains standard 5775, which says that for 700c wheels, the BSD must be 622 mm.
“700”, on the other hand, is just a rough estimate of the outer diameter of a tire fitted to a 622 mm rim. It can be affected by many factors, including tire width, rim width, and tire tread – so doesn’t provide an accurate measurement.
Nowadays, tires for 700c wheels come in a variety of sizes. Sizes 700 x 23c through 700 x 28c are most common in road bikes, where the second number readers to the width of the tire.
Tires of 28 mm width are going to have a slightly larger outer diameter when installed than a 23 mm tire. Yet, both tires can be described as 700c (and will fit a 622 mm rim).
So to recap, while 700c is a common name, tires of differing widths will result in outer diameters that vary from 700 mm. However, thanks to ISO Standard 5775, we can trust that 622 mm is the uniform size of a 700c wheel.
Now you’re probably starting to see why the BSD of modern wheels – 622 mm – is a more useful number in talking about wheels.
The total diameter can vary from 700 mm depending on what tire you’re running, but the rim itself maintains a BSD of 622 mm.
A History of “c”
You may remember we said that the “c” in 700c means almost nothing anymore.
That’s the truth. Strap in for a brief history lesson to understand what “c” means for bike wheels, and why you don’t really need to worry about it.
Let’s start by clearing up some common misconceptions. “C” is not the same as “cc”, which would be a volumetric measurement of the tire. Nor is “c” short for centimeters – a 700-centimeter tire would be the size of a house!
The terminology of 700c wheels traces its roots back to French bicycle tire manufacturing.
Back in the early twentieth century, there were not only 700c wheels, but also 700a, 700b, and 700d. The letters referred to the tire width, while the tires themselves all retained roughly the same outside diameter of 700 mm.
This meant you knew you could swap between them and you’d still have enough clearance in your frame.
However, these tire widths required different BSDs to ensure they still matched the 700 mm outer diameter – requiring different wheels for each tire size.
Amongst a variety of tire sizes, 700c was considered the “performance” wheel, proving popular at the Tour de France.
As Europe’s road surfaces improved in the decades after WWII, 700a, b, and d wheels were gradually consigned to history – a process formalized in 1980 when ISO Standard 5775 was established, and the BSD of 622mm was introduced.
We can likely attribute this to people’s desire for “racing” parts, a bit of marketing, and the fact that the 700c wheel size represented a happy medium between durability and performance for most bike enthusiasts.
The 700c wheel is a phenomenal all-arounder that rolls well and balances efficiency, maneuverability, and traction.
So, while the history of it all is quite interesting, you don’t really need to worry about the “c” because it’s nominal – a hangover from a bygone era of bicycles.
This brings with it its own headaches though.
700c is used when labeling any tire or wheel that has a BSD of 622mm. The problem is that although the 700c wheel is the standard, it could represent anything from the skinniest of tires all the way to a 2-inch 29er on a downhill mountain bike.
This means the outer diameter of the tire on a 700c wheel can vary significantly, and you’ll need to check you’ve got enough clearance on your frame and brakes to install 700c tires of different widths.
Is 700c The Same As 29 inch Mountain Bike Wheels?
Put simply: Yes, 700c wheels and 29 inch mountain bike wheels are the same size.
With the variety of tire widths available for different cycling disciplines, 700c means only that the rim’s BSD is 622mm.
Tires of greater width have larger outer diameters. When mounted on a 622 mm rim, the large-width tires used in mountain biking end up being about 29 inches (735 mm) in diameter – giving us the “29er“.
However, in practice, mountain bike rim beds tend to be much wider, so the tires aren’t always compatible despite fitting the same BSD. You’re also unlikely to have the clearance for a 29 inch mountain bike tire on a road bike as they run to a larger outer diameter.
Why Go 26 Inch?
– The tyres and tubes are easier to find in developing parts of the world – 26inch wheels use shorter spokes than 700c to build a stronger wheel – 26inch touring frames generally have greater tyre clearance for fatter tyres – There are more 2 inch touring tyres available in 26inch – 26inch wheels are MTB tyre compatible, for off-road adventures – A 26inch bikes lowest gear is effectively smaller than a 700c due to the smaller wheel size
– Larger in diameter, therefore they can roll over holes and depressions on roads in a smoother manner – There are more slick and city tyre options
Touring in Remote Locations
Riding in remote locations is the main reason bicycle tourers turn to 26-inches.
But just say that you are running 26inch tyres and your sidewall blows out while you have no spare. The tyre that you find in the closest bike shop (for argument’s sake, in northern India) is low-quality with no puncture protection. It’s going to get you going but isn’t a great long-term solution.
My point is: you won’t find good quality spares for any wheel size in remote locations.
In places like India, I suggest carrying a spare tyre, 2-3 tubes, 1-2 rim tapes and a bunch of spokes. That way it really doesn’t matter what size wheel you’re rolling on.
My last pair of Schwalbe Marathon Mondial tyres lasted 25000km with only a couple of slow leaks (review HERE). Spare tyres work out at about 650g each, which isn’t much for the piece of mind. If you do need additional spares, freight companies will get gear to you all over the world at good rates (provided you shop with the right companies).
What About 650B (27.5 Inch)?
650b wheels (or 27.5″) have been a popular size on randonneur bikes for some time, but have only recently become the must-have size in the mountain biking world, driven by huge marketing campaigns. 650b is the middle size between 26inch and 700c (actually it’s a bit closer to 26inch), so a bike with these wheels tends to have a mix of both 26inch and 700c riding characteristics.
The issue with 650b currently is spare parts. There are barely any touring specific rims and tyres available in this size. Good luck finding 650b tyres and tubes in your average bike shop: 700c is sometimes hard enough! In the next 10-20 years we may well find that 650b will replace 26inch, but until there are the parts available, it’s best to stick to the mainstream sizes.
Traditional Sizing Systems
The traditional sizing systems are based on a measurement of the outside diameter of a tire. This would usually be measured in inches (26, 27, etc.) or millimeters (650, 700, etc.).
Unfortunately, evolution of tires and rims has made these measurements lose contact with reality. Here’s how it works: Let’s start with the 26 x 2.125 size that became popular on heavyweight balloon tire bikes in the late ’30’s and still remains common on beach cruiser bikes. This size tire is very close to 26 inches in actual diameter. Some riders, however, were dissatisfied with these tires, and wanted something a bit lighter and faster. The industry responded by making middleweight tires marked 26 x 1.75 to fit the same rims. Although they are still called 26 inch, these tires are actually 25 5/8, not 26. This same rim size was adopted by the early pioneers of west-coast klunkers, and became the standard for mountain bikes. Due to the appetite of the market, you can get tires as narrow as 25 mm to fit these rims, so you wind up with a 26 inch tire that is more like 24 7/8 in actual diameter!
A second number or letter code would indicate the width of the tire. (26 x 1.75, 27 x 1 1/4. 650B, 700C. )
Does Point Seven Five Equal Three Quarters?
Inch-based designations sometimes express the width in a decimal (26 x 1.75) and sometimes as a common fraction (26 x 1 3/4). This is the most common cause of mismatches. Although these size designations are mathematically equal, they refer to different size tires, which are NOT interchangeable. It is dangerous to generalize when talking about tire sizing, but I would confidently state the following:
Brown’s Law Of Tire Sizing:
If two tires are marked with sizes that are mathematically equal, but one is expressed as a decimal and the other as a fraction, these two tires will not be interchangeable. (well, there are three exceptions, noted in the tables below. )
Dishonesty in Sizing
Competitive pressures have often led to inaccuracy in width measurement. Here’s how it works: Suppose you are in the market for a high-performance 700 x 25 tire; you might reasonably investigate catalogues and advertisements to try to find the lightest 700-25 available. If the Pepsi Tire Company and the Coke Tire Company had tires of equal quality and technology, but the Pepsi 700-25 was actually a 700-24 marked as a 25, the Pepsi tire would be lighter than the accurately-marked Coke 700-25. This would put Pepsi at a competitive advantage. In self defense, Coke would retaliate by marketing an even lighter 700-23 labeled as a 700-25.
This scenario prevailed throughout the ’70’s and ’80’s. The situation got so out-of-hand that cooler heads have prevailed, and there is a strong (but not universal) trend toward accurate width measurements.
Some road bicycles have extremely tight clearances and will not fit an honest 28mm tire. See Комментарии и мнения владельцев in our article on fenders.
B.S.D.
ISO, the International Organization for Standardization, has developed a universal tire and rim sizing system that eliminates confusion. (This system was formerly known as the E.T.R.T.O. system, developed by the European Tyre and Rim Technical Organisation.)
The ISO system uses two numbers. The first is width in millimeters. For the rim, this is the inner width between the flanges, as shown in the diagram; for the tire, it is the inflated width. This will vary a bit depending on the width of the rim.
The second ISO number is the critical one: it is the diameter of the bead seat of the rim, in mm (B.S.D.). Generally, if this number matches, the tire involved will fit onto the rim; if it doesn’t match, the tire won’t fit.
For example, a 700 x 20 C road tire would be a 20-622; a 700 x 38 hybrid tire would be a 38-622. The width difference between these sizes would make them less-than ideal replacements for one another, but any rim that could fit one of them would work after a fashion with the other.
A general guideline is that the tire width should be between 1.45/2.0 x the inner rim width.
If you pull the beads apart and measure the total width from bead to bead, it should be approximately 2.5 x the ISO width.
If your tire is too narrow for the rim, there’s an increased risk of tire/rim damage from road hazards.
If its too wide for the rim, there’s an increase risk of sidewall wear from brake shoes, and a greater risk of loss of control in the event of a sudden flat.
The tables below give a partial listing of traditional tire sizes, with their ISO bead-seat equivalents. The ISO comparison list at the bottom of this page covers all sizes which we know to be in production as of 2016. The fractional, decimal and French lists cover common sizes.
Most Common Bike Wheel Sizes
Bike wheel sizes have settled into a few popular sizes. You can see these popular sizes in the bike wheel size chart below. In the chart, we’ll give you the American size, the ISO equivalent, and the French equivalent, where applicable. We’ll also tell you what each size is typically used for.
The Most Common Wheel Sizes Explained (in order of popularity)
29″ / 700c (ISO 622 mm)
The most common size bike wheel for a road bike is 700C, also known as ISO622 mm. However, more recently, mountain bikes have also taken on ISO 622 MM, but in the mountain biking world, it’s typically referred to as 29”.
And while the diameter of both types of wheels is the same, mountain bike rims are typically wider to accommodate wider tires, and road bike rims generally are thinner.
27.5″ / 650b Wheels (ISO 584 mm)
The second most common size is probably ISO 584MM, known as 27.5” in the mountain biking world and 650B in the gravel and road world.
Typically, 650b wheels are used on extra small road bikes which have smaller frames, or on gravel and mountain bikes to accommodate wider tires.
20″ Wheels (ISO 406 mm)
BMX bikes and folding bikes with small wheels often have 20” wheels or ISO 406. As a result, they’re easier for maneuvering and doing tricks, but of course, they don’t do as well over rocks and obstacles as their larger counterparts.
16″ Wheels (ISO 305 mm)
This wheel size is usually found on children’s bikes, but they are also sometimes found on adult folding bikes. However, they don’t handle like a full-size wheel and can be subject to steering issues and obstacles. In addition, they are difficult to climb hills with and will have trouble keeping up with bikes with larger wheels.
24″ Wheels (ISO 507 mm)
These are not very common, but you may find them on junior mountain bikes and some BMX models for larger riders.
26″ Wheels (ISO 559 mm)
These wheels were initially used for cruisers and mountain bike wheels.
27″ (ISO 630mm)
This size is pretty rare and generally found only on vintage bicycles.
Oversized
32″ (ISO 686 mm) and 36″ (ISO 787 mm)
These oversized wheels are generally used on custom bikes for extremely tall riders.
Tips on Bike Wheel Sizing
If you ride a typical, average-sized road bike, you’ll probably have standard 700C bike wheels, which will use anywhere from 23 to 28mm. Some can go a little wider, making it possible to use gravel or CX tires. A standard mountain bike will use either a 27.5 or 29-inch wheel. Most mountain bikers won’t use the French 700C to describe their wheels, though, even though it is the same as a 29”.
If you ride a women’s specific or a very small frame, you might have 650b wheels.
A few manufacturers, such as Salsa, make junior mountain and gravel bikes that will take a 24-inch wheel. For example, my Salsa Journeyman 24 is a gravel bike for riders under five feet tall and uses a 24inch wheel. Their standard Salsa Journeyman uses a 650b instead. The 24inch wheels have a more challenging time keeping up their speed than the larger wheeled version.
Frequently Asked Questions
If you need to know your bike’s wheel size, there are a few places you can look. First, look on the rim itself. If it isn’t there, there might be a sticker on your bike’s frame. You might also check the manufacturer’s website under tech specs or look in your user manual.
The most common wheel size for road bikes is a 700c. The most common sizes for a mountain bike are typically 29 or 27.5 inch tires.
Most hybrid bikes will use a 700c wheel with a knobby tire for extra grip. However, some hybrid bikes will have a tire that is as small as 26 inches.
Folding bikes tend to have smaller wheels to save on space. Typically, you’ll find either 20inch or 16inch tires on these types of bikes.
650bs are a little bit smaller than 700c wheels. They typically serve 2 purposes. For example, you might find a 650b wheel on a very small road bike, such as a Canyon Ultimate 3x. commonly, you’ll find 650b wheels with a wide, grippy tire on gravel bikes. This gives more room for an extra wide tire on the bike.
Amanda Whittington is an expert writer, impassioned cyclist, and musician. Coming from a diverse educational background, Amanda discovered a deep-rooted passion for encouraging others through her love of all things cycling, writing, and inspiring hope.
You’ll likely find Amanda pouring over bike specs, comparing the hottest cycling tech, and sporting the latest jerseys while juggling the demands of her editorial calendar, training schedule, tiny homestead, and 6 busy kids.
She spends her free time absorbed in her own gardening and fitness, cycling, and reading, all while encouraging adoption and foster care, championing the underdog, and of course, working with her chickens and goats.