Cycling is a sport of numbers.
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?
Put simply, it’s the most common road bike wheel size, used on almost all adult-sized road bikes (and 29er mountain bikes). But it’s worth taking the time to understand what 700c really means, and how the measurement translates to other standards of bike wheel sizing.
We’ve got you covered!
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.
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.
Are 700c Wheels Standard For Mountain Bikes Too?
622 mm (29 inch) mountain bike wheels weren’t always commonplace.
The first mountain bikes were retro-fitted beach cruisers. They used the 26-inch tire size, as was common for cruiser-style bikes. Also common is the 650b French wheel size, which corresponds to the 27.5” mountain bike wheel.
You might find yourself wondering what’s going on with the lack of a standard unit of measurement between road and mountain bike wheels.
This is largely geographic. With the advent of mountain biking culture being primarily American, imperial measurements were used, and are generally accepted as standard in the MTB industry.
So, you’re unlikely to see a 29 inch mountain bike wheel described as “700c” – even though they both have the same 622 mm BSD.
29 inch wheels are not considered “standard” for mountain biking in the same way 700c is for road cycling, however.
Though 29ers are probably the most widely used for modern mountain bikes, 27.5 inch wheels are still fairly popular too.
Just remember, a 700c is a 29 inch wheel, 650b is a 27.5 inch wheel, and the 26 inch mountain bike wheel has been largely phased out.
How Did 29 Inch Wheels Get So Popular?
It’s actually a quite sensible story.
On the terrain mountain bikers encounter, a smaller wheel has a steeper curve angle when approaching uneven features.
This creates a more unstable ride as the bike will pitch up and drop down at a steeper angle when riding over uneven terrain.
During the ’80s and ’90s boom of mountain biking in California, early mountain bikers fitted their bikes with a larger wheelset – the 700c – better equipped to approach and roll over terrain by creating a shallower angle between the tire and uneven surfaces.
The introduction of 700c wheels wasn’t immediately accepted.
While the larger wheel rolled over terrain better, it was notably less responsive. As such, the 650b (27.5”) tire became very popular as a happy medium.
The “27-five” was less likely to get hung up in uneven terrain than the smaller 26 inch wheel, but snappier and lighter than the newly adopted 29 inch wheel.
The 29er grew in popularity with the first purpose-built 29er mountain bike being produced by Wilderness Trail Bikes in 1999.
The 27.5 inch wheel is considered to be faster accelerating, more maneuverable, and lighter. The 29 inch wheel is more efficient at top speed, more stable, and better suited to tough terrain, inspiring confidence to take on obstacles in many riders.
With the modern advancements in alloy and carbon wheel production, the difference in wheelset weight between 27-fives and 29ers is becoming negligible.
As such, 29 inch mountain bike wheels continue to gain popularity amongst the mountain bike community.
Putting It All Together
There’s no denying that the conventions for talking about wheels and tires are confusing.
Though it may seem complex, it starts to make sense once you’ve wrapped your head around it.
700c wheels are the industry standard for road bikes. Outside of mountain bikes running a 27.5 inch wheelset, kids bikes, and some gravel bikes, you’re most likely already running the tried and true 700c.
Look at your bike’s tires. Somewhere on them, you’ll find numbers along the lines of “700 x *Width* c”. For example, “700 x 23c”. 700 is the diameter, and the second number is the tire width.
Sometimes the “c” will be written after the 700 instead of after the tire width (i.e. 700c x 23).
Some manufacturers have chosen to write this as “23-622”, opting to list the width and BSD instead. If you see this, don’t panic – just apply what you’ve learned!
With your knowledge of the 700c wheel, you should now know that this is exactly the same thing. Thanks to the ISO, 700c wheels have a standardized BSD of 622mm.
With this understanding of the 700c wheel, you can confidently discuss, shop for, and geek out about wheels with other cyclists.
Just remember not to call it 700 “cc”!
Can I put a wider 700c tire (35) on a Bontrager wheel that has 23 size tires?
Hi Robert, that really depends on two main things: the internal rim width of the wheel, and the tire clearance on the frame you want to fit the wheel to.
We have a complete guide to rim width and tire compatibility here, but in short for a 35c tire we’d typically recommend an internal rim width of around 19-23 mm (you could probably go down to 17 mm, but you might lose some of the performance benefits of the wider tire).
As for the frame clearance, the only real way to know for sure is to try it! Manufacturers sometimes include a recommended range of tire widths compatible with a given frame, but these are sometimes a little conservative. As a rule of thumb, we’d recommend making sure there’s a minimum of around 3 mm of clearance between the tire and the closest part of the frame to reduce the risk of tire rub or damage to the frame if the tire picks up debris. If in doubt, take the wheel and frame into your local bike store – they should be able to give you a much better idea, and might let you try it out with a 35c tire so you don’t have to wait until you’ve bought one first!
With such a large jump from 23c to 35c, we’re guessing you’re looking at a road bike to gravel bike conversion – but if you’re just looking to ride a road bike with wider tires, a smaller jump to 28c or so should still provide a very noticeable change in ride quality, while increasing the chances that the wider tire will be compatible with your current frame and wheelset.
Let us know how it goes! And if you have any other questions, don’t hesitate to get in touch.
Best,
Rory
BikeTips Editor