If you find yourself thinking, “why can’t all mountain bike companies get on the same page and just develop industry sizing standards already?”…join the club.
Lack of common standards can make it difficult to buy aftermarket components for your bike. Wheels are no exception. 27.5 or 650b? 29er or 700c? Are these sizes actually different, or are they just two ways to say the same thing – to confuse us all?
29er and 700c are in fact the same: both wheels have an outside diameter of 700mm. So you could put 700c wheels or tires on your 29er mountain bike. However, tires are designed to only fit rims of specific widths, so you’ll need to check if they are compatible before swapping wheels or tires.
Let’s dive a little deeper into the 700c vs. 29er conundrum so if you’re thinking about swapping out wheels or tires, you don’t end up with components that don’t play well together!
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Are 700c and 29er the Same Size?
In a nutshell, these two sizes are the same. However, if you can make quick calculations in your head, you may have noticed that 700mm is not equivalent to 29 inches. And you’d be right. 700c refers to the outside diameter of the wheel, whereas 29er refers to the outside diameter of the tire that goes on that wheel.
So yes, 700c and 29er are the same size; they’re just defined by different measurements. Just another example of why we need standardized measurements in mountain biking!
What’s the Difference Between 700c and 29er?
If 700c and 29er are the same size, why bother using different names at all? Typically, 700c is used in the road bike world. As it’s in metric units, it’s the international designation for wheels or tires, since most of the world (outside the USA) uses this measurement system. The “c” is the width code, which is an old system of measurement ranging from “a” (narrowest) to “d” (widest).
29er is the term used exclusively in the realm of mountain biking. It was popularized by a few early adopters, including Gary Fisher and his U.S.-based bike company Fisher Bikes. Though he wasn’t the first to create a bike with 29-inch wheels, his 2001 bike model (the “Two Niner”) did give rise to the name we all use today.
Can You Put 700c Wheels on a 29er?
700c and 29er wheels are both the same diameter, so technically a 700c wheelset would fit with the geometry of a 29er bike. You may encounter a few challenges when making the switch, however.
First, 700c road rims may not be built for off-road use. Mountain biking places a higher demand on a bike’s components; therefore, they are designed with durability in mind. Road bike components often prioritize lightness over all else – anywhere material can be shaved off to save weight, it will be done.
This creates a very efficient machine for smooth pavement, but there is usually an inverse relationship between weight and durability (it’s why downhill bikes are so heavy…weight doesn’t matter when you get to take a chair lift to the top of the mountain!). Expecting light-weight road rims to survive the abuse of aggressive trail riding is a tall order.
Now you might be thinking, “Hey wait a minute! Carbon fiber frames are lighter and stronger than aluminum, so that inverse relationship is nonsense!”
You’re partially correct. But we need to compare apples to apples here. A carbon fiber road bike frame will be lighter than a carbon fiber mountain bike frame, but it won’t be as durable because it won’t be reinforced as heavily in key areas to stand up to the abuse of mountain biking.
Second, road rims may not be wide enough to support chunkier mountain bike tires. Road bike wheels typically use rims that have an internal width less than 30mm. Mountain bike rim widths start at 30mm, with many being 35mm or even wider (you may see these wider tires designed WT for “Wide Trail”).
Mountain bike tires are wider than road tires, and require a larger rim to seat properly. A wider rim also prevents them from deforming and unseating themselves when hitting trail obstacles or cornering aggressively.
Unseat a tire during your ride and you may be rewarded with a loud bang, a spray of sealant, and a high-pitched yelp you didn’t even know you could make!
To learn more about road and mountain bike rim width and how to pair your rims with the perfect tire width, check out THIS ARTICLE.
Can You Put Road Tires on a 29er?
So let’s talk about road tires on a mountain bike.
If you follow the guidelines in the section above and replace your mountain bike rims with narrower road bike rims, then you can put road tires on your mountain bike. And if you really want to learn about doing that, check out our separate article on replacing mountain bike tires with road tires.
But in the meantime, let me explain why this isn’t a great idea.
If you have a mountain bike, it would be safe to assume you’re doing a fair amount of off-road riding. Sounds obvious, right? That bike probably came with some pretty burly tires with huge knobs that really dig into the dirt.
And that’s important.
Tires are the only part of a bike in contact with the ground. Therefore, they’re the only part of a bike that provides traction to keep you from contacting the ground. Mountain bike tires are designed specifically for maximum grip and cornering ability on a multitude of different terrain.
Road bike tires are only designed for one type of terrain: smooth pavement. These tires don’t have large knobs to improve grip and cornering. They’re also very thin; the thinner the tire, the smaller the contact point between your bike and the ground.
If you put road tires on your mountain bike, you’re going to have a rough time finding any grip on the trails. You’re also going to feel very unstable, as the surface area of those thin tires is just too small to provide any cornering confidence on anything other than the flattest of terrain.
This combination of minimum grip and maximum instability is just not a safe way to ride.
So what if your intention was to use your mountain bike on the road? Well, if you’re only using it for commuting or short trips, you won’t find your mountain bike tires to be that much less efficient than road tires. Sure, they’ll offer up a little more rolling resistance because they’re bigger and chunkier, but it won’t inhibit you that much.
If you’re serious about road cycling and planned on your mountain bike pulling double-duty, you should really just consider buying a road bike instead; because the tires aren’t the only difference between a road bike and mountain bike. The added weight of a mountain bike (along with the suspension) will really make those long-distance rides a challenging experience.
So while it is indeed possible to put road tires on your 29er mountain bike, it’s probably not worth the hassle…or the extra cost of new tires and rims!
Ever wondered if you can take your road bikes off road? Click here to get an answer.
700c and 29er: The Same…but Different
On paper, 700c and 29er tires are identical. It’s in the application where the differences begin to appear. And when it comes down to actual on-trail performance, application is much more important.
So if you’re in the market for new mountain bike wheels or tires, just remember that 700c and 29er are the same…but not always. And if that’s not the most ambiguous way to end an article, I don’t know what is.