If you want to start some drama at the trailhead, just ask a group of mountain bikers if you should buy carbon wheels. The aluminum faithful will be quick to call carbon wheels a waste of money. Carbon converts will preach about pure performance. Somewhere in between is the truth.
In road cycling, stiffness, weight, and aerodynamics make carbon wheels the clear choice for performance. But mountain biking is a bit more complicated. Rocks, roots, and other trail features have the potential to damage rims. Mountain biking websites have plenty of jokes, horror stories, and myths about carbon failures, and that can instill doubt in a lot of riders’ minds.
What wheels are you running?
But in the last 10 years, carbon technology has matured. Though not perfect, modern carbon wheels are more reliable than ever. More mountain bike manufacturers are including carbon wheels as standard equipment. And the industry has made a huge push to introduce generous carbon wheel warranties. Out on the trail, it’s obvious that carbon wheels are becoming popular.
So are carbon mountain bike wheels worth it for you? Read on to find out more about the advantages and disadvantages of carbon wheels, and what experienced riders at The Pro’s Closet have to say on the subject.
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Thanks to lightweight carbon wheels this Niner AIR9 RDO weights less than 20lbs.
Carbon fiber possesses a very high strength-to-weight ratio. It has almost half the density of aluminum; it’s more than five times less dense than steel, but it is stronger than either metal. This is especially important for bicycle wheels.
Wheels (and tires) make up rotating weight on your bike. Increased rotating weight increases inertia and wheel inertia matters in cycling because the rider has to use energy to overcome it and accelerate. Heavier wheels require more energy and lighter wheels require less.
Lightweight carbon wheels make a bike feel snappy and easier to get up to speed. They can help you climb faster and save energy on long rides. Naturally, carbon wheels enjoy widespread use in high-level XC racing where riders are focused on saving weight to maximize performance.
As we’ve discussed previously in our “Does bike weight matter” article, wheels are a key place to cut weight. Many riders, even novices, can actually feel the difference when riding lighter wheels. Reducing an equivalent amount of weight elsewhere on the bike is much less noticeable.
To show how much lighter carbon wheels are, let’s look at two wheelsets in our inventory: the aluminum DT Swiss XM1501 Spline One 25 and the carbon DT Swiss XRC1200 Spline 25. At The Pro’s Closet, we weigh every bike and component we sell on our scales to publish accurate weights.
I chose these wheels because they come as standard equipment on several XC mountain bikes, and they feature rims with the same diameter (29”) and internal width (25mm), the same lightweight DT Swiss 240s hubs, and the same spoke count (the XRC1200 uses slightly lighter spokes, but it only accounts for a few grams). The only part of the wheels that will significantly affect the overall weight is the rim material.
On our scales, the aluminum wheel weighs 1,700g while the carbon wheel weighs 1,390g. This is a difference of 310g or .68 pounds. In cycling, anything over half a pound is significant, especially when the weight is located at the rim. When you’re pedaling and spinning a wheel thousands of times in a single ride, it will add up. If you’re looking to maximize your performance on climbs, a lighter carbon wheel is the best option.
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Stiff wheels are great for railing turns.
Well-built aluminum wheels can be stiff, but when compared to similar carbon wheels they don’t come close. Stiff wheels are desirable because they:
- Respond faster to pedaling and acceleration
- Make steering feel sharper and more controllable
- Make the bike feel more “lively” and responsive
- Track better when aggressively leaning the bike over and cornering
- Help you maintain speed as less energy is lost to wheel flex
- Deflect predictably off obstacles
As a heavier rider, I notice aluminum wheel flex, and it can cause some nervousness when attacking corners or rock gardens. Stiffer wheels increase my feeling of control, which increases my confidence. It allows me to ride consistently and aggressively.
It is possible for wheels to be too stiff. Some older carbon wheels were criticized for having a punishingly harsh ride. In fact, some riders still choose aluminum wheels because the increased flex is more comfortable. Fortunately, ride quality has been a bigger priority for modern carbon wheel designs.
The video above shows a Stan's NoTubes carbon Bravo rim designed to deflect up to 10mm during impacts.
Carbon fiber can be engineered to act differently in different directions. This allows engineers to design wheels that are rigid in a specific direction, while still compliant in another direction. The key to high performance with good ride quality is combining lateral stiffness and vertical compliance. This maintains all the performance benefits of a stiff wheel while providing more shock absorption for a more pleasant ride. Most modern carbon wheels absorb shocks and vibrations so well that they now match or exceed the ride quality of aluminum wheels.
Cost scares away most carbon curious wheel buyers. Let’s look at the two high-end DT Swiss wheelsets we compared earlier. The retail price is $1,200 for the aluminum XM1501 Spline One 25 wheelset and $2,130 for the carbon XRC1200 Spline 25 wheelset. That is nearly a $1,000 difference.
In general, it’s common for carbon wheels to retail for nearly double their aluminum competitors. If you’re buying a new set of carbon wheels expect to spend in the $1,500-2,500 range. High-quality aluminum wheels will be in the $600-1500 range. Of course, buying pre-owned wheels will save a lot of money.
Why is carbon so much more expensive? It’s down to the manufacturing process.
Carbon rims need to be hand laid and require skilled labor. | Photo courtesy of ENVE Composites
Aluminum rims are extruded and then welded (or pinned for budget wheels) into a circular shape. Aluminum manufacturing has been refined over decades, and it can be largely automated so manufacturers can produce thousands of rims in a single day. Add in the lower cost of raw materials and aluminum rims are unbeatable on price.
Carbon rim manufacturing, on the other hand, is more labor-intensive, and the tooling and raw materials are more expensive. Creating any carbon cycling component requires molds. The molds themselves are costly, and carbon sheets need to be laid into the molds by hand in a specific order. This requires skilled labor and it means production numbers are much lower. All this needs to be done in a climate-controlled environment, adding even more to the cost.
Unfortunately, with carbon, you have to pay to play. For some riders, especially those on a budget or who are hard on wheels, it may not be worth the high cost.
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Beyond cost, durability is the biggest concern most riders have with carbon. This is the crux of the carbon vs. aluminum debate. Surf the comment section of popular mountain bike websites and you’ll find plenty of commenters who like to dismiss carbon rims as too fragile.
As stated above, carbon has a very high strength-to-weight ratio. In theory, a carbon wheel should be stronger than an aluminum wheel, especially if they’re built to be similar in weight. The reality is that many riders have experienced carbon rim failure and this has colored people’s opinions.
Above is a video of a wheel failure I experienced. A sharp rock at the bottom put a crack in my rim. It was fast and unexpected. Fortunately, my rim held air and I was still able to ride out.
Aluminum and carbon will both fail under the right conditions but their failures are different. Aluminum will usually dent, deform, or flat-spot. Carbon will usually develop a crack. It is simply the nature of the material. Carbon is brittle and doesn’t deform or dent the way an aluminum rim will. A cracked carbon rim is compromised and should be replaced as soon as possible.
Some riders prefer aluminum because dents can potentially be repaired and if a rim fails catastrophically, it’s much cheaper to replace. Bending dents back is easy, but in my experience, it’s often better to leave minor dents alone if the tubeless seal isn’t compromised. Sharp and heavy dents that prevent a proper tubeless seal usually indicate that the rim should be replaced. Bending back a dented aluminum rim will also compromise its strength.
If your riding style or trails are likely to damage rims, carbon might not be for you. | Photo courtesy Orbea
Unfortunately, in mountain biking, wheels are very prone to damage. Wheel damage is especially common for downhill and enduro riders who attack gnarlier trails at high speed. This type of riding generates larger forces that will make rim damage more likely. Aluminum rims are inexpensive enough that many riders can easily accept it as a part of the sport. But the high cost of a carbon rim can turn people sour when they experience a similar failure.
There is one piece of technology that is making carbon more popular — the tire insert. Tire inserts provide extra rim protection by placing foam between the rim and trail obstacles. They do add weight, but they allow you to worry less about rim failures while enjoying the stiffness of carbon wheels. (To learn more, check out our article “What are tire inserts? Do you need them?”)
As a general piece of advice, you should ride wheels that you can afford to replace. For many, that means aluminum. Some manufacturers, however, are introducing generous carbon rim warranties that offer easy, no-questions-asked rim replacement for the original owner. This benefit has the potential to offset the initial cost of a carbon wheelset.
Keep in mind there are also plenty of riders out there that have never experienced a rim failure. If you ride smooth and smart, use proper tire pressures or a protective insert, there’s a good chance you’ll avoid major issues.
Carbon MTB Wheels vs. Aluminum MTB Wheels: What do riders think?
The Pro’s Closet is the world leader in used bikes. Our employees love cycling, obsess over bikes and tech, and have access to a huge selection of products. They are all knowledgeable and opinionated so I polled mountain bikers in our shop to see whether they preferred carbon or aluminum wheels. We had over 60 respondents to this poll and many explained why they would pick one over the other.
The chart below shows the results.
When asked which wheel material they would buy with their own money, the results were evenly split between carbon and aluminum, with carbon having a slight edge. The majority of those who selected aluminum were downhill-focused riders who are hard on equipment. As a bonus, I also asked which wheel material our riders would choose if given wheels for free. In this hypothetical scenario, our riders overwhelmingly preferred carbon.
Riders who like aluminum:
- Are concerned with cost
- Tend to destroy multiple rims in a season
- Enjoy riding far from civilization
- Feel the ride quality of carbon wheels is too harsh
Cost was the biggest factor for riders who choose aluminum. A few hard-hitting riders mentioned they go through multiple rims a year and replacement aluminum rims are significantly cheaper. A couple of riders enjoy doing backcountry excursions, far from civilization. In the event of catastrophic rim failure, an aluminum rim has a better chance of being bent back into shape and ridden to safety. You can’t fix a cracked carbon rim out on the trail. Only one rider said that carbon wheels feel too harsh.
Riders who like carbon:
- Seek performance gains
- Look to shed weight off the bike
- Want to true wheels less often
- Hate denting wheels
- Have experienced no prior carbon failures
Those who preferred carbon wheels seemed more performance-focused. Many said the stiffer feel of carbon was the most attractive benefit. A couple of respondents also made the interesting point that good carbon wheels rarely go out of true due to their stiffness. Interestingly, just over one-third of respondents said they have never had durability issues with carbon rims. Over half of carbon users also said they use tire inserts with their wheels.
As a final point, I decided to ask an expert skills coach what he thought. Lee McCormack is a world-renowned mountain bike skills author and instructor. He’s the author of the highly popular “Mastering Mountain Bike Skills.”
Lee attacking rocky trails with carbon wheels. |
“I run carbon wheels on all of my trail bikes,” McCormack says. “I find them to be lighter, stronger, and nicer-riding than aluminum. Beginners won't likely notice anything but the weight. But the more advanced and in tune you are with your bike, the more you'll appreciate the stiffness, ride quality, and durability.”
I love the feel of stiff and light carbon wheels. As a rider with less than stellar fitness, I like to use technology like carbon wheels to get every advantage possible. I’m the same way with many hobbies. I like to tune up car motors to achieve maximum horsepower. I like overclocking my computer. I’m the type of person who gravitates toward high-performance gear even if it might have some drawbacks. I’d rather chase performance than compromise.
And Carbon wheels can be extremely reliable. I’ve only cracked three wheels in my now 10-year cycling career. I’ve had no issues at all since adding Cushcore Pro tire inserts in all of my carbon wheels. All of my current bikes use carbon wheels — except one.
Enduro racing is hard on bikes. Last season I raced on carbon wheels. When I return to racing it will be on aluminum...for now.
The one bike that I have aluminum rims on is my long-travel, enduro bike. I chose aluminum here for two reasons. First, during my build, my wallet was feeling light and I decided to save money on the wheels. Second, this bike is intended to be a race bike for racing my local enduro series. In one season, I expect to break and replace everything on this bike. I have successfully raced enduro before on carbon rims, but with my new bike, I wanted parts that I would feel less guilty about destroying.
If my results are bad, I might go back to carbon wheels with my next bike. Of course, it’d be my fault and not the bike’s. But having high-performance parts like carbon wheels can make me more confident and mentally stronger. That’s alone is worth it to me.
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Do you ride aluminum or carbon wheels? What would you choose if price was no object? Let us know in the comments!