Forget the technical marketing bafflegab and long-winded feature/benefit rhetoric and ignore the plethora of anecdotes from excitable and well-meaning cyclists. In the boots (or tires) on the ground real-world, what is the difference between carbon and alloy? And should you pay for it?
I am, perhaps, in a great position to answer this question. After more than a decade riding alloy wheels on all my road bikes, I was recently gifted a set of brand spanking new 38mm carbon clinchers from a friend with the means and opportunity to acquire them. (No, they didn't fall from the back of a truck - he works in the industry!)
image: Christian Woodcock | BikeRoar
First off, no one can deny the visual appeal of a set of carbon wheels. It is typically (as far as I can tell) one of the main reasons people buy them – they make your bike look awesome(r)! You can have your carbon wheels in any base color, as long they are naked carbon stealth black. Excellent for the stealth or 'murdered out' look. There are different finishes on offer, like fine to fat carbon weave, plus the usual passes and fails in the decal design department, but generally your bike will look faster and more pro once fitted.
My concern was the fact the wheels arrived just a week out from the Peaks Challenge – a 240km (150 mile) Gran Fondo ride with 4000m+ (13000 feet) climbing, which included nearly every conceivable road condition possible when asphalt/bitumen is applied to the naked contours of the earth. When I shared my concerns about using an untested wheelset in this event with my mate, (and suggesting that perhaps I would stick to the faithful old alloys), he laughed and said "As if". Yep, as if...
Thankfully, a few training rides leading up to the Peaks Challenge put my mind at ease somewhat. The wheels instantly felt lighter, more comfortable, and stiffer than my alloys. (Although I describe the alloy wheels as "old faithful" they are pretty much new and were stock on my mid-level Di2 carbon road bike).
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The next worry was braking performance. I had stories echoing in mind of major rim failure from overheating brake surfaces after long and/or steep descents – of which this fondo could have plenty. I was secretly and strongly hoping the wheel makers had got their stuff together regarding this very real concern of mine – I was clinging to our discussion with Michael Hall from Zipp that even a Chinese factory was only a year behind on wheel technology these days, and also that my meager 65kg frame would minimize the chance of needing to grab a whole handful of brake. Oh, and also wishing that the sun would be shining. And that I wouldn't flat because I had a bugger of a time getting the tires onto the rim originally. To say there were nerves would be an understatement!
Still, in spite of the many scenarios an overactive imagination could create, my bike looked awesome and I was feeling pro and cool, and like I knew what I was doing.
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My initial discovery was that the wheels felt exactly like everything I had read about them, and these initial feelings have since morphed into longer drawn out knowings! In terms of riding feel, carbon wheels provide all the performance you would have read about: They climb wonderfully because they are so light at the rim, they feel super stiff as a result of the deep, wide carbon shape, and they are super comfortable with the manner in which they soak up feedback from the road.
In fact, it is this comfort that I most appreciated after being in the saddle for the 9+ hours riding the fondo. I often felt "beaten up" on my alloy wheels, especially on the roads the Peaks Challenge covered, which were at times like someone had smeared a paper thin veneer of tarmac onto a Paris-Roubaix cobbled sector. The carbon rims simply soaked it all up. There was none of the harsh jarring and vibration of which I had become accustomed after 10 years riding alloys.
If it was the comfort that was most appreciated, it was the performance that was most surprising. Even though I was expecting marked improvements, the way in which the wheels gracefully ascended the 19% grades of "Henri's Hell" has become a story of legend – in my own mind at least. I have always been a very good climber, but the way the lighter wheels allowed me to be almost at the limit and then up the cadence again was exciting (only a climber would call extremely painful increases in cadence on a steep climb exciting!) Sure, having less weight is certainly not the only factor here, but it definitely helped.
But, the best part of all was regarding a discipline I have always backed off from: descending. I'm okay at it, but going downhill is definitely one of my weaknesses. You would imagine from my earlier concerns that perhaps I would back off on the descents, but nothing could be further from the truth. I tore the downhills apart! Not only did I post my fastest times, I also beat the times of other riders who have always had my number when going downhill. I felt totally confident with the integrity of the wheel. This is what I consider the best quality of carbon wheels: the stiffness of the rim and spokes and the control it allows inspires enormous confidence.
Braking, both real and my confidence of it, was helped by a wheelset with a specially treated braking surface and my purchasing a good quality set of carbon rim specific brake pads. It has always been necessary to use carbon-specific brake pads when using carbon rims and should be considered part of the package. The weather was fine and I have yet to test the wheels in truly wet conditions, but on moderately wet roads, and being mindful that a carbon rim will rarely stop as well as alloy, no problems so far.
So, what is the difference between carbon and alloy wheels? The answer is a lot. Beyond the science and marketing I found that the carbon wheels I used are lighter, stiffer, more aerodynamic, and more comfortable to ride.
I can honestly say that I feel a better rider on carbon wheels. I was more confident and rode faster uphill, downhill, on rough and undulating roads, in the wind (although the rims are only 38mm, so not super deep) - basically in every area of the ride I was faster and less fatigued.
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Although these wheels cost me nothing, I was saving to upgrade to carbon at the time of receiving them so the decision to upgrade had already been made. But are they worth the money? If you want the most out of your road cycling and are a semi-serious or serious rider, than I feel definitely; You will be a better rider for it. If you are new to the sport, the learning curve may be a little steeper and it makes greatest sense to buy a known brand with advice from your local bike shop. Not all wheels are made equally, so if you are determined to shop online, I strongly recommend cultivating your online shopping savviness - be smart and take care.
I stated that carbon wheels make you a better rider. Well, we know that isn't exactly true – long training miles, intervals and consistent hard work make you a better rider – but add carbon wheels into the mix and see how far you can really go!
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