Aluminum vs Carbon for Cyclocross


I get asked A LOT about the differences between aluminum rims and carbon rims for cyclocross use. In the days of rim brakes there was a lot of things going for the aluminum side. That being said nothing beats the feeling and strength of the carbon setups. That last bit usually comes with the following caveat: “if you can afford them”.

The thing is that if you’re reading this you probably already know what we here at PSIMET are about and that’s simply being the “racer’s choice”. We know racing because we do it and support it all of the time and cyclocross tends to be our thing. Why is that important? I’m not a large OEM that made a bunch of stuff because a couple of engineers or marketing guys told me it was what the public should want (*cough* tubeless *cough*). I’m the guy who has to make all these wheels and glue the vast majority of them and actually face the racers one on one in my tent when their races are over.

If they have problems – they get to ask me directly to my face about them. I don’t like problems. If I have problems then everyone jumps ship in a hurry. I can’t have problems. As a result when people ask my advice on a build it’s from the standpoint of, “hey – these are going to be issue free but these you may notice that x will happen after a really cold race if you hit y.” This is instead of my conversations being, “Model AX150 supports a wide base rim with the possibility of tubeless use and comes with swappable endcaps for your ability to transfer the set from bike to bike….and we have TONS in stock”

Why the preface? Alloy rims. Great entry point into running tubulars for cyclocross. Great pricing and great durability and performance on a rim brake setup for sure. Drawback? This is cyclocross and alloy rims can dent/flatspot.

We have a race in the Chicago series that takes place over Halloween weekend. It is usually one of the first cold races of the year and it has this long section of climbing (midwest style ‘climbing’) up through the woods over rail road ties that serve as small steps to help slow erosion. Every year I walk away tons of wheels and¬†receive phone calls on Monday morning. All from racers who say, ¬†“Can you take a look at my wheel? I think I may have dented it at Campton…”

Every year it’s the same exercise – take the wheel – swap the rim if it’s bad or hammer it out and re-deck the braking surface if it’s OK to re-use. Number of these wheels that are carbon? 0. Aluminum? 100%.

It’s always been hard to explain this and how it impacts you when talking with customers on the front end. “Well – you may get a dent but then we can rim swap it to fix for roughly $100….” but that will be in the middle of the season where you will fear missing the next week’s races and oh I forgot to say that if you want me to re-glue that tire it will cost an extra $$ in addition to the time involved that it adds….

What made me think of all of this was that I was working over a triathlete’s….errr….reformed triathlete’s cyclocross rig. She’s powerful on the bike and a helluva racer. She’s one of those racers who can ride 100 miles with her brakes dragging, beat everyone there and then when you point out the brakes she would say something like, “huh…so that explains why it seemed a lot harder than normal.” She showed up to an elimination race a couple of weeks ago sans bike. Borrowed mine, and my shoes and won the elite women’s division. Yup…THAT kind of reformed triathlete.

When I went to clean up her rear wheel – her bike was dirty – shocking, right, I noticed that there were these telltale marks that almost look like those wood plugs they use on plywood when they cut the knots out. This is where the rim has bent – protruding out but then has been shaved back down through braking after the fact.

Alloy Rims

I counted up at least 5 of these on one side of the rim alone. She’s never been one to notice a little bit of brake ticking but something like this would have driven myself and many of you absolutely crazy. Granted she rides all out: equipment be damned, but I still felt it was a wonderful illustration of the shortcomings of alloy over carbon.

We’ve had the 38W carbon cross rim for 3 full seasons now entering the 4th IIRC. In that time I have had 3 or 4 rims crack. All of them have been due to SEVERE impact. Roughly 1 a year. I have yet to have one throw in the towel at Campton. You don’t hear this much in the media filled marketing releases from the other guys. You hear about aero. You hear about “compliance”, “feel”, weight…”performance”. I’m here to tell you that carbon is just plain stronger in this specific application. The time and numbers have proven it out.

Don’t get me wrong – not all carbon is equal. I got a great text exchange with a pro wrench last season who had been working with my wheels the whole year. Paraphrased it said that he was concerned at first that his riders has so few wheels and he had feared he would have lots of issues through the year. Instead he found he never had to bother with the wheels- ever. He found it a stark contrast to entering into the team trailer of one of the big teams running all their road wheels for cyclocross and was shown a stack of cracked rims that were piled up two wide and floor to ceiling from being broken so far that season.

You don’t have to take my word on it- simply ask any racer who has run those speedy rims for more than a season or two and no doubt they have a story about how they sent theirs in for a new rim or how many they have cracked. Even a local shop has taken to perfecting their epoxy rim repair techniques to save their clients time.

Maybe it’s just my opinion but that’s what happens when you use road wheels for cyclocross.

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