In last week's Tech Talk I answered a question about whether you need to routinely replace carbon frames, forks and components. I said that worn and, especially, damaged carbon should be replaced. Otherwise, I said you could keep riding yours – unless you were worried about it, in which case I recommended getting new carbon for your own peace of mind.
After writing that, some funny examples of broken carbon on my bikes and that I’ve seen on other riders’ machines came to mind – though they weren’t so funny when they happened!
This week, I’ll share some of these stories from the road. They illustrate what can go wrong and how you can damage and ruin carbon components, in the hopes they help you avoid such calamities.
Stupidly crunching $250 carbon handlebars technique 1
This happened to my friend John, who is a far better racer than mechanic. After purchasing a beautiful matching carbon Zipp stem and handlebar setup for his Trek, he also purchased a torque wrench to do a careful and proper installation.
Everything went fine attaching the trick tiller to his Trek. Yet, in his excitement, when he attached his brake levers, he mixed up inch pounds with foot pounds on his new wrench, overtightened and crushed the handlebars. $250 down the drain!
Tip: Most brake levers have metal clamping bands and most carbon bars are roughened up at clamping areas to help keep the levers tight. Be sure to read the instruction on the brake levers and on the handlebars to know the torque spec before tightening. And understand your torque wrench before using it.
Stupid pricey bar crunching technique 2
I’m a better mechanic than John, but I made a bonehead move trying to upgrade to a set of Kestrel carbon bars on my Litespeed. I first spoke with Kestrel and described the custom Litespeed titanium stem I was putting their bars in. They thought it would work okay.
The gloss black bars slipped in and fit just fine, but after only two turns of the allen wrench on the single-bolt clamp, a loud “crack” tipped me off that the parts in no way were made for each other. Tightening the screw drove the tip of the stem binder right through the carbon. Another $250 gone!
Tip: This is an example of my carbon rule from last week, to make sure the parts you plan to use are made to work together. I failed to realize that a single-bolt one-piece clamp constricts when tightened, which allows the clamp’s edge to cut into and crack the carbon. Expensive mistake.
I’ve broken steel, aluminum and carbon forks, and I can assure you that it’s better NOT to break your fork. The steel and aluminum forks broke because a small crack was created over many miles from the stress on the parts from riding. Both bikes had been crashed, too, which is never a good thing. Eventually the small cracks grew, and the parts broke.
But, the carbon fork broke because during assembly I had cut the carbon steerer inside while inserting and adjusting the expander. I didn’t feel or see this mistake. Slowly but surely, as I racked up the miles enjoying my new superlight, vibration-damping front end, that little crack grew and spread.
Luckily for me, it finally broke when I was crossing a rough set of railroad tracks and was traveling only 15 mph (24 kph). Because I was moving so slowly, when the fork flew off, I fell mostly straight down. My foot at 6 o’clock stayed locked into my clipless pedal, which meant that it hit the ground first. Somehow, though, I crumpled to the ground and rolled my ankle way too far over, and too fast, but I didn’t break it. Still, it was one of my most painful crashes.
So why did I say, “luckily for me?” Because five minutes before crashing on those tracks, I had descended Bonny Doon Road and hit 48 mph. I try not to think about the consequences had the fork failed there.
Dropouts that “drop out”
Dropouts are the parts of the fork that the wheel axle fits into and is clamped to with the quick release. On carbon forks, the dropouts can be aluminum or carbon, but they’re two separate pieces attached to the fork blades when the fork is constructed. When locked in place with the wheel clamped tightly, the dropouts are super strong.
But, when the wheel is removed, the dropouts are very vulnerable. And, the greatest threat to a carbon fork’s dropouts is car bike racks that hold the bike by the front fork, such as roof racks and truck bed racks. As long as you’re careful, it’s pretty safe to mount your bike by its carbon fork in these racks.
But, be extra careful when removing your bike, because if either dropout is still in the clamp and you pull the bike off the rack at an angle, you can catch the dropout in the clamp, bend the dropout sideways, and it can snap right off (or drop right out, if you will).
Tip: Another dropout hazard is dropping the bike. Aluminum and carbon dropouts are no match for pavement. So hold on tight to your bike when the front wheel’s been removed.
How not to park a carbon bike
Assuming that you don’t use a kickstand on your road bike, you may have heard that the safest way to park your baby is to lay it down on its left side. That way it can’t possibly fall over. (Note that even bicycles with kickstands can fall over if the stand digs into the ground or hot pavement, or if the wind blows the bike over the other way.)
But, some roadies don’t like to lay their bike down for fear it’ll get stepped on or scratched. They prefer to lean it somewhere safe. This is how my buddy Ron ruined his carbon frame.
He parked his bike by resting the side of his seat against one of those old splintery telephone poles. While he was gone, the bike crept backwards, allowing the carbon top tube to slam into and slide down the telephone pole. Amazingly, the bike snagged on a sharp splinter on the pole that drove straight through the top tube neatly skewering the bike to the pole!
Tip: If you want to lean a bike to park it, rest the hollow of the seat against the pole, but then keep the bike from rolling by backpedaling until the pedal on the pole side comes up and hits the pole. The seat hollow keeps the bike from rolling forward and the pedal keeps it from rolling backward locking it in place. This method is much safer, but a strong-enough wind or bump can still knock down your bike.
Beware those jaunts into the brush
If you’ve gotten in the habit of riding through the woods on some of your road rides, Tom Ritchey-style, beware this tale of carbon cruelty. It occurred to my neighbor Brian, who had only recently purchased a Cervelo with pencil-thin seatstays.
Santa Cruz is full of car-free shortcuts through the woods, and while Brian was taking one, he ran over a small branch – more a stick than a branch, he told me later. As sticks like to do, it flipped and went into his rear wheel. Not noticing, he kept riding, causing the stick to travel up and around and smash into those impossibly small seatstays. “Crunch!”
The result: 2 crushed seatstays and one Cervelo in need of major repair.
When rubber is tougher than carbon
My last cautionary carbon calamity involves a modern low-spoke-count wheel. Because there are so few spokes on these wheels, when you break one, the wheels can go way out of true. So far out, in fact, that the wobbly wheel can start hitting the frame. Even if you have a spoke wrench and the skills to get the wheel straighter, the tire could still brush the frame.
In the days of metal frames, you could usually keep riding, even if the tire brushed. It might scratch your paint, but it usually wouldn’t do any major damage. All that went out the window with carbon frames. A rubbing tire can quite quickly cut a deep groove, or even a hole, in that carbon frame.
So, don’t chance it. If the wheel’s rubbing, either fix it so it doesn’t, or call for a ride home.
Tip: Some on-the-road mechanics will whack a wheel against the ground to bend it straight enough to ride home. That can work, but it can also ruin a perfectly good wheel that just needed one new spoke and truing. So, think carefully if it’s worth it before using that approach.
Hopefully these tales of carbon woe will help you avoid trouble with yours.
Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.