Six mistakes that risk snapping your carbon frame

Six mistakes that risk snapping your carbon frame

Carbon fibre is a great material for bikes, but it can be fragile. Here's how to avoid damaging your bike.

Carbon fibre bike frames are great to ride, but they are more susceptible to damage than alloy, steel or titanium frames. When working on, moving or storing a carbon bike you need to be careful not to do anything that could lead to preventable damage. Here are six common mistakes that you need to avoid.

Don't clamp the frame

Clamping your bike in a work stand to carry out routine maintenance on the surface is a simple task. However, clamping in certain places could ruin your frame.

Carbon fibre is designed to be very strong in its intended axis, but carbon tube profiles are not designed with clamping forces in mind. Therefore, clamping on the main tube profiles of the frame could lead to cracking and damage.

Instead, clamp your bike via the seatpost, which is usually designed to withstand clamping forces.

This applies when clamping your bike to a bike rack on a car too. Many bike racks rely on clamping the top tube, so avoid using these with a carbon bike. Look for a bike rack that is sold as 'carbon-friendly', as they do not exert the clamping force on the tubes. For complete peace of mind, check with the manufacturer for suitability before you attach your bike.

Don't lean it up precariously

How you leave your bike, either at a cafe mid-ride or at home, could lead to completely avoidable damage to the frame. If you lean your bike precariously, it can fall over, but additionally, the bars can whip around and damage your top tube. This can be especially damaging if your bars are not fully wrapped, since an unprotected carbon or aluminium bar rotating into the frame could easily have enough force to crack your frame or chip your paint.

To ensure this mistake does not happen, lean your bike against a fixed surface with the saddle and the handlebar firmly in contact with whatever you're leaning it against. Make sure the bike is leaning into the surface at a slight angle so that it cannot fall away to the side.

Don't crush the dropouts when flying

When flying with your bike, you'll probably have to remove the wheels of your bike to fit it into your bike box or bag. If that's the case, make sure you look after the dropouts. Without the wheel in place to strengthen the dropouts at the fork and the rear triangle, the frame is weak in these areas. That means that if your bike gets squashed at all, say when it's stacked up under another bike box, there's a risk that your dropouts could be damaged.

The best way to mitigate this is to use a combination of a hard-shelled bike box and a dummy hub that sits in between the dropouts to act as a compressive brace. Depending on the design of your bike, you might be able to use your thru-axles for this.

Don't exceed the weight limit

Bikes are becoming more versatile, and with the rise of bikepacking and multi-day adventure riding, we're using carbon fibre bikes to carry more and more on our bikes. When loading up your bike for your next adventure, it's important to bear in mind that carbon fibre components will have a stated maximum weight limit. This is the safe limit that the frame or component will have been tested to, so loading up more than this limit could be very costly.

This maximum weight limit is often displayed as a maximum rider weight but it's actually a whole system weight taking into consideration yourself, your riding kit, luggage and its contents. Essentially anything that is going to be on the bike should be taken into account.

Don't pedal a dropped chain into your bottom bracket shell

This is arguably the most common and likely mistake to inadvertently cause damage to your carbon frame: you drop your chain, you keep pedalling for a second, and the chain is dragged into your bottom bracket shell.

If you drop your chain on a carbon bike, stop pedalling immediately, and pull over as soon as you can to sort it out. Extract the chain by hand, as even the process of replacing the chain on the chainrings can lead to the chain pinging into your frame.

The best course of preventative action is to ensure that your front derailleur is correctly set up and your lower limit screw is set correctly. For a belt and braces approach, if your frame does not come as standard with a chain catcher, install one via the front derailleur bolt. A chain catcher is a small metal piece that sits between the front derailleur and the frame, fills the gap between the inner chainring and the frame.

Don't overextend your seatpost

The final mistake that could cause damage to your carbon fibre frame is setting your seat height above the minimum insertion depth that is marked on the seatpost. The seat tube and seatpost are both areas that take a lot of load and stress, so there needs to be enough overlap between them to share this stress. Incorrectly setting the seat post height above the minimum insertion line will put a lot of pressure both on your seatpost and seat tube, and could lead to carbon failure.

If you are a tall rider who needs to over-extend your seatpost to get your saddle height right, there are two ways of solving the issue. Firstly, you can fit a longer seatpost, so you can run a higher seat height without exceeding the minimum insertion depth. Of course, make sure it's the right size and fit for your frame.

Secondly, you could get a larger frame size. Bike manufacturers stock each size bike with a seat post that should cover the range of rider size expected to suit that frame, and if you need to raise your seatpost beyond the minimum insertion, it could be a telltale sign that your frame is too small for you.

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