Look After Your Carbon Fibre Bike Frame


9 September 2013

I own a Cannondale Synapse Carbon 105 and I love it, but all my ‘metal framed’ friends are always going on about how the frame will snap from under me when I’m doing 40 down the Caldbeck to Wigton hill. Naturally, at that speed, I’m a bit worried about my handle bars and front forks leaving me and the rest of the bike behind, so I’ve tried to find out the truth.
image On my quest, I was hoping to unearth a lot of evidence to say ‘nope, definitely won’t happen’ or ‘don’t be silly’ ‘ridiculous’ that sort of thing - but I didn’t. The truth is carbon fibre frames don’t bend or flex or do any of that metal related stuff, they just snap when they’ve had enough.


This is a worry.
All frames fail eventually (if this is a comfort to you). Metal frames usually fail due to small repeated stresses over a period of time. Steel and titanium do the same but have a ‘minimum fatigue limit’ so any stresses smaller than this limit don’t shorten the life of the frame at all. Aluminium frames don’t have this fatigue limit so every stress brings the bike close to its end. But, unless you hit a wall, all these bikes bend and flex a bit to give you a warning before snapping on you.

All right, enough of the doom and gloom, let’s have some good carbon fibre news. Have a look at this table:
image2
Who’s laughing now, ‘metal framed’ friends? Carbon fibre’s strength to weight ratio is miles better than all the others, so it can take a lot of abuse, as long as it’s normal bike riding abuse.

It’s only when it’s mistreated that problems can start.

So what’s the definition of mistreated? For carbon fibre, mistreated means minor crashes, falls, bad storage, poor transportation, repeated abrasions from lamp posts or walls or the chain coming off and jamming between the chain ring and the frame. Anything that impacts the frame or scratches it may cause problems.

But that’s okay, because if you’re spending a lot of money on a bike, I expect you’ll look after it. If you do, it will last as long as any other bike, probably longer. Chain Reaction Cycles reckon you’ve got a good chance of getting 35,000 miles out of it, which is the same lifespan as a lightweight steel frame bike.

Regular Inspections


Regular inspections are a good idea and this, according to my Cannondale manual, is what you should be looking for.

Cracks

Every time you clean it, which should be frequently, inspect the frame for cracks, splintered areas, gouges and deep scratches. Don’t ride the bike if it’s got any of these. Take it to your dealer and let them have a look at it.

Delamination

Carbon fibre is made of layers of fabric, if the layers are not bonded together properly this is delamination and could indicate a weakness. Signs of delamination are:

- Cloudy or white area that looks more opaque than the undamaged areas
- Bulging or deformed shape. If delamination occurs there may be a bump or a soft spot and it won’t be smooth.

Creaking Noises

A crack or delamination can cause creaking. If you hear creaking don’t ride your bike and take it to be checked over. Buy a torque wrench, over tightening is one of the main causes of delamination.

The Coin Test

If you suspect an area is damaged, a good test is to tap the area gently with a coin. If there is a dull sound compared to a hard, sharp sound this is an indication there may be some damage.
So, a well maintain carbon fibre bike that hasn’t been in a crash, or dropped, or banged about a bit will last you a long time. For your own piece of mind inspect the frame regularly and every year or two take it into a shop for them to have a quick look, because they know what they’re looking for.

Let's end with some general positivity. Here’s the pros of owning a carbon fibre bike:

- It’s the lightest frame you can get.
- Quarter of the weight of steel and the same amount of stiffness.
- It has better fatigue life than steel, titanium or aluminium.
- Extremely good vibration damping, far superior to metals.
- Gives you a smoother ride.
- Non-corrosive.
- It looks great, as will you on it.
- A block of carbon fibre is virtually indestructible
- All the professionals use them, and fall off them regularly without the bikes splintering.

So what if carbon fibre frames snap when they've had enough, we all do, all you have to do is look after them and keep an eye on the frame and they'll last you just as long as any other heavier, bendy bike.

Don't worry just enjoy the ride.

Thanks for reading.

Ian Young


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