Looking After Your Carbon Frame
Philip Leah of carbon frame repair specialists, Target Composites, provides some advice for looking after your carbon frame.
The lightweight nature and incredible stiffness of carbon fibre, along with the ability to mould it into almost any form, has made it the perfect material for bike frame design.
Concerns over its fragility are misplaced as carbon fibre parts are universally used by both the aerospace and automotive industries; in fact, it is one of the main materials used in Formula One, a high stress, dangerous and vigorously tested environment.
Carbon fibre does, however, need to be looked after to ensure it can perform to these high standards, so here are our top tips for looking after your carbon frame.
Tip 1 – Buy a torque wrench
Although incredibly resistant to forces in the direction it is designed for, crushing can easily damage carbon fibre. Over-tightening of clamps and bolts, such as around handlebars and seat posts, is one of the most common causes of carbon fibre damage and failure in bikes.
All components on a carbon fibre bike will have recommended torque values given in newton metres (Nm), that will either be marked on the relevant component, available in the supplied manual, or on the manufacturer’s website. A torque wrench ensures that you don’t tighten beyond these values, and should be considered essential if you own a carbon fibre bike. If you have only previously owned metal framed bikes, you’ll probably be surprised how little force is required with a carbon frame.
You can find a useful article on choosing the right torque wrench here: Bike Radar: The best cycling torque wrenches
Tip 2 – Take care clamping to bike racks and stands
Carbon fibre is designed to be incredibly strong under riding forces. The compressional stress put on frames when clamped in a bike stand, or put on a car rack, are completely different though. Frames with hard edges in their design, such as Canyon and Cervelo, are particularly susceptible to clamp damage as the force is concentrated on the edge. Never force a clamp shut on your frame, it’s much better to hold your bike in the stand by the seat post if possible.
Tip 3 – Use assembly paste.
Apply carbon interface paste at contact points such as stem clamps and seat posts. Galvanic corrosion can occur at points where carbon fibre meets aluminium or steel (titanium is an exception).
Tip 4 – Dry It Down
After training make sure you’ve washed your bike down and ensure no sweat is left to seep in anywhere.
Salt in sweat acts as an electrolyte that accelerates galvanic corrosion and will gradually eat away aluminium parts that are in contact with exposed carbon. If you’re using your bike on a turbo trainer then it’s a good idea to put a towel across the handlebars to catch your salty sweat.
Tip 5 – Reinforce and Protect
Protect any contact points on the frame from movement abrasion which can occur easily in areas such as around mudguards or race numbers that are zip tied in place. Applying electrical tape or a scrap piece of inner tube is ideal for this.
Most bikes come with a chain suck plate to protect the frame from occasions when the chain gets jammed between the chain stay and ring.
We hate this so much that we supply frames that come to us without a suck plate with one of our own carbon Kevlar armour plates. This is the same material used in Armed Forces style anti-stab vests, so it stands up extremely well against bike chains.
Stone Chips and Scrapes
Fitting your frame with a Heli tape kit gives your bike a protective skin to against stone chips and other scrapes. It does an amazing job of maintaining your bikes value when it’s time to sell it on. Peel the Heli tape away and your well ridden bike looks brand new again.
Tip 6 – How to Test and Monitor for Carbon Damage
There are 4 simple tests you can conduct yourself:
1 – Situational evidence
Learning what happened to the bike and gathering evidence about the situation is an obvious one. If the bike has been in a crash, and taken a direct side impact, then the chances of damage are obviously greater than if the bike crashed into a hedge, where the impact force will have been absorbed. Recap the incident and try to locate the collision contact points on the frame.
2 – Sound
If the suspected fracture is on a seat stay for example, you can knock a coin against the tube and note the sound it makes. First, tap the edge of a coin gently on an undamaged area of the seat stay and note the sound; then tap the coin against the area of suspected damage and see if there is any difference. A damaged tube will sound dull because the sound waves are escaping through the fracture instead of resonating without obstruction.
3 – Movement
Lightly press your thumb against the damaged area and see if it flexes any more than further up the tube at an undamaged section. If there is movement there you might also hear a creaking noise as the fracture flexes. Only press lightly though as you don’t want to cause further damage.
Hairline cracks can be a tricky one. Quite often it is purely paint damage but it can also indicate a manufacturing fault in the carbon lay-up. If a creaking noise can also be heard, then it is worth investigating a little further.
4 – Time
Sometimes a crack or fracture can appear without any apparent reason, and this may be the result of a manufacturing fault that has weakened over time.
If the carbon cloth becomes creased when pressed into the mould during manufacture, then the strength of that section is weakened significantly as the fibres are no longer running how they should. This is a lot easier to see in a naked carbon finish as the fibres will appear bunched up around the area where the hairline crack is. It’s not so easy to diagnose this with a painted frame.
The best option is to mark both ends of the crack with a permanent marker, or simply record its length. Every time you take the bike out for a ride check the marks or length to see if the crack has grown over time. If it does then stop riding the bike and look into getting it fixed.
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