Carbon fiber composite inspection and use

This section explains the special requirements of  frames, forks, and parts made of carbon fiber composite, or "carbon fiber."

Inspection is important, but safety is more important

Carbon fiber requires regular and frequent inspection. The Inspection section below tells you how to do this. But even if you perform regular inspections, if you exceed the limit of strength of your bicycle or a given part, it will break. The Limited Lifetime warranty offered with your bicycle does not mean that your bicycle cannot break; it only means the bicycle is subject to the terms of the warranty. The manner in which you ride will determine whether your bicycle and its parts will last your lifetime. If you ride hard or aggressively, safety requires that you replace the bicycle and/or its parts more often than riders who ride smoothly or cautiously. There are many variables to this equation: weight, speed, technique, terrain, maintenance, riding environment (humidity, salinity, temperature, etc.), and the frame or part itself- so it is impossible to give a precise timetable for replacement. If you aren't sure, ask your dealer. But as a rule, it is better to err on the side of safety and replace the bicycle or parts more frequently.

Some carbon fiber parts or tubing (frame or fork) are constructed with very thin walls, so thin that you may be able to flex the walls with your fingers. During an inspection, you may need to use this technique. However, it is not good for the carbon fiber and adds stress to the structure. Such stress accumulates over time, so avoid unnecessary flexing of the carbon fiber when possible.

Carbon fiber is different from metals

Pound for pound, carbon fiber is stronger that steel or aluminum. But it behaves differently when it is overloaded in an accident or impact. An overloaded metal part will bend or deform before it breaks, showing evidence of the load (Figure 1). An overloaded carbon fiber part will not bend or deform, so a damaged carbon part (with reduced strength due to the damage) may look normal—even after the same load that bent the metal part. But when the sum of the forces finally exceeds the strength limit of the carbon fiber, the carbon fiber part breaks, it does not bend (Figure 2).

In an accident or impact that does not visibly break the carbon fiber part, the carbon fiber could still have internal or hidden damage. If there is any possibility of hidden damage, please carefully read these instructions and examine the carbon fiber. The following tests are not conclusive. If you are not sure a part is safe, replace it. We offer a very generous crash replacement program. If you crash your carbon bicycle or part, you should visit your dealer to learn more about this program.

Warning—Carbon fiber parts with damage can break suddenly, causing serious injury or death. Carbon fiber can conceal damage from in impact or crash. If you suspect your bicycle has had an impact or crash, immediately stop the bicycle. Replace the part before riding or take the bicycle to your Gary Fisher dealer for service.

Figure 1:

Metal fork bent when overloaded

Figure 2:

Carbon fiber fork broke at a much higher load, but separated


Carefully inspect your frame and components for signs of fatigue before and after each ride.

Unlike metal parts, carbon composite parts that have been damaged may not bend, bulge, or deform; a damaged part may appear to be normal to a cursory glance. After any high force load, like a crash or other impact to your bicycle, thoroughly inspect all the parts of your bicycle, and use the following procedures to inspect carbon composite parts:

• Check for scratches, gouges, or other surface problems.

• Check the part for loss of rigidity.

• Check the part for delamination.

• Listen for unusual noises.

These tests may not be conclusive. The tests are difficult to describe, so as an aid to describing the tests we provide a movie of a composite part inspection. If you have any doubts about the integrity of a part, do not ride the bicycle.

To check a part for surface problems (visual test)

Be very careful when handling carbon fiber parts that are suspected of damage. When a composite part is damaged, there is a possibility that individual fibers may be exposed. Carbon fibers are thinner than a human hair, but quite stiff. If the point of one of these fibers is pressed against your skin, it could pierce your skin like a needle.

1. Clean the part thoroughly with a damp cloth.

2. Look closely for problems:

· Scratches

· Gouges

· Cracks

· Loose fibers (which will appear like thin hairs)

· Other surface imperfections

If the part has any problems, do not ride the bicycle. Take the bicycle to your Gary Fisher dealer for replacement or further inspection.

To check a part for loss of rigidity (flex test)

Use the part in a normal manner (without actually riding) while someone watches carefully for unexpected movement. As an example, if you suspect a composite seatpost has been damaged, sit gently on the saddle while someone watches to see if the seatpost flexes. If the helper sees the part flex unexpectedly, or if the part feels less rigid than it should be, do not ride the bicycle. Take the bicycle to your Gary Fisher dealer for replacement or further inspection.

To check a part for delamination (tap test)

Delamination is a separation of layers. Carbon fiber composite is made of many layers. If the layers become separated, the strength of the part will be greatly diminished.

1. Clean the part thoroughly with a damp cloth.

2. With a nickel or other coin, tap the part near any possible damage and places where the part is known to be in good condition (or use a similar part).

3. Listen carefully for variations in sound, especially a hollow sound, "dead" tone, or any sound indicating that the part is not solid.

If the part makes any noise other than a hard, solid tap sound, do not ride the bicycle. Take the bicycle to your Gary Fisher dealer for replacement or further inspection.


The carbon fiber composite parts of your bicycle, both frame tubes and parts like rockers or dropouts, are not as ductile as steel. If you attempt to bend or twist a carbon fiber part, you may break it. Readjustment of  carbon fiber frame alignment is not recommended.

Check clamping surfaces

Before assembling a carbon part, make sure the clamp is compatible and that the parts are clean.


For any interface with a part made of carbon fiber composite, avoid grease or other lubricants on clamping surfaces, such as between the stem and handlebar, or on the seatpost inside the frame. Before assembling a carbon part, clean both the part and its mating surface with rubbing alcohol and a shop rag; clean until the rag shows no discoloration.

The carbon part can be assembled in a clean, dry state. As an alternative, we recommend the following special carbon prep products:

· Tacx carbon assembly compound

· Fiber Grip™ carbon fiber assembly gel from Finish Line

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