Fixing a clicking noise, Trek 7.4 FX

A clicking noise on a bike can be one of the most maddening faults to trace. It rarely announces itself on demand, it disappears the moment you try to demonstrate it, and it often turns out to have more than one cause. That was certainly the case with a Trek 7.4 FX hybrid that had run quietly for a long time before developing an intermittent click.

The sound was hard to place. Sometimes it seemed regular, sometimes not. It appeared on uneven surfaces and when standing out of the saddle, but the bike stayed silent on smooth tarmac and while freewheeling. It could be heard clearly enough, but its source was another matter entirely.

The pedal seal

The first breakthrough came with help from a friend who runs a bike shop. He stood at the roadside and watched as the bike was ridden past. At first there was nothing, but as soon as the rider stood up and pedalled, the click returned. His suspicion fell immediately on the pedals, and swapping the left pedal for a different one silenced it straight away.

The cause was a broken O-ring seal where the original pedal screws into the crank arm. The pedal still felt tight, but the failed seal was producing the click. As a temporary measure the pedal was refitted without its seal. It was not completely sealed, but it was greased and tight enough to ride while new pedals were ordered.

The saddle post and clamp

The following day a different click could still be heard occasionally, this time on uneven surfaces rather than from the pedals. With little expectation of success, the saddle post clamp was tightened slightly, and the noise became less frequent.

That pointed to the seat post as the second culprit. The clamp was loosened, the saddle and post were removed, and bicycle grease was applied where the post is clamped. The saddle went back on, the clamp was tightened, and the second click disappeared.

Two apparently unrelated problems had been producing similar sounds, which is what made the fault so difficult to diagnose. Once both were dealt with, the bike ran smoothly again.

Why intermittent clicks are so hard to pin down

Noises of this kind are notoriously awkward to reproduce. A dealer may adjust everything and find nothing, only for the click to return on the next ride. Recording the sound can be equally frustrating, since the bike often falls silent the moment a microphone is switched on.

The lesson is that a click does not always come from where it seems to. Pedals, crank arms, seat posts and saddle clamps are all worth checking, and it is entirely possible for more than one of them to be at fault at the same time. Greasing the contact point between seat post and frame, and inspecting pedal seals for wear or damage, are simple checks that cost little and can save a great deal of irritation.