Help diagnose noise

thescouselander

My bike seems to have developed a strange noise from the free hub. In addition to the usual clicking noise when freewheeling there is a tapping sound that seems to occur about once per wheel revolution. Also the noise only appears when travelling over 20mph. The sound is also there if I lift the back up and spin the wheel - it also happens while stationary if the pedals are spun backwards very quickly.

Does anyone know what this might be?

proto

thescouselander wrote:

My bike seems to have developed a strange noise from the free hub. In addition to the usual clicking noise when freewheeling there is a tapping sound that seems to occur about once per wheel revolution. Also the noise only appears when travelling over 20mph. The sound is also there if I lift the back up and spin the wheel - it also happens while stationary if the pedals are spun backwards very quickly.

Does anyone know what this might be?

there is a tapping sound that seems to occur about once per wheel revolution

it also happens while stationary

The first would suggest wheel out of true, hitting something, brake block maybe. However if it does this when staitionary, then it's not the wheel, or the wheel hub or hub bearings.

If it happens when you are freewheeling, then it's not the chain.

Which leaves the freehub or the cassette. Either the bearings inside the freehub or the pawls and springs (ratchet) that makes the normal 'ticking' noise, or the cassette is loose on the freehub, or the freehub loose on the hub itself.

It sounds a bit odd, to be honest, and without looking it's difficult to diagnose but I'd suspect the freehub bearings, but before you do much more, check the cassette is on tight.

Job for a bike shop, me thinks.

graeme_s-2

I had a rattle on my road bike recently, which I finally tracked down to a couple of cogs on the cassette which were very slightly loose. Tightening the lockring fixed the problem.

I struggled to diagnose mine because it would happen when I was pedalling, and when I was freewheeling, but I couldn't replicate the noise off the bike at all.

woodywmb

Can't quite follow this. The noise appears to be coming from the wheel - yet it can also be heard when the bike isn't moving. Assuming that the pedals and crank ARE moving in all three instances above, I suggest you look at the crank arm. Is it touching something on the way past the chain stay - velcro sleeve, zip tie holding a sensor? Or it could be something even simpler like a loose lace hitting the frame.
I came across a new noise source last week. The inner pad adjuster knob (on BB7 disc calipers) hadn't been tightened and worked free as I cycled. The protruding torx headed bolt was gently rubbing the spokes as the wheel went round. Took me ages to find it. Seconds to sort.
"Noises could fill up a whole new bike forum.

thescouselander

I don't think its the cranks - they are stationary when freewheeling but the noise is still there.