Thump-thump question

[bjf]

Riding today, slowly, then went to slow down even more with light pressure on the brakes. I got a thump-thump that I would have thought was either a badly out-of-true rim (except they aren't) or a loose headset (it isn't). Not at a good place to stop, so just kept going. As I pushed on the pedal to accelerate, the chain popped from one cog to another on the rear. I'm not sure whether it went up or down, but in any case, the next time I slowed the thump-thump was gone.

Obviously the chain had not shifted completely when I was slowing, but I can't figure out why this would cause a thump-thump sound. Any ideas? Old Potatoe?

[Matthew]

Was the thump only when brakes applied? Seam in the rim? Wear indicators used in your particular rims? I have had spots where a little rubber build up will occur in certain areas of the rim from the brake pads that would cause a thump during braking.

[bjf]

Thump only when the brakes were applied, but it went away after the chain seated itself on the proper cog. Before and after this one stop, no thumping all day.

[dr50470]

Was the noise/vibration from the rear wheel, if so check how tightly your skewer is securing the wheel.

[dekindy]

How old are the rims?

Is the bicycle frame metal? If so, phantom cassette shifting might be a cracked dropout. Have you had any hard impacts to the frame or hit any chuckholes?

[bjf]

How old are the rims?

Is the bicycle frame metal? If so, phantom cassette shifting might be a cracked dropout. Have you had any hard impacts to the frame or hit any chuckholes?

It was just an incomplete shift that finished when I applied a little torque. Naked Ti frame, no cracks. Rims nearly new.