Can U Diagnose This Problem? Funny Noise


Apr 3, 2015
I have a Trek 7.3 fx hybrid. A lot ofm iles but well maintained. When sitting on the bike and riding, I hear a metallic "tong" sound.

The sound repeats faster the faster I go. The sound continues whether I'm pedaling or not. If the crank arms are still, I still hear it. The sound is absent when I put it on a bike stand. It only makes the noise when I'm sitting on the bike.

I doubt my safety is at stake as I have had a professional tune up and maintenance on the bike recently but the sound is so ****ing annoying. I just want it to stop.

My wife can hear it riding like 5 feet behind me. It appears to come from the middle or back of bike not front. It almost sounds like a loose spoke, but I check them all. No such luck.

So, amateur wrenches, what could it be??? Help me!!!

I'm dropping it off at a pro shop tomorrow and I'd like to give him an idea of what it could be.
The first thought that came into my head was a loose spoke, too, but you checked them. I had a mystery metallic noise once, too. Turned out that my cassette lock ring had somehow worked itself loose.
"The sound repeats faster the faster I go. The sound continues whether I'm pedaling or not" - means it has to be related to the wheels going round.
If all spokes are healthy and there's nothing touching the wheels as they rotate, the only thing I can think of is a damaged bearing or a busted axle.

At slow speeds, mystery sounds CAN be caused by something loose either inside the hub or inside the rim, a ball bearing gone astray or a nipple dropped into the rim at build etc. But at higher speeds, rotational forces tend to stick these in position, making the noise disappear.
nice information
Thank you folks.. I directed the professional mechanic who did my recent tune up to the the rear hub. To add insult to injury I got a flat on the way home (my second in two days) so I am upgrading my Bontrager 700x 32 stock tires to Gator Skins 700X32. Should help with the flats.

It should be ready by Thursday night!
My guess is that it's coming from a rear spoke. Even if the spokes seem tight enough, a slight bit of corrosion or dirt at the X crossing (mid-spoke) could cause the "tong" noise you describe as a spoke goes round under load. Your mechanic should check the spokes by squeezing each crossed pair together. If that's it, a drop of oil on the spoke junction will usually silence it.
OK I got the bike back. He repacked the rear hub and tightened the spokes as well. Noise gone!!! Wahoo