Bicycle Mechanics - mystery sound

It sounds like the noise that a poorly adjusted rear derailuer would make scraping against a dork disk that was out of round, that is only once per revolution of the wheel. It makes this sound while pedaling or while coasting. It does it in all gears.

Not sure if it is from the front or the back, as it does not make the sound unless I am on the bike and the roads here are rough and loud chip seal, so its hard to pinpoint. When its on the stand all I can hear is the hubs, which sound good(using a length of tubing as a stethoscope)and if pedaling it on the stand just some drivetrain noise.

It is a Univega Gran Turismo, from the original owner who claims under 500 miles on it. I have since put about 1200 on it. All the derailers are suntour blueline in very good condition with a suntour freewheel. Derailer is not touching anything, It does have the spoke protector(metal, and its not coming off no matter what level of mockery I get)but that does not appear to be rubbing anything. All the spokes are tight, wheels are true, no brake rub.
It has fenders but I see no contact, at least 2.5 centimeters from tire.

Its driving me nuts. Its probably somthing pretty obvious, but thought I would take a stab at getting suggestions.

Bent derailleur hanger?

the valve on the tube might be moving around enough to cause noise.

computer magnet on wheel hitting PU..

It sounds like the noise that a poorly adjusted rear derailuer would make scraping against a dork disk that was out of round, that is only once per revolution of the wheel. It makes this sound while pedaling or while coasting. It does it in all gears.


Check both tires & wheels to see if they're round and true. I'll bet something is rubbing the tire when you're sitting on the bike.

Seatbag slipped down?

Hanger is strait, no computer on the bike, took the bag off the rack while I was out. Also the rim is true, as is the tire. no leaves in the fenders, or cables hitting the tire.

I did just put new chain pulleys in the rear der, but that would not be it because the chain doesn't move when coasting.

[[[Check both tires & wheels to see if they're round and true. I'll bet something is rubbing the tire when you're sitting on the bike. ]]]

Once I had a tire rub when I put weight on it. it was just hitting the fender mount when my weight expanded the tire. This was on a different bike but means I know what to look for. Thats what I have been trying to find with no luck here.

I will check the valve for movement. that would be a new one on me.

Probably going to tear everything down and check it out. Again. things like this drive me nuts, but as I live several miles from pavement its hard to track these things down. Listening for creaks on gravel is a pain.


{{update**** I believe its the freewheel. seems good, looks like I will be tearing it apart for a good cleaning though. I bet its not that bad, but I'm pretty obsessive about my bikes being quiet. Or I may just put a new shimano unit on. That may be best for a regular rider.

Aluminum nipples will make this noise when they get a little corroded. It's amazing how much it sounds like chain noise. Try putting on different wheels or swap wheels with a friend and see if the noise swaps too.

Fix is to lube them, sometimes from both sides (remove rim tape etc) and work the lube in with a couple back and forths on a spoke wrench.

[QUOTE= and work the lube in with a couple back and forths on a spoke wrench.[/QUOTE]

I did oil them from the back when I did the original teardown, but did not move the nipples any because the wheels were so true that it seemed like a shame to risk wonking them up even the tinyest bit. It does sound like a possibility, I will give that a go, thanks.

When I first got it, for 40 bucks at a yard sale, my first plan was to update everything making it a light Randonuer, but this bike is so pristeen that I just could not do it.
The freewheel is my only complaint, there is no ramping on the teeth, so I might just bite it and get a new shimano. I've gotten used to the 34 tooth "overdrive" 6 speed units with a triple on my other bikes, so that may be the way I end up going. Anyway, 100 miles from home is no time to have an old freewheel give up on one, so this might be the best move