Squeek when peadeling ~20mph
 

My bike (Scott cross comp) recently started squeaking when I am pedaling and going ~20mph or greater. The noise only occurs when I am pedaling at higher speeds and does not occur at low speeds. It goes away the instant I stop pedaling regardless of the speed I am going so I think i can safely assume it is in the drivetrain. It also seamed to get louder by the end of my ride.

I was thinking this may be my bottom bracket going out, but I would like to get a more experienced opinion. Do the symptoms I am getting seem to match a shot BB?

Thanks

People usually blame the bottom bracket prematurely on things like this. It could be a number of things. Sheldon Brown and others have good diagnosis checklists out there.

The first things to check are the pedals, the chain, and the seatpost. Seat posts can make all kinds of weird noises as they flex. Stranger still, quick release skewers can also be the culprit. They may be flexing harmonically as you pedal.

The only surefire way to test the bottom bracket is to remove the chain from the cogs and tuck it somewhere where it won't in anyway catch on anything. Spin the crank without anything connected. If need be, balance on something and pedal the crank hard without the chain connected. If you don't hear the squeak then, it is likely not the bottom bracket.

If you only hear the squeak after a few miles, it can be the grease in the bottom bracket thinning with heat of friction. This is pretty common and is nothing to worry about. On mountain and cross bikes, a bit of dirt or grime makes its way through the seal and starts squealing as the grease gets worked a bit. The noise could even go away on its own, as it has on my mountain bike several times.

It's very likely to be your chain. Oil your chain.

While the bike is leaning and standing still, spin one of the pedals backwards. Position your bottle of lubricant over a fixed point just above the chain and squirt while spinning the chain around, with several revolutions of your hand on the pedal. This will distribute the oil on the chain. Then take a rag and wipe the chain down, using the same spinning technique.

Could be a lot of things. I had something similar, turned out to be my seat. My weight shifting from side to side at high speeds caused a squeek. Sounded like my bottom bracket.

First one of the day! Here you go. This should be required reading:

http://sheldonbrown.com/creaks.html

Ditto - Spent over 2 years trying to tighten and retighten Pedals and pedal arms thinking it was the problem. Finally one day saw Sheldon Brown's article on squeaking and my squeak was gone forever in under 2 minutes.

Got a nasty squeak the other day -- turned out to be the inside of my shoe rubbing against the crank. I moved the cleats in slightly and I'm hoping that will fix the squeak.