AvatarX17

I've got this weird problem, after about 1 hour of cycling the back or middle (I'm honestly not sure where it is coming from) my bike will start to make this clunking noise while pedaling, it stops when i stop pedaling and if i pedal faster the clunking noise will get louder and faster.

Does anyone know what this is?

I'm pretty new to bikes so I don't know what any of the parts are called.

Thank you.

aixaix 

Try cleaning & oiling the chain. Chains sometimes get noisy after about an hour, though I wouldn't describe their noise as a clunk. To give you more help, I'd need to know what kind of bike you have: fixie, single speed, hub or derailleur gears, e.g. Also, do you feel the clunk in your feet or seat, or just hear it?

AvatarX17

I have derailleur gears and i mostly feel the clunking in the pedals.

FBinNY 

I can't think of anything that would change on the bike during a ride, unless you're using an extremely short- lived chain lube.

The only thing I can imaging is that after an hour or so you might be getting a bit tired and losing your pedaling rhythm a bit. This means that the wheel can overrun you a little bit, and you catch it and re-engage the freewheel with a noticeable clunk.

When you're a bit tired, you might slow down a bit as your pedals reach 12 & 6 o'clock, and therefore get the clunk as you come into the power position.

It certainly could be a mechanical issue, but then you'd need to figure out why it doesn't happen for the first hour.

BloodMoonGrrl

That is most likely an issue with the bottom bracket, probably the bearings, but maybe an issue with cups/rings. That happened to my bike, with the clunking sound only starting after about 20 miles of riding. Your best bet for a fix would be a trip to the LBS.

hillsbreakme

Bottom bracket may be getting loose when it warms up. What's the year/model of the bike?

FBinNY 

**********

Bicycles aren't cars. But like cars, about the only thing that warms up is the engine. Otherwise the bike operates pretty close to the ambient temperature, though rims do heat from braking.

In my experience riding in temperatures from near zero, to above 100, I've never noticed any change, or need to compensate anything throughout the entire range. I did have a headset get so stiff the bike was nearly unrideable at minus 6 degrees, but that was just grease that was too stiff.

Tundra_Man 

If your clunk happens once per pedal rotation, then it's something in the crank/pedal area. I agree with the others that it's most likely the bottom bracket.

The bottom bracket on one of my bikes clunks when it gets above 60 degrees outside. It would be fine on the way to work, and clunk on the way home. Since I relegated this bike to a winter-only ride I've never bothered addressing it.

FanaticMN

Are the cranks/pedals hitting a kickstand, or the end of the front derailleur cable?

hillsbreakme

--Otherwise the bike operates pretty close to the ambient temperature, though rims do heat from braking.--

Not true because I had a cup/cone bottom bracket that used to knock after riding it awhile, especially when I rode uphill. The bearing assembly will get warmer when riding because a bearing is not 100 percent efficient and it will generate heat just like anything under friction. When things get warm they expand, which may cause the knocking.

aixaix 

I have experienced chain noise (clicking) which only started after an hour of riding, but only on a fixed gear bike. Heard from others who have experienced the same thing on fixies, but I've never figured out why. Clearly it is not the OP's problem. Bike shop is your best bet, I think.

Mondoman

I've also had a BB noise that only started after about 30 minutes of riding. It turned out to be a not 100%-torqued-down BB.