I just today got my first single speed. While bearing down (pedaling hard) I'm sensing a "throbbing" somewhere in the drive train. It's a bit hard to describe, but think of it as a low frequency vibration that is felt on the down stroke while pedaling. It also could be described as the feeling one would get while riding over a light, tight "washboard" pattern in pavement, but it happens while I'm riding on smooth, newly paved asphalt. I'm wondering if it might be the chain vibrating.
This "throbbing", or vibration is very noticeable, mainly because everything else about riding the bike is so smooth. I'm putting a bit of torque on the drive train, as I'm geared with a 46 chainring and a 16 cog. Again, it's only when I'm pedaling hard and at a higher speed.
Any help or suggestions would be appreciated. Thanks..