I have a Trek 520 that was new in August 2005 and I use Speedplay Frogs. It has about 2500 miles on it. I just changed out the chain and greased the pedal bearings. I know the chain should last longer, but I wanted a fresh chain and some spare links for my upcoming loaded tour. Now, there is an intermittent grinding sensation in the down stroke on each side. I do not hear anything, but it is annoying. It usually comes up when when pushing higher gears rather than while spinning. I didn't mess with the bottom bracket at all and the vibration/grinding sensation didn't start until after I changed out the chain and greased the pedals.