I've got a Trek 7.2FX that I've put a little less than 400 miles on so far. Within the last week or so I started getting a "pop" when pedaling. It is restricted to a specific speed/cadence, so if I accelerate through it it will pop once and if I pedal at the steady "popping" speed it will pop on every downstroke of the right crank unless I speed up, slow down or shift gears.

I replaced the busted stock pedals, made sure the new pedals were on tight, tightened the cranks, tightened the bolts holding the crank on the chainrings, tightened the bolt on my seat, nothing seems to help. The store I bought the bike from does the first tune-up for free so I took it to them tonight hoping they could figure it out. I told them about the popping and they checked and adjusted the derailers and brakes and said everything else looked good to them.

Of course, it was still popping on the way home About the last thing I can think of would be something with the bottom bracket, but since I'm new to bicycles I am really stumped on this. It's not such a big deal to be honest, but I'm just worried that if I ignore it it will come back to bite me. What do I do next?

Check your spokes for any loose ones. Sometimes if they have been loose a while they can make a pop from sliding against each other. Does it happen when standing or sitting. Sometimes if it is only sitting it can indicate a seatpost or seat rail clamp issue.

this sounds like a bottom bracket issue.
What bbs are on your bike?

I've been trying to look this up but still can't come up with anything. I'll keep looking.

I doubt this is your problem, but I had a similar experience a while back. I was getting a click in the right pedal, and it happened in exactly the same pedal position every time (approximately 2:00). I tried tightening the pedals, and it didn't help. Like you, I started to suspect a problem in the bottom bracket. I mentioned it to the LBS, and he told me to make sure the threads on the crank were lubricated with grease before I installed it. Huh? That didn't even make sense, but I did it. The click went away. I have no idea what the grease did except possibly allow me to more fully seat the pedal when torquing it down.

Are you talking about the crank or the pedals? I did put grease on the threads of the pedals when I put the new ones on, but I haven't taken the crank off.

I'm talking about the pedals. Apparently that's not your problem then. Good look figuring it out.

First (and easiest) place to look for a phantom creak/click is to swap out the pedals.

Okay, so I think I figured this out...

Went out to the garage and started futzing around with the bike again. Went back to Sheldon Brown's site and went down the list. Check everything off, and then got to "loose bottom bracket". He says to line the cranks up with the seat tube and squeeze the towards the tube and listen for a pop.

Well, surprise surprise, when I squeeze the left crank towards the seat post I get a pop. So now I need to take it back to the guys at the shop or I need to get my own bottom bracket tool. I don't relish either option to be honest, lol.

Hello ShartRate,

Pretty sure I know what your problem is... I have a Trek 4.7 (also a carbon frame) and had the exact same problem a little while after buying the bike (from new). It seems carbon frames are prone to this but I've cured mine now.

Initially I took it back to the bike shop; they tightened the BB bearing cups into the frame (with that Shimano tool - which I now have 2 of), and for a while it was good. Then it started again so I did it myself this time... Nearly broke the veins in my hands getting the cups out, as the shop had overtightened them way above the 50Nm recommended! Anyway, to keep a long story short-ish, I cleaned the threads; tried them dry; tried them greased; tried them with a greased washer (in case the noise was from where the cup face sits against the frame); some worked for a short time until I finally cured it...

Basically, the noise comes from the very slight movement of the bearing cup's threads against the opposing threads of the bottom bracket in the frame, and this noise is amplified (massively) by the thin carbon walls! So I went to town cleaning all the sets of threads - using Isopropyl (which is pure alcohol, that you get from a chemist). I then coated the cup threads with Loctite 641 Bearing Fit! I'd already used this to stop the bearings 'moving' in my Zipp 188 hubs to great effect, so knew it would 'lock' the thread better than even thread lock! (I've since gotten rid of the 188 hub and replaced it with a Tune Mag 170. Way better!)

I did that months ago and have not had a single click or pop since, no matter how steep the hill and how heavily I'm stomping on those pedals! :-)


darth.

I may have to go back and do all this grease-and-loctite business on the bottom bracket, but for now this is solved. Ordered a crank puller and bottom bracket tool from my LBS and snugged up the left side BB cup. Voila, problem solved! But, as you say darth, I may have to go back and do a little more work to make sure it stays fixed