Slight wobble under weight

[Axelf]

Greetings everyone! Long time reader first time poster.

I just got a new bike and when I'm riding it there is a slight wobble in the sprocket. Just enough to rub on the front derailer. It's not all the time. Only at certain gears (not extreme gears). When I spin the gears on the stand there is zero wobble. Is this normal?

I will add I am NOT light. I weigh around 225. Maybe that has something to do with it?

Thanks in advance!

[RBurrelli]

When you are adding weight to the equation, then I would think you might be causing an issue with the crankset to appear. Prehaps your bottom bracket needs to be looked at.

[1FJEF]

(10-25-2013, 11:18 AM)RBurrelli Wrote:  When you are adding weight to the equation, then I would think you might be causing an issue with the crankset to appear. Perhaps your bottom bracket needs to be looked at.

Ditto.
Your weight isn't the issue.
Triple crank?
How many rear speeds?
You know about cross chaining?
If you spin on a stand & they turn true, grab the crank arms and check for (lateral) play. Check with the drive arm at 12, 3, 6 & 9 o'clock.

[Axelf]

Hey guys thanks for he quick response!

It's a triple crank yes with 7 rear gears. I do know about cross chaining yes.

It's turning true on the stand. I grabbed the crank arms and there was very little play. Like not much at all. I'm not sure what the drive arm is to be honest. is that the arm on the gear side? i'm going to assume it is. At 12 oclock there is a tiny bit of play. Same with 3, and 6 but zero play at 9.

[GeorgeET]

The drive arm is the pedal on the crank side you can grab pedals on both sides and pull them toward and away from the bike to see if there is any play. Sounds like your bottom bracket needs some tightening, that's the shaft that holds the pedal arms and front sprockets, or your pedal arm is not fully tightened....

[1FJEF]

I would have expected some play, verging on rattle when he checked the BB with the crank at 3 or 9 o'clock. Weird loose chain rings? Maybe the frames BB opening is drilled untrue & canted, so that fractional flex & play become an issue? Does the chain rink hit the FD in exactly the same spot during rotation? I'm not sure I can be helpful on this one.