Apologies for mangling any of the terms, I'm somewhat new to this.

Also, of course I'll take this up w/my LBS, but I'm the type who tries to figure things out on his own as well.

While riding my 2011 Felt Z6 after a recent general maintenance by my LBS I started hearing a noise.

I paid close attention and the noise only occurred when pedaling, not coasting.

I finished my ride and checked out the bike when I got home. That's when I noticed the crank arms slide back and forth, by almost 1/2 inch I'd say!

Question: what's going on here? That is, what's wrong such that the cranks slide back and forth like this? It seems clear the problem arose after the maintenance; is this a common error or situation?

Followup: could any damage have been caused? I want to know what additional questions to ask LBS beyond having them fix what I'm pretty sure broke only after their maintenance.

Thanks for any advice or feedback you may have.

Have you looked at the manufactures FAQ for this? https://www.fullspeedahead.com/produc...mpact-Crankset here you will find an FAQ describing your exact problem, and other useful tech doc links.

For any long term damage, you doubt it, the crank will have been held on by the plate with the pint protruding from it on the Non Drive Side arm, adn will have been sliding in the groves or the spindle, not rotating in them , for the LBS, they should have checked the crank was installed correctly, FSA MegaExo cranks have a slighly different setup process to Shimano, so that could possibly have confused them, but really shouldn't.

Thanks Jim! I was not aware of the info provided, and it's very helpful.

From the FAQ it sounds like they didn't properly reassemble, perhaps even missing a small part!

Also good to know there's no likely damage, whew.

It is easy to assemble incorrectly, i did exactly that a few years ago, and experience what you have described, with no lasting damage, I'm a home mechanic, only working on my own bikes, so if I make a mistake, it's my fault, a shop should really get it right, as they are being paid for it.

When I did this, it lasted for about 15 miles before the movement started, no parts were missing in assembly, just one not fully tightened, neither the bottom bracket or crank in my case suffered any damage, hopefully yours won't have either.

Good job finding that!