So I called the LBS to find out if someone could tell me if a set of cranks would work in my Trek Mamba. The guy on the phone says "what do you want to upgrade the cranks for? The Trek Mamba frame is not worthy of upgrades. Usually people just trade in their bike and get half their money back and upgrade the whole bike. Any bike that runs less than $1000 isnt worthy enough to upgrade." Then he says if your buying online then im not making a penny and I was waisting his time. Same place I have purchased two bikes and quite a few accessories from. I am quickly learning to buy upgrades online and do the work myself.
The guy who answered the phone fell into a familiar trap and could have handled it differently. Correct me if I'm wrong, but from what I'm reading, here's what he heard:
"Hi, you don't know me and I've found some cranks online, but don't know if they fit my bike. I'm calling you for free advice so I can buy something off eBay because the eBay retailer can't or won't offer me any customer service, but I expect you to do this for me out of the kindness of your heart."
He gets this all day long. He did want to dust you off his shoulders because, in his view, you will, likely, waste a lot of his time in the future by calling or coming in for advice and buying online and watching videos online and installing it yourself.
The way he should have handled it was, "Those are great cranks and a little out of spec for that bike, what's wrong with the ones you have now?"
Or, better yet, the way you could have handled it was, "Hi, I bought a Trek Mamba from you a while back and I'm really disappointed with the cranks because one of the arms keeps coming loose. I saw a pair of cranks online and I'm thinking about buying them so I could replace the stock ones because I don't want to waste my or your time with a warranty claim, but don't know if they will fit my bike - is this something you can help me with?"
His response should have been, "Man, I'm really sorry you have to deal with that. I've got a pair of loaner cranks here in the shop. Why don't you bring the bike in and we'll swap them out real quick so you can stay on the trail while we get this warranty thing sorted out. As for upgrading the cranks, you probably won't see much of a performance increase by swapping out cranks. It's usually the last thing I upgrade on my bikes. Besides, from my experience, once you start upgrading an entry-level bike, it will be so much more expensive replacing part by part than if you just buy an entire upgraded complete bike. What is it about your bike that you'd like to be different?"
See the difference? This is where a lot of bikes shops could differentiate themselves. That's the value of a LBS over online retailers. Online guys can't do that.
Now, I'm going to talk out the other side of my mouth because it is so rare an LBS provides that level of service. If you're considering a Trek Mamba, Consider this:
Sette Razzo X7 10 Speed 29er Alloy Mountain Bike at Price Point