Back story: Purchased bike several months ago. After about 300 miles the spokes were loose and the wheels slightly untrue, so I tightened them and spent a few hours truing both wheels as per instructions found on the internet. All spokes seemed tight, and appoximately the same tension. I don't have a tension meter but they all felt the same to me and the wheel spun very straight (within a millimeter). Rode for another couple hundred miles, all was well. Friday I pulled my bike out after a week of not riding and noticed several back spokes were very very loose and making noise if I tried to ride. I usually inspect the tires and the spokes once a week and never noticed any spokes going loose, but now all of a sudden 6 or 7 were extremely loose. So I started the tedious process of tightening all the spokes up a quarter turn at a time. Once of the super loose spokes snapped off as I was tightening it (it was definitely not from being over tightened - it never got that far).
It looks like I am going to have to remove the cassette to be able to feed the spoke through. I watched a bunch of youtube videos to see other people doing it. I think I am going to need a special tool to remove the cassette, but I can't tell exactly which one will fit my specific bike.
So I stopped at the local bike shop with the wheel. I asked if they sold spokes, and also if they had the tools I could buy to do it myself. I explained that I want the tools and the know how to do it myself for the next time it happens. He kept urging me to just leave it with him and have him take care of it even though I thought I adequately explained that I don't want to continue to rely on someone for my simple repairs. He didn't have the tool in stock. All the cassette removal tools on the wall were labeled "FR-7", and "FR-5" and so on. He pulled one from behind the counter that his shop uses and it fit, and when I asked what size it was he said "oh it's just a standard shimano cassette remover". So I said "um, so what differentiates it from these other 7 (approximately) differently sized tools on the shelf", and he didn't really have an answer, just said it was a standard shimano cassette remover. He just gave me some string of numbers (that I don't remember) from the part, so I left without knowing what size will fit my cassette. He also tried to sell me a $28 chain whip and said it's needed in addition to the cassette removal tool (which he didn't have so I don't know why he thought I would just purchase a chain whip). From the videos i've seen on youtube it appears you can just wedge the wheel against a wall and spin the tool counter clockwise to remove the cassette with no chain whip needed. Not sure if those were on a different cassette mechanism than I have, or what.
So how do I tell what size cassette removal tool I will need for my wheel? All I can see on the cassette is "Epoch Hyperwave System DnP 40N.m" and it has 12 teeth
Is a chain whip really necessary or can I simply wedge the wheel against the ground/wall to stabilize it like I witnessed multiple people on youtube doing?