This is my first attempt at bike mechanic work beyond swapping out simple parts that wear out.

My 2007 GF Rig (the black version with Reba) came stock with a 18T cog, a simple flat one. Since I was in FL and there were no hills or mtns, I wanted to convert it to a city bike. I brought it to Retro City Cycles outside Orlando and they hooked me up with a $30 freewheel cog (has a spacer built in). I'm now in NY, in the Hudson Valley, and wanted to switch back to stock cog which I saved. I decided that I wanted to learn how to change it myself and got myself extra tools: BBT-18 (ISIS adapter) for the lockring, SR-2 chain whip, wrench for the adapter, and a chain breaker for the new chain (since I didn't have extra links and the original chain was stretched already with 1000-1500 miles on it).

My problem started out with the lockring. The BBT-18 didn't fit exactly on it, but fit snug enough (halfway on) to loosen it. I notice the freewheel is threaded all the way in, which clues me in that the lockring can go in all the way in. Now, I slide the 18T on and thread the lockring back in by hand until it gets a bit tight. Now the lockring is too far in to fit the BBT-18 on it... obviously I need a spacer now if I'm going to be able to tighten it with this adapter. Now that makes me wonder, did the Rig have a spacer on it to begin with and, if so, why didn't I get it back from the shop that changed it? I wonder if a LBS has a spacer for sale.

Now, I kind of wonder if I got the wrong tool to begin with. The BBT-18 is for ISIS external bearing cups. I got it since the lock ring seemed to be that exact pattern, but I could be wrong since it doesn't fit. Is there a tool for this lockring specifically? One that can tighten it all the way without need for a spacer and actually fits? I'm doubting I could get any decent torque on the lockring even if it could reach.