What is the Torx size I need for the rear fender side mounts on a 2004 and
later Sportster.

There's 2 bolts per side and the Torx I have are too big (45 and 50). I was about to install the docking kit but I had to give up pretty quick

 

im not sure the size of those, but I can tell you I just went out yesterday to sears and bought a set of craftsman socket torx bits for $18, came with 20. I only needed one, but I figured for the price I couldn't pass that up.

 

Its a T-40

 

T40. Be careful when tightening down the rear bolts. They screw into a nut plate and the threads on them are not too strong.

 

Thanks for the tip!
I don't have a torque wrench. I've been going by common sense, if that makes any sense.

I'll go out and pickup a T40 tonight.

 

For those bolts, I haven't been able to find a torque value, so I just get them tight, but not to the point where your putting your body into it to get them tight.

 

I was able to get them pretty tight.... as tight as I could get them with my allen key (the new bolts in the docking kit are Allen Key, the orginal fender bolts are Torx).

The torque value is listed in the instructions. If I remember correctly, it states 15N/M.

I got a bit a blue loctite on there too and even re-did the crash bar bolts with the loctite (the instructions for the crash bar didn't mention the loctite but it did for the docking kit).