I've read that a breaker bar is much easier on nuts and that you should never tighten a nut with a impact wrench like tire places do. It should always be done with a torque wrench.
I've probably snaggled more nuts with a breaker bar...there is always some twisting component with the breaker bar...by that, I mean a force at a right angle to the applied torque. This is exaggerated with deep well sockets, or if you have to use an extension. But an impact wrench is true torque.
I wouldn't tighten a nut with an impact gun...you have no idea how much torque it's really putting out. I suppose if you have adjustable setting on the impact wrench to limit the torque (mine has 6 levels) and you start the thread by hand so you're sure it's not cross threaded - then it should be OK to run the nut down with the impact and use a torque wrench for final tightening.
Have any of you found that nuts get worn from impact wrenches?
Seems just the opposite. Nuts come out in good shape with the impact and get boogered up using the breaker bar. Now sockets on the other hand...so far, I 've had one Wal-mart socket split down the side after 7 years of home garage work.
When you use an impact wrench for the front sprocket, do you have to have someone sit on the bike and put pressure on the front brake?
I didn't...with an impact, the torque is high, but the duration is so short that it doesn't transfer much overall torque to the wheel...plus, the nut busted loose so fast I don't think the wheel even had a chance to turn.
But impact wrenches work the same for things like flywheels, harmonic balancers, etc. Things you would have to block up to keep from spinning while using a breaker bar, you can just pull the trigger on the impact wrench and let the high impact force do the work.
Does the socket have to be rated for an impact wrench?
That would be ideal although even seemingly cheap tools (wal mart) have lifetime warranties now. If you do use a "regular" socket, there is always a chance of it splitting or breaking...sometimes with flying pieces. So if you don't feel like investing in a complete set of impact sockets, it may at least be good to get a pair of safety glasses.