Good concept, but unfortunately slow

The principle: A mass in the impact wrench is made to rotate. Once it reaches a certain speed of rotation, engages a kind of coupling and the mounted nut is a blow to, so it rotates. This mass is brought to a standstill, the clutch is opened and brought the crowd back into the swing, etc .. rotates the nut, the rotation speed of the mass is maintained. Does not rotate, the mass is more accelerated and brought to a higher rotational speed in order to exert more force / a stronger impact. Also finds no motion, the speed is again increased to the maximum torque of 250Nm. Moves the screw, is again continued to work with the output speed.

When tightening can be digitally selected a torque with which the bolt to be tightened. I would not trust (be sure to use a torque wrench!), Since the torque is determined similarly to the loosening of the screws in with the rotation speed. If the screw is already slightly (by hand) is tightened must be firmly screwed. Sits the screw still loose and only a few turns should be rotated until it rests on the wheel, it is not enough tightened. The selected torque is just a guideline - I recommend adjusting 80NM and tighten with a torque wrench to 110 / 120nm (aluminum / steel rim).

Now, the functionality is given and stubborn screws can loosen the impact wrench. But, all happened a bit slow for my taste. If you have time and only the tires have to change from a vehicle, this impact wrench is a really good alternative to air driven units. Especially for people in the city who have no outlet nearby and no place for compressor and equipment this impact wrench as made for it. I wechlse within my relationship 2x a year at 4 vehicles tires. But the thing is just too slow and undersized.
On the positive side I have noticed that the capacity of a (loaded) car battery is sufficient distance to all 4 tires and to screw again and anschließden to start the vehicle without difficulty. So it is not necessary to run the engine, so that all 4 tires can be changed.

Conclusion:
+) Works, despite the "only" 12V very well, even with tight screws
+) Optimal in town when no power outlet is nearby and no compressor is available
+) Practically no effort required - you need the screwdriver just "stall". The gentle Beleunigung the internal mass almost no forces are transmitted to the arm
+) The capacity of a car battery is enough to switch 4 tires and then to start the engine

-) The operation, however, is good, the speed slowly - for a vehicle safe enough (though there already annoying). If possible, I recommend a compressor (there starting at around 100 EUR) with air-operated impact wrench.
-) Setting of torque only a guideline - a torque wrench can not be around (even in a air-operated impact wrench)
-) Are successively changed the wheels of several cars, is a cooling advisable (not you think it, the device has a built protection against overheating and stops until the device has cooled down). 4 tires in a row (from and to) have not led me to overheat. Here it is adequately dimensioned

~) While there are 4 sockets included, these I have not used. On the one hand, because they have been classified by other reviewers as inferior and there is a risk that they split up, on the other hand, because I have quite a good sockets at home, I have long been in use. The sockets I bought here on Amazon (the 3 colored in red plastic box).