1. Any physics major or experience techs out there explain to us why and what’s better to remove a nut a breaker bar or an impact wrench.

2. When I was working on R/R of my rear wheel bearings I was trying to remove the main nut with a breaker bar but have a hard time but when I tried the impact wrench just for fun, it came right off!?

Thai GI sends…

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If you could produce the same torque as the impact wrench, and the bolt or nut in question was fairly new (i.e recently installed), then you can achieve the same results with either tool.

The truth is, most sizeable fasteners are already torqued to some ungodly spec in the first place. The other issue is that the fastener is located in an area that is subject to heat, dirt, or environment (translation: welded to the threads of the part it's attached to). That makes it even more difficult to remove.

The breaker bar can only produce the torque necessary to loosen the fastener, but if it's seized, enough torque may just snap it right off...then you have a more expensive problem!

The impact wrench can produce a lot of torque (assuming it's attached to a sufficient air supply), but more importantly, it can produce this torque while hammering against the sides of the fastener at very rapid successions (hence the name "impact"). This vibration aids in shaking loose particulates, rust, etc. from around the fastener, making removal easier. When the fastener is free to turn, then torque takes over completely and the impact wrench is only rotating the fastener. That is why you hear the "hammering" sound of an impact wrench when in the initial stages of loosening, or final stages of tightening. But the "woosh woosh" sound when the fastener is turning freely.

The other advantage of an impact wrench is that it can be used in tighter areas than a breaker bar. A breaker bar is essentially a lever, so the amount of torque it can provide is dependent on the force the user can apply times the length of the bar. That means the breaker bar has limited applications...you need to have lots of room around you when using it!

As a footnote, air impact tools require special heavy-duty sockets for the job...you can't use those standard off-the-shelf sockets you buy for hand tools. The hammering action would shatter those in seconds!!!

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I have found that you have to be carefull on tight smaller diameter bolts with an impact wrench as not to snap them. where as if you use a sturdy rachet and apply pressure with one hand as you tap the handle with a hammer with other hand that you are less likely to break a rusted or tight bolt, I relize that some times there's not enough room to do this. A bit of carefully applied heat can sure do wonders.....
William Rogers........

I'm neither a physics major nor a tech but a problem with breaker bars particularly when used with a socket extension is that you exert forces other than torque on the fastener. Conversely, not all the effort you apply at the far end is converted to torque on the fastener.

Sixto
91 300SE
87 300SDL