Ed, Fasteners have a dry torque setting and a wet (lubricated) torque setting.
When you tighten any fastener to a specific torque, you are really pre-tenseling the bolt shaft - it stretches & acts like a spring and the spring tension keeps everything locked together. This is why you can cut off the head of a rounded off bolt then you can easily unscrew the threaded shaft. That is unless the bolt is locked in with corrosion, which is a completely different issue. Some fasteners, like head bolts, have a maximum stretch because the manufacturers understand that the bolts can loose their tensile strength if stretched too far. This is why Mercedes instructs you to measure the fastener length before reusing them. Fasteners like head bolts are spec'd wet (lightly oiled) because lubricated torque is more repeatable. Wet torque settings are lower than dry torque settings because the lubricant helps to overcome the thread friction and you need less torque to reach the proper pre-tenseling of the bolt shaft. In other words, a fastener that has a 85 pound feet dry torque spec may only have a 75 pound feet wet torque spec. The following web site does a better job of explaining torque specs than I can. Look up a 1/2-20 bolt in the chart then look across to the 5 column (SAE 5). You'll note that the dry torque is 90 pound feet while the wet torque is only 65 pound feet. The same fastener in SAE 8 is spec'd at 120 dry / 90 wet. There is also a de-rating chart on the bottom - Anti-sieze is not on the chart & I don't know how much it de-rates the torque setting. They also mention that a bolt that has been over tightened can be as lethal as one that has not been tightened enough. Why? Because you can weaken the bolt enough to make it shear off or make the threads fail. http://www.raskcycle.com/techtip/webdoc14.html Thanks, Tom Hargrave www.kegkits.com 256-656-1924 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of E M Sent: Sunday, July 22, 2007 9:11 AM To: Mercedes Discussion List Subject: Re: [MBZ] Anti-sieze on wheel lug threads (was: [OT] tool quality.) Many say not to use it, but I always use a little. When I took the first wheel on my benz, you could feel and unever drag on the threads, as you often do with dry lugs. More than the treads, I like a little on the bell of the bolt, where it meets the rim. A little goes a long way, as you get near the end of the threads and the bell starts to seat, and drags, I don't know how you get a really accurate torque without a little AS. That's what I do anyway, and I haven't worped a rotor or lost a wheel yet. :-) ps. I think the "official" word is do them dry as many have told me. Ed 300E On 22/07/07, Allan Streib <[EMAIL PROTECTED]> wrote: > > I used a bit of parafin on the threads last time, per Dr. Booth's > recommendatian. > > "Tom Hargrave" <[EMAIL PROTECTED]> writes: > > > Anti-size acts as a lubricant & actually lets you over torque your > > lug nuts/bolts. > > > > Thanks, > > Tom Hargrave > > www.kegkits.com > > 256-656-1924 > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto: > [EMAIL PROTECTED] > > On Behalf Of LWB250 > > Sent: Sunday, July 22, 2007 8:14 AM > > To: Mercedes Discussion List > > Subject: Re: [MBZ] [OT] tool quality. > > > > Pretty much. They flex above a certain torque value. > > > > It's good that they are using them, however, all cars don't have the > > same lug nut/bolt torque. > > > > As soon as I get home from a tire replacement or wheel removal, I > > bust 'em all loose and retorque them to spec myself. I also use > > anti-seize on the threads (don't EVER get it on the shoulders of the > > nuts/bolts!) > > -- > 1983 300D > 1966 230 > > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
