TonyDtorch said:
couple more questions Mike
we all know 'tight' is very important on every lug nut .. My motorhome even has a warning label to check the lug nuts.
It appears that some people and or tire trucks still don't use a proper torque wrench procedure to tighten the lugs, and it appears there is no real history or evidence of stud, lug and or wheel failure common in the industry due to improper torque .....so is proper torque really that important ?
I could see if there were wheels were falling off and trucks were crashing all the time, then I'd go out and buy a 200 f/lb torque wrench and throw my impact gun back in the box.
last thing....have you seen those 'color coded Torque extensions' used on impact guns? are they a joke or are they ever used on wheels ?
Tony, sorry for the delay, been away from the computer for a bit.
I would not say there is no evidence of problems, are there wheels falling off all over our highways? No. However, there is still evidence of problems or we wouldn't spend so much time ensuring the wheels are torqued on properly. Most if not all shops err on the side of over-tightening the lugs to ensure the wheels stay on. When this is an immediate problem is when that stud snaps off right then and there where the mechanic is installing the wheel, which does happen more frequently than it should. Wheel stud torque spec's on heavy trucks and large RV's is in the 450-475 ft/lb range and it is nothing for a 3/4" or 1" impact gun to be upwards of putting out in the 1400-1800 ft/lbs of torque, even my little 1/2" IR gun puts out 1200 ft/lbs of torque. The main reason we adopted the SOP of properly torqueing the wheels on about 10 or so years ago was the rash of broken studs going through our shop. The less frequent issue is over-tightening the stud at installation and weakening the stud but not immediately snapping it off. This is generally recognized by two scenarios, first it is stressed just enough additionally going down the highway that it breaks off the remaining way OR the next time the wheel is being removed the mechanic applies reverse torque on the fastener removing it and it breaks off. Both scenarios still result in the same outcome that the stud needs to be replaced. Replacing studs is not a difficult task at all but does take some additional time compared to merely a tire/wheel R&R.
As far as the torque sticks go, I have my own personal opinion about them even though I see them used a LOT, almost exclusively in the automotive industry. I have played with them and performed my own "bench tests", which is not scientific at all.
My opinion is that they do fall within a "range", however, I feel that range is broader than acceptable to me, again this is my personal opinion and I guarantee not recognized nor agreed upon by the industry as I am sure anyone using them feels the range is perfectly acceptable. Most of the torque sticks that me and my co-workers tested fell in the 10% +/- range or even broader depending on quality of the tool. Just for a comparison, the ANSI (American National Standards Institute) requirement for torque specifies that torque wrenches must fall within a 4% +/- range when used within the 20-80% range of a torque wrench, however, this seems to be overlooked or not scrutinized when talking about wheel studs. :-\ All of my torque wrenches fall within the 1-2% +/- range. As you can see torque sticks are well beyond that range yet perfectly acceptable on wheel studs by the industry.
Is this range of 10% +/- bad? In my opinion it is better than not using anything and just rattling the lug nut onto the wheel not having any idea of where the torque falls, but it is not as accurate as I would like on my personal vehicles. Again, I am NOT speaking for the industry, just my personal opinion and the way I do things in my shop on my vehicles or any I personally work on.
Mike