How accurate and well do these work? What is the science behind them? They have been around for ages and mechanics usually tend to use them.

It seems these would give a consistent rating of torque, whereas a torque wrench can and will be uncalibrated.


Modified by Understeer at 4:27 PM 6/2/2006

 

They work awesome, that's how they work.

No, the metal twists a certain amount at a given torque rating, by the time the hammer on the impact goes to hit again the metal untwists. Keeping pretty close to the given torque rating of the stick.

 

I personally would much rather use a torque wrench. I would rather know that I physically put that much torque on each lug. Never know with a gun...

I have had them done that way when I got new tires put on at a shop. When I came home, I checked the torque on each stud and it was drastically different. Whether it was his gun, or my torque wrench I don't know for sure, but I tend to think it was his stuff over mine.

 

Don't get torque sticks. only lazy mechanics use them!

To use them properly you have to "set-up" the gun and adjust the amount of pressure going in to the gun. After all that they are horribly inaccurate (I have seen 20% variance). Get a good torque wrench. You'll be able to use it for more things than just tires, like suspension parts too :-)

 

In my experience they are very inaccurate. Some people use them to limit how much torque a impact gun is going to put on the lug but most impact guns I have used don't hit full torque until after several 'impacts'. Whatever setup you use you should always finish with a torque wrench.

 

Guns are for removing bolts, not hammering them on...always use a torque wrench.

 

Only time to use the sticks is during pits stops during an enduro when you can't afford the time for the torque wrench.

 

Well, now I am thinking of buying a 75ft/lbs torque stick so that the lugnuts are not overtightened and then use a torque wrench to set them to 80ft/lbs.

 

Why even bother with a torque stick? Run the nut down until the gun 'hammers' for the first time and stop. Then use the torque wrench after that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nfn15037 &raquo;</TD></TR><TR><TD CLASS="quote">Why even bother with a torque stick? Run the nut down until the gun 'hammers' for the first time and stop. Then use the torque wrench after that.</TD></TR></TABLE>

 

As stated above, torque sticks are not accurate enough.

If needed, use an impact gun to very lightly tighten the lugs after starting by hand but always make sure to torque with a torque wrench. Also make sure that the nut/bolt you are tightening moves slightly before the torque wrench clicks or you are not accurately torqued. This is the old static friction being greater than dynamic friction theory...

A cordless drill can also be used to run the lug nuts down before being torqued.

Also, make sure to back your clicker style torque wrench down to 0 after use to make sure the calibration does not change!!!

 

Why all this worry about torque accuracy? Has anybody taken the time to check how accurate you have to be? Does anyone think it actually matters if torque spec for wheel nut is 80 ft-lbs and you torque it less to 75 ft-lbs or more to 85 ft-lbs? Just take the time to study machine design/fastener technlogy and you will see that you just do not need to be that accurate.

See here:
http://www.utm.edu/departments...8.pdf
http://www.utm.edu/departments...9.pdf

And on the slide with Experimental Data on this lecture:
http://www.utm.edu/departments...0.pdf
you can see that for torque of 90 N-m, they get a standard deviation of +/- 29% on un-lubricated joints and +/- 17% on lubricated joints. Slide also says: "there is considerable scatter in torque vs preload data"

Or read Carroll Smith's book on Nuts and Bolts

Typical torque setting is 75% of maximum proof load which is the point at which the bolt begins to permanently change its length. But if you torque it to 80% or 70% of maximum proof load, you still have a very good joint. Actual torque you should use is so dependent on various friction factors such as bolt plating, thread quality, lubrication, head friction (think of aluminum galling where the wheel nut contacts it), that if you look up 20 charts for recommended torque settings you will get 20 different values. Some give torque based on % of proof load, some on % of yield strength or % of maximum tensile strength (point where bolt breaks). Some charts say torque it to somewhere between 60-90% of yield strength, but you need to know the friction in the joint to know the torque value to get bolt to that value of preload.

Plus your torque wrench can very easily be off by 5-10% unless you've had it calibrated. That means you torque bolt to 80 lbs but it could actually be set to torque anywhere from 72 to 88 ft-lbs. And how many people have actually had their torque wrench calibrated at say 80 ft-lbs???????

Based on all these factors, I think the use of a battery powered impact wrench and a torque stick are the greatest thing since sliced bread. It makes a fantastic combo at the track. After I finish, I just double check all the nuts with a torque wrench, mostly to make sure I didn't forget one while someone was talking to me. But I sure wouldn't worry about going out on track having just used the torque stick. Just do 20 wheel nuts with the torque stick and check them with your torque wrench. See how much they move. It will vary, as some nuts always have more friction than others, and torque wrench puts a side load on fasteners that the torque stick does not.

Worry more about forgetting to tighten nuts on a wheel and going out on track. That happened to me, and I felt really dumb. But it happens!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jlucas &raquo;</TD></TR><TR><TD CLASS="quote">Only time to use the sticks is during pits stops during an enduro when you can't afford the time for the torque wrench. </TD></TR></TABLE>

The ITC car I was crewing for a couple years ago at the ARRC almost had multiple wheels fall off because of the torque stick/electric impact not working correctly. You can guess if its been used since then.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ryan12321 &raquo;</TD></TR><TR><TD CLASS="quote">

The ITC car I was crewing for a couple years ago at the ARRC almost had multiple wheels fall off because of the torque stick/electric impact not working correctly. You can guess if its been used since then. </TD></TR></TABLE>

I would bet the problem was that the electric impact didn't have enough torque to twist the torque stick. I vaguely remember reading somewhere that the impact gun needed to have at least 400 foot pounds of torque for the stick to function properly. I use them at work all the time and every time I check them they are within 5% of the stated torque. They're good enough that I use them on my own car, not just customer cars.

But to answer the original question, no I wouldn't use an electric impact with torque sticks.

 

when i first saw them used at a friends shop, i was in disbelief that it would be effective. i checked with my torque wrench, it was definately within 5 ft-lbs accurate. it was an air gun and maybe the gun was tuned properly for it, but they do work.

now with an electric impact, it may be a different story. i couldnt vouch for that.

 

air is best but electric can be used with a torque stick, just make sure the battery charge is kept topped off because the torque output is dependant on the charge level

 

Just put a torque stick on a good quality cordless impact (DeWalt, Milwaukee, Snap On, etc), add a torque stick and torque a set of wheels. Then check them all with a torque wrench. Then you will know (within 10% unless you've had your torque wrench calibrated) what the nuts are torqued to. If they require a minor top up in torque with the torque wrench, you wil still have saved a ton of time first taking wheels off, and then putting them on. Changing wheels at the track a bunch of times is a pain. Anything that makes it better is welcome by me. No way I am going back to the old way and not using my Dewalt cordless impact and torque stick.

Look here:http://www.tomorrowstechnician.com/tt/tt100506.htm
"One manufacturer says their torque sticks can accurately limit torque to within plus or minus 5% of a specified value. Evaluation tests conducted by General Motors found that accuracy was actually even better - within plus or minus 2%!"

or here:http://www.procutinternational....html
"TorqStik now the only torque limiting socket approved by all of the Big 3 Automakers"

I have the TorqStik one, which for 80 ft-lbs is a blue color.

Here is some info onhow they work:http://www.procutinternational....html

You guys think that the car manufacturers think torque sticks are good enough for them but not for you? They make millions of cars!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote">
You guys think that the car manufacturers think torque sticks are good enough for them but not for you? They make millions of cars!</TD></TR></TABLE>

Manufacturers are not using cordless impacts. And the failures we had were with fully charged good quality impacts if I remember correctly.

I use them with good air supply with a high quality air gun, but will never use one with a cordless.

 

I agree with you about the manufacturer's not using cordless impacts. In your failures, had you ever checked your calibration of the electric impact/torque stick with a torque wrench?

My Torqstik came with instructions to set the air pressure on my impact gun to between 90-100 psi as I recall. Then you torque some nuts and check them with a torque wrench. Then re-adjust pressure to calibrate your setup. Manufacturer's instructions say to use the Torqstik with an air powered 1/2' impact gun that produces 250 ft-lbs of torque. I did that in my garage where I have air. Then I got a battery powered impact and checked my calibration. Most nuts were bang-on 80 ft lbs when I checked them with my torque wrench and a few needed an extra 1/12 of a turn. So now I just use the electric impact at the track, and go around the car and check or tighten them with my torque wrench. Saves a ton of time. (it is great for removing the nuts too, using a conventional socket, which I use on the torque wrench). I just don't see how they can be a problem if you finish up with a torque wrench.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nfn15037 &raquo;</TD></TR><TR><TD CLASS="quote">Why even bother with a torque stick? Run the nut down until the gun 'hammers' for the first time and stop. Then use the torque wrench after that.</TD></TR></TABLE>

That's what I do and have been doing it for 3 years without a broken stud or any wheel or nut damage (God, how I hate nut damage :-)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by descartesfool &raquo;</TD></TR><TR><TD CLASS="quote"> I just don't see how they can be a problem if you finish up with a torque wrench.</TD></TR></TABLE>
then you are defeating the purpose if you are going to torque them anyway. I impact them snug and then use the torque wrench, and I dont have to mess with any torque sticks.