I was wondering if using an extension with a torque wrench reduces the accuracy of the torque wrench itself. The extension i bought is about 10 inches or so. I bought one that long cause i need one long enough to clear my fender to reach the lug nuts for my spacers.

Will the extension affect the accuracy by a great amount ??

thanks

 

Extensions do not affect the accuracy

 

maybe a little but not a whole lot.
the longer the extension, the more inner twist force it can take. means you applying less torque than you actually want.

 

^ Where did you get that information, because that is not true.

 

I think I heard it somewhere. cant remember.

 

If you use anything that changes the length of the arm it will change the torque...ie like a crowfoot. Changes that do not change the length will not change the torque...

 

Common myth that an extension will change the overall torque.

Even if you used a (theoretical) extension made of rubber, that twisted half a turn as you wound it up - the torque wrench would still 'click' at the exact correct torque at the other end.

Counterintuitive, no?

 

Torque = Force x (perpendicular)distance. The extension doesn't matter. It's the length of where you apply the force that can help or hurt your torque. That's why we use long cheater bars to break loose a tight bolt, nut, etc. Using the same force, you increased the torque with a longer handle.

Wow, I just used my engineering degree!!

 

i think this comes from people using extensions and swivels on impact guns and seeing reduced torque. impact guns definitely suffer the more joints are introduced.

 

Um, yes it does change it.

We (Lexus) just recently(well 3-4 months old) released a fuel pressure sensor torque recall. In the instructions they want you to measure from the end of your particular torque wrench to yield the ideal torque spec since it's critical for gasoline not to leak in the engine bay.

The difference in correlation to length vs torque was 1-8" varied between 2-10ft. lbs.


Point in case, there are many times at work I can't break something loose with my impact...until i use a smaller extension. Think of the energy required to transfer torque across a 100ft driveshaft VS. a 1 foot driveshaft. That's relativity.

 

lol im actually asking cause i remember someone saying it does. But as some of you have said it doesnt. It makes sense i guess

 

Here, end the myth.

Torque your lug nut to 80ftlbs with the longest possible extension you have.


Now torque it with the shortest socket you have.

If it moves with the short one - it's under-torqued and thus inaccurate.

 

Torque does change if you use the extension on the socket. They have a whole formula for it. Now the length of the wrench it's self or the extension on it doesn't really matter just gives you more leverage. We had one in the squadron for wing bolts that was huge over six foot long and 1200 or 1500 foot pounds.

 

Great read
Sub'd to an interesting topic.

Call in the Myth Busters I SAY!

Edit: Found this on the interwebz

http://www.freeinfostuff.com/TorqueE...eExtension.htm

I have no opinion on this topic .... just finding the topic interesting .... hanging around to see if we can come to a conclusion ...

 

Torque changes if you change the length of the lever arm.....

 

This is definitely very interesting. I would argue that the wrench itself stays accurate, in that it will indicate the amount of torque at the point where the extension (or socket, or whatever) actually mates with the wrench itself. I do NOT think that it would be an accurate measure of the amount of torque that is being applied at the end of the extension, which is really what you would be curious about. Now, that being said, I'm sure it's a miniscule amount, especially when using something like a 10 inch extension, but let's say that extension was 100 feet long, it would take a LOT of torque to spin a 100 foot long bar, and the amount of torque applied at the end of that bar would not be the same as it is at the wrench.

I'm just a silly computer engineer not a mechanical engineer so I could be off there, but that's what I think is happening.

 

The torque wrench may click when it has "satisfied" it's [rotational force] setpoint, but the longer the extension the less torque that has actually been applied to the nut (regrets also to our young mechanical engineer who was correct in his cited context, but not in answering the OP's question).

 

Haha thanks for the responses guys.

Alright so lets say i set my wrench to 100 pounds ... What is the actual torque applied on the lug nuts considering im using the 10 inch extension. I doubt itll be more than a 10 pound difference less at the end . Whats the formula ??

 

this actually probably becomes a materials science question (I know there is a mat. sci. guy or gal lurking around here somewhere) because the metal that you are using probably has an impact on the "formula" - but honestly, just set the wrench to 100 ft-lb and you'll be fine.

 

^ Actually, 108 ft-lb.

 

Thanks wcs. That link is great. Looking for crowfoot socket extension that can be purchased. Like the one that he welds together at the link.

 

Rotary-RX8, you need to clarify the type of extension you're referring to.

If it's a socket extension for your torque wrench, it won't affect torque.
If it's an extension to lengthen the torque wrench itself, then it will affect torque readings.

 

well, if we want to get that accurate, 100ft-lb would probably be too much (although I argue it would be "fine" as long as the bolt doesn't break).

let's RTFM...

 

UM, there is a TSB that ups the recommended torque specs to 108ft/lb. So you RTFTSB

http://www.finishlineperformance.com...2-04-1301b.pdf

 

A straight extension will not effect torque readings, a swivel or flex extension would change the final torque.

Anything that displaces the point of rotation from the lever that you are using would change the torque reading, unless it is linear to the axis of rotation.