Thread: Do you lose torque through a straight extension?

Okay, I've been doing a lot of internet searching and I was surprised at how big a split there is on this question:

Do you lose torque when tightening a bolt or nut using a straight extension?

A lot of people say something like this: You should add X ft-lbs for each 6" when using a torque wrench with an extension. The reasoning is that you lose torque in twisting the extension. A lot of people say you don't lose any.

I'm really curious what you all think. Please throw back a reply and give your justification, or just participate in the poll.

EDIT: For the sake of simplicity, for the poll I'm asking about tightening a bolt with a torque wrench, and whether I'd need to increase the setting on my torque wrench if I slap an extension on there. But feel free to throw in your thoughts about the same question applied to an impact.

you definitely lose some torque because of the connection points.

Torque = force x distance. Plain and simple.

if you stack extensions you for sure lose torque, but if you use one straight one you would lose a little torque still. but not as bad as stacked ones

well, i guess it also differs with how you're using it.

are we just using a ratchet or are we using an impact?

want a physics diagram to prove that you do?

example...im taking box bolts off of a chevy duramax, my impact has 1050lbs of breakaway torque..it struggles when i have a 6in extension on it taking an 18mm bolt off, when i remove the extension it doesnt struggle at and it zips the same bolt off on the opposite side much easier.

The only reason you'd lose torque is if by the extension you end up tilting the extension because you would then be decreasing the distance from your hand to the bolt. However, it would be very slight.

Torque Value Change when using a liner extension? - Topic

hmm other people are having the same discusion

That's in a perfect world where the extension it'self has no twist.

Torque sticks are the perfect example. They twist and only allow so much torque to be applied because of this twisting motion. Any flex or twisting of the extension (even though it's not visibly noticable) will cause decrease in the amount of torque delivered.

You definitely lose torque with an extension.

Just yesterday I was doing a timing belt service on a 3000GT and had one bolt that was refusing to come out. I had an extension on the ratchet because the short socket wasnt long enough to get inside the pulley.

After pissing with it for a minute we found a deep well socket (wasn't at my house so I was stuck using the owners tools) and it came loose with little to no effort.

You DO NOT lose torque because of an extension. I spent literally this entire semester going through this exact kind of problem in my mechanics of materials class.

By "lose torque" you mean that you exert X ft*lb of torque on one side, whereas the bolt only experiences Y ft*lb where X<Y. But according to statics, the sum of the forces about the rod must equal zero. So, if there is X going clockwise, and Y going counterclockwise, with no other moments being applied, then X must equal Y.

Edit: What some of you may think of as "losing torque" may actually just be your thoughts that you must be twisting the extension, which is absolutely correct. You do twist the shaft because of the equation theta= Torque * radius of the shaft / (J*G). where Theta is the angle of twist in radians. Regardless of the twist, you still have the same amount of torque on both sides. The only difference is that you must turn the wrench farther in order to compensate for the twist of the shaft.

If you dont loose torque then why can I take a bolt off with my impact with no extension but with an extension I cant?>riddle me that.

To anyone that believes you don't lose torque due to an extension: Please test what you are saying. There is a certain amount of give in an extension. The relation and importance depends on what you are working with. Want a semi scientific test, use 4 feet of extension to take out or put in the backwards trans bolt. There is a lot of flex in that length and it is noticable. A very stubborn bolt may visibly show a twist in the extensions.

OP, if you search on Google etc for the scientific truth about this, you will find that all extensions are prone to a bit of reduction in torque. If your question is .. do you need to worry about using a 6" extension when torquing LIM or SC bolts, then no. The change in overall torque change isn't enough to make it necessary to be a concern in our application.