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My car lug\wheel nuts need to be torqued to 80 ft pounds. I know some people go by feel. Does it matter if you are a bit lower or higher e.g. 70 or 90? what if the difference is 20 ft pounds give or take?

I'm thinking of all the garages out there they probably dont look up the workshop manual and find the torque specs and instead have a generic idea e.g. 70-90 ft pounds are ok for wheel nuts on standard cars. suvs have a different range. Would I be correct?

So yeah can we have variation and how do garages decide what a particular car wheel nut/or other nut for that matter should be torqued down to?

  • No, it doesn't matter at all. Unless you expect your car to be safe and reliable. The specified torque for wheel nuts is important. Too loose and you risk them loosening on their own, obviously a dangerous situation. Too tight and you risk cracking or warping the wheel, hub, or breaking one of the lugs. Also a dangerous situation. A reputable shop will torque all fasteners to the correct specification using calibrated tools. – jwh20 Nov 17 '19 at 11:44
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    Unless you have brand new studs and nuts and everything is carefully cleaned and lubricated before assembly, the difference between 70 and 90 is well within the random variation caused by friction. In fact where high accuracy is required, the assembly procedure is usually to torque to a low value (to take up the slack in the joint) and then rotate the nut through a specified angle, without measuring the torque at all. – alephzero Nov 17 '19 at 12:29
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    … and for really high accuracy (i.e. about 1%) you use bolts and studs with a built-in force transducer, so you can measure the actual clamping force in the joint, not the torque you applied to the nut. But wheel studs at $100 each would be overkill :) – alephzero Nov 17 '19 at 12:39
  • @alephzero Comments in comments and answers in answers! – Kitsunemimi Nov 18 '19 at 14:28
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+- 10 ft-lbs off of 80 ft-lbs base is fine. However, when a repair shop takes an impact gun to lug nuts, they may well tighten them to 100 ft-lbs or more. That is not as good.

Over time one does develop a sense for when a bolt is sufficiently tightened. Personally I can't tell if a bolt is overtightened well. Maybe other people are better in this regard.

If lug nuts are not tightened enough, the wheel may eventually come off the vehicle. This is very bad.

If lug nuts are overtightened, the car is fine until the next service. Usually repair shops have powerful tools to take lug nuts off, and given that most cars don't have their wheels removed that frequently it's not an issue in practice. Problems may arise if the car is driven on salty roads and the fasteners seize together - then they are more difficult to remove, especially if overtightened.

In the event that a repair shop does break a lug nut, they can simply replace it along with the stud, if needed. The parts are cheap and the time saving on not torquing lug nuts to spec probably justifies the infrequent lug nut and/or stud replacement. Some of the shop may charge the customer for replacing these parts even though it's not really the customer's fault that shops tighten lug nuts with impact guns.

People who drive race cars, including amateurs, always tighten lug nuts by hand to torque specs because the wheels get removed much more frequently and the parts get a lot hotter than in regular street driving, and so the likelihood of problems if lug nuts are overtightened is much higher. Some people may choose to use non-factory torque specs but everyone I know tightens their lug nuts to their chosen specs by hand.

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  • Great answer but one additional note - significant overtightening lugs on alloy wheels can cause damage to the wheel in some cases. I had a shop torque mine to ~400ft-lbs (or at least that's how much it took to remove them) and it ruined my wheels. – cscracker Dec 19 '19 at 18:40
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The materials used and purpose of the nut, bolt etc are all part of the setting value.

Good garages have the information easily to hand, but cars they work on often, well you remember the numbers.

Bad garages aka cowboys have 3 torque settings : loose, tight and f****** tight.

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