Wheel Nut Torque

[shogun32]

Sorry to necro-thread but nobody posted any actual engineering! A wheel is held in place by friction between the clamped surfaces. If the wheel stud or the 'nose' of a hubcentric spacer is taking sheer loads you're a goner. It means your friction limit has been overcome and you didn't have the parts clean but definitely not clamped tight enough.

https://www.fastenal.com/content/feds/pdf/Torque-Tension Chart for Metric Fasteners.pdf

The reason for the difference between <2015 cars and after is the fastener size and thread pitch. The yield on the threadforms are different. Basically you want 75%+ of yield strength. That's why everyone's lookup table spits out basically the same value.

In practical terms you want absolutely no less than 9,000lbs (85ft/lb) of clamping force (unless you have data otherwise) or alternatively 65% of yield on a bare AL wheel. 12-14K (110-130ft/lb) is a MUCH better place to start. If you have spacers especially ones with slick surface treatments, you'll want to consider 16K (148ft/lb) your lower bound and maybe shoot for 18K (165ft/lb) not to exceed 19K (175ft/lb) assuming your fastener (M14x1.5) can withstand it. All the above assumes clean threads and an accurate torque wrench and technique.

In any event, RE-CHECK YOUR TORQUE shortly after you initially set it to catch anything amiss. Nuts can loosen from vibration, wheel wasn't seated square, changes in temps, etc. It's not a one and done task.

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[Ewheels]

There's no "feel" to this. Hell Ford doesn't even have anything to do with the torque values. It's all calculated by nationally standardized fastener organizations. Think SAE, Society of Automotive Engineers. Taking into consideration the bolt diameter, thread count, thread pitch, material hardness, lubrication, and applying an industry controlled factor of safety you get the required bolt torque for proper clamping force.

For any M14 x 1.5, Class 10.9 bolt, the required torque is right around 150 lb-ft. There's no reason to go lower.
The only reason this seems higher than your average car is because your average car doesn't use M14, 10.9 bolts. That's it.

 

[BmacIL]

There's no "feel" to this. Hell Ford doesn't even have anything to do with the torque values. It's all calculated by nationally standardized fastener organizations. Think SAE, Society of Automotive Engineers. Taking into consideration the bolt diameter, thread count, thread pitch, material hardness, lubrication, and applying an industry controlled factor of safety you get the required bolt torque for proper clamping force.

For any M14 x 1.5, Class 10.9 bolt, the required torque is right around 150 lb-ft. There's no reason to go lower.
The only reason this seems higher than your average car is because your average car doesn't use M14, 10.9 bolts. That's it.

I'm at the point where I'm just going to be like, "OK yeah sure just go for it bro, yolo!" There's no technical reason why a torque needs to be specified.

 

[Ewheels]

Interesting engineering.

Do you normally torque other critical fasteners in the cars you work on to lower torque than the manufacturer recommends? For example the strut to spindle bolts on the 2015 Mustang are 16 mm with a torque spec of 184 ft-ft. Would you torque those to a lower number?

FYI for anyone who is looking for a 1/2 inch drive 250 lb-ft torque wrench this one from Lowes appears to be good quality and works well so far for me. http://www.lowes.com/pd_337334-22328-85602_0__?productId=3381202

The fact that a "Diamond Sponsor" vendor does not use factory torque specs is alarming. I'm actually glad this came up. Now I know never to take my car there.

 

[Ewheels]

This seems like a good place to add some educational nerdi-ness...

You hear "foot pound" and "pound feet" used interchangeably when discussing torque all the time. Most people understand that these values are multiplied, therefore the order does not matter. HOWEVER, torque is a vector, not a scalar value. It is calculated using cross-product multiplication and therefore the order DOES matter. Torque has a magnitude and a direction so if you were to say "150 ft-lbs" you'd actually be specifying 150 torque in the loosening direction. The force has to come before the radius. The mathematically correct way to say this is "pound-feet"

 

[BmacIL]

The fact that a "Diamond Sponsor" vendor does not use factory torque specs is alarming. I'm actually glad this came up. Now I know never to take my car there.

Yep...applicable.

 

[shogun32]

@Ewheels, all you posted was the 'standard/default' 75% of yield chart. There's nothing wrong with just blindly sticking to it - ignoring for the moment your chart assumes a 0.14 friction coefficient (black oxide) instead of 0.2 for uncoated studs. Other factors exist like crushing the lands on AL wheels - some can't actually take the prescribed clamping force. I listed a variety of values and why you might use them for a reason.

No, your wheel isn't going to come off if you use only 72% of yield torque. You will run a significant risk if you're only at 50% though. Anywhere around 70-80% of yield is fine. If your nuts are coated, taking 20% off is de rigueur - just as if you had put anti-seize on the bolt. Torque is just a handy proxy for clamping force which is what we're actually interested in.

 

[GTthree50]

The torque required to hold the wheels in should be used per spec. Torque is the force required to impart the amount of stretch into the bolt or stud to hold securely. Using less is a risk, because many do it and have not had a problem does not prove that it is correct. One would never use less torque on head bolts for example, significant leaking or head warpage would be the likely results. For 14mm studs 150 ft. Lbs. is the recommended torque, beyond any +\- less is incorrect.
https://www.gedore-torque.com/service-centre/torque/

https://www.mountztorque.com/What-is-Torque_3

 

[Kermitz]

I've been setting mine at 150, because that's what the service manual said to do.

 

[Emilbadal]

Had discount tires near me mount my aftermarket wheels on and I asked him what he torque the lug nuts to knowing that user manual asked for 150ft/lb. He said 80, then I told him about the user manual and I showed him the specs, still he refused to do it per manual, saying he doesn't want to strip the threads. I had to buy a damn torque wrench to torque them to spec myself

 

[GTthree50]

That’s just a situation where someone doesn’t know his job. That you felt the need to buy a torque wrench is the silver lining here. It’s indispensable to have.

 

[Monopoly]

Same. The Ford Racing manual that came with my track pack suspension kit said to reinstall lug nuts to 150lb ft.

 

[kz]

Torque is just a mean to achieve clamp load - since it's not easily measureable without strain gauges. And to correct someone above - torques aren't "calculated" - they're typically result of torque - tension test for specific bolt - nut - lubricant trio.

 

[jmeiers]

125 is what I use on both my PP1 wheels and VMS drag pack wheels. No issues.

 

[EFI]

125 is what I use on both my PP1 wheels and VMS drag pack wheels. No issues.

How did you arrive at that value?

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