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What's up with 150ft/lbs on the lug nuts??

Champale

TMO Addict
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Hey guys - I know the 350R wheels are supposed to be torqued to 150ft/lbs and was just curious if anyone had any insight into why Ford specs it so high? I am running aftermarket alloy wheels and wondering if such a high torque spec is necessary for them. I've owned a ton of cars and trucks but never seen such a high setting on lug nuts.
 

byronj

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I only TQ mine to 130 ft lbs. Although, I swap wheels all the time and it’s not stressing the materials as much. I am trying to extend the life of my ARP studs.
 

JDee

Ancient Racer
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halfway between Mosport and Shannonville
W2W Racing
20+ Years
I only TQ mine to 130 ft lbs. Although, I swap wheels all the time and it’s not stressing the materials as much. I am trying to extend the life of my ARP studs.
And that's a good question. How many cycles is an ARP stud good for? They sure do get a lot of use, probably in my case 30-40 or so on/off cycles a year? Which is more than most cars would see in a lifetime.
 

byronj

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@JDee, I read in HotRod Magazine a while back about ARP fasteners and the studs lasted (insert exaggeration here) 1 billions cycles. I don’t recall what the number was but it was very high. I just don’t over torque and alway clean my threads after each wheel R/R.

Here is a nice ARP article
 

Thub

TMO Beginner
5
1
Chicago
Normal bolt/ stud ( as opposed to torque to yield fasteners) torque specs keep a bolt within the elastic part of it's stress/ strain curve. That means they're acting just like a spring. Their fatigue life in that range is millions and millions of cycles. Don't worry about fatiguing and breaking your wheel studs by using the appropriate torque to ensure proper vlamping.
 

Dave_W

Cones - not just for ice cream
30
29
Connecticut
Autocross
20+ Years
As Thub says, the designed torque spec is in the elastic deformation range of the lug, and ensures proper clamping load. Using less torque doesn't significantly lengthen the fastener life, but does reduce the clamping force, possibly enough to cause problems. Carroll Smith goes over this in excruciating detail in "Nuts, Bolts, Fasteners, and Plumbing Handbook" aka "Screw to Win."
 

JAJ

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The formula for computing the clamping load as a function of fastener dimensions and torque is easy to find on the internet. To do the calculation properly requires a lot of data - type of steel etc - that we don't have, but if you just want to compare two fasteners that are made of the same stuff, figuring out the difference is relatively easy.

Just after I got my 2016 GT350, like the OP, I got curious about the 150 ft-lb torque, so I compared the clamping force of a 1/2" lug at 100 ft-lb (S197) to a M14x1.5 lug at 150 ft-lb. It was substantially the same. The only difference is that the M14 stud has a larger cross-section, so it's stronger, but the pressure on the rim is the same.

There must have been a new standard or test in the auto industry at that time - my wife's 2016 BMW also has M14 wheel bolts while our 2008 has the M12 bolts that BMW started using back in the 1950's.
 

ronaldwalterfilho

TMO Intermediate
19
8
Long Beach
What about coated wheel studs and lug nuts like the ones OP sells and says to torque to 100 ft/lbs. I feel like 100 ft/lbs is not enough. What are your thoughts? Torque to OP’s suggestion or 150 ft/lbs that Ford suggest.
 
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ronaldwalterfilho

TMO Intermediate
19
8
Long Beach
The formula for computing the clamping load as a function of fastener dimensions and torque is easy to find on the internet. To do the calculation properly requires a lot of data - type of steel etc - that we don't have, but if you just want to compare two fasteners that are made of the same stuff, figuring out the difference is relatively easy.

Just after I got my 2016 GT350, like the OP, I got curious about the 150 ft-lb torque, so I compared the clamping force of a 1/2" lug at 100 ft-lb (S197) to a M14x1.5 lug at 150 ft-lb. It was substantially the same. The only difference is that the M14 stud has a larger cross-section, so it's stronger, but the pressure on the rim is the same.

There must have been a new standard or test in the auto industry at that time - my wife's 2016 BMW also has M14 wheel bolts while our 2008 has the M12 bolts that BMW started using back in the 1950's.
How did you measure the clamping force on the studs and lug nuts?
Thank You
 

blacksheep-1

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you may want to consult the wheel manufacturer as well since it is their parts that are being "clamped". where is the Apex dude on this?
 

Dave_W

Cones - not just for ice cream
30
29
Connecticut
Autocross
20+ Years
Any kind of lubrication (dry film, anti-seize, 30wt, assembly lube) will typically reduce the friction at the thread interface, reducing the torque needed to obtain the same stretch and clamping force. Or create more stretch if you torque to the same amount as for dry threads. The gotcha is if the dry vs. lubed difference is significant enough to push the lubed stretch from elastic to plastic (permanent) deformation when torqued to the dry number. That's why ARP will often give torque specs for their major engine fasteners that include what lubricant, if any, is to be used. And likely why the torque spec for a lug nut with lubricant coating is 100 lb-ft instead of 150 lb-ft for dry.
 

JAJ

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How did you measure the clamping force on the studs and lug nuts?
Thank You
I didn't measure it, I calculated clamping force for the two different threads using the same equation and assuming the same steel, the same friction and so on. So, even though the calculated value was probably a ways off, it was off in both calculations by roughly the same amount. What surprised me at the time was that even though the torque level was different by a lot, the clamping force results were pretty close for both bolts, M14x1.5 and 1/2-20.
 

byronj

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Any kind of lubrication (dry film, anti-seize, 30wt, assembly lube) will typically reduce the friction at the thread interface, reducing the torque needed to obtain the same stretch and clamping force. Or create more stretch if you torque to the same amount as for dry threads. The gotcha is if the dry vs. lubed difference is significant enough to push the lubed stretch from elastic to plastic (permanent) deformation when torqued to the dry number. That's why ARP will often give torque specs for their major engine fasteners that include what lubricant, if any, is to be used. And likely why the torque spec for a lug nut with lubricant coating is 100 lb-ft instead of 150 lb-ft for dry.

I literally just got off the phone with ARP about anti-seize on their wheel studs and they said do not use it because it will reduce the friction and it will take more TQ to get the proper friction which will in turn yield the studs. The rep stated that the gold plating on the studs acts as a lubricant. And TQ the studs to 150 +- 15 ft lbs
 
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Tonymustang302

TMO Race
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287
Chicago, IL
I literally just got off the phone with ARP about anti-seize on their wheel studs and they said do not use it because it will reduce the friction and it will take more TQ to get the proper friction which will in turn yield the studs. The rep stated that the gold plating on the studs acts as a lubricant. And TQ the studs to 150 +- 15 ft lbs
op ‘s website says 120 with arp studs......thats what i stick with un lubed, but i always keep the shaft clean
 

byronj

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op ‘s website says 120 with arp studs......thats what i stick with un lubed, but i always keep the shaft clean
OP also doesn’t make the studs. Call ARP yourself and verify. But then again I was recommended to TQ to only 130 by another track rat. Another vendor states add anti seiz. Who’s right, who’s wrong? Best to go with the manufacturers recommendations IMHO
 

TymeSlayer

Tramps like us, Baby we were born to run...
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Brighton, Colorado
I literally just got off the phone with ARP about anti-seize on their wheel studs and they said do not use it because it will reduce the friction and it will take more TQ to get the proper friction which will in turn yield the studs. The rep stated that the gold plating on the studs acts as a lubricant. And TQ the studs to 150 +- 15 ft lbs

It's not really Gold Plating but rather a zinc with a yellow trivalent finish.
 

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