Is 150 ft-lbs for lugs overkill?

[Spacebird]

Engineers are stupid. I know best. I do it hand tight. No problems so far, except I died when my wheels fell off.

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[Trackaholic]

150 seems high, but the alternative is worse:
[ame]

-T

 

[Hack]

Factory service spec for the S550 is 150 ft-lbs, +/-15 ft-lbs. So technically you could be between 135-165.

I opt to the lighter side. Tracked the car over a 3 day weekend and 130 was just fine.

Engineers are stupid. I know best. I do it hand tight. No problems so far, except I died when my wheels fell off.

So the purpose of the torque spec is to get the bolt to stretch in length. That bolt stretch means that there will always be a pull on the nut/threads and that is what keeps the nut from backing off. The steel wheel studs are clamping an aluminum wheel, so CLTE are different between the materials. You want to always keep an adequate amount of stretch on the bolts, whether it's a hot track day or a cold morning.

If there is any dirt or corrosion on the threads of the nut or the wheel stud, when you torque you will get less stretch on the bolt, because the corrosion adds friction in the threads. That is why I would not recommend going to the low end of the recommended torque spec - and to try to keep the threads clean.

I'm not sure why everyone thinks they know better than Ford's engineers. They actually spent some time thinking about the stuff and testing it.

 

[kz]

So the purpose of the torque spec is to get the bolt to stretch in length. That bolt stretch means that there will always be a pull on the nut/threads and that is what keeps the nut from backing off. The steel wheel studs are clamping an aluminum wheel, so CLTE are different between the materials. You want to always keep an adequate amount of stretch on the bolts, whether it's a hot track day or a cold morning.

If there is any dirt or corrosion on the threads of the nut or the wheel stud, when you torque you will get less stretch on the bolt, because the corrosion adds friction in the threads. That is why I would not recommend going to the low end of the recommended torque spec - and to try to keep the threads clean.

I'm not sure why everyone thinks they know better than Ford's engineers. They actually spent some time thinking about the stuff and testing it.

Hack is correct.

The purpose of the torque is because it is easily measureable way to somewhat ensure appropriate clamp in the bolted joint - which is the only thing that matters but to measure it you essentially need strain gages.

Engineers come up with a torque by doing a torque tension test so they more or less know what clamp they get for given torque, (lack of) thread lubrication and so on.
Also correct more friction on the thread vs. what has been used to develop torque tension relationship (assuming they used brand new, clean thread - maybe they knew better ;-) ) means less clamp.
Given the accuracy of an average torque wrench and all the other factors, it isn't critical to be dead accurate, but I would rather target higher than lower...

 

[nastang87xx]

I'm not sure why everyone thinks they know better than Ford's engineers. They actually spent some time thinking about the stuff and testing it.

:first:

 

[jasonstang]

It's not high. 150lbs is the only way so that they are not loosening. I tried 120 before and they would slowly loosen.

 

[stanglife]

If there is any dirt or corrosion on the threads of the nut or the wheel stud, when you torque you will get less stretch on the bolt, because the corrosion adds friction in the threads. That is why I would not recommend going to the low end of the recommended torque spec - and to try to keep the threads clean.

(going a little OT) - Good point - and this is partially why the manufacturer uses torque-to-yield fasteners in many places (not wheel studs). These fasteners are usually torqued to a low amount (lower torque is more likely to be accurate because friction of the threads has not come into play - also reduces the variance caused by different lubricants) and since the thread pitch and predetermined stretch vs clamping load is know, they tell you how many degrees to rotate the fastener to achieve this. On these types of fasteners, there is a range of stretch where the correct clamping load will be achieved..too little stretch = not enough clamping load...too much stretch = exceeded fasteners ability to achieve measurable clamping load.

SO I guess I'm saying that, no matter what the fastener, we are first wanting to achieve a specific clamping load. Stretch is how we get there and maintain it ;)

 

[Tank]

Thanks. I guess it's to 150 lbs

That is going to be a bitch.

https://www.amazon.com/CDI-2503MFRMH-Micrometer-Adjustable-Torque/dp/B002LA1EDO

Peace of mind, 150 ft-lbs. easily achieved

 

[Paul@PKAUTODESIGN]

[MENTION=27078]Paul@PKAUTODESIGN[/MENTION]

What would happen to the BC Forged Rims I bought if I torqued to Ford's original spec as opposed to the 100ft/lbs you recommended after I swapped wheels?

Nothing should happen we have done it before for people that truly want the 150 rating done on the lugs.

 

[Eritas]

Nothing should happen we have done it before for people that truly want the 150 rating done on the lugs.

So why do you recommend 100ft-lbs?

 

[Paul@PKAUTODESIGN]

So why do you recommend 100ft-lbs?

Industry states 100 lbs for aftermarket wheels so we abide that, honestly I have had this conversion publically before on the board when no other vendor wanted to do so because they feared being bashed.

OEM Lugs and wheels state 150

Aftermarket wheels and lugs are different we do those at 100 lbs our own shop cars

GT350
1400 HP S550
478 HP S197

All on aftermarket wheels use 100 ft lbs nothing more or less without issues.

 

[Eritas]

Industry states 100 lbs for aftermarket wheels so we abide that, honestly I have had this conversion publically before on the board when no other vendor wanted to do so because they feared being bashed.

OEM Lugs and wheels state 150

Aftermarket wheels and lugs are different we do those at 100 lbs our own shop cars

GT350
1400 HP S550
478 HP S197

All on aftermarket wheels use 100 ft lbs nothing more or less without issues.

What "Industry"?
Who makes these statements?
***For what stud size?

The old standard of smaller M12 wheel studs can be torqued to 100ft-lbs for track use (normal street recommendation is 80ft-lbs), but the stock Ford Mustang M14 (16% larger) wheel stud calls for 150ft-lbs. Same for the Carbon wheels on the GT350R.

 

[krt22]

Engineers are stupid. I know best. I do it hand tight. No problems so far, except I died when my wheels fell off.

seriously man, not sure why anyone listens to those dweebs

 

[Paul@PKAUTODESIGN]

What "Industry"?
Who makes these statements?
***For what stud size?

The old standard of smaller M12 wheel studs can be torqued to 100ft-lbs for track use (normal street recommendation is 80ft-lbs), but the stock Ford Mustang M14 (16% larger) wheel stud calls for 150ft-lbs. Same for the Carbon wheels on the GT350R.

Aftermarket wheels, once again I have had this conversation before not looking for arguments everyone is allowed to do as they wish.

I kindly request ask any vendor here and some of the wheel companies on the board what torque rating they use i am certain they if stating honestly and without fear will say 100 ft lbs sir.

150 ft lbs for once again factory wheels and factory studs. for factory we use 150 lbs

I am speaking of aftermarket wheels and lugs

 

[DickR]

How does changing wheels and/or lug nuts allow 33% less lug nut torque to provide the same amount of tension in the oem studs that 150 lb-ft provides? Also how does 33% less lug nut torque provide the same amount of clamping force between the wheel and mounting surface on the hub?

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