Owners manual for my cav states 100lb/ft. I remember 100 something, I'm pretty sure it's lb/ft I'd have to look again to make doubly sure.
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wheel lug nut torque
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Originally Posted By: onion
I have my own story about stupid engineers and lug nuts. When I was 18 year old... young and dumb, didn't know [censored]... I worked in a small-scale factory that manufactured industrial equipment mounted on trailer skids- in the range of about 4,000 to 12,000 pounds, depending on the setup. These skids were set up to use standard trailer axles and hitches, and one of my jobs was to bolt the wheels onto the hubs. Now, as some of you will know, lug nuts generally don't use an interference thread... you know, 'cause wheels have to come off at some point, and you don't want to damage the stud threads. But the engineers at this company were kinda paranoid about wheels falling off these trailer units- it had happened in the past (can't say why, as I wasn't there). They were afraid that the lug nuts would back off; their solution was to use a crimped lug nut- i.e. an interference thread. Nobody made one for this application (wonder why?), so these clowns built a jig that we could use in the 30-ton press to crimp our own. Well, you take a poorly designed crimping tool, use it on nuts that were never designed to be crimped, and make some $7/hr. shop-monkey run the press... what do you THINK is going to happen? The results were not uniform. So when installing these wheels, I noted that lots of these lug nuts were [censored] hard to turn. I measured it with a torque wrench. It was taking up to 80 ft-lbs to turn the lug nut... while the spec was 120 ft-lbs or thereabouts. I pointed this out to TWO engineers; it was never addressed. A few months later, TWO wheels came off a 12,000-pound trailer unit (thankfully, not one that I'd worked on). All eight lug studs had snapped on each hub.
Doesn't take a rocket scientist to see what happened here... but it gets better. The chief engineer (not one of the two that I'd discussed the lug nut problem with) addressed this problem by specifying different wheels. He didn't address the lug nut issue (I was pretty disgusted by then and didn't bother to point out the obvious). I actually asked him WHY he'd specified different wheels (I expect the engineers on this forum to see what's wrong with this statement right away... while ya'll mere mortals won't see what I'm getting at):
He said that the new wheels had a greater surface area contacting the hub, and therefore would have more friction against the hub.
I sincerely hope that some of ya'll will get a laugh out of this.
Now that long and only marginally interesting story is to demonstrate this: engineers make mistakes. They are OFTEN wrong. Don't even get me started on warranty campaigns that I've dealt with from assorted diesel engine & heave equipment manufacturers over the years.
So appeal to authority doesn't hold much water for me when it comes to technical discussions. Or really ANY discussion.
Believe it or not, this story isn't a comment about the competency of engineers and technicians in general- so much as difficulties we face. The 'real world' (unlike say, a man-made system of rules, laws, procedures, etc.) is a [censored], and it'll make your mistakes known (whether they were on paper or in implementation).
Originally Posted By: rudolphna
Owners manual for my cav states 100lb/ft. I remember 100 something, I'm pretty sure it's lb/ft I'd have to look again to make doubly sure.
That's kinda what I figured. Pablo meant that 100ft-lbs is too low for the motorhome discussed in the OP.
I have my own story about stupid engineers and lug nuts. When I was 18 year old... young and dumb, didn't know [censored]... I worked in a small-scale factory that manufactured industrial equipment mounted on trailer skids- in the range of about 4,000 to 12,000 pounds, depending on the setup. These skids were set up to use standard trailer axles and hitches, and one of my jobs was to bolt the wheels onto the hubs. Now, as some of you will know, lug nuts generally don't use an interference thread... you know, 'cause wheels have to come off at some point, and you don't want to damage the stud threads. But the engineers at this company were kinda paranoid about wheels falling off these trailer units- it had happened in the past (can't say why, as I wasn't there). They were afraid that the lug nuts would back off; their solution was to use a crimped lug nut- i.e. an interference thread. Nobody made one for this application (wonder why?), so these clowns built a jig that we could use in the 30-ton press to crimp our own. Well, you take a poorly designed crimping tool, use it on nuts that were never designed to be crimped, and make some $7/hr. shop-monkey run the press... what do you THINK is going to happen? The results were not uniform. So when installing these wheels, I noted that lots of these lug nuts were [censored] hard to turn. I measured it with a torque wrench. It was taking up to 80 ft-lbs to turn the lug nut... while the spec was 120 ft-lbs or thereabouts. I pointed this out to TWO engineers; it was never addressed. A few months later, TWO wheels came off a 12,000-pound trailer unit (thankfully, not one that I'd worked on). All eight lug studs had snapped on each hub.
Doesn't take a rocket scientist to see what happened here... but it gets better. The chief engineer (not one of the two that I'd discussed the lug nut problem with) addressed this problem by specifying different wheels. He didn't address the lug nut issue (I was pretty disgusted by then and didn't bother to point out the obvious). I actually asked him WHY he'd specified different wheels (I expect the engineers on this forum to see what's wrong with this statement right away... while ya'll mere mortals won't see what I'm getting at):
He said that the new wheels had a greater surface area contacting the hub, and therefore would have more friction against the hub.
I sincerely hope that some of ya'll will get a laugh out of this.
Now that long and only marginally interesting story is to demonstrate this: engineers make mistakes. They are OFTEN wrong. Don't even get me started on warranty campaigns that I've dealt with from assorted diesel engine & heave equipment manufacturers over the years.
So appeal to authority doesn't hold much water for me when it comes to technical discussions. Or really ANY discussion.
Believe it or not, this story isn't a comment about the competency of engineers and technicians in general- so much as difficulties we face. The 'real world' (unlike say, a man-made system of rules, laws, procedures, etc.) is a [censored], and it'll make your mistakes known (whether they were on paper or in implementation).
Originally Posted By: rudolphna
Owners manual for my cav states 100lb/ft. I remember 100 something, I'm pretty sure it's lb/ft I'd have to look again to make doubly sure.
That's kinda what I figured. Pablo meant that 100ft-lbs is too low for the motorhome discussed in the OP.
ls1mike
$50 Site Donor 2026
I had an 89 Fleetwood Southwind...It required 125 ft/lbs of torque on a GM frame, the John Deere frame...
was more
was more
The wheels are on, lubed, and torqued to 145 ft lbs, which is about 88% of the high torque value of 150-165. I am happily surprised some of you agree with me on "lubing the threads" being a good thing, not many others ever have over the years.
BTW the engineer who said "He said that the new wheels had a greater surface area contacting the hub, and therefore would have more friction against the hub." should have his engineering credentials checked! That is just inconveivable.
BTW the engineer who said "He said that the new wheels had a greater surface area contacting the hub, and therefore would have more friction against the hub." should have his engineering credentials checked! That is just inconveivable.
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FWIW, I have always done my own tire rotations on two cars and I lightly lube lug bolts whenever they get somewhat difficult to turn, maybe two drops per lug every couple of years. I can't help but think that the fellow who's wheels fell off must have had some other factors involved, since I've never even had a lug nut loosen up even a little bit in 15+ years. I'm no engineer, maybe just very lucky.
As far as lube goes, cleanliness is key to start, then I too use a light lubricant, just a thin film really, with no issues when torqued to specification. Never had a wheel bail out in 30+ years of motoring.
Here's the solution: install the nuts dry and torque to proper value. Mark the position of the bolt in reference to the wheel. Remove bolts, grease threads and reinstall nuts to the same studs they were on before. Tighten down so that they match the marks and measure the torque required. That's your greased torque value. Maybe add a little more if it doesn't feel right.
(To be super precise, you could count revolutions. But I doubt that would be necessary, if you can't tell the difference between one revolution too loose or too tight, you probably shouldn't be engaging in this exercise...)
Reasoning: the torque value is just a measurement to try and approximate the proper clamping force, which is the pressure between the nut seat, through the wheel contact face to the hub. Grease doesn't change how much the wheel seat deflects nor how much the bolt stretches, so as long as you replicate the proper clamping force and prevent the nut from backing up, you are good.
We all know the heck created when a tire changer cranks the lug nuts down to "11" and how much tighter than standard they end up being, without any ill effects besides making it impossible to remove without an impact wrench. So a little extra clamping force isn't going to hurt anything.
I too grease everything, and have never had any trouble. (Beyond forgetting to torque the wheel down after dropping it off the jack one time.)
(To be super precise, you could count revolutions. But I doubt that would be necessary, if you can't tell the difference between one revolution too loose or too tight, you probably shouldn't be engaging in this exercise...)
Reasoning: the torque value is just a measurement to try and approximate the proper clamping force, which is the pressure between the nut seat, through the wheel contact face to the hub. Grease doesn't change how much the wheel seat deflects nor how much the bolt stretches, so as long as you replicate the proper clamping force and prevent the nut from backing up, you are good.
We all know the heck created when a tire changer cranks the lug nuts down to "11" and how much tighter than standard they end up being, without any ill effects besides making it impossible to remove without an impact wrench. So a little extra clamping force isn't going to hurt anything.
I too grease everything, and have never had any trouble. (Beyond forgetting to torque the wheel down after dropping it off the jack one time.)
Back in late 90s, i owned a Saturn SL1 and it warped rotors very badly, at that time i started using a light dab of neversieze to each lug nut and torquing them to spec. From that time on i have used this technique on all my trucks and family's cars and have yet to have an issue. I feel like i get a more even torque across each lug nut if they are clean and slightly lubricated.
More importantly, do not trust tire shops to torque your lug nuts properly. I have watched many times a guy run them on with an air gun then check to see if they were at least some value ft/lb on the torque wrench. This is not the proper technique.
The authority on bolt torques is MIL-HDBK-60. You might be able to find it online with a Google search. Figure 13 gives the important information.
I have been using moly based anti-seize compound on my lug nuts and bolts for over 20 years and have never had a problem. Prior to that I had several nuts seize up on a relatively new car and had to twist the studs off to get the wheels off. Haven't had that problem since. You should lower the torque value when using a low friction factor lubricant. The previously mentioned 80% value is probably in the right ballpark. The use of low friction factor lubricants on bolt threads is standard Aero-Space industry practice.
I have been using moly based anti-seize compound on my lug nuts and bolts for over 20 years and have never had a problem. Prior to that I had several nuts seize up on a relatively new car and had to twist the studs off to get the wheels off. Haven't had that problem since. You should lower the torque value when using a low friction factor lubricant. The previously mentioned 80% value is probably in the right ballpark. The use of low friction factor lubricants on bolt threads is standard Aero-Space industry practice.
"swalve" I agree with your reasoning.Torque resistance is from the nut seat to the wheel contact area.Only about 20% of the resistance is from the actual threads of the nut to the wheel stud threads. just my opinion
Swalve is correct but in theory all that matters is bolt stretch and the subsequest clamping force created, and not the resistance from the nut seat to contact area. Although probably some compression happens there too.
It's all about bolt stretch when it comes to fastener clamping force. But in the real world friction has to be accounted for to determine the torque spec needed to reach the clamping force.
This is a case where installing lug nuts dry when new works fine but once their corroded not so much.
I think if the engineers wanted to get serious about lug nut torque spec they could also specify a low torgue value plus a certain amount of degrees and this would eliminate the friction variable more. For example, 30 lb-ft+90 degrees.
It's probably not a good idea or necessary to lube wheel lug studs if they aren't corrode unless you slightly lower the torque. After they get corrode from use it probably isn't a bad idea to lube and you may not even need to lower the torque all that much.
I think Ford use to list 2 torgue specs for most all of their fasteners. I think one lower for new and a higher one after use and corrosion. Anyone else seen that?
It's all about bolt stretch when it comes to fastener clamping force. But in the real world friction has to be accounted for to determine the torque spec needed to reach the clamping force.
This is a case where installing lug nuts dry when new works fine but once their corroded not so much.
I think if the engineers wanted to get serious about lug nut torque spec they could also specify a low torgue value plus a certain amount of degrees and this would eliminate the friction variable more. For example, 30 lb-ft+90 degrees.
It's probably not a good idea or necessary to lube wheel lug studs if they aren't corrode unless you slightly lower the torque. After they get corrode from use it probably isn't a bad idea to lube and you may not even need to lower the torque all that much.
I think Ford use to list 2 torgue specs for most all of their fasteners. I think one lower for new and a higher one after use and corrosion. Anyone else seen that?
Lots of consensus here that the key elements are to keep the threads clean and use a lube sparingly IF required. Torque to spec. or maybe 10 to 20% less...not sure about this yet.
Here is an interesting talk from an engineering forum. Some of it is off a bit (talks of helicopter fasteners), but there is interesting opinions about the nature of lug torque. The author "guesses" its ok to use lube AND the specified torque. It's a long read....the 5th post or so:
http://www.engineersedge.com/wwwboard/posts/13070.html Some of his OPINIONS:
"... if you can keep the anti seize off of the contact point between the end of the lug nut where it seats in the rim, you are probably better off staying with the manufacturers specified torque."
"if the information is reliable, there is a huge change in axial load when you coat both the threads and under the bolt head or nut, as compared with hardly any change in axial load when you apply anti seize to *only* the threads and not under the bolt head or nut."
"They say that about 90% of the input torque of the torque wrench is consumed by friction, with 50% of the friction being between the bolt head and mounting surface, 40% of the friction being in the threads, & only 10% being the stretch of the bolt which produces the axial force or preload. "
There's other stuff such as "transverse joint movement"....just one person's opinion. Take it for what it's worth.
FOR HOW LUGNUTS ARE ABUSED, THERE MUST BE A HUGE MARGIN OF ERROR BUILT INTO THEIR DESIGN, IMO.
Here is an interesting talk from an engineering forum. Some of it is off a bit (talks of helicopter fasteners), but there is interesting opinions about the nature of lug torque. The author "guesses" its ok to use lube AND the specified torque. It's a long read....the 5th post or so:
http://www.engineersedge.com/wwwboard/posts/13070.html Some of his OPINIONS:
"... if you can keep the anti seize off of the contact point between the end of the lug nut where it seats in the rim, you are probably better off staying with the manufacturers specified torque."
"if the information is reliable, there is a huge change in axial load when you coat both the threads and under the bolt head or nut, as compared with hardly any change in axial load when you apply anti seize to *only* the threads and not under the bolt head or nut."
"They say that about 90% of the input torque of the torque wrench is consumed by friction, with 50% of the friction being between the bolt head and mounting surface, 40% of the friction being in the threads, & only 10% being the stretch of the bolt which produces the axial force or preload. "
There's other stuff such as "transverse joint movement"....just one person's opinion. Take it for what it's worth.
FOR HOW LUGNUTS ARE ABUSED, THERE MUST BE A HUGE MARGIN OF ERROR BUILT INTO THEIR DESIGN, IMO.
ls1mike
$50 Site Donor 2026
Originally Posted By: doitmyself
FOR HOW LUGNUTS ARE ABUSED, THERE MUST BE A HUGE MARGIN OF ERROR BUILT INTO THEIR DESIGN, IMO.
I would bet you are correct about that one!
FOR HOW LUGNUTS ARE ABUSED, THERE MUST BE A HUGE MARGIN OF ERROR BUILT INTO THEIR DESIGN, IMO.
I would bet you are correct about that one!
Kestas
Staff member
Originally Posted By: doitmyself
"... if you can keep the anti seize off of the contact point between the end of the lug nut where it seats in the rim, you are probably better off staying with the manufacturers specified torque."
It's interesting that they say that. During our lug nut testing, we found that the worst case scenario is when antiseize is applied to the lug nut mount face (in addition to the threads). Torqueing to the specified values resulted in a cracked stud.
"... if you can keep the anti seize off of the contact point between the end of the lug nut where it seats in the rim, you are probably better off staying with the manufacturers specified torque."
It's interesting that they say that. During our lug nut testing, we found that the worst case scenario is when antiseize is applied to the lug nut mount face (in addition to the threads). Torqueing to the specified values resulted in a cracked stud.
Kestas, please re-read my post, the second quote. I think they are saying the same as you. His opinion...if you only lube the threads lightly, you can use the spec'ed torque. If you lube both the threads and the nut face, you will end up with heavier axial load if you don't reduce the torque.
It's his opinion that lightly lubed threads(only)can still use the spec'ed torque vs. the opinion of many here to reduce the torque 10 to 20%. His big point is NOT to lube the nut face.
The torque reduction really is the unknown element here. We just don't know! And, the use of a torque wrench can easily be off +/- 30% because of these friction factors. I did a simple lube/no lube test on a vice mounted bolt and it was startling.
It's his opinion that lightly lubed threads(only)can still use the spec'ed torque vs. the opinion of many here to reduce the torque 10 to 20%. His big point is NOT to lube the nut face.
The torque reduction really is the unknown element here. We just don't know! And, the use of a torque wrench can easily be off +/- 30% because of these friction factors. I did a simple lube/no lube test on a vice mounted bolt and it was startling.
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Kestas
Staff member
Yup, that's how I understood it as well.
Oops, I thought you were disagreeing!
What scares me about all this is conveyed in this table:
http://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf
Go to the second page for hex bolts, and they say "if using antiseize, reduce the torque of the LUBED value by 20%. In other words, they are recommending to reduce the dry thread value by about 40% if using antiseize.
example: grade 8,1/2" 13tpi 110ft.lb. dry, 80 lubed, 64ft. lb. antiseize.
Everyone here is talking about 10 to 20%.
What scares me about all this is conveyed in this table:
http://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf
Go to the second page for hex bolts, and they say "if using antiseize, reduce the torque of the LUBED value by 20%. In other words, they are recommending to reduce the dry thread value by about 40% if using antiseize.
example: grade 8,1/2" 13tpi 110ft.lb. dry, 80 lubed, 64ft. lb. antiseize.
Everyone here is talking about 10 to 20%.
Originally Posted By: doitmyself
Oops, I thought you were disagreeing!
What scares me about all this is conveyed in this table:
http://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf
Go to the second page for hex bolts, and they say "if using antiseize, reduce the torque of the LUBED value by 20%. In other words, they are recommending to reduce the dry thread value by about 40% if using antiseize.
example: grade 8,1/2" 13tpi 110ft.lb. dry, 80 lubed, 64ft. lb. antiseize.
Everyone here is talking about 10 to 20%.
OK I didn't look at that link but maybe they are including lubing the bolt head? Whereas others here are suggesting to just lube/anti-sieze the lug threads and reduce torque by 20%, and that would account for some of the 40% difference if anti-seaze was also applied to the contact seat? That's interesting that anti-sieze reduces friction more than lube does.
To be honest I almost never lubed lug studs. I was always told that the spec was dry. and generally I don't see a lot of corrosion on lug studs that had not been mishandled. Besides like someone mentioned there's probably a lot of margin in error built in and the lug nuts spec are probably overkill.
Oops, I thought you were disagreeing!
What scares me about all this is conveyed in this table:
http://www.imperialsupplies.com/pdf/A_FastenerTorqueCharts.pdf
Go to the second page for hex bolts, and they say "if using antiseize, reduce the torque of the LUBED value by 20%. In other words, they are recommending to reduce the dry thread value by about 40% if using antiseize.
example: grade 8,1/2" 13tpi 110ft.lb. dry, 80 lubed, 64ft. lb. antiseize.
Everyone here is talking about 10 to 20%.
OK I didn't look at that link but maybe they are including lubing the bolt head? Whereas others here are suggesting to just lube/anti-sieze the lug threads and reduce torque by 20%, and that would account for some of the 40% difference if anti-seaze was also applied to the contact seat? That's interesting that anti-sieze reduces friction more than lube does.
To be honest I almost never lubed lug studs. I was always told that the spec was dry. and generally I don't see a lot of corrosion on lug studs that had not been mishandled. Besides like someone mentioned there's probably a lot of margin in error built in and the lug nuts spec are probably overkill.
Kestas
Staff member
This may explain some designs (VW) I've seen where the wheel bolt has an integral pair of washers. I imagine that instead of having the bolt head seat against an aluminum surface, the friction is controlled by the washer faces, ensuring repeatable torque and clamp loads. Some conventional surfaces get really buggered up over time.
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