Lug nuts falling off and shearing off studs

[RosellaLives]

Hi all.  I have a 2009 Subaru Impreza that I love.  About a year ago several lug nuts fell off of one of the rear tires, and 2 of the studs sheared off and I almost lost the tire while driving.  I had it towed to my Subaru dealer, who had recently done a tire rotation as part of my maintenance.  They could come up with no explanation of how/why it happened, so I kinda blamed them that they must have not tightened the lug nuts sufficiently and thereby caused the problem.  They split the cost of the repair with me and I went on my way.  About 6 months later, 2 days after they had again rotated my tires, I found several loose lug nuts on a rear tire.  I found it hard to believe they would make the same error again (especially after I raised such a stink and got them to pay for part of the repair), but they just tightened my lug nuts and that was it.  No harm, no foul. 

Now, about 1 year after the first instance, I again lost 3 lug nuts off a rear tire, and sheared off 2 studs again, almost lost the tire while driving and am lucky to be alive.  The car had not been serviced in several months, and the tires had last been rotated 6 months ago (11,000 miles ago), so I don’t think this is a situation of someone, for the 3rd time, not tightening my lug nuts.  Subaru has the car now and can find nothing wrong with it that would be causing the rear lug nuts to fall off and the studs to be sheared off.  They are repairing the damaged wheel, but I am very concerned about this situation.  I don’t think lightning strikes 3 times in the same place, so something must be wrong with the rear of my car.  Anyone else ever have this happen?  Any ideas what could be causing this?  Any thoughts or advice would be greatly appreciated.  Thank you!

 

[CNY_Dave]

They suck at torquing lug nuts, that's all there is to it.

 

If they are left too loose, you can actually have all 5 shear at once and have the wheel sail right off.

 

When they are not tight enough, they flex every time the wheel rotates.

[Fairtax4me]

2 things.

1: X2 to what Dave said. The dealer isn't torquing the lug nuts properly. Someone is just zipping them on with an impact wrench which is an absolute no-no! I'd raise some more stink.

 

2: Go Buy a torque wrench and a 19mm deep socket, 6 point, 1/2" drive. Torque the lug nuts to the proper torque yourself after they have serviced it.

Lug nut torque on aluminum wheels needs to be rechecked after driving about 50 miles. Torque them yourself before leaving the dealership, then recheck them the next day.

[idosubaru]

*** The rear rotor needs replaced (not turned). There's an uneveness that's fatiguing the bolts, it happens very rarely on 00+ subarus and I've only seen it happen on the rear.

Get that rotor off, throw it away, give me their address so I can bill them $75 for proper diagnosis....or at least give you a discount for not knowing. lol

 

1. Replace the rear rotor

2. Replace all 5 lug studs since they've likely been stressed and it's super easy/cheap

3. Torque them properly

 

It could be them not tigthening properly but i doubt they're "not tightening" properly only on one wheel or only on the rears. The consistency and that I've seen it before on the rear of 00+ models makes me think you need to replace that rotor.

[john in KY]

Friend back in the mid 1970s had all 4 tires changed on his Impala. Left the tire store, driving on the beltway around DC, and all 4 wheels sheared off. Tire store swore up and down it was not at fault and got away with it. 

[CNY_Dave]

There was a time period where subaru spec'd the wrong lug nut torque, wonder if they missed the update ?

 

I do not believe that aluminum wheels need to be retorqued, IF the hub is clean, both rotor surfaces are clean, the wheel is clean, and the nuts are properly torqued. I might amend that philosophy if a credible loosening mechanism can be described, but torque mine with an electric impact wrench, I go a certain amount of turning after snug, and my nasty LL bean alloys have always stayed tight.

 

I think I recall reading here or elsewhere the phenomena GG mentions about the bad rotor, man, when you can't even trust a rotor...

[1-3-2-4]

They suck at torquing lug nuts, that's all there is to it.

 

If they are left too loose, you can actually have all 5 shear at once and have the wheel sail right off.

 

When they are not tight enough, they flex every time the wheel rotates.

I had something like that happen 3 years ago, I felt a shimmy in the front wheel, and it was summer so I had the window down and going around the curve and I saw my lug nut fly off across the road.. It sheared the lug nut.. It's a pain to get out with the ABS sensor on the hub but I did it.

[idosubaru]

the rear studs are very easily replaced.  i just did a rotor/stud replacement this year on an 03 OB.

 

I do not believe that aluminum wheels need to be retorqued, IF the hub is clean, both rotor surfaces are clean, the wheel is clean, and the nuts are properly torqued.

 

true, i think the issue is aluminum is less forgiving with any grime, debris, lower torque values, heat cycling of dissimilar metals, poor attention, etc. all perfect, should be good to go, i never retorque or think to and i change my wheels out multiple times a year.  i've had loose lugs and wheels a couple times over the decades.

 

Friend back in the mid 1970s had all 4 tires changed on his Impala. Left the tire store, driving on the beltway around DC, and all 4 wheels sheared off. Tire store swore up and down it was not at fault and got away with it. 

 

which is more surprising: tire store refusing culpability or 4 wheels simultaneously sheering off without any signs to pull over or check them out?

[Bushwick]

Several years ago I bought a mid 90's F150 to scrap. It's rear drums were frozen up from sitting, so both rear tires were yanked to get the drums freed up. Put both on, tightened down, ratcheted it up on the dolly, and off I went. About 60 miles later, (I was pulling the dolly with a 96' Lincoln Mark VIII- had air bag suspension so it could pull anything w/o squatting) I looked in the mirror and saw sparks. Pulled over and the wheel was missing LOL. Couldn't even tell from in the car to be honest other than the car lurched briefly but still pulled it fine w/o bogging.

 

Anyways, the lugs apparently were NOT tightened enough, and the force from the rotation caused all 5 to loosen and fall off. Lug threads were 100% OK. I grabbed 1 nut from the remaining 3 rims, stuck the spare on, and quickly left before a state trooper happened along. Thankfully the missing wheel didn't run anyone off the road.

 

 

What you should be doing is taking a 1/2" drive breaker bar with you and a socket the correct size, and hand tighten all 4 rims after getting tires rotated. Since it's happened twice, why are you risking it?

Edited December 7, 2013 by Bushwick

[hellsbelle]

This is happening constantly on my 05 Legacy.

 

I bought the car used in 2008, it was a trade in at an Audi dealership where my friend works. I know it's not a Subaru dealership but that's where my warranty came from.

 

In 2009 I had to have a rear wheel bearing assembly replaced, I had no trouble with the lug nuts then.

The wheels were off for tire and brake maintenance and replacement maybe 6-7 times over the next three and a half years and once for another wheel bearing assembly and I did not notice any problems then. Some of the work was done at the dealership and some at my friend's home garage, but this is the same guy who is a mechanic at that dealership so it's not as if he can't be trusted to change a set of brakes at home.

 

Last summer I was driving along and heard a thumping that got progressively worse so I pulled over and all 5 lug nuts on the rear driver side were loose. The last time the wheels were off was for tire replacement maybe 3000-4000 miles prior to that. My first thought was that they didn't tighten them up enough.

 

I put winter tires on around November. In February the same thing happened to the same wheel. My friend put the tires on last so I accused him of not torquing the lug nuts enough and he was sure that he torqued them according to specs so he looked at it and found that all 5 studs on that wheel needed replaced, he did that and checked the other 15 lugs nuts for tightness. 

 

Last week he replaced all four brakes and rotors for me and said that every wheel had loose lug nuts ranging from all 5 to only 2, but every wheel had lug nuts that were only hand tight at best even on the wheel with the new studs. I'm thinking that wheel itself might be damaged from this happening so much and maybe the holes have become bored out and that's causing stress on the studs, but I'm not a mechanic.

 

He fixed everything that he could find wrong, except another wheel bearing that we have to order, the car has a healthy appetite for wheel bearing assemblies. At this point he is watching for this problem and put a lot of care into making sure it's as safe as he can get it. I drove to work and back, a total of 20 miles, and when I got home the front driver's side had all 5 lug nuts loose enough to spin with your fingers again and the rear wheels had a few that were loose enough to feel with the lug wrench. 20 miles after he went over these things with a fine tooth comb and the front wheels were never a problem before.

 

Right now I guess I'm looking at getting 20 new studs, 20 new lug nuts, and possibly new wheels if I'm right about them being damaged like I think. And like someone else mentioned a torque wrench would probably be a wise investment.

 

I love my car, really I do, but in the past I have had much lower quality vehicles worked on by people who aren't even hobby mechanics working with the bare minimum of tools, they certianly didn't have a way to measure the torque on the lug nuts, and this has never happend to any other car I've had. One of those lesser quality vehicles was a Cavalier with after market aluminum wheels, you guys say the aluminum is a little touchy, I still didn't have this problem and that car's wheels were off almost every 3-4 weeks for a variety of things that kept breaking.

[heartless]

Any time a wheel is off the car - for any reason - the lug nuts should be retorqued after 50-100 miles - period - regardless of wheel type (alloy or steel).

 

Failing to at least check the lug nuts after a wheel has been off is asking for trouble.

 

Repeated loosening does need to be investigated further (bad rotors, etc) there has to be a reason for them loosening multiple times after being retorqued.

[idosubaru]

This is happening constantly on my 05 Legacy.

 

Hey, I'm in Morgantown, welcome aboard.  Feel free to PM me a link to any future questions.  A friend was taking his Audi down to that dealer since there isn't one up here.

 

On the rear studs breaking *** It was definitely the rotors. ***

Which you already replaced, good job!

 

Here is what I would do:

 

1.  Replace the rear rotors (DONE!)

2.  Clean up the corrosion on all the wheel and rotor mating surfaces which the rotors won't have since they're new, so just clean the wheels - with winter and such corrosion builds up.

3.  Torque the nuts on properly - google for the proper torque number and make certain it's being reached. 

 

*** There have been incorrect torque values posted for some Subarus, even confusion from Subaru.  Maybe your friend found the incorrect numbers?

I would err on the high side and go a bit more than recommended.

 

The most recent bout and the front lugs is likely not being torqued properly.  There are 10's or 100's of thousands of Subaru's without mysteriously loosening lug nuts.  Once it's fixed it's never going to happen again.  There's nothing magical or "lucky" about it, something is wrong or it's not.  You're wise to be uneasy now, but once it's fixed and properly maintained it will never happen again.

 

My guess is that torque is less of an issue if the wheel/rotors are perfectly clean and the wheel is installed perfectly flat (not one lug tightened while the other side 180 degrees away is still a millimeter off the rotor mating surface) - but those variables are tricky when working "in the field".

 

doubt you need new wheels, but I'm not sure how badly they can get damaged with repeated/prolonged driving on loose lugs. 

I would get a used set, new would be prohibitively costly.  Pick up City in fairmont usually has a good number of Subarus.

www.car-part.com

 

Then i'll take your old wheels and see what they do on my cars, LOL.

 

Most tire shops have a note on the invoice saying the lugs need retorqued after XYZ miles on aluminum wheels.  I'm sure you can google it and find all the technical reasons, but retorquing aluminum wheels is a known issue.

[MilesFox]

It is standard practice to re-torque the wheel lugs after 75 miles or so.

 

Anyone who performs tire mounting or rotation professionally should require you to come back for re-torque.

 

I work at an oil change center that does tire rotations. We have to customer sign a waiver agreeing to come back for re-torque. We use a chart to determne torque, use torque sticks with an impact to set the lugs, and then foloow through with a torque wrench. Usually the torque sticks fall a few pounds short of their rating, thus requiring the torque wrench to be certain.

 

This is most important with aluminum wheels. It is also important to not overtorque the wheels.

 

The wheel fell off the managers car a week after he rotated, as he dod not re-torque. this also happend to a buddy whom i did his brakes on his subaru, which i told hom to go back to his tire man for a re-torque since he had not yet after rotating the tires just before having me do the brakes.

 

The symptoms would give you fair warning to pull over ans check the lug nuts before the wheels fall off. But in any case, a loose lug not will start wobbling, get exponentially worse, and then fail right away. It is up to you to recognize the lugs are loose, as if you are wondering what the noises are, the wheel will soon fall off to let you know that is what is happening.

[1 Lucky Texan]

what is the likelihood of sabotage?

 

good relationship with neighbors?

 

upset ex-spouse?

 

when I went to the track, I was advised to take my torque wrench to check lugnuts after my first run - they were fine.

 

Also, is this more likely with aftermarket wheels? Maybe someoen has put wheels on that are not 'hub centric'.

Edited April 16, 2014 by 1 Lucky Texan

[CNY_Dave]

The nuts on my stock AL wheels never needed to be retorqued... until they needed to be. Weird.

I would swap 'em on or do brakes and check 'em, always tight, until swapping out my snows a week ago.

[1 Lucky Texan]

does anyone else feel lug nuts should be replaced after a several years? I have replaced them on our 03. They get a lot of 'cycles' with tire rotations. And they sorta 'gall' on the contact area.

[idosubaru]

does anyone else feel lug nuts should be replaced after a several years? I have replaced them on our 03. They get a lot of 'cycles' with tire rotations. And they sorta 'gall' on the contact area.

 

sounds like a good idea for having smooth thread and easy to use lug nuts and heavier vehicles now.

 

in general though lug nut or lug stud issues are rare and they'll last 300,000 miles, with 1980's and early 90's stuff having no issues so sounds like overkill to me. the guys offroading with 30 year old lifted rigs are breaking stub shafts and stuff before they break lug studs.

[tirod]

The guys coming in with off brand wheels using spacers break studs regularly. The offset and much larger tires are death on studs. Two sizes larger and more than a half inch outside displacement are enough to exceed the design limits. Add that the owner now thinks he has a race car and runs it much harder than normal, it's a studbreaker. 

 

When I worked at an auto center selling new rims we always torqued to spec and advised customers to check every 50 miles for the first 500 - five hundred - miles. And when they didn't we would fix everything right back up, eat the loss, and invite them to shop elsewhere in the future. And enforced it. 

 

It was a problem with chromed wheels in the '70's and '80s, and it's always been a problem with any wheel. 

 

When I rotate or service brakes, I torque back to spec, and once in a great while, despite the extra work, the wheel loosens. It's why I always carry a decent lug wrench rather than the emergency excuse the maker provides. 

 

Overtightening the stud will stretch it, it yields and relaxes, done repeatedly it will eventually break it. Don't overtorque, it's only accelerating failure. It's why two or three studs suddenly break off for "no reason." There IS a reason, the load exceeded their strength rating repeatedly and they fatigued, causing failure. 

 

When fasteners fail, it's not voluntary, it's either a lack of proper selection or correct maintenance. It has nothing to do with the part, it's all controlled by humans and they make errors. Some humans just refuse to admit it, tho. 

[1 Lucky Texan]

my dad had a Studebaker once.

 

oh - wait, STUD-breaker

 

nvrmd

[hellsbelle]

My wheels were always checked and re-torqued as recommended after they were put back on. I thought that should go without saying because it's not only a standard part of vehicle maintenance but it's also basic common sense. The majority of the time they were either fine or just slightly off at various points in the first few hundred miles. Which is why I found it so concerning that they were coming loose after 3000-4000 miles the first few times. Then most recently all 5 on the front wheel being so loose I could remove them by hand after driving only 20 miles, that is not normal. When you go to re-torque you expect to find a loss of, what, 0-15lbs? Losing 60+lbs of torque in 20 miles is not typical. It's not impossible for that to happen in a car with no underlying problems, nothing is impossible, but I would rather take this as a warning to explore any potential problems that might be causing, or at least exacerbating, this instead of just saying "Oh well, re-torque and go on about life".

 

These are the stock aluminum wheels from Subaru, the original ones as far as I know. Consistently torquing to the wrong specs that Subaru provided in error makes sense. But I'm going to call Subaru for the right ones because google is bringing back results ranging from 60 to 90.

 

1 Lucky Texan: Lol, I actually considered that someone might be loosening the lug nuts and after telling another mechanic what happened that was the first thing he said. But I can't think of anyone who would have the motivation or opportunity to do it.

 

grossgary: I would love to avoid buying new wheels and I'm a little uncomfortable buying used ones. I'm afraid this may have caused them to become a bit rounded out, maybe not even enough to notice visually and using them would just repeat the process of weakening the studs. Do you think that's likely if it's not noticeable to the naked eye?

[idosubaru]

I found some instances on line of people tigthening to 70 ft-lbs and having them come loose - so that's too low. What value did he use?  If we can confirm he used a value that others have used and had them come loose - that's telling.

 

*** I think yours calls for 81 ft-lbs but I'd torque them in a proper alternating sequence to 90 ft-lbs as Subaru allows for that on other models (i probably use even more than that i just have a setting a find higher than needed on my air gun and use that 100's of times without issue).  One day I'll test it maybe and see what mine are at.

The dealer can confirm or it should be in your owners manual as well.

Subaru is flaky with their changes over the years:

http://www.subaruoutback.org/forums/81-wheels-tires-brakes-suspension/15339-lug-nut-torque-2.html

 

Unlikely to be wheel related.

1. they're coming loose on wheels that weren't previously an issue.

2. Subaru wheels are robust and this would be an unheard of symptom/failure mode.  hard to imagine that stastical improbability outweighing the far more probable idea of improper torque.   if you google "subaru lug nut torque" or loose lugs, etc you'll get myriad of hits on the subject.

 

One could suggest rotations may spread the issue but that's statically improbable.

 

Experience tells us that subaru wheels don't cause lug loosening. Many people have wobbled around on a loose wheel, flat tire, been in wrecks, I've repaired wrecked/salvaged/recertified cars many times, people in the offroad crowds lift, modify and abuse these things and wheel damage that causes lug loosening is not a normal failure mode under stress.

 

As an engineer with stuff I've built on NASA birds flying right now, I can be as technical as need be and make guesses materially, structurally, etc...I see no need for that here.

 

All that to say, It almost has to be a simple torque issue.

 

it's actually normal for the lugs to loosen all the way, that's what they always do if they loosen.  Retorquing is not an attempt to abate a loss of 10 pounds, but an attempt to mitigate complete loosening.  Granted you *might* catch it when it's a "little" loose, but more often than not they're hand tight.

 

Good luck and thanks for the feedback, hope it works out for you.

[Fairtax4me]

A couple things I've found through my years as a DIY mechanic.

 

Torquing the lugs ONE time in order often does not bring all of them to the proper torque. Because of the way the wheel moves slightly as you tighten the lugs, it often means the first lug nut tightened will be under-torqued by the time you finish tightening. Torquing the lugs a second time in order will bring all of them to the proper torque.

 

Because every wheel these days is "hub-centric", any rust or corrosion of the hub or the center bore of the wheel can prevent full seating of the wheel against the hub. This can cause the lugs to be tight to the proper torque, but once the car is driven the wheel can shift on the hub and the lug nuts will then be loose. Rust, dirt, or corrosion on the flat face of the wheel or on the surface of the hub or brake rotor can cause similar issues. It's best to thoroughly clean these areas when the wheel is off, and apply a rust preventive grease or anti-seize to the hub center and wheel-hub face.

 

Do not apply Anti-seize on the lug studs. Good idea in theory. It keeps the lug nuts from rusting to the studs. The problem is it also lowers the static friction co-efficient of the threading on the studs. This makes it easier for the lug nuts to loosen. Apply a light coating of thin oil rather than anti-seize to help prevent rusting of the lug studs. If rust is a major issue in your area, buy closed end style lug nuts.

 

Make sure your torque wrench is calibrated properly. Click-type torque wrenches use springs in the click mechanism which stretch with time and use, and need to be adjusted or replaced periodically. Make sure the wrench is set to its lowest setting when not in use to extend the life of the springs. Keeping the setting high all the time will cause the springs to relax and the wrench will click at a much lower torque than the setting.

Beam type wrenches do not have this problem, but if the wrench is old and has been frequently used for many years the beam can start to deflect more than its supposed to. These are much easier to determine torque with though, and you can figure out how much extra torque to add, if necessary, without special tools to get the accurate torque.

[1 Lucky Texan]

^^^ great point - maybe why I've never seen this problem is because I usually sneak up on full torque in stages.

 

kinda like; hand tight - very tight - final torque. always in a star pattern but usually with different start-point/different order each time.

Edited April 18, 2014 by 1 Lucky Texan

[idosubaru]

 

Torquing the lugs ONE time in order often does not bring all of them to the proper torque.e.

 

I'll add that they're almost never to full torque with one order.  i usually hit them three times in a star pattern but i'm using air tools so it's easy.  they almost always move a good bit more the second time through.  third time they almost never do.

[presslab]

Maybe the mounting face of the wheel is messed up after being loose.  It's aluminum after all, and if it's not flat (like the edges are pushed in) it will move around and the lug nuts will loosen.  So I'd recommend checking the wheel mounting faces with a machinist straightedge.  If they are not flat, it might be possible to take just a little material off to make them flat again.

 

If your lug nut seats are messed up it's possible to drill them out and install new steel seats.  This would be a job for a machine shop as the wheel needs to be machined correctly to accept the new seats.

http://www.prestigewheel.com/Imagewi510.asp#Cone Seat Inserts