removed my wheels for the HID install and one of the lugs actually snapped with 85lbs of torque (i know it was set too high)... I have never seen this happen before to any car! Good thing the fix was easy only required the removal of 2 brake caliper bolts to hammer out the broken stud, took longer to find a dealer that had the wheels stud in stock.
Since the lug nut torque spec is 76 ft-lbs, the stud certainly should not have broken at 85. I think you're looking at a defective stud. Since people often have to change tires without having a torque wrench at hand, torques >85 ft-lbs could easily be applied. I'd bet the specified breaking point for a wheel stud is way higher that 85 ft-lbs.
"When too much torque is applied to a wheel, really bad things happen as well. Studs actually stretch a bit as they are put into tension when the nuts are installed. "When the nuts are removed, they spring back to their original length. However, when they are overstretched due to overtorquing, they “yield,” meaning they do not spring back and subsequently lose their ability to retain tension. "As a result, you get no clamp force at all. In addition, the bolt diameter is reduced as the stud is stretched and breakage of the stud is imminent. Even if the stud doesn’t actually break, though, once it has “yielded,” it has failed. "Overtorqued lugs typically result in broken studs. They’re a common cause of vehicle vibration problems since they can distort the wheels, brake discs and/or drums. "In fact, when customers complain of a brake pulsation immediately following a tire change, it is usually the result of overtightened lugs. At that point the affected rotor or drum must be replaced. Improper torque also can cause fatigue cracks and alignment problems." From tirebusiness.com
I thought I was the only one. I didn't post this problem before because I thought it was my own fault. Guess waht I snaped the studs too!! It came off like butter! The problem is because I cross treaded the bolt when I used the power gun in the toyota dealer (very powerful gun) and when I torque it it was too late. The studs is so bad quality.
You cross thread the nut, hit it with an impact wrench set too high, and then complain when the stud breaks? The breaking stud probably saved your wheel. Tom
The fact is the prius wheel studs ARE soft. Before i knew anything about car i use to drive on a lug nut w/ a impact gun set to the max and NEVER have any studs snap off. I was able to use with my hands snap off a stud like a piece of plastic...
I noticed you have to be pretty close to lining the studs up in the center of the holes on the wheels or you can easily begin to work the nuts onto the edges of the wheel, and slowly create small metal shavings. I set my air compressor output to 70 psi when I put the nuts back on, and use my torque wrench for the rest, set at 76. I wonder if they used a different metal combination for the lugs?
Only use air wrenches to remove the lug nuts. To put them on hand start them, and run them down finger tight. That way you'll never cross thread. Then finish the job with a hand torque wrench using the correct sequence. I do not trust the "Torque Stick" extensions that tire shops use. If I have tires put on at a shop I'll always bust them loose and hand torque them when I get home. A good torque wrench is a handy tool that every DIY'er should have. They come in different ranges so you can't really have one for all jobs. For lug nuts I use a 150 ft/lb 1/2" drive wrench. It's a good investment for knowing the wheels are on right. Imolas54, I'd venture a guess that your lug nuts were put on with an air wrench at some point, and that damaged the stud. Better finding it the way you did than having it fail on the road. BO
I always hand torque the lugs myself. At tire stores I have had to insist that they let me tighten the studs on my cars so they don't over tighten them. My Jeep no longer gets its tires rotated by the dealer. They installed a stud so tight once, that a breaker bar with a two foot entension and the body weight of two men applied to it did not Budge the lug nut. The dealer had to use a torque wrench for removal. Fortunately the tire was not a flat on the side of the road some dark rainy night. I even have had arguments with so-called experienced men who warned me that tightening the lugs to the recommended torque setting would cause my wheels to come loose, and even fall off the car. This fellow worked for a major tire retailer, so I'm sure many a customer has had their lugs improperly tightened by this clown. NEVER assume the people who should know these things ever do.
I should have clarified. I start them by hand until I can't tighten them anymore, then use the air gun to get them to around 70 and finish off with a torque wrench. Didn't mean to imply that I start right off with the air gun, but thanks for pointing it out! That way no one else should read that and go right at it with an air gun!
Yep, that method will work if the rattle gun doesn't take them beyond the torque range, but it sounds like you have that figured out. For the most part the importance of proper wheel lug nut torque is not understood by many. That includes many working in the tire industry. Proper lug nut torque gives the five fasteners a uniform clamping pressure, and prevents over tightening. Uniform clamping pressure means the rotating wheel mass is attached to the hub equally. If there is a great deviation of torque on the lug nuts, such as some at 60 ft/lbs and some at 110 ft/lbs, it could affect the wheel balance. If a lug nut is over torqued it will stretch, deform and weaken the stud, many times resulting in failure of the stud. If all five studs on one wheel are over torqued you can foresee the potential disaster. Most tire shops are all about Time=Money, and you run as many vehicles through in an hour as possible. It takes time to correctly install a wheel using a torque wrench so many don't bother. Most use Torque Sticks.Torque Sticks, Torque Sockets and Other Discount Tools They have a certain elasticity and flex that allows them to flex in sync with the blows of the Impact wrench once a certain amount of torque is reached. The flexing at its torque limit prevents the stick from exerting any more force on the nut and over tightening it. In theory anyway. I might be too old school, but I place a lot of value in proper torque and always use a hand torque wrench. I have several, each with a different torque range. Torque wrenches come in basically three styles, dial, beam and click release. I think the beam style is the most accurate, but the click release is the easiest to use. They are usually longer than a ratchet wrench, which means they don't take as much strength to achieve higher clamping force. Most anyone can torque a lug nut to 76 ft/lbs using a 1/2" drive 150 ft/lb capacity torque wrench. TORQUE WRENCH -1/2" 10-150 LBS-CLICK TYPE : eBay Motors (item 280502265200 end time May-09-10 11:06:09 PDT) There's many different levels of quality in torque wrenches but even an inexpensive on will get you close enough for accurate lug nut torquing. The are precision tools though, so don't drop it or use it for anything but a torque wrench.
Your lucky. My second rotation ever and the mechanic broke off 6 lug nuts. I had to wait 4 hours for them to get more from the toyota dealer. I then took the car to the dealer and told them they had bad lug nuts. He laughed at me and said he would love to charge me to replace all the lug nuts and blamed the mechanic before this last rotation. I then took the car to Big O who had done the first rotation and the paperwork was signed off by the manager himself. He said lug nuts should never break off with only the 2nd rotation. Toyota does not care. Oh well four days later something happened to the car and it drove itself into a tree so I don't have to worry about those lug nuts anymore.
"Nuts", "tree", "something happened to the car"...Sorry to hear that. Does the police report mention mechanical problem? Because if not, you maybe have "log nuts" at the moment...
