The shop spec says the lug nut torque shall be 104 newton·meter or an equally odd 77 lb·ft. Let’s not get into quibbles about the differences between lb·ft and ft·lb here, OK?
Anyhow, based on the wildly differing and grossly excessive tire pressures left by the guys who installed the new tires, I figured the lug nuts would be over-torqued… as, indeed, they were. My bending-beam torque wrench goes up to 140 n·m and didn’t even come close to breaking those puppies loose.
So I deployed a manly breaker bar and applied most of my weight to the far end. A back of the envelope guesstimate says they were well over 200 n·m, with a few grunt outliers.
Yes, the breakaway torque can be higher than the tightening torque, but they were far beyond even that level.
Lubed the threads, tightened to spec, and it’s all good. I’ll check them next week just to be sure, but sheesh if we had to fix a flat on the road, it would have gotten ugly.
The Smell of Molten Projects in the Morning 
Comments
6 responses to “New Tires for the Van: Overtightened Lug Nuts”
That’s why I roll loose wheels in to the tire shops and just let them mount and balance. Gives me an excuse to own a torque wrench, anti-sieze, and pressure gauge too. (I also carry a breaker bar and 6 point socket in my primary car, but that’s just because I like tools.) If I have a stubborn lug nut on the road, at least I know that I’m to blame.
Gives me an excuse to own a torque wrench, anti-sieze, and pressure gauge too.
Makes perfect sense to me!
One of the annoying things about the van is that it’s a big empty box with no places to put stuff like that. I want my loads tied down so they can’t get loose in a panic stop, but the interior is completely void of tiedown points. Makes a crew-cab pickup with a bed cover look downright attractive, it does… [grin]
at least I know that I’m to blame
And you know how it got in that condition, so you know what to do about it. Beats wondering if they used epoxy on the lug nuts …
I’ve friends who claim that tire installation places do that purely to encourage people to bring cars back because of their inability to get the lug nuts loose on their own.
Never ascribe to malice what can be laid at the feet of stupidity… or something like that.
*Sigh*
I had a small hatchback that I bought new in 1982. Took it in a year or so later to get the tires changed, and the same thing happened – with not so pleasing results. I went to rotate the tires a while later, and one of the studs broke as I was UNdoing the nut. The guys at the tire place replaced it under warranty, but it makes you think – it had clearly been overstressed, as had all the other studs. What if that stud had broken while I was driving?
Likely you’d have just heard a strange rattling sound as the nut & broken stud scuffed up the inside of the wheel cover. The remaining nuts should have held the wheel in place on that central spigot (or whatever they call that round dingus in the hub).
I’m mildly surprised the shop didn’t deny all responsibility or accuse you of turning the wrench the wrong way or something equally obtuse.
But, yeah, it’s much better to find that sort of problem in the garage rather than beside the road!