Over tightened wheel nut found ?

[robinessex]

Call from step daughter, slow puncture on her car. Wheel off, down to repair tyre shop. Pop wheel back on, and that 'feeling' you get when it's obvious that one nut isn't tightening down 'hard'. Sure enough, a bit more oomph on the wheel brace, and it snaps off. In 50yrs of taking off, putting on wheels, I've never yet broken a stud off through over tightening. In fact my wheel brace isn't long enough to get enough torque on to break one. So I suspect that when the cars been in for a service, some tt has tightened the wheel nuts up with an impact wrench. Can't see how else enough torque would be generated unless you used a stupidly long breaker bar. Anyway, the car is now booked into dealer to have it fixed. I suggested that all 5 studs on that wheel are changed just to be safe. Take you car in to be serviced regularly to keep it safe eh?

[MJK 24]

Had exactly the same on one of our 7.5ton trucks. Had a pair of front tyres fitted. I tapped the wheel nuts at the front to check for tightness during a weekend inspection and one was lose. Wouldn't tighten - stud had snapped.

Replaced studs and nuts on the front axle just to be sure they're ok. 12 studs and 12 nuts were nearly £200 believe it or not...

[jimmy the hat]

Both vehicles have probably previously belonged to those who have "put a dab of grease on the threads for years and never died once".

On the plus side, both scenarios are the preferred method of finding a fatally weakened stud. Given the alternatives, that is.

Cheers, Jim

[xjay1337]

Did you tighten it up with a torque wrench?
Just because you have 50 years of experience does not mean you are not able to make a mistake.
While it's possible previous over tightening caused the stud to weaken in my experience they are either OK or snap, there's no half baked limbo state of weakness..

[jimmy the hat]

xjay1337 said:

Did you tighten it up with a torque wrench?
Just because you have 50 years of experience does not mean you are not able to make a mistake.
While it's possible previous over tightening caused the stud to weaken in my experience they are either OK or snap, there's no half baked limbo state of weakness..

No, there's no such thing as plastic extension.

Cheers, Jim

[robinessex]

xjay1337 said:

Did you tighten it up with a torque wrench?
Just because you have 50 years of experience does not mean you are not able to make a mistake.
While it's possible previous over tightening caused the stud to weaken in my experience they are either OK or snap, there's no half baked limbo state of weakness..

I tightened ALL the nuts with the same breaker bar. It's the one off my car, had it years, never had a problem using it. It's only 12" long, impossible to overtighten with it. 4 of the nuts tightened up perfectly, one wouldn't go 'tight'. The first clue that it's about to break. Then it snapped. I knew it would.

[jimmy the hat]

robinessex said:

I tightened ALL the nuts with the same breaker bar. It's the one off my car, had it years, never had a problem using it. It's only 12" long, impossible to overtighten with it. 4 of the nuts tightened up perfectly, one wouldn't go 'tight'. The first clue that it's about to break. Then it snapped. I knew it would.

Without wishing to start an argument, this is one of my bugbears.

I would only need to lean on your breaker-bar, with half of my body-weight, to apply an appropriate torque for your average passenger car wheel nut. I am by no means a big chap but I'm confident I could apply an excessive force if I tried.

Give it a go with a torque-wrench, I guarantee you'll surprise yourself.

What car, btw?

Cheers, Jim

[kambites]

Sounds plausible. The Elise's wheel nuts go to 105Nm. I can easily get them to that with my normal ratchet. Conveniently the lowest setting on my impact wrench gets to them to about 80Nm so I can do them up with that, then put the final half turn or so on with a torque wrench.

Edited by kambites on Wednesday 1st October 16:42

[Mr2Mike]

jimmy the hat said:

Both vehicles have probably previously belonged to those who have "put a dab of grease on the threads for years and never died once".

How many people have died from doing this in your experience?

[aka_kerrly]

This is another of my pet hates and why I try to use "professionals" as little as possible.

I was in a "national tyre" chain watching the guy change the tyres on my car and saw/heard him with the impact gun do 1, 2, 3, 4 wheel nuts (it was a 4 stud car)

Then he had the cheek to walk over with the head of a wheel bolt and tell me "someone" had overtightened it and when he took the hub cap off this fell out.... total load of bks.

[xjay1337]

robinessex said:

I tightened ALL the nuts with the same breaker bar. It's the one off my car, had it years, never had a problem using it. It's only 12" long, impossible to overtighten with it. 4 of the nuts tightened up perfectly, one wouldn't go 'tight'. The first clue that it's about to break. Then it snapped. I knew it would.

So that's a no to my answer then.

[jimmy the hat]

Mr2Mike said:

jimmy the hat said:

Both vehicles have probably previously belonged to those who have "put a dab of grease on the threads for years and never died once".

How many people have died from doing this in your experience?

Is that the point I was making, do you think?

Is it outrageous of me to assume that you're one of these people?

Cheers, Jim

[jimmy the hat]

The Crack Fox said:

jimmy the hat said:

I would only need to lean on your breaker-bar, with half of my body-weight, to apply an appropriate torque for your average passenger car wheel nut.

If you weigh 80Kg (=784N) and have a 50cm bar in a horizonal position and stand on the very end of it, you'll be applying 392Nm, maximum. A Mondeo's wheel nuts (off the top of my head) need something like 150Nm minimum, I guess they'll yield at a minimum of something like 5 or 6 times the specified torque, so 600Nm. Consider that the shorter the bar the less torque you'll apply. "Give me a place to stand and I can move the earth".

I'm a bit rusty with some of this.

Off the top of my head, I wouldn't swear to it but, 150Nm as a minimum sounds high. That sounds more like a max service torque, so the highest anyone would recommend. My small PSAs are all 100Nm, not sure about the bigger variants.

I would also suggest that you'd be extremely fortunate to be able to apply 600Nm without yielding a 12mm stud. Let alone snapping it clean off. Around 200Nm would be absolute max for a 12.9 grade M12 fine.

Don't listen to me though, try it.

Cheers, Jim

[996TT02]

xjay1337 said:

While it's possible previous over tightening caused the stud to weaken in my experience they are either OK or snap, there's no half baked limbo state of weakness..

Not sure about my "experience" but it is very easy for me to realise I have overcooked it, and I could just as easily back off leaving the bolt or stud seemingly intact, in a "half baked limbo state of weakness..".

Rotation and no increase or even a decrease in torque resistance is the clue and very easy to feel before complete failure.

Next time anyone would try to tighten said fixing, it would fail.

No worries I'm not a mechanic and part of the story is hypothetical, just to fit in with the topic.

[Huntsman]

The cause might not be over tightening, it could be crevice corrosion.