Kwik-fit and a puncture.

No, it's covered by BS AU 159f.

This may help:

The problem is with the dealer; it should have been checked as part of the PDI.

Chris

Was it rechecked after 60 miles from its last removal?

Dave Plowman (News) used his keyboard to write :

They can settle in a little, especially so on a new car. The advice is to recheck them after a period.

By what process would a wheel bolt, tightened to the correct torque, become significantly less tight?

Chris

Every garage and manufacturer and main dealership must be wrong. If you don't know the answer then you might as well give up ! Still, it's given us all a laugh. On this odd occasion, Kwik Fit was correct. Did you get a receipt from the garage that did the puncture repair as you might need it for a legal claim against them in the future.

Dirty joint face. That's why you always retighten them, it's fairly common.

I would consider myself a fastidious owner. I have always re-torqued wheel fastenings every time someone else has removed/replaced a wheel on one of my own vehicles. I have done this for more than 30 years; I have never, ever experienced one becoming less tight.

Of course, I would never re-mount a wheel on a dirty joint face...

Chris

When the wheel heats up during the journey. Or do you drive a magical car where the brakes don't get hot?

If that plastically deforms your bolts then retorqueing them won't help.

I've never experienced the wheel nuts on any car I've owned becoming loose by a process of the brakes becoming hot, no. And that includes some experience of motor sport where the discs would glow bright red!

The manufacturer would have taken into account thermal and other effects when deciding a suitable tightening torque, otherwise we would be seeing the country brought to a halt by unintentional three-wheeled cars stranded at the roadside.

I'm aware of vehicles in regular use that have not had the wheel nut torque checked for perhaps three or more years.

From experience, I think it far more likely that the problem would be one of removing the wheel nuts of those cars, rather than them becoming significantly loose!

Chris

By what process do you divine that Kwik fit were correct?

Am I being daft - or does it not take less force to UNDO a nut than to tighten it? If it takes 120 Nm to get as tight as you like, does it take

New studs and can stretch , wheel rims bed when put under load , subject to heat , cold etc for the first time .

you need far more force to undo, mainly because of friction and corrosion, using a torque wrench to undo would not give a meaningful result and might overload and damage the accuracy of the torque wrench. in addition most people do not understand how to use a torque wrench to re-check the tightness of a bolt.

Corrosion aside, that just seems to be 'anti' common sense..

Tightening, you are overcoming (increasing) friction and trying to make a piece of steel longer than it wants to be - so two components to the force in Nm required to get the nut to where you want it.

Loosening, you need to overcome the same friction (decreasing) but do not have the stretching element of the material..

So in principle, if you tighten up new, greased nuts on a thread and then immediately take them off using a torque wrench - it should take less effort? This just seems so obvious, i can see I'm going to have to have a go to test the theory. ;-)

the friction is the problem, when tightening you have the mating surfaces already sliding and it easier to keep them sliding than it is to re-start them sliding, especially in the opposite direction, the metal itself acts a bit like a one-way clutch. How about this for an analogy: Imagine two pieces of spiky carpet (giant size version of the faces of the nut and wheel) if you were to rotate and compress the carpet then the fibres would all get squashed and interlock, to undo in the opposite direction you have to overcome the bent fibres and get them going the other way.

Ah ok, I was considering the fact that some low torque is used to get the carpets closer togther , then bigger torque to lock. Sensibly the same torque would then be needed to break the bond, and then a much lower than low torque to continue as you are then just spinning the nut rather than parting the objects.

This I found intersting:

"In one release angle study, a part had a tightening angle of 120 degrees. Once the part sat overnight, the release angle was 20 degrees. The vendor was already aware there was a major problem because the parts were falling apart. The study showed that relaxation in the threads was causing an approximately 80% loss in clamp force over a 12 hour period. The release angle method provided a quantitative answer as to how much clamp force was being lost and clearly showed that there had to be a redesign of the parts."

which must have a bearing on the original question.

Did I say significantly?

Check your cars handbook, most do recommend that the torque is rechecked after a few miles. All/most car manuals also recommended that cylinder head bolts are retorqued after 500/1000 miles it's all the same process of settling in. The slightly high spots between the faces settle in and the tightness declines.

steve robinson was thinking very hard :

Correct!