I would like to relate an issue which is dear to my heart and rarely gets an airing. I am sure you boys and girls out there will have something to say.
Rather more years ago than I care to remember I was part of an investigation into an accident where a lorry lost a trailer wheel. The end conclusion was that the wheel had been recently changed, all the studs were of the correct design material etc, and had been done up to the correct torque, allegedly. Yet, because the threads had not been cleaned and oiled, so much of the torque was lost in overcoming the friction due to the crap in the threads, that there was insufficient clamping pressure to hold the wheel still under braking and cornering. Wheel shuffle resulted thus wearing the studs and hence a lost wheel when sufficient of the studs had stretched and fractured. Fortunately it was a single vehicle accident, no injuries involved.
The point of the story is that I then looked into this a bit more and was horrified how many lost/loose wheel incidents were reported each year and how many people were killed and injured as a result. Plus how many are not reported? It got to the point, having actually seen a wheel bouncing down the road towards me one evening, that I almost got a bit paranoid about night time driving especially on a dark motorway having visions of another wheel bouncing across the central barriers.
Now to put it bluntly this is still going on, the Transport Industry has been buggering around since the 1970's and still has not come up with a proper solution. The yellow arrows you see stuck on wheel nuts is one manifestation but this like most of the other "solutions," including locking nuts, are total B****CKS. The issue comes down to money, as usual, but it's your and my kids lives that is being put on the line.
I work in a different job now, but does anyone have up to date figures for this type of incident and casualty figures?
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Everytime I get a replacement car I find the wheel nuts difficult to remove because of rust. Removing the brake drum on back time consuming. After greasing the studs it is so quick to check wheels and brakes in servicing. I have never found the wheel nuts lose tension.
HGV vehicles seem a different class as regards wheels coming off. The DVLC research body looked into it several years ago. Recommendation was just to regularly check the tension.
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Strange as it may seem rusted or dirty studs are a cause of wheels nuts being insufficiently tightened. The torque applied goes into overcoming friction, and not applying the correct tension in the stud. So clean studs are what's needed. Be a bit careful if they are lubricated, as most torques are given for clean dry threads. Lubrication can allow overtightening.
Regards
john
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I got to look at some research into this subject a couple of years ago when I was asked to be an expert witness for a chap who swerved to aviod a loose wheel. He was trying to sue the driver, the operator, the maintenance engineers and anyone else in an effort to apportion blame. The pile of research papers from all over the world which came with the case notes was about 4 inches thick! Much research has been carried out by some very clever and well respected teams, who still cannot find a definative reason. Practices have changed- the wheel stud diameter standard is now thicker allowing for the torque to be applied without risk of stretching the stud. One cause was also established to be paint on the hubs, which if recently applied, was found to compress allowing the nuts to loosen. Poor tightening practice was also another factor, with a long wheelbrace being used instead of a torque wrench, but is is much more commonplace now for torque wrenches to be used. There have been many designs of nuts, wheels and studs to try and help, and I think a small fortune could be made by coming up with a useable idea! I could not help the chap in the end, as everything known at the time was done to the truck, and it did look as if the driver, who was following the truck, was not concentrating properly, and swerved violently on a wet motorway at speed.
I suppose the moral is, be prepared for the unexpected, and keep your wits about you!
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Only last week I saw this happen to a 1960s Jaguar which had been fitted with wire wheels, on the approach to junction 29 of the M1 near Chesterfield, Derbyshire I believe these are secured in place with one Spinner.
I was obliged to brake heavily and my pipe fell out of my mouth, casusing ash to be scattered on the car interior, my wife was annoyed as she had to get the hoover out and clear up the mess.
Steel wheels as fitted to most ordinary cars have some degree of "give" or springiness which forgives overtightening, whereas aluminium alloy wheels don't, so care must be taken with this type of wheel, also the bolts required to attach such a wheel must be almost an inch longer.
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