I have found they usually use their air wrench thingy and it does them up to tight. (makes a good noise though)
My husband told me to ask them to only use a manual torque wrench and make sure they got the right torque. My local (and fantasic) tyre fitters were only too happy to oblige.
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It's a "best practice" procedure, one of the few we motorists can actually take charge of in this increasingly automatised, computerised world, along with a flick of the dipstick and a burst of the air hose to check tyre pressure (all checked for you in top end models nowadays).
Spark plugs need correct torque, too, but how many of us actually touch the things these days?
Man goes to the doctor's for a medical. Drops his trousers and the doctor exclaims "Good grief, look at that! I've never seen anything like it! Did you know you had a steering wheel in your underpants?!?"
"Yes, I know, it's driving me nuts!"
:-)
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Can i go slightly off topic, but still with wheel nuts.
I'm going to get slated again as i use coppaslip on the threads and bolt head seating faces on my alloy wheels and i do so with steel wheels too.
Hang on NC, i'll explain.
Back some years when on contract tip work with tipper skip loaders, the 2 of us had at least one truck tyre puncture every day, we carried spare wheels and changed our own on the side of the road, or more usually at the landfill (don't see drivers changing truck wheels any more, ever).
When we started that contract, the wheel stud threads were as rusty as all are when left non oiled, and the wheels would sometimes loosen (Seddon Atkinson and Leyland constructor, IIRC the Seddon had taper bolts, possibly left and right hand thread, the Leyland spigot fitted wheels with flat washered bolts, all right hand thread), every time we changed a wheel we oiled the threads well, and found that the wheels always stayed tight once well lubricated, as against trying to tighten against a film of rust. We rechecked torque, and every time the oiled threads never needed retightening, but the non oiled nuts did.
Now i know that oiling truck wheelbolts is no longer recommended, but it worked well at the time.
So whats the view on oiling/coppaslipping the wheel bolt threads and faces on a car/van/4x4 etc?
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Slightly off tack but still relevant. I fitted a towbar to my Sorento. I decided to waxoil everything on assembly including the mounting bolts. After ripping out two threads whilst torquing up I realised the error of my ways. Cleaned all the bolts and captive nuts, a couple of helicoils and all was well. The lubricant had reduced the friction and thereby increased the torque required. The consequence was that I had over stressed the weakest component.
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25 years ago when British Rail started using torque wrenches we had a similar problem with bolts snapping....
Was it the plating. . . tried black, EZP, ECP, etc
Was it the oil film . . . dipped them in the paint shop degreasing tank - not a place you want to stand tooo close to, it degreased your skin!
Still snapping bolts . . .
Was it the torque wrench calibration . . . . re-calibrated but still snapping bolts.
After three weeks the problem was sourced to the testing machine that a third party calibration house used to calibrate the works calibration machine annually. It was out by 15%.
Now a question to all those with thier own torque wrenches - when did you last have it calibrated and how do you know it is right.
I trust the little skill I have and in 31 years of motoring nothing has come loose.
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Now a question to all those with thier own torque wrenches - when did you last have it calibrated ..........
It was last checked about 6 years ago in the Metrology Lab at work. Since retiring, this perk is unfortunately no longer available to me. I suppose I could carry out a rough check myself by putting it in my vice and hanging a known weight on the handle.
Edited by L'escargot on 23/07/2008 at 10:16
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I just tighten them by feel and they've not fallen off yet!
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Calibrating Torque wrenches - if the wrench is kept clean and not used too often (ie DIY use) calibration may not wander too much. The Torques required to snap large bolts must be very high and certaininly if I was putting on a cylinder head and other critical applications -Torque calibration is important. But I'd imagine Torque on wheel nuts has fair degree of tolerance. I have re tightened wheel nuts on cars where tyres have probably not been off in two years or more and found them only very slightly loose or corroded on solidly. Many cars now have 5 or more bolts on the wheel, whereas years ago it was mainly 4, so I guess there is less stress on each bolt?
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Not commenting on the rights and wrongs of this precaution but faintly realising that either I have been very lucky or perhaps it is not quite the issue some would have us believe.
I have never re-checked wheel bolts or nuts after they have been fitted either by me or a garage. I do not own a torque wrench and I am not sure if I would recognise one if I saw it. I have never applied any form of "wizards compound" to the nuts or bolts either. In 33 years over 40 or so cars and 1.1 million miles. Never had a wheel come loose or fall off or seize on, or indeed had any issues at all as a result. I just tighten them up until they feel tight ( or assume someone else has ) and get on with driving the car !
Just lucky I guess ?
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I'm going to get slated again as i use coppaslip on the threads and bolt head seating faces on my alloy wheels and i do so with steel wheels too.
Gordonbennet, as I am sure you know, you are completely missing the point.
It's not the torque on the nut that matters. It's the extent to which the bolt is placed in tension. And an easy way of knowing how much in-tension a bolt is, is by knowing the torque used to do it up. And that torque is defined with dry surfaces. So your 75Nm will stretch the bolt by (NC tells us) one-third of a hair's width.
I'm not surprised the oiled ones never needed retightening. They were being stretched by far more than the recommended torque, so the force holding the nut against the wheel was much higher...
For a given bolt it is perfectly acceptable to use grease, but then the torque required is much lower, and you are guessing...
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Regarding torque wrenches - it's not just calibration that's needed, but they're also supposed to be exercised regularly, ideally before and after every use).
I think the issue of re-torquing wheel nuts is odd - tyre places always have always made a fuss about it, yet in many years of using dealers for servicing on company and private cars I can't recall it ever even being mentioned.
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Motor car wheelbolts are quite tolerant of abuse. They are significantly overdesigned. But, that's not an open invitation to behave like vandals with them! If you follow the manufacturers guidlelines, you are most unlikely to have a problem. If you make the rules up yourself, you have no idea how close to the wind you are sailing.
They are of course overdesigned because manufacturers know the bolts will be abused, badly fitted, greased, buzz gunned, etc, etc. If you were to fit the bare minimum, and rely on good practice, I would imagine most cars, with a decent central spigot, would make do with 2 wheel bolts.
For GB's Seddon, with its taper wheel nuts, Mapmaker is bang on. What happened with these vile taper located wheels was that owing to the impossibility of ten tapers all being in alignment, the wheel would move relative to the hub, and this would provide the off torque for the wheel nuts. Greasing them, and hence stretching them further provided enough clamp force to overcome the wheel's relative motion. This was done, at the expense of the margin between the nominal wheel stud stress and the failure stress
Tapers are OK for four, or at a push five bolts, especially when the bolts are slender, but beyond that, and especially with the stubby wheel studs found on truck, it's a bad idea.
The constructor on the other hand with its spigot wheels and flat wheel nuts was a much better method of wheel location. So good in fact, I remember having to use a bottle jack between the chassis and the back wheel rims to free them off on a Constructor 8!
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NC>> Mapmaker is right.
No. Mapmaker is inaccurate. I'm not surprised the oiled ones never needed retightening. They were being stretched by far more than the recommended torque, so the force holding the nut against the wheel was much higher...
Should of course have read: I'm not surprised the oiled ones never needed retightening. They were being stretched by far more than the recommended amount, so the force holding the nut against the wheel was much higher...
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Hang on chaps, do you seriously think that 2 hairy armed tipper jockeys would be messing about with a torque wrench on the side of the M40 or deep in the filth at Denham or Beaconsfield landfill?
Nay chaps it was the good old long bar with the weight of a slightly slimmer GB applied;)
We never had a single broken wheelstud either despite some of the most gruelling work, in fact so heavy we had to have the Seddon's fuel pump richened up to actually get the vehicle to power itself through the slurry, no such problem with the conctructor as you would probably know NC, that would go anywhere the track layer could, quite amazing really.
So are you saying we were wrong to be oiling the bolts, as in practice, our method worked and we became quite dab hand at the quick change, and could well have shown some tyre men how to do the job, mind you the various aches and pains from this and many other 'get on with it' jobs over the years show themselves now.
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Got a puncture once in a rear tyre of my VW 411, in Highbury near where I used to live and where I got the 411 (I bet some people here know where too). One of the nuts (or bolts, can't remember) was rusty and overtorqued, and I couldn't budge it. Put a ring spanner on it with a bit of scaffold pole over the other end and jumped up and down on it, without a result. Two helpful coppers then both jumped up and down on it at once, until the spanner ring exploded. But with a good-quality socket, huge tommy bar and the scaffold pole they budged it in the end.
A wee bit of copper ease under the bolt head isn't a bad idea.
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>>One of the nuts (or bolts, can't remember) was .....overtorqued, and I couldn't budge it.Put a ring spanner on it with a bit of scaffold pole over the other end and jumped up and down on it,
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I had a similar situation after some toerag let a tyre down.
The difference was I was on holiday in Capetown, it was a Renault Scenic hire car from one of the big two, just a few weeks old and of course a did not have a pump.
I was lucky to find a pole to add to the standard wheel nut tool.
At least I was in the city area outside our bungalow rather than in the boondocks.
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That's Copper ease...
Two helpful coppers then both jumped up and down on it at once.. until the spanner ring exploded. But with a good-quality socket, huge tommy bar and the scaffold pole they budged it in the end.
..and copper ease then?
A wee bit of copper ease under the bolt head isn't a bad idea.
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:o}
The price of copper is sky high at the moment... coppers of course can't be bought at any price...
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>>So are you saying we were wrong to be oiling the bolts...
Having had to resort to a six foot extension pole, my full weight, and the No 18 jet in the oxy-acatylene welder to free wheel nuts from various Leylands and AECs, I would be hypocritical to say you were wrong. Until the mid eighties, we didn't have a torque wrench for truck wheelbolts either - a wheel coming off one of our Merc 6 wheelers, and making an unconventional entrance into a Magnet & Southern showroom changed that!
Of course, there's a world of difference between the clean and dry conditions under which bolts should be fitted. Under more general haulage conditions, it's probably OK, but, many of my father's trucks were typically used off-road, up to their axles in mud. Under these conditions even bolts fitted with lubricant would seize up.
We used to fit our fair share of wheel studs, and the wheel rims, where thin because of the taper would often succumb to fatigue cracks. Awful design.
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