Checking wheel bolt torque?

[Oldsalt49]

When I check the tightness of my wheel bolts, I always back off the nut first and then re-tighten to the recommended torque. Am I doing the right thing or not?

OS

 

[parker1158]

Theoretically what you are doing is re-torquing your wheels – this will leave you knowing they are done up to the exact tightness. Checking wheels are tight can be done by using any wrench and just feeling that there is no significant movement, although clearly this does not guarantee they are at the correct torque. In short though backing them off first is the most accurate method.

 

[TD42]

There seems to be 2 schools of thought on this. Wheel nuts should be checked 30 miles after being tightened!! So IMO if you back off /'loosen' the nut & retorque it do you have to back it off & re torque 30 miles later? If you use a torque wrench that "clicks" at the correct torque then I do not see any need to back of the nut.It will not,'as some say "overtighten the nut"

 

[Damian]

I quite agree with TD42, initial setting of the torque is done when the wheels are replaced.
Simply checking that they are remaining at the correct torque needs a torque wrench set to the correct setting and listen for the click as it is tested.
It cannot overtighten providing no more force is used once the click is heard,
Backing off the nut puts you back at square one,when checking the nuts is required after 30 more miles.

 

[Oldsalt49]

Thank you shipmates!!! I will revert to the last 2 suggestions from now on. I was just concerned about imposing cracks on the bolting surfaces of my alloys. Thanks for your help and thought provoking suggestions.

OS

 

[parker1158]

OK someone fits your wheels and whacks them on with an airgun set on full – almost certainly the incorrect torque i.e. to tight (If you wanted to change the wheel you might not get them undone, damaged threads, stretched threads leading to stripping when backed off etc)If you use a torque wrench set to the correct setting you would get a click without the bolt moving – so these are done up to the correct torque are they?

Most tyre centres tell you to check your wheel nuts/bolts after having tyres fitted why? Because they have no faith in their fitters, basically you are double checking their work and the blame for a lost wheel is put in your lap. In my opinion it should not be necessary to check a wheel bolt once it has been tightened correctly

 

[Dustydog]

I'm with Damian and TD42.
There were numerous threads on this subject last year when I lost a wheel off the car in Scotland.
It was my fault!.
The mobile tyre fitter asked me for the torque setting which I correctly gave him. I watched him tighten all wheels and heard the click.
However I didn't recheck after 50 miles as stated on the invoice.
Bedfore each journey I now check both car and caravan wheel nuts as described on here. Do not loosen and start again!!

In fact the torque wrench lives in the car boot.

 

[Oldsalt49]

Sir Barkin,
Very fair comment. I know what you mean, had a tyre centre use a windy tool on a previous car. One day, had a puncture and could not undo the wheel nuts. A mechanic friend had to use a 4 foot scaffold pole on the wheel wrench, and even had to jump up and down on it to get them free.
I think most caravan dealers now torque up the wheel nuts with you in attendance now? Mine did a few weeks ago.

OS

 

[chrisbee1]

OK someone fits your wheels and whacks them on with an airgun set on full – almost certainly the incorrect torque i.e. to tight (If you wanted to change the wheel you might not get them undone, damaged threads, stretched threads leading to stripping when backed off etc)If you use a torque wrench set to the correct setting you would get a click without the bolt moving – so these are done up to the correct torque are they?

No, they're overtightened but unlikely to work loose.. However, any damage has already been done and by slackening off and retorqueing without checking your torqueing after 50 kms or so does run the risk of the wheel becoming detached.

 

[parker1158]

Incorrect.A bolt that is over tightened and thus stretched is weakened and can shear or back off because its strength and grade have been compromised. If a bolt could be over tightened and still be safe then manufacturers would state torque settings as ‘‘X’ minimum but the more the merrier’. They don’t, they quote a specific figure between a narrow band.

Based on the assumption all wheel bolts require retorquing after ‘x’ miles presumably when we have an engine rebuild, on getting home, we swing under the car, remove the sump and check the end caps do we? If we have new shocks we drive home get the car on axle stands and retorque all the suspension do we? No i thought not.
Wheels are no different if they are correctly fitted and tightened there is no reason they should need to be checked.

 

[seth1]

But bolt makers do make bolts that stretch and still remain good exceptible tensile strength,these bolts are known as wait for it stretch bolts.They work in a slightly different way regarding elasticity.I would have thought it not possible to compare a conrod big end cap and fixings to a road wheel and hub.Since when would you get a build up of corrosion and other foriegn matter on an internal engine part as you would on a road wheel and hub?It is the disappearance of this foriegn matter after fitment that makes a roadwheel come loose therefore leaving a space between the companian faces.

 

[parker1158]

It is not the treads on a stretch bolt that ‘stretches’ it is the unthreaded plain shaft. These bolts are one use only and are designed to stretch, again within a very specific band of tightening criteria. It is wrong to compare them with other bolts on a vehicle.

So it is acceptable to fit a wheel to a hub covered in rust and debris? Basically goes back to someone with very poor working habits asking you to ‘check their work’ by retorqing the wheel bolts. Personally if I had got myself into a position that that type of person had been working on my car I would feel the need to re-check the whole job not just wheel bolts. Wheel bolts should present no more or less of an issue than any other bolts and nuts.

 

[seth1]

What you have said is exactly right,i wasnt comparing a stretch bolt with a normal bolt just merely pointing out another bolt form in responce to your post.But some stretch bolts can be used more than once,this is determined by a simple measurement.
Sadly though regarding the loose wheel syndrome,this seems to be the case concerning the issue-debris which is not removed prior to fitting.

 

[colin-yorkshire1]

Based on the assumption all wheel bolts require retorquing after ‘x’ miles presumably when we have an engine rebuild, on getting home, we swing under the car, remove the sump and check the end caps do we? If we have new shocks we drive home get the car on axle stands and retorque all the suspension do we? No i thought not.
Wheels are no different if they are correctly fitted and tightened there is no reason they should need to be checked.

I agree, ok so i am not a trained engineer but done my own maintaince on both cars and my vans and can't ever remember a nut or bolt comming loose ever;
besides the van and the m/home had those yellow thingy's that show the position of the nuts once tightend and set you can see if a nut has moved just leave the covers off for the first bit of the journey walk round and look.
besides has anyone seen wheeler dealers lately, dont think ED has a torque wrench in his tool box. he never uses one he acctually tighend the wheel nuts of an elan on the last program with a rubber hammer very technical and then "hammered" it up a hill race course..

 

[Dustydog]

Hi Colin
Like Ed China's Elan my old TR4A had knockons. From memory the threads were different on each side so that the forward motion of the wheel tended to tighten the knockon rather than loosen it.
I understood all wheel bolts were high tensile steel , meaning they can take loads of abuse and it is more likely the thread will strip before the bolt shears.
One for Lutz maybe

 

[chrisbee1]

OK someone fits your wheels and whacks them on with an airgun set on full – almost certainly the incorrect torque i.e. to tight (If you wanted to change the wheel you might not get them undone, damaged threads, stretched threads leading to stripping when backed off etc)If you use a torque wrench set to the correct setting you would get a click without the bolt moving – so these are done up to the correct torque are they?

No, they're overtightened but unlikely to work loose.. However, any damage has already been done and by slackening off and retorqueing without checking your torqueing after 50 kms or so does run the risk of the wheel becoming detached.

Sir Tainly, note I said unlikely to work loose and any damage has already been done. If you're concerned that your bolt's safety has been comprimised then the only safe option is to replace them all.

 

[parker1158]

Based on the assumption all wheel bolts require retorquing after ‘x’ miles presumably when we have an engine rebuild, on getting home, we swing under the car, remove the sump and check the end caps do we? If we have new shocks we drive home get the car on axle stands and retorque all the suspension do we? No i thought not.
Wheels are no different if they are correctly fitted and tightened there is no reason they should need to be checked.

I agree, ok so i am not a trained engineer but done my own maintaince on both cars and my vans and can't ever remember a nut or bolt comming loose ever;

Exactly.
Now for the record I am a trained engineer (Engineering degree) Twenty years with Audi in motorsport and then on research and development. I must have fitted hundreds of wheels and literally thousands as a department, from my knowledge I have never experienced a wheel coming loose that had been fitted correctly. I have just checked an invoice from recent tyres I had fitted at a local reputable tyre fitters. Nowhere does it ask me to check the torque and I certainly was not asked to – clearly a company that has faith in its fitters. Anyone who effectively asks you to check their work clearly has no faith in themselves.

By far one of biggest mistakes made is from people who do not know their Nm from their ib’s ft and kg m (something I come across on a daily basis from the year ten and elevens I teach) Clearly this could and would lead to a bolt being under tightened with the potential to come loose – would i want someone like that working on my vehicle, in any capacity?...No.

For accuracy torque should always be applied to a nut/bolt in one fluid movement, to do this the nut/bolt would need to be backed off first.

 

[seth1]

I seem to remember this subject being debated a while back,and i think all whats been posted is correct.I can remember as an apprentice,long before vosa was called vosa,and was refered to as the ministry of transport carrying out an investigation on what they called" loose wheel syndrome".The wheels in question were always a pair on the n/s/r,even though left handed studs were fitted which was norm on British tackle of the day.I think if i remember correctly the outcome was put down to dirty faces,debris dropping out,leaving a space,thus lowering the clamping force and the end result being loose nuts.This then led to studs shearing off,and putting more strain on the stud next to it which then sheared as well,and a pair of wheels pass,s you.We went agaist the grain,by fleet engineer instructions by oiling the threads with light grade motor oil,the industry standard is threads should be clean and dry.His view was this should reduce frictional losses during tightening and give a more acurate figure towards tightening.In actual fact certain manufactures do recommend a wheel securing device retorque after a set time or distance,some now refere to an angle torque method instead.

 

[colin-yorkshire1]

hi all.
thats all fine and dandy and good theory but is that not what the yellow thingy's are for so a visual check can be done prior to moving the vehicle, from my driving days I distictly rememer it being on the daily check sheet no-one ever got the torque wrench out after the moblie mechanic had been out to change a tyre. 50 miles down the road to the next delivery.
all surfaces should be clean and rust free on any fixing be it a wheel or anythig else and the nuts/studs should be free enough to tighten finger tight and not binding in the threads.
surely two nuts the same, one tight one free will be under different load tensions at the same torque figure and how many wheels get rechecked after a roadside wheel change not many I will bet.
the truth is the recheck after 50 miles is just a get out clause "it's not our fault guv" and an excuse for poor workshop practices and you don't have to be an engineer to work that out.

colin

 

[Guest]

Interesting that yield bolts have come up and prompted me to finally discover the reasoning behind them, already knowing, a bolt 'in yield' is useless, the answer is simple, the more correct term is 'torque to yield' or to be precise, just below it's yield point.
The reason is simple, more generally, bolts are correctly torqued to a safe 60% of their yield point, this is a 'waste' 40% of it's abilities, (albeit a large and useful safety margin for error), by being more accurate and using more, you cut down on size, therefore material and cost.
In the common use case of a cylinder head of an engine, you also cut down on size of holes to take those slimmer bolts in the block, proportionally, this will reduce the required thickness of material around those holes, therefore an even greater saving in materials, machining cost and weight.

 

[ValA.]

Outside of the technical issues to do with this subject, I'd reiterate to make sure that your torque wrench is correct, too. We had a problem with a knock from the tow hitch (outlined and solved with the help of members of this forum) and discovered that our torque wrench settings were not correct - and solved the problem with another torque wrench where the settings were correct.