Jacking issue (back to basics)

[Sean Regan]

when it comes to removing a wheel yourself after a service, you take pot luck.

Quite often, wheel nuts are overtightened by mechanics, after all, they don't want to be held responsible if a wheel comes off after a service.
I've never relied on the wheel brace supplied with any car.  I use a socket and the bar from my comprehensive socket set. I also have a length of steel tube, which fits over the end of the bar to increase the mechanical advantage.

[Lord Voltermore]

best not get up tight about it   

[davejazz]

best not get up tight about it   

Methinks you’re torquing through yer hat, but that would be nuts!

[aphybrid]

Back to basics is the sub heading to this topic.

The car industry has universally deciided that torque applied to wheel nuts is to be dry, i.e. without lubrication.

By doing so then no variations in applied end load (tension) to the stud due to different lubricity from different greases/oils is applied.

Torquing nuts/bolts results in a tensile load to the stud which is the clamping force that hold the wheel in place.

Some lubricants can result in several times the tensile load applied (copper slip?) and failures have resulted.

for accuracy in some applications nuts are tightened not by torque but applying tensile load via hydraulic means and simply running the nuts up by hand and then releasing the tensile load on the thread end.


Read https://www.boltscience.com/pages/failure4.htm
and note-

"Not all cases resulted in the preparation of a defect report but those which were prepared showed that some 72% of the failures were related to maintenance or abuse. Common problems were failure to tighten wheel nuts to the specified torque, overtightening of wheel nuts causing damage and failure to regularly check tightness of wheel nuts."

Also found this excellent demonstration of the effect of lubricants - not overly precisely scientific but totally
correct -

Lubricate the wheel nuts at your peril![/b]

[coldstart]

sorry (not sorry)
This thread somehow got me all "lubed up" 

Folks, are we still talking about changing wheels?

I was just advocating (like LV) that the main torque should be applied while the car has (at least some kind of) ground contact!

No more, no less!

[Lord Voltermore]

It has gone off topic slightly, but I think a thread  ( )  about jacking issues, should also progress to general comments about the safety aspects of jacking techniques  and  wheel nut tightening.  For those willing  and able to change a wheel themselves.   

Thread lubrication status   and torquing techniques  may be a bit over the top  for some readers  ,although its more important  on some engineering tasks such as tightening cylinder heads.  As always, if in doubt use a professional.   
Wheel nut/bolts/studs are quite robust  . I suspect the advice to concentrate on a particular  torque setting is partly to ensure you dont inadvertently leave the nuts only finger tight. 

Unless you are particularly frail or inept  you may not go far wrong  using the old diy rule of thumb...
 Tighten the nuts  as tight as you can  by hand using a fairly short  wheel wrench, as was typically supplied in the past for this purpose. Dont stand on it to increase leverage or use an extended wrench  except for undoing tight nuts.   I did this for many years without problems before starting to use  a torque wrench. I suspect I used to overtighten them slightly in the past.     

coldstart. Americans often complain  that the British constantly apologise without really meaning it     Sorry if you find this comparison insulting     

[Sean Regan]

It's important to ensure if you are changing a wheel yourself, that the jack is positioned exactly on a jacking point, these are usually a part of the welded seam where the sill meets the floor pan.

The metal in cars for decades has had  the density similar to that of "a biscuit tin." Putting the jack anywhere else could mean when you try to raise it  the car doesn't move at all, you're just making a dent in the sill or the pan.

[CB72]

I've always used a scissor jack under the axle, but I've never tried it on the Jazz.
Probably best to torque the wheel nuts when wheel is on the ground, don't use lube.

[FMIB]

Hi all, whenever I jack up my Jazz (level ground, e-brake, Park), the car shifts forward enough that my jack visibly bends and the front tire stopper gets stuck tight. I’ve tried two scissor jacks and a trolley jack, always on the right points as per manual. Tried putting plywood under jack, different angles, a rubber jack pad, stoppers. The movement is worse when lifting rear axle. Movement seems to be symmetrical.

I’ve changed tires myself for years, never had this happen on any other car.

Anyone else seen this? Is it something to do with the jack points, geometry of the Jazz or my particular Jazz? I know for sure that alignment is close to perfect.

Thanks!

I've seen this on some cars I have owned in my younger days when i maintained my own cars. Surely the movement you see when you raise the car is the due to suspension compression on the corners where the weight is being transferred to.
I would think that a cars specific suspension geometry would be why some cars exhibit this, others don't.

[John Ratsey]

Probably best to torque the wheel nuts when wheel is on the ground, don't use lube.

And also get the nuts slightly loosened before using the jack.

[CB72]

Don't forget to regularly calibrate your torque driver, a shop bought torque driver has a tolerance of +-4% so that you will torqueing the Jazz wheel nuts anywhere between 104 to 112Nm.
Personally I let the garage fit my wheels then you will have no problem with insurance if something goes wrong.

[Sean Regan]

Don't forget to regularly calibrate your torque driver, a shop bought torque driver has a tolerance of +-4% so that you will torqueing the Jazz wheel nuts anywhere between 104 to 112Nm.
Personally I let the garage fit my wheels then you will have no problem with insurance if something goes wrong.

Good advice.

Only use the manufacturer's supplied wheel brace to tighten the wheel nuts, but keep something stronger in the car, in case you're miles from anywhere, have a puncture, the rescue services are going to be hours, you want to change a wheel yourself and someone at the garage has over-tightened the nuts!
I've a socket, a tommy bar and a bit of steel tube by which I can extend it, if I ever have that problem.

[stefan]

Thank you everyone for your replies & advice. Love the forum and how a simple jacking questions forks into a discussion on torque. I ended up buying another jack and additional stoppers (put them under every tire, all directions, went bananas with it) and swapped this weekend. There was still some movement but it was limited to how much the car could lean on the stoppers so I was much more confident. The strange thing is that it's the first time I had to use stoppers in general (or see any movement while jacking for that matter).

Surely the movement you see when you raise the car is the due to suspension compression on the corners where the weight is being transferred to.
I would think that a cars specific suspension geometry would be why some cars exhibit this, others don't.

That makes sense and might be the case.

I believe the forward movement of the car during jacking happens because of the geometry of the rear suspension pivoting point. Perhaps the torsion beam suspension, which Jazz uses on the rear, is just prone to this?

The rear suspension indeed connects to the body at angle (looks like around 45 degrees on this image?).
 

My new 2 tonne trolley jack  did the job with ease and no signs of distortion. (it is quite sturdy) .  £32 from Halfords  (I got it for £30 )  Its small enough to fit in the Mk 4  underfloor boot compartment  if required.

I bent a jack that looks very similar but bears a different brand, Big Red 2 ton I believe?