Is it important to diagonally tighten wheel nuts?

[Submariner1]

I was surprised when I picked up my donor wheels and the fitter tightened them in a circular pattern.
I was pretty sure, it even stated in the manual to do each nut in a diagonal pattern ( like you tighten a cylinder head to avoid warping).

Any way when I got home (30 miles) I read the manual, and yep it said tighten in a criss cross fashion.

So as the donors will be on the car for 6 days, I jacked them up and loosened them off and then retightened, in a criss cross pattern, and did them to the 150 Nm.
They were tightened to 120 NM.

If, and I say if, tightening them in a circular pattern (one after the other ) distorts anything, what gets distorted the wheel, or the hub and or the disk?

If it distorts either the hub and or the disc, is the damage done when its tightened up, or over time? i.e. Was it worth me undoing them jacked up and then retightening them in a criss cross pattern.
Also if they didnt do them up to 150NM but only 120 NM would that have helped prevent distortion of the disc and or hub?

I ask as although the wheels were firmly on when I got home, lets say I missed my stable non-vibrating, go where you point them, wheels on the way home.

I assumed the donor wheels were buckled and a tad out of balance. And or possibly somewhat incompatible tyres, weird make "Lands xxxx" something or other.

 

[John Laidlaw]

Yes, should be criss cross to give a uniform pressure. Were the donor wheels alloy? My E and SL were 130nM - presume your manual says 150 sub?
Oh, and ive seen those weird tyres 'Landsail' Chinese I think make a lot of truck tyres

 

[Submariner1]

Thanks John, Yes the wheels were 20" AMG Alloys. And yes my manual says 150 Nm, but I set them at 140Nm cos the threads are wiped with Coppa slip, but not on the contact face just the threads . i.e. Semi greased so lowered the torque.

Plus wth RSI, ungreased at 150Nm when they lock up I can hardly u do them with a 700 mm lug nut arm. :-/

As I only do short journeys, they seem to stay at the right torque ... maybe if I was doing a long journey like Leeds etc., I would clean off the threads and put them at 150Mn .... just to be sure for safety sake.

I assume not using a criss cross pattern especially as they were only at 120 Nm would not have damaged the "trueness of the discs or hubs?

 

[John Laidlaw]

Thanks John, Yes the wheels were 20" AMG Alloys. And yes my manual says 150 Nm, but I set them at 140Nm cos the threads are wiped with Coppa slip, but not on the contact face just the threads . i.e. Semi greased so lowered the torque.

Plus wth RSI, ungreased at 150Nm when they lock up I can hardly u do them with a 700 mm lug nut arm. :-/

As I only do short journeys, they seem to stay at the right torque ... maybe if I was doing a long journey like Leeds etc., I would clean off the threads and put them at 150Mn .... just to be sure for safety sake.

I assume not using a criss cross pattern especially as they were only at 120 Nm would not have damaged the "trueness of the discs or hubs?

Not after a short period no....

 

[Craiglxviii]

Sub, the torque is set at 140Nm because that lies in the elastic zone for the bolt/ hub metal interface. At that point the metallurgy is such that the bolt metal will just start to bite into the hub metal at a molecular level.

Reducing the torque due to copperslip will just make it more likely for the threads to disengage due to precession over time. You don't reduce torque with lubrication in there!

 

[Mic]

I do not believe it to be good practice to grease the threads.

"cross tightening" in itself is not the point and nothing I believe to do with possible warping.

Surely the point is to lightly "cross tighten" all wheel "nuts" (no longer nuts these days) to ensure that all nuts are seated fully and correctly prior to "cross torquing".

Just precautionary good practise?

Mic

 

[Naraic]

I do not believe it to be good practice to grease the threads.

"cross tightening" in itself is not the point and nothing I believe to do with possible warping.

Surely the point is to lightly "cross tighten" all wheel "nuts" (no longer nuts these days) to ensure that all nuts are seated fully and correctly prior to "cross torquing".

Just precautionary good practise?

Mic

You are correct.
Clean the threads really well...but no grease.

Then tighten in a 13524 pattern till all are tight.

 

[Yugguy]

I've greased me nuts for the last 30 years with narry a problem.

 

[JBell]

You put opposite BOLTS in a wheel to hold it on the hub better when initially fitting the wheel, this also gives even pressure across the hub when putting the remaining bolts in.

When final tightening is done with a Torque wrench it does not matter which order you do them in.

Lubricant should NEVER be used on bolt threads and you should always tighten to the manufacturers recommendation.

 

[Craiglxviii]

Can you tell I've just done my Bolts course?

 

[JBell]

Can you tell I've just done my Bolts course?

Bet that was fascinating ;-) I sat in on a Pirelli tyre fitting course once

 

[Craiglxviii]

From an engineering aspect it really was. The strength margins, how threads actually work once torqued up, how correct torque is calculated etc. Most interesting thing was the pull out strength of welded on body studs. Err... don't overtighten

 

[JBell]

From an engineering aspect it really was. The strength margins, how threads actually work once torqued up, how correct torque is calculated etc. Most interesting thing was the pull out strength of welded on body studs. Err... don't overtighten

The weird thing is most cars only need 3 bolts to hold a wheel on, 4 or 5 are used to make people feel safer!!!!!!

 

[Craiglxviii]

It's what is called the safety margin

Most cars don't need a fuel tank capable of resisting whole- vehicle weight without structural disruption either

 

[JBell]

It's what is called the safety margin

Would make me chuckle seeing someone buying a new SL65 and looking at wheels held on by 3 bolts, I can imagine the reaction

 

[Submariner1]

Not after a short period no....

Thanks, so it was worth the effort of resetting them.
Must confess I was surprised they didnt know this ... but then the lot in Wales put both rear 9.5Js on the left and both 8.5Js on the right. :-/ and then accused me of doing it!
Stupid prat didnt realise my response would be "and how could I do that when you had sheared off the teeth on both locking wheel nuts"
And people wonder why I am cynical until I have tried workmen lol

 

[Craiglxviii]

Would make me chuckle seeing someone buying a new SL65 and looking at wheels held on by 3 bolts, I can imagine the reaction

The jet turbines on the C-130 Hercules are held on to the wing by only 3 bolts...

 

[Submariner1]

Sub, the torque is set at 140Nm because that lies in the elastic zone for the bolt/ hub metal interface. At that point the metallurgy is such that the bolt metal will just start to bite into the hub metal at a molecular level.

Reducing the torque due to copperslip will just make it more likely for the threads to disengage due to precession over time. You don't reduce torque with lubrication in there!

thanks Craig always up for learning something.
The tech at Norbar said if one greased a bolt then you had to reduce the torque, as a greased bolt will "do up more than a clean non greased bolt"

 

[JBell]

The jet turbines on the C-130 Hercules are held on to the wing by only 3 bolts...

Bet they are a little bigger than 14mm though

 

[Submariner1]

From an engineering aspect it really was. The strength margins, how threads actually work once torqued up, how correct torque is calculated etc. Most interesting thing was the pull out strength of welded on body studs. Err... don't overtighten

Bet that was enlightening!
The Norbar manager said they ran a course and as part of it was to see how accurate experinced mechanics were at guessing torque of 10Nm and 20Nm . Even they were surprised at just how bad nearly all the mechanics were ... often being 100% or more out. His quote enough to pull studs out and strip or partially strip threads.