Author Topic: 80 to 108 !!!  (Read 1401 times)

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Offline Canada_Bob

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80 to 108 !!!
« on: January 16, 2018, 02:32:02 PM »
The car will be going in for the 2 year service next week, the standard stuff, but the Dealer asked me if I'd like to have the wheels rotated, sounds like a plan to me, there's just 15k on the car. The concern I have about wheel rotation is, I can't remember ever seeing a dealership or a mechanic calibrating nut runners, "one size {torque} doesn't fit all" it's a sore topic for me as an Acura Dealership mechanic stripped the studs on all 4 wheels on a car I had 20 years ago.

I'm keen not to have that happen again, so I'll be asking them what their nut runner is set at before they do any damage that folks wouldn't be aware of until they lost a wheel. On looking at the Manual {page 7:19} the recommended torque is 80 ft/lbs to 108 ft/lbs, I'm an old guy, I can't think in Newtons  ??? but the range from 80 to 108 seems a hell of a lot, why would a mechanic / Dealership set at 108 when 80 would do ?

108 sounds high to me, might be a struggle for some folks to change a wheel if it's torqued up to 108, at the same time 80 seems a bit low ?

Maybe somewhere in the middle would be the way to go, but it's the scale of the range 80 to 108 that has me concerned, the wider the scale the higher "mid range" is going to be, a bit like tyre pressures, 35 to 37 seems a sensible target range but you'd think that Mazda {et-al} would be able to narrow the scale closer than presented in the manual, or am I missing something here ? it's  not something that {like tyres} that's "load dependant".

I'd appreciate any thoughts on this...

Thanks.


Offline bobmax

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Re: 80 to 108 !!!
« Reply #1 on: January 16, 2018, 03:55:46 PM »
did a notice about rotation show on the Dashboard?
It did an mine a t about 18000 miles.
So wondering if it will show again since I had all my tyres changed?
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Offline Willpower

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Re: 80 to 108 !!!
« Reply #2 on: January 16, 2018, 04:19:20 PM »
An interesting question, which I also asked some 12 years ago with my Gen 1 when we didn't have the tyre gunk option and had no choice but to change the wheel at the side of the road.
 
At the time, the dealer informed me that they were instructed to torque the wheel nuts to between 100 ft/lbs - 135 ft/lbs (a margin of 35ft/lbs). But this is in a considerably higher range than you have been quoted. 
As it is, your margin is only (28ft/lbs)

The problem as I see it is, the torque applied, has got to be subject to the inherent tensile strength of the bolt. But perhaps with modern casting methods, the specification of the wheel bolts has been reduced over the years.   

If I were in your position I would consider using the middle value, i.e  somewhere around 90ft/lbs.   
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Offline moozmooz

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Re: 80 to 108 !!!
« Reply #3 on: January 16, 2018, 05:24:25 PM »
Can't say without looking, but the stud size and offset may be different from Gen 1 to Gen 3. The range might also be to allow for different wheel sizes.

And studs, bolts, nuts are usually forged from round bar.

Offline Willpower

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Re: 80 to 108 !!!
« Reply #4 on: January 16, 2018, 05:47:30 PM »
Can't say without looking, but the stud size and offset may be different from Gen 1 to Gen 3. The range might also be to allow for different wheel sizes.

And studs, bolts, nuts are usually forged from round bar.

Totally get what you are saying and you are quite correct regarding different sizes vs generations.  But that doesn't get away from the fact that the steel, when forged as round bar will have differing tensile strengths dependant on the component elements that make up that steel. It then comes down to whether the Mazda spec requirement was changed at some time.

Forming round bar into bolts, has no effect on the inherent strength of the steel.  It's also unlikely that stud size and offset or wheel size would have any relevance. 

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Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #5 on: January 16, 2018, 06:56:48 PM »
An interesting question, which I also asked some 12 years ago with my Gen 1 when we didn't have the tyre gunk option and had no choice but to change the wheel at the side of the road.
 
At the time, the dealer informed me that they were instructed to torque the wheel nuts to between 100 ft/lbs - 135 ft/lbs (a margin of 35ft/lbs). But this is in a considerably higher range than you have been quoted. 
As it is, your margin is only (28ft/lbs)

The problem as I see it is, the torque applied, has got to be subject to the inherent tensile strength of the bolt. But perhaps with modern casting methods, the specification of the wheel bolts has been reduced over the years.   

If I were in your position I would consider using the middle value, i.e  somewhere around 90ft/lbs.

The thing is, 28ft/lbs is quite a lot, it's 35% of the lower end of the recommended scale, that seems a lot to me. I'll probably go with 90ft/lbs but I'm surprised that Mazda {and probably other Manufacturers} can't/don't nail it down closer than they do.

As for the tensile strength of the steel, well Mazda would know that within <1% my concern is the nut runners over torquing and damaging or stripping the studs.

Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #6 on: January 16, 2018, 07:07:01 PM »
did a notice about rotation show on the Dashboard?
It did an mine a t about 18000 miles.
So wondering if it will show again since I had all my tyres changed?
No, there wasn't any indicator light, the car only has 15k on it, looks like yours {at least} was set from new by Mazda or the Dealer, but it's EASY to set that up on your cars computer to flag up to when you'd prefer it to be based on the type of driving that you do.

Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #7 on: January 16, 2018, 07:09:57 PM »
Can't say without looking, but the stud size and offset may be different from Gen 1 to Gen 3. The range might also be to allow for different wheel sizes.
I hear what you say, but, if that was the case why don't they say that in the Manual ?

Offline Willpower

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Re: 80 to 108 !!!
« Reply #8 on: January 16, 2018, 08:09:20 PM »
Doing a bit more searching amongst data referring to my Gen 1  I found this .


Wheel and Tire Installation
1.   When installing the wheels and tires, tighten the wheel nuts in a criss-cross pattern to the following tightening torque.

Tightening torque
88.2-117.6 N·m {9.00-11.99 kgf·m, 65.06-86.73 ft·lbf}


Of course the first and very obvious item is the discrepancy between what I was told verbally and what is written here.  Quite bizarre...   

However what strikes me is the value shown in N-m  i.e.   88.2 - 117.6 N-m     Are you sure it said ft/lbs in your manual ?   because the values shown here are not too far away from those you quoted in your initial post, but in different units.

I shall see if I can find anything further relating to the Gen 3
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Offline moozmooz

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Re: 80 to 108 !!!
« Reply #9 on: January 16, 2018, 08:25:40 PM »
"Forming round bar into bolts, has no effect on the inherent strength of the steel" Absolute rubbish. The various heating processes, including drawing, forming and threading, along with quenches during the processing are what determines the final molecular and physical properties of the steel.

"It's also unlikely that stud size and offset or wheel size would have any relevance" Wrong again. Think of basic mechanics/principle of the lever. Different wheel size and tyre size will exert different loads at the studs, as will different ride height. Think back to the days of wide boys fitting spacers and subsequently having their wheels fall off due to overloaded/failed studs as one example.

"As for the tensile strength of the steel, well Mazda would know that within <1%" I wouldn't bet on it. They'll most likely specify a minimum tensile strength. Anything over that is an increased safety margin they're not particularly interested in and don't pay for.

"I hear what you say, but, if that was the case why don't they say that in the Manual ?" The manual isn't specific to any one spec. What I find pretty disgraceful is that the manual doesn't even attempt to make clear which parts apply to which spec, something that in the computer age would be very simple to do.

On torquing in general. In more years of motoring than I care to remember, I've never used a torque wrench on wheel nuts or studs, and nor did garages/tyre fitters until fairly recently. How often do they check the calibration of their torque wrenches? Many are probably no more accurate than you would achieve using a known wheel wrench/known force.
Everybody will have experienced the rock solid nut/stud due to moronic use of air spanners, and some will have been unfortunate enough to experience the consequential failed studs.

I'd tend to let the garage get on with it, but if you're really bothered, check the nuts for tightness after the service, and, if necessary, back them off slightly and retighten them. If they're rock solid and won't move, go back and ask them to refit them so that you don't need a length of scaffold pole to loosen them.





Offline misar

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Re: 80 to 108 !!!
« Reply #10 on: January 16, 2018, 09:03:36 PM »
I looked in two owners manuals:

2010 (Gen 2)
Nut tightening torque
N·m (kgf·m, ft·lbf) 88 ― 118 (9 ― 12, 65 ― 87)

2013 (?Gen 3)
Nut tightening torque
N·m (kgf·m, ft·lbf)
108—147 (12—14, 80—108)

So my Gen 2 is the same as Willpower's Gen 1 but later models went much higher as in the thread subject.

No mention in either manual about alloy versus steel wheels but if any models came with steel I would have thought the torque should be different. Mine has alloys but no idea what torque has been used.

PS I just noticed the OP's name and flag! I wonder if the wheel type varies between N America and Europe. However, the 2010 manual I quoted was a USA download but the 2013 one was a UK download.

PS2 Google found some tyre supplier recommendations:

Continental Tyres chart (2015, USA)            Torque in Nm
                                                         Steel rim     Alloy rim **
Mazda all current types – except *        103             103
* CX-5, 3 2013>, 6 2013>                    128                –
* MX-5                                                    98               98
** Please observe different specifications of rim manufacturer where required.

Pure Tyre (2018, UK)
Wheel Nut Torque setting for: 09 - 14 Mazda Mazda 3
(All tyre options)
Torque:  103 NM,  76.0 ft-lb

So 103 N.m falls nicely into the 2010 set of Mazda values whereas the Continental 128 N.m for steel is in the middle of the 2013 range. I would be inclined to go for 103 N.m unless I found specific advice to go higher for my alloy rims.

« Last Edit: January 16, 2018, 09:52:16 PM by misar »

Offline misar

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Re: 80 to 108 !!!
« Reply #11 on: January 16, 2018, 10:15:38 PM »
An interesting question, which I also asked some 12 years ago with my Gen 1 when we didn't have the tyre gunk option and had no choice but to change the wheel at the side of the road.
 
At the time, the dealer informed me that they were instructed to torque the wheel nuts to between 100 ft/lbs - 135 ft/lbs (a margin of 35ft/lbs). But this is in a considerably higher range than you have been quoted. 
As it is, your margin is only (28ft/lbs)

The problem as I see it is, the torque applied, has got to be subject to the inherent tensile strength of the bolt. But perhaps with modern casting methods, the specification of the wheel bolts has been reduced over the years.   

If I were in your position I would consider using the middle value, i.e  somewhere around 90ft/lbs.

The thing is, 28ft/lbs is quite a lot, it's 35% of the lower end of the recommended scale, that seems a lot to me. I'll probably go with 90ft/lbs but I'm surprised that Mazda {and probably other Manufacturers} can't/don't nail it down closer than they do.

As for the tensile strength of the steel, well Mazda would know that within <1% my concern is the nut runners over torquing and damaging or stripping the studs.

I am not an engineer but surely the range is set by two different factors. The low end would be the smallest torque required to ensure the nuts don't come loose. The high end would be the maximum torque before you exceed the tensile strength of the bolts or strip the thread - or in the case of alloys distort the rim or the stud hole surfaces.

Hence any value within the range is fine but the key issue is to be above the minimum recommended. This might depend on whether the wheel is steel or alloy and also the shape of the nut/wheel mating surfaces.

Feel free to discuss further!
« Last Edit: January 16, 2018, 10:20:48 PM by misar »

Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #12 on: January 17, 2018, 03:38:37 PM »
Doing a bit more searching amongst data referring to my Gen 1  I found this .
Wheel and Tire Installation
1.   When installing the wheels and tires, tighten the wheel nuts in a criss-cross pattern to the following tightening torque.
Tightening torque
88.2-117.6 N·m {9.00-11.99 kgf·m, 65.06-86.73 ft·lbf}

Of course the first and very obvious item is the discrepancy between what I was told verbally and what is written here.  Quite bizarre...   
However what strikes me is the value shown in N-m  i.e.   88.2 - 117.6 N-m     Are you sure it said ft/lbs in your manual ?   because the values shown here are not too far away from those you quoted in your initial post, but in different units.
I shall see if I can find anything further relating to the Gen 3
Thanks for the above, "two heads" and all that, the values I got were direct from the M3 Manual, and they are in ft/lbs, I can't get my head round ft/lbs it's easy for me {at my age} to visualise, can't say the same for Metric units or Newtons {even though he was a local lad}, but the 80 to 108 is ft/lbs as shown on page 7:19 of the M3 Manual.

Having said that about Newtons, I know that you just add 35% to go from ft/lbs to Newtons, but why convert to something you don't want to work in anyway sigh, add to that although my torque wrench isn't as old as Newton it is almost as old as me, so the only calibrations on it are in ft/lbs...

Like you say, it is bizarre at times, no matter what units we prefer to use though that 35% from low to high seems way too much to me...


Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #13 on: January 17, 2018, 03:54:20 PM »
Hello Misar,

I'm not an engineer
Aye, well, I was {retired now}, but, you don't have to be a jockey to know a horse when you see one  :)

but surely the range is set by two different factors. The low end would be the smallest torque required to ensure the nuts don't come loose.
Agreed...

The high end would be the maximum torque before you exceed the tensile strength of the bolts or strip the thread - or in the case of alloys distort the rim or the stud hole surfaces.
We would need a hefty spanner or even a hefty air tool to exceed the tensile strength of the bolts, but damaging the threads isn't beyond the ability of a mechanic, been there, had that done. Distorting the alloy wheels certainly is a concern though...

Hence any value within the range is fine but the key issue is to be above the minimum recommended. This might depend on whether the wheel is steel or alloy and also the shape of the nut/wheel mating surfaces.
The thing is, far as I know all M3's have alloys, if that's the case then it doesn't make sense to have such a wide margin for the torque, add to that 108 ft/lbs might be too high for some folks to remove a wheel in an emergency or just to do their own tyre rotation etc...

Feel free to discuss further!
Thanks for your thoughts Misar, appreciated...

Offline Canada_Bob

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Re: 80 to 108 !!!
« Reply #14 on: January 17, 2018, 04:05:20 PM »
[PS I just noticed the OP's name and flag! I wonder if the wheel type varies between N America and Europe. However, the 2010 manual I quoted was a USA download but the 2013 one was a UK download.
Err, well, bit of an explanation required there Misar, although originally from Lancashire {and back there now} I lived/worked in Canada for 31 years, during that time when I came back for visits the lads "back home" awarded me the nom de plume of "Canada Bob" and it kinda stuck  :)

Have to say I've been called worse in my time  ;) resulting in someone rigging my car {a Mercury Montego} with 6oz of C4 plastic explosive, thankfully the RCMP discovered it and defused {removed the 5v detonator} from the C4, if it had gone off I'd have been spread thinner than the paint on the car...

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Re: 80 to 108 !!!
« Reply #14 on: January 17, 2018, 04:05:20 PM »