Sheared off Lug Bolts
03-04-2019, 10:27 PM
#51
VM
I see your mention of both bolts and wheels having matching 'spherical' (ie ball or radius) seats - what was the measurement of the bolt's radius seat?
Bolts come in a variety of measures 12R, 13R, 14R, etc. (Unfortunately many sellers fail to state this measurement)
If the 17" AMG Wheels are OEM Mercedes, then MB predominantly uses 14R ball seats (and the occasional 12R in certain applications), reference my post here:
https://mbworld.org/forums/c63-amg-w...ml#post7229095
Clamping force can be compromised if using even a 13R bolt in a 14R wheel.
I see your mention of both bolts and wheels having matching 'spherical' (ie ball or radius) seats - what was the measurement of the bolt's radius seat?
Bolts come in a variety of measures 12R, 13R, 14R, etc. (Unfortunately many sellers fail to state this measurement)
If the 17" AMG Wheels are OEM Mercedes, then MB predominantly uses 14R ball seats (and the occasional 12R in certain applications), reference my post here:
https://mbworld.org/forums/c63-amg-w...ml#post7229095
Clamping force can be compromised if using even a 13R bolt in a 14R wheel.
Last edited by MBNRG; 03-04-2019 at 11:11 PM.
03-05-2019, 12:09 AM
#53
Good catch!
Yes, the W203 chassis states wheel bolt torque = 110 +/- 10 Nm (81 +/- 7 ft-lbs)
VM, i think you may have your culprit if you were doing 100 ft-lbs, and/or using different ball/radius seat sizes
Yes, the W203 chassis states wheel bolt torque = 110 +/- 10 Nm (81 +/- 7 ft-lbs)
VM, i think you may have your culprit if you were doing 100 ft-lbs, and/or using different ball/radius seat sizes
Last edited by MBNRG; 03-05-2019 at 12:13 AM.
03-05-2019, 12:18 AM
#54
MBWorld Fanatic!
with bailey and coffee in hand....now I'm wondering aloud if the weight of the wheel, along
with the extended length (the 'moment'), plus the spacer (is that what they call shear points?
i dunno, beyond my grade school level brain) all contributed to the potential for movement
to occur (as well).
(everything i said above is stuff I hear on Star Trek the Next Generation so, lah dee dah)
with the extended length (the 'moment'), plus the spacer (is that what they call shear points?
i dunno, beyond my grade school level brain) all contributed to the potential for movement
to occur (as well).
(everything i said above is stuff I hear on Star Trek the Next Generation so, lah dee dah)
Last edited by raymond g-; 03-05-2019 at 12:34 AM.
08-23-2019, 11:16 PM
#55
Wow! What a thread! 8-)
Hey @vmontijo ... hope you resolved your busting bolts problem! (and I am so jealous you have a bridgeport!!)
It's been a while since I had to determine torque via material stretch etc etc
Though typically 80ftlbs is for the 12mm diameter bolts and 96ftlbs is for the 14mm bolts, giving some room for cte related headroom needed blah blah blah
But doesn't bolt length factor in? Say comparing a typical 12x1.25_27 vs your longer 12x1.25_47 (the +20mm thing), wondering if stuff like the increase in
ductility (in tension and torsion) and material relaxation from the added length could have been bad actors since the 12's were a bit over torqued to 100
(either that or your torque wrench's 100 is actually a tad higher? I cal mine once every year or so and boy sometimes it is a bit off)
Just my 2 cents
Hey @vmontijo ... hope you resolved your busting bolts problem! (and I am so jealous you have a bridgeport!!)
It's been a while since I had to determine torque via material stretch etc etc
Though typically 80ftlbs is for the 12mm diameter bolts and 96ftlbs is for the 14mm bolts, giving some room for cte related headroom needed blah blah blah
But doesn't bolt length factor in? Say comparing a typical 12x1.25_27 vs your longer 12x1.25_47 (the +20mm thing), wondering if stuff like the increase in
ductility (in tension and torsion) and material relaxation from the added length could have been bad actors since the 12's were a bit over torqued to 100
(either that or your torque wrench's 100 is actually a tad higher? I cal mine once every year or so and boy sometimes it is a bit off)
Just my 2 cents
08-24-2019, 01:07 AM
#56
Senior Member
Reading the above, and the conclusions / believes involved is scary, to say at least.
To take on the wheel fitment first.
The hub centering is NOT for load carrying, but only for centering. The hub centering has a fitment tolerance of 1 to 2 tens of a millimeter, witch means that if it had to be load carrying, the wheel hub would constantly slide on the hub surface, against the brake disc. That again would lead to abrasive wear, and the lug bolts would get loose in no time. Anyway, the plastic center rings are not capable of carrying any load.
What is carrying the load, both radial an torque wise is the friction generated between all surfaces, generated by the pretension of the lug bolts, nothing else. Therefore correct torque and coming with that, correct pretension of the lug bolts is crucial. The lug bolt act as a spring, and applying a torque of 130Nm ( equivalent to 96 ft.lbs., utilization of the bolt strength 60% ) generates a pretension on a grade 10.9 M14x1.5 mm bolt of 65KN ( equivalent to 14612 Lb force ) each. With 5 bolts, in total 325 KN. and if we assume a friction coeff. of 0.2, then this bolt connection will be able to carry a radial load ( cars weight ) of 65KN, or 6625 KG. / 14626 lb, before any movement between the surfaces occur. I think the numbers speaks for them self.
Bolts must be grade 10.9 quality, to have a fair safety margin. 10.9 means tensile strength is 1000 N/mm2 and yield strength being 90% equal to 900 N/mm2.( an grade 8.8 bolt would be utilized 75% )
Could make a calculation on brake and drive line torque as well, but I think I made my point.
In regard to the sheared of bolt's, the pattern is typical for loose bolts, shearing off / the fracture site being exactly between the two surfaces where they split. This is typically caused by tensile overload ( hard braking ) or fatigue, due to long time run without pretension. Can't see the surface of the break, so cannot determine if fatigue or what.
In regards to the rims, if the lug bolt holes in any way are damaged, DON'T use the rims again. The bolts WILL get loose again, and the rim hub will not be able to transfer the required load, through friction, so the bolts will start carrying load, and fail again.
To take on the wheel fitment first.
The hub centering is NOT for load carrying, but only for centering. The hub centering has a fitment tolerance of 1 to 2 tens of a millimeter, witch means that if it had to be load carrying, the wheel hub would constantly slide on the hub surface, against the brake disc. That again would lead to abrasive wear, and the lug bolts would get loose in no time. Anyway, the plastic center rings are not capable of carrying any load.
What is carrying the load, both radial an torque wise is the friction generated between all surfaces, generated by the pretension of the lug bolts, nothing else. Therefore correct torque and coming with that, correct pretension of the lug bolts is crucial. The lug bolt act as a spring, and applying a torque of 130Nm ( equivalent to 96 ft.lbs., utilization of the bolt strength 60% ) generates a pretension on a grade 10.9 M14x1.5 mm bolt of 65KN ( equivalent to 14612 Lb force ) each. With 5 bolts, in total 325 KN. and if we assume a friction coeff. of 0.2, then this bolt connection will be able to carry a radial load ( cars weight ) of 65KN, or 6625 KG. / 14626 lb, before any movement between the surfaces occur. I think the numbers speaks for them self.
Bolts must be grade 10.9 quality, to have a fair safety margin. 10.9 means tensile strength is 1000 N/mm2 and yield strength being 90% equal to 900 N/mm2.( an grade 8.8 bolt would be utilized 75% )
Could make a calculation on brake and drive line torque as well, but I think I made my point.
In regard to the sheared of bolt's, the pattern is typical for loose bolts, shearing off / the fracture site being exactly between the two surfaces where they split. This is typically caused by tensile overload ( hard braking ) or fatigue, due to long time run without pretension. Can't see the surface of the break, so cannot determine if fatigue or what.
In regards to the rims, if the lug bolt holes in any way are damaged, DON'T use the rims again. The bolts WILL get loose again, and the rim hub will not be able to transfer the required load, through friction, so the bolts will start carrying load, and fail again.
Last edited by SLcharge; 08-24-2019 at 01:27 AM.
08-24-2019, 03:01 AM
#58
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Just stop this thread already. We have hubcentric wheels. The hub is load bearing. It’s a settled fact. Just stop it, you’re going to get someone hurt with the stupidity.
And agree that Otis bolts are awesome.
And agree that Otis bolts are awesome.
08-24-2019, 07:19 AM
#59
Senior Member
You are mixing up things, getting it wrong. Steel wheels usually are hub centering, with no air gap, so that the forces go through the centering and not the lug bolts and surface friction. This is necessary because of the small contact surface between rim and hub flange.
With Aluminum rims it's a different story. They are hub centered, but not hub carrying. The load is transferred through friction between rim and wheel hub.
Just found this on a quick search.
https://www.onallcylinders.com/2016/...-rings-wheels/
Quote :
According to a second common myth, the weight of the vehicle is supported by the hub pilot mating with the center bore of the wheel. If you don’t use hub centric rings, you transfer the weight of the vehicle to the lug hardware, and the wheel studs will break.
Fact is, the hub centric rings do not bear a load. The weight of the vehicle is actually supported by the friction between the wheel and its mounting surface on the axle. The friction is established and maintained once the lug hardware is properly installed and torqued to specs.
Quote end.
Although this is not a scientific report, they got it right.
I don't know who you are, what you are, or what your background is for dismissing everything, but unless you can prove your accusations, I suggest you keep quite.
08-24-2019, 11:10 AM
#60
MBWorld Fanatic!
I know the ridge in my hubs are NOT bearing any road force loads. Bearing the load of the (hub-centric) wheel for mounting is all it's used for.
My car must be different than everyone elses?
My car must be different than everyone elses?
08-24-2019, 12:04 PM
#61
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I don't know why you are so aggressive, but being in here for a long time, don't make you a " I know all "
You are mixing up things, getting it wrong. Steel wheels usually are hub centering, with no air gap, so that the forces go through the centering and not the lug bolts and surface friction. This is necessary because of the small contact surface between rim and hub flange.
With Aluminum rims it's a different story. They are hub centered, but not hub carrying. The load is transferred through friction between rim and wheel hub.
Just found this on a quick search.
https://www.onallcylinders.com/2016/...-rings-wheels/
Quote :
According to a second common myth, the weight of the vehicle is supported by the hub pilot mating with the center bore of the wheel. If you don’t use hub centric rings, you transfer the weight of the vehicle to the lug hardware, and the wheel studs will break.
Fact is, the hub centric rings do not bear a load. The weight of the vehicle is actually supported by the friction between the wheel and its mounting surface on the axle. The friction is established and maintained once the lug hardware is properly installed and torqued to specs.
Quote end.
Although this is not a scientific report, they got it right.
I don't know who you are, what you are, or what your background is for dismissing everything, but unless you can prove your accusations, I suggest you keep quite.
You are mixing up things, getting it wrong. Steel wheels usually are hub centering, with no air gap, so that the forces go through the centering and not the lug bolts and surface friction. This is necessary because of the small contact surface between rim and hub flange.
With Aluminum rims it's a different story. They are hub centered, but not hub carrying. The load is transferred through friction between rim and wheel hub.
Just found this on a quick search.
https://www.onallcylinders.com/2016/...-rings-wheels/
Quote :
According to a second common myth, the weight of the vehicle is supported by the hub pilot mating with the center bore of the wheel. If you don’t use hub centric rings, you transfer the weight of the vehicle to the lug hardware, and the wheel studs will break.
Fact is, the hub centric rings do not bear a load. The weight of the vehicle is actually supported by the friction between the wheel and its mounting surface on the axle. The friction is established and maintained once the lug hardware is properly installed and torqued to specs.
Quote end.
Although this is not a scientific report, they got it right.
I don't know who you are, what you are, or what your background is for dismissing everything, but unless you can prove your accusations, I suggest you keep quite.
08-24-2019, 12:35 PM
#62
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Join Date: Jun 2008
Location: Los Angeles
Posts: 8,045
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2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
I also suggest you please put non hub centric wheels on your car and drive very fast on a very twisty road, preferably one with a cliff. Good luck. 
Last edited by BLKROKT; 08-24-2019 at 12:39 PM.
08-24-2019, 02:15 PM
#63
MBWorld Fanatic!
I always thought it was friction of mating surfaces that keep the wheel from moving laterally once the lugs/bolts are torqued. The type (hub vs llug) is just for centering purpouses.
08-24-2019, 03:01 PM
#64
Senior Member
How do plastic hubrings work then for road forces? I'm sure they may even get maluable with heat from braking.
I always thought it was friction of mating surfaces that keep the wheel from moving laterally once the lugs/bolts are torqued. The type (hub vs llug) is just for centering purpouses.
I always thought it was friction of mating surfaces that keep the wheel from moving laterally once the lugs/bolts are torqued. The type (hub vs llug) is just for centering purpouses.
Dunno that.
08-24-2019, 03:24 PM
#66
Senior Member
08-24-2019, 04:18 PM
#67
come to think of it ... cte of aluminum is ~22 and steel is ~12 so over the course of heating and cooling that circular gap will change
and looking at the mechanical marks left behind during wheel rotations the machining and centering tolerances of both the hub and rim show
but i did try to squeeze one of my hairs (83um diameter) into that gap at normal conditions (about 23c 52%rh) ... in my case that gap is smaller apparently on the order of 50um
which is about 2 thou so that makes sense considering typical mass machining tolerances
this thread gives me a tad more appreciation of how my car "rolls" 8-)
and looking at the mechanical marks left behind during wheel rotations the machining and centering tolerances of both the hub and rim show
but i did try to squeeze one of my hairs (83um diameter) into that gap at normal conditions (about 23c 52%rh) ... in my case that gap is smaller apparently on the order of 50um
which is about 2 thou so that makes sense considering typical mass machining tolerances
this thread gives me a tad more appreciation of how my car "rolls" 8-)
08-24-2019, 06:25 PM
#68
Senior Member
come to think of it ... cte of aluminum is ~22 and steel is ~12 so over the course of heating and cooling that circular gap will change
and looking at the mechanical marks left behind during wheel rotations the machining and centering tolerances of both the hub and rim show
but i did try to squeeze one of my hairs (83um diameter) into that gap at normal conditions (about 23c 52%rh) ... in my case that gap is smaller apparently on the order of 50um
which is about 2 thou so that makes sense considering typical mass machining tolerances
this thread gives me a tad more appreciation of how my car "rolls" 8-)
and looking at the mechanical marks left behind during wheel rotations the machining and centering tolerances of both the hub and rim show
but i did try to squeeze one of my hairs (83um diameter) into that gap at normal conditions (about 23c 52%rh) ... in my case that gap is smaller apparently on the order of 50um
which is about 2 thou so that makes sense considering typical mass machining tolerances
this thread gives me a tad more appreciation of how my car "rolls" 8-)
In regard to cte, aluminum has the bigger one anyway, as you point out, but the actual thermal working window is only about 50F on normal use of brakes, unless you are doing track day's, then it can clime a lot higher. The wheel hub surface does usually not slide on the brake rotors surface, due to the friction force applied, but the radial ( lateral ) tension in both materials do rise, as a function of temp rise, but only to elastic deformation, not plastic.deformation. Plastic deformation will require higher temp diff. Elastic temp induced deformation of the wheel can actually lead to the hole diameter in the rim to shrink, creating less air gap, or even contact. .Aluminium having a low Young's modulus aluminum can deform a lot without getting into plastic deformation. Also the corrosion between wheel and brake rotor is a thermal insulator, reducing heat transfer. Many things in play here, and more than listed.
08-24-2019, 06:56 PM
#69
If you take a sliding caliper and measure inside of rim centering hole, and there after hub centering diameter on car, you will usually get a diff of 1-2/10 of a mm. If the hub where to be load carrying, the airgap had to be 0 or better -0.2 mm. means shrink fit.
In regard to cte, aluminum has the bigger one anyway, as you point out, but the actual thermal working window is only about 50F on normal use of brakes, unless you are doing track day's, then it can clime a lot higher. The wheel hub surface does usually not slide on the brake rotors surface, due to the friction force applied, but the radial ( lateral ) tension in both materials do rise, as a function of temp rise, but only to elastic deformation, not plastic.deformation. Plastic deformation will require higher temp diff. Elastic temp induced deformation of the wheel can actually lead to the hole diameter in the rim to shrink, creating less air gap, or even contact. .Aluminium having a low Young's modulus aluminum can deform a lot without getting into plastic deformation. Also the corrosion between wheel and brake rotor is a thermal insulator, reducing heat transfer. Many things in play here, and more than listed.
In regard to cte, aluminum has the bigger one anyway, as you point out, but the actual thermal working window is only about 50F on normal use of brakes, unless you are doing track day's, then it can clime a lot higher. The wheel hub surface does usually not slide on the brake rotors surface, due to the friction force applied, but the radial ( lateral ) tension in both materials do rise, as a function of temp rise, but only to elastic deformation, not plastic.deformation. Plastic deformation will require higher temp diff. Elastic temp induced deformation of the wheel can actually lead to the hole diameter in the rim to shrink, creating less air gap, or even contact. .Aluminium having a low Young's modulus aluminum can deform a lot without getting into plastic deformation. Also the corrosion between wheel and brake rotor is a thermal insulator, reducing heat transfer. Many things in play here, and more than listed.
i have to pull wheels off for rotation cleaning and waxing anyway ... think I will do the caliper thing (think mine will read down to 10um or 1/2 thou) and match the rim i.d. to the hub o.d. best i can per wheel to attain an averaged out "gap" over the set of 4 and prep the contact surfaces for observation at the next rotation (hoping for the same hub rung / rim bore contact surface features next time as right now they are inconsistent across the 4)
btw its really only 50f/27c temp change? thats interesting though it would be more ... will stick a thermocouple inside the bolt port next time i do a long run ... but yeah well within the elastic region
