[BroDoze]

Besides potentially more road rash on the rockers/sides or possibly rubbing?

It is a fairly significant geometry change. Did the steering or driving feel change for anyone after installing spacers?

There’s a guy in the G80 forums that had his steering tighten up (really bad, sounds like) when he installed 12mm spacers and go back to normal when he removed them.

Another said, on a positive note, his on-center feel is stronger (a good thing).

Most are saying they didn’t notice a single change in feel whatsoever.

I’ve got 12mm spacers coming today and am hoping I didn’t make a mistake.

[jessejericho]

Originally Posted by BroDoze

Besides potentially more road rash on the rockers/sides or possibly rubbing?

It is a fairly significant geometry change. Did the steering or driving feel change for anyone after installing spacers?

There’s a guy in the G80 forums that had his steering tighten up (really bad, sounds like) when he installed 12mm spacers and go back to normal when he removed them.

Another said, on a positive note, his on-center feel is stronger (a good thing).

Most are saying they didn’t notice a single change in feel whatsoever.

I’ve got 12mm spacers coming today and am hoping I didn’t make a mistake.

I had 15mm front and 12mm rear on my stock wheels and I didn't notice anything at all (only street driving).

[tylerdurdem]

I've put about 500 miles on since my recent suspension work (H&R VTF, Millway monoballs, Vorshlag plates, 15/18 spacers), and my steering actually got lighter, I suspect due to much more front camber (about 2.7 degrees up front). I personally really like what it's done to the front end, it's sharper, more direct, and seems to have more feedback.

[jmg]

Originally Posted by jessejericho

I had 15mm front and 12mm rear on my stock wheels and I didn't notice anything at all (only street driving).

Any pics of your setup?

[jessejericho]

Originally Posted by jmg

Any pics of your setup?

Spacers on, prior to springs:




After springs (Eibach Pro-Kit):

[ourlee]

JJ, please take another rear garage shot with your springs, thanks. I’m trying to dial in my offsets with MPHAS.

[IanH]

Spacers have no effect on steering and it is not a significant change in geometry as no angles have changed due to their installation. Maybe you could notice if you put like a 30mm spacer on.

[jessejericho]

Originally Posted by ourlee

JJ, please take another rear garage shot with your springs, thanks. I’m trying to dial in my offsets with MPHAS.

I have my new wheels on, not running spacers at the moment. Once I swap for winter I can take a pic if you still need.

[ourlee]

Can you put them back on before I buy a set on Black Friday?

[tom @ eas]

Originally Posted by BroDoze

Besides potentially more road rash on the rockers/sides or possibly rubbing?

It is a fairly significant geometry change. Did the steering or driving feel change for anyone after installing spacers?

There’s a guy in the G80 forums that had his steering tighten up (really bad, sounds like) when he installed 12mm spacers and go back to normal when he removed them.

Another said, on a positive note, his on-center feel is stronger (a good thing).

Most are saying they didn’t notice a single change in feel whatsoever.

I’ve got 12mm spacers coming today and am hoping I didn’t make a mistake.

Don't expect much handling improvement as the track width isn't changed significantly. But its one of the most popular starting mods.

Spacers will be mostly aesthetic, especially on lowered vehicles.

[BroDoze]

Been rolling my 12mm/12mm spacers for a few weeks and they look great and feel fine. No perceptible change for me. I slathered copper anti-size on them (both sides) FWIW.

[aerobod]

Originally Posted by BroDoze

Been rolling my 12mm/12mm spacers for a few weeks and they look great and feel fine. No perceptible change for me. I slathered copper anti-size on them (both sides) FWIW.

Best to only put a small amount of anti-seize on the hubcentric boss to ease wheel or spacer removal. Applying to the clamping surface can cause an increased shearing force due to braking (and in case of the rear wheels acceleration) on the wheel bolts due to possible wheel movement, with lower than design friction of the clamping surface.

BMW has put out TSBs on some models to increase the wheel to hub clamping friction using diamond washers behind the brake rotor to stop slight wheel movement under braking, which is often indicated by a clicking sound from the hub.

[BroDoze]

Originally Posted by aerobod

Best to only put a small amount of anti-seize on the hubcentric boss to ease wheel or spacer removal. Applying to the clamping surface can cause an increased shearing force due to braking (and in case of the rear wheels acceleration) on the wheel bolts due to possible wheel movement, with lower than design friction of the clamping surface.

BMW has put out TSBs on some models to increase the wheel to hub clamping friction using diamond washers behind the brake rotor to stop slight wheel movement under braking, which is often indicated by a clicking sound from the hub.

Well, to be clear, when I said “slather”, it was around the center hub areas that I did it. Plenty of bare-metal clamping surface all around the wheels, hubs and spacers for those surface to bite. Good post though. Truth is, those wheels will probably be coming on and off so often for various other reasons no A/S was needed.

[Dave07997S]

If you have the Oem wheel of 19X9.5 with an ET20 adding a 15mm spacer is just like having a 19X9.5 ET5. The only downside I would see if they are improperly installed and the added rotational weight added. Even though that weight is very close to the hub and would probably have a minimum affect. My car with the Eibach ProKit and 15mm spacers drives just like OEM.

[aerobod]

Originally Posted by BroDoze

Well, to be clear, when I said “slather”, it was around the center hub areas that I did it. Plenty of bare-metal clamping surface all around the wheels, hubs and spacers for those surface to bite. Good post though. Truth is, those wheels will probably be coming on and off so often for various other reasons no A/S was needed.

It is good that you are only lubricating the centre boss. Just to demonstrate the sort of effect of putting anti-seize all over the contact surfaces, I did a few basic calculations:

An M14 bolt torqued to 140Nm with a dry thread will exert a clamping force of about 50,000N, so 250,000Nm (nominally 25 tonnes of clamping force) for all 5 wheel bolts.

If the contact surfaces are clean and dry aluminium, the friction coefficient is about 1.0, if clean and dry steel about 0.6 and steel with aluminium somewhere in between (values have some dependency on surface finish). If a good grease or anti-seize is applied to those surfaces, the friction coefficient drops to about 0.2.

Under maximum braking with about 35% of the car weight transferred to each front tyre and good summer tyres with a friction coefficient of 1.2 on grippy asphalt, about 2,800Nm of torque can be applied to the wheel, leading to 50,000Nm of torque at the 112mm bolt pitch circle.

At the dry and clean hub to brake rotor or wheel to brake rotor surface that gives 4 or 5 times safety factor, but with the lubricant on the surface the clamping friction force and wheel torque at the bolts is about equal and the wheel will likely move on the hub.

As the shear strength of steel bolts is nominally 60% of the tensile strength, there is going to be a lot higher fatigue loading on the bolts if the wheels move due to insufficient clamping friction. An M14x1.5 10.9 bolt has a tensile strength of 125,000N, but only about 75,000N shear strength.

[SpaceGhost]

Originally Posted by aerobod

It is good that you are only lubricating the centre boss. Just to demonstrate the sort of effect of putting anti-seize all over the contact surfaces, I did a few basic calculations:

An M14 bolt torqued to 140Nm with a dry thread will exert a clamping force of about 50,000N, so 250,000Nm (nominally 25 tonnes of clamping force) for all 5 wheel bolts.

If the contact surfaces are clean and dry aluminium, the friction coefficient is about 1.0, if clean and dry steel about 0.6 and steel with aluminium somewhere in between (values have some dependency on surface finish). If a good grease or anti-seize is applied to those surfaces, the friction coefficient drops to about 0.2.

Under maximum braking with about 35% of the car weight transferred to each front tyre and good summer tyres with a friction coefficient of 1.2 on grippy asphalt, about 2,800Nm of torque can be applied to the wheel, leading to 50,000Nm of torque at the 112mm bolt pitch circle.

At the dry and clean hub to brake rotor or wheel to brake rotor surface that gives 4 or 5 times safety factor, but with the lubricant on the surface the clamping friction force and wheel torque at the bolts is about equal and the wheel will likely move on the hub.

As the shear strength of steel bolts is nominally 60% of the tensile strength, there is going to be a lot higher fatigue loading on the bolts if the wheels move due to insufficient clamping friction. An M14x1.5 10.9 bolt has a tensile strength of 125,000N, but only about 75,000N shear strength.

I bet you are a wizard at Excel....

[IanH]

Didn't reduce the torque by a factor of 5 on the braking. You are nowhere near the shear yield of the bolts under braking, low friction or not.

Also 2800nm at the tire is roughly 16000nm at the bolts circle. (641mm/112mm) * 2800

[aerobod]

Originally Posted by IanH

Didn't reduce the torque by a factor of 5 on the braking. You are nowhere near the shear yield of the bolts under braking, low friction or not.

Also 2800nm at the tire is roughly 16000nm at the bolts circle. (641mm/112mm) * 2800

Looks like I didn’t check my values for the torque at the bolts, with the 275/35-19 tyre 675mm diameter it is 16,875Nm, not sure how I introduced a 3x error there, probably when not multiplying by the wheel radius.

Yes it is still quite a bit above the shear yield. That is at about 67,000N (335,000N for the 5 bolts), as opposed to 75,000N for the ultimate shear strength of a 10.9 M14x1.5 bolt.

The clamping surface friction can be reduced by a factor of 2.7 to 5, based on dry surface μ values of 0.8 to 1.0 for interfaces between steel and aluminium and those surfaces with high pressure grease μ values of 0.2 to 0.3 on steel. So the force to move the surface clamped at the 5 bolts 56mm radius could be reduced from 250,000N, i.e. 14,000Nm torque, to between 2,800Nm and 5,200Nm torque. Of course, these calculations and values are only approximations, the forces and clamping around the bolts will be a lot more complex than this linear calculation.

This seems to indicate with sticky tyres that the wheel could be close to moving with dry clamping surfaces, perhaps the reason why BMW has introduced the diamond washers to prevent that between the rotor and hub in some circumstances, as the steel to aluminium and steel to steel has a lower friction coefficient than the aluminium wheel to the aluminium rotor hat.

The whole assembly is designed for clamping in compression without movement between the components, lubricating the surfaces goes against that principle. Fretting of the clamping surfaces and unexpected loosening of the bolts may be side effects.

[IanH]

I'm assuming your 2800nm is correct, that's nowhere near the resultant loads that you are quoting above.

My calc spits out roughly 30,000n shear force per bolt without friction losses factored at all

[aerobod]

Originally Posted by IanH

I'm assuming your 2800nm is correct, that's nowhere near the resultant loads that you are quoting above.

My calc spits out roughly 30,000n shear force per bolt without friction losses factored at all

I haven’t looked at the shear force imparted on the bolts, just the bolt shear limits. Without friction 2800Nm at the tyre contact point would only correlate to 3375N of shear at each bolt, but doesn’t take into account the axial tensile loading of the bolt that is already stressed to 50,000N (assuming 0.20 thread K-factor, 14mm major diameter and 140Nm torque), so the bolt is already at 43% of it’s 115,000N tensile yield strength.

I don’t think there is a shear strength issue, only a potential fatigue issue due to the additional shear load cycling if the wheel is moving radially on the hub due to insufficient friction, if lubrication is applied.

[aerobod]

Originally Posted by aerobod

Looks like I didn’t check my values for the torque at the bolts, with the 275/35-19 tyre 675mm diameter it is 16,875Nm, not sure how I introduced a 3x error there, probably when not multiplying by the wheel radius.

The clamping surface friction can be reduced by a factor of 2.7 to 5, based on dry surface μ values of 0.8 to 1.0 for interfaces between steel and aluminium and those surfaces with high pressure grease μ values of 0.2 to 0.3 on steel. So the force to move the surface clamped at the 5 bolts 56mm radius could be reduced from 250,000N, i.e. 14,000Nm torque, to between 2,800Nm and 5,200Nm torque. Of course, these calculations and values are only approximations, the forces and clamping around the bolts will be a lot more complex than this linear calculation.

I will have to disagree with myself here, lots of confusing myself and others where I’ve interchanged torque and force at a radius. The hazards of trying to think coherently on a Saturday night while doing other things!

The torque at the wheel bolts stays at 2,800Nm, which equates to a radial force of 8,300N at the tyre contact patch and 50,000N at the bolt circle under full braking.

The default dry friction of 0.8 to 1.0 gives plenty of safety factor before movement radially with a total radial friction force due to clamping of 200,000 to 250,000N at the bolt circle. The lubricated friction of 0.2 to 0.3 would equate to a radial friction force due to clamping of 50,000 to 75,000N at the bolt circle, close to the 50,000N imparted by the wheel on the hub under full braking.

[BroDoze]

How do you guys feel about spacers with little or a lot of surface area? The high-dollar lightweight ones have huge openings on them for weight reduction. This leaves much less mating surface area. Does that mean more or less bite/clamping? Or, does the smaller surface area bite that much harder into the other surfaces?