[IconicM2]

Hello Everyone,
I have a situation, BMW notified me I have both front struts pushed passed the knuckle on my G87 M2. See Pics Attached.

I have read a few threads on this matter and I’m sure a few of you have as well. BMW’s approach is to replace everything including front steering rack.

What is interesting the car is within alignment spec. I’d assume if something was bent the car would be way out alignment.

Does anyone have experience with this is issue?
How serious is this issue? Should I start small and replace knuckles and go from there? Or is best to replace everything.

I appreciate the help on this matter.

[BroDoze]

W T H ??

[IconicM2]

Originally Posted by BroDoze

W T H ??

That bad??

[RockCrusher]

Something I've never seen before.

W T H indeed...

With problems of this serious nature I tend to do with what the dealer senior techs recommend. And what they recommend is based on what the factory calls for -- or what their experience has been -- in order to avoid bring backs and have the problem addressed in repeated revisits to the service department.

While a steering rack replacement may seem unnecessary with other cars in the event of any collision damage to the front of the car -- suspension/steering -- the rack gets replaced.

Sure your car has not (as best you/we can know) not suffered a collision but something happened, some force experienced, which caused the issue you show in the pics. There is the possibility this put excessive stress on the steering hardware which of course includes the rack.

[aerobod]

Hitting a kerb straight on or a road resurfacing edge that is deeper than the tyre sidewall depth could cause this sort of damage. If both sides are overloaded evenly compared with hitting a pothole only on one side, then the alignment could still be within spec.

I would also check the integrity of the strut tower tops and all four wheels for straightness and cracks.

[IconicM2]

Thank you for the insight. It seems to me the only thing holding the strut from sliding down is the small tab on the knuckle. The two screws that clamp the strut are providing tension but even if those were torqued if the tab in the knuckle broke the strut would slide down.

This is what I imagine the case to be? Thoughts on this?

[aerobod]

Originally Posted by IconicM2

Thank you for the insight. It seems to me the only thing holding the strut from sliding down is the small tab on the knuckle. The two screws that clamp the strut are providing tension but even if those were torqued if the tab in the knuckle broke the strut would slide down.

This is what I imagine the case to be? Thoughts on this?

The tab is just for alignment, the clamping force from the screws is of the order of 50,000N / 5 tonnes per bolt. Typically a very large vertical force on the strut due to the suspension bottoming forcefully will cause distortion of the knuckle clamping ring and compress the strut tube, such that the bolts are no longer providing the high clamping force and will allow the strut to slip down in the knuckle.

[KC87ZB]

I'm going out on a limb here and guessing that you are asking for direction since you are paying this out of pocket or turning it into insurance.

If you are paying out of pocket then you might think twice about the plan. Us understanding that may help with an answer. Certainly you are replacing the struts and the knuckles at a minimum.

If BMW is paying for the repair then let them replace whatever they want.

[IconicM2]

Originally Posted by aerobod

The tab is just for alignment, the clamping force from the screws is of the order of 50,000N / 5 tonnes per bolt. Typically a very large vertical force on the strut due to the suspension bottoming forcefully will cause distortion of the knuckle clamping ring and compress the strut tube, such that the bolts are no longer providing the high clamping force and will allow the strut to slip down in the knuckle.

Thank you for the thorough breakdown. Seems like I may have a situation on my hands then.

[IconicM2]

Originally Posted by KC87ZB

I'm going out on a limb here and guessing that you are asking for direction since you are paying this out of pocket or turning it into insurance.

If you are paying out of pocket then you might think twice about the plan. Us understanding that may help with an answer. Certainly you are replacing the struts and the knuckles at a minimum.

If BMW is paying for the repair then let them replace whatever they want.

This is exactly correct, I’m seeking help for what would be the best way to tackle this if paying out of pocket.

It seems starting with the wheel knuckle and struts might be the route to go. Thoughts?

Again I appreciate the help on this, I’m trying to just resolve this the best way I can.

[KC87ZB]

First, I would talk to the selling dealer and see if they can do anything to help, parts at cost, labor at cost, etc…

If no and you are going to do it yourself it kinda depends if you are truly doing yourself or just paying. If paying I would find a reputable shop that isn’t the dealer and get another opinion. Even if you pay for it to get a parts list.

If I was wrenching myself I’d buy parts and start. I would ensure I can return parts and buy a pile of them, including struts, knuckles and associated control arms and links. Ensure you get all bolts.

First thing I would replace are the struts and the bolts on the compression ring of the knuckle. I’d try that and see how it drives. If that’s all you disassemble your alignment should be close enough to be able to drive a short distance. And go from there.

Those are just my thoughts. Honestly I have a local shop I have a lot of respect for and would turn it over to them with it being such a new car.

[FAN460]

What caused this? Some big impact? They protrude the same amount on both sides?

Improperly torqued clamping screw is the only reason I can think of if the car has no other damage. That screw should be torque sealed from the factory. I will check it for sure.

[KC87ZB]

Originally Posted by FAN460

What caused this? Some big impact? They protrude the same amount on both sides?

Improperly torqued clamping screw is the only reason I can think of if the car has no other damage. That screw should be torque sealed from the factory. I will check it for sure.

I cannot imagine the impact the car took to move those struts if the pinch bolts on the knuckle were properly torqued. There should be obviously damaged/broken crap in there. The cast wheels shouldn't have survived.

[FAN460]

Originally Posted by KC87ZB

I cannot imagine the impact the car took to move those struts if the pinch bolts on the knuckle were properly torqued. There should be obviously damaged/broken crap in there. The cast wheels shouldn't have survived.

The only reason I can think of is there has been some suspension work done to the car and those bolts were not torqued to the spec. Only OP could answer tho.

[youloze]

Hmm, mine are the same as yours on both sides. I installed AST HAS kit. When I installed them I simply jacked under the control arm at the knuckle until the strut stopped sliding in the knuckle, then installed and torqued the pinch bolt.

I just went out and removed the driver side strut from the knuckle and find two things interesting.

1 - the nipple on the back of the strut that alligns the strut into the knuckle does not actually make it's way into the slot in the knuckle unless you bottom the strut like both of ours are. Otherwise it sits on top of where the split is at the pinch point. This leads me to believe that yours (and mine) are correct.

2 - there is no lip or otherwise similar stopping force on the strut or the knuckle that would keep the strut from sliding any further than what would be determined OEM position. I believe the strut has a taper on it, so that it naturally bottoms out in the knuckle. If you jack the knuckle up without spreading the pinch point, the strut will naturally stop at the top of the taper. This is the exact position that we are seeing in the OPs and my pictures.

I honestly don't think anything is necessarily wrong here. Can anyone else confirm? Also, does anyone have the toque specs for the pinch bolt by chance?

[KC87ZB]

Originally Posted by youloze

...

I honestly don't think anything is necessarily wrong here. Can anyone else confirm? Also, does anyone have the toque specs for the pinch bolt by chance?

I was going to pull my wheel off and look this weekend just out of curiosity. I think you may be on to something. Could it be the service tech that looked at the car doesn't know what they are talking about? That comment aside, it does explain why there is no other damage.

[youloze]

Originally Posted by KC87ZB

I was going to pull my wheel off and look this weekend just out of curiosity. I think you may be on to something. Could it be the service tech that looked at the car doesn't know what they are talking about? That comment aside, it does explain why there is no other damage.

My thoughts exactly. I'm thinking he maybe knows about the issues on other BMW chassis and thought this may be the same? I went ahead and loosened the pinch bolt just now on the driver side and then tried to reset the strut. It goes right back to where it was in my photo without any pressure.

I'm not an expert in suspension but I've done my fair share of installs and nothing seems out of the ordinary to me in this particular situation.

[Polo08816]

Originally Posted by youloze

Hmm, mine are the same as yours on both sides. I installed AST HAS kit. When I installed them I simply jacked under the control arm at the knuckle until the strut stopped sliding in the knuckle, then installed and torqued the pinch bolt.

I just went out and removed the driver side strut from the knuckle and find two things interesting.

1 - the nipple on the back of the strut that alligns the strut into the knuckle does not actually make it's way into the slot in the knuckle unless you bottom the strut like both of ours are. Otherwise it sits on top of where the split is at the pinch point. This leads me to believe that yours (and mine) are correct.

2 - there is no lip or otherwise similar stopping force on the strut or the knuckle that would keep the strut from sliding any further than what would be determined OEM position. I believe the strut has a taper on it, so that it naturally bottoms out in the knuckle. If you jack the knuckle up without spreading the pinch point, the strut will naturally stop at the top of the taper. This is the exact position that we are seeing in the OPs and my pictures.

I honestly don't think anything is necessarily wrong here. Can anyone else confirm? Also, does anyone have the toque specs for the pinch bolt by chance?

That's my thought. I don't have an F87, but a F30 335i and it's normal for the strut to be in that position on the knuckle.

There's a shoulder on the strut that acts as a stop for the collar on the steering knuckle. If the shoulder truly pushed past the collar on the knuckle, the collar would no longer clamp down properly on the strut. It would not be circular and you would see a gap(s) at some point around the interface of the strut body (above the shoulder) and the collar of the knuckle. It would be visibly f'ed and the camera position the dealer SHOULD have provided you would be a picture looking down on the area where the collar is trying to clamp around the strut body. The camera position of the provided pictures wouldn't show you that.

I've (DIY) modified my front suspension enough times - -0.5, 0, and +0.5 camber knuckles, stock 704 sport suspension, M Performance Suspension Kit, and Ohlins R&T.

It'll be incredibly rare for the front end to take a significant hit and push the strut through it's normal position on the knuckle and STILL maintain alignment.

I think you're dealer is trying to extract $ out of you because this would not be covered under warranty since they're trying to say the root cause is a collision. A collision would either be insurance pay or customer pay and would not face the same scrutiny that it would for BMW NA to cover under warranty.

[youloze]

Originally Posted by Polo08816

That's my thought. I don't have an F87, but a F30 335i and it's normal for the strut to be in that position on the knuckle.

There's a shoulder on the strut that acts as a stop for the collar on the steering knuckle. If the shoulder truly pushed past the collar on the knuckle, the collar would no longer clamp down properly on the strut. It would not be circular and you would see a gap(s) at some point around the interface of the strut body (above the shoulder) and the collar of the knuckle. It would be visibly f'ed and the camera position the dealer SHOULD have provided you would be a picture looking down on the area where the collar is trying to clamp around the strut body. The camera position of the provided pictures wouldn't show you that.

What I found interesting when I removed the strut from the knuckle on my G87 is that the knuckle does not have that same shoulder as the older chassis. It seems that there is a taper on the strut so that it naturally bottoms out in the knuckle and won't have the same issues that the old setups had. This is of course just conjecture from me.

It would be interesting if someone else that has not done any suspension work could check to see where there strut is at in the knuckle. I still maintain that nothing is wrong though and I agree, either it's and overzealous tech or a shady dealership - again just a guess.