[COChris]

Hey guys, was hoping I could get some clarity on the M Performance rear lip spoiler.

I have opted for port install of the CF diffuser, but the dealer told me to hold off on the CF rear lip until the M Performance front splitter is available.

The dealer (parts dept) said BMW recommends for the pieces to be installed together to maintain aerodynamic balance. Can anyone shed more light on this, because I've seen a few cars delivered so far with that awesome looking rear lip, but without the front splitter — which is available later this fall. I'd love to run the rear lip until the splitter is available, but obviously want the car to feel balanced.

Thanks in advance!

[IAF]

I can't imagine the rear lip spoiler has a massive aerodynamic function that will be noticeable in daily driving (its mostly cosmetic).

The big rear wing spoiler on the other hand, will certainly have some impact - and I think is recommended in conjunction with the front splitter

[///M Houbi]

Wondering the same.

Personally i think it does matter, but only at rather high speeds like 160kmh or more. So for normal/legal street use it will most likely be absolutely irrelevant if you have both or just one of them.

What i can confirm is that bmw does recommend you to get both but will definitely not hinder you ordering just one of them. This means its absolutely street legal to do so and at least in switzerland this means its no problem after all having only one of them..

I'm speaking of rear lip and front splitter, not the big rear wing

[AlpsRider]

Originally Posted by ///M Houbi

Wondering the same.

Personally i think it does matter, but only at rather high speeds like 160kmh or more. So for normal/legal street use it will most likely be absolutely irrelevant if you have both or just one of them.

What i can confirm is that bmw does recommend you to get both but will definitely not hinder you ordering just one of them. This means its absolutely street legal to do so and at least in switzeröand this means its no problem after all having only one of them..

I'm speaking of rear lip and front splitter, not the big rear wing

I agree, driving on the autobahn at 130 mph could make a difference but not at 70 or even 80 mph. The car is heavy enough :-)

[chris719]

Tiny lip spoiler held on with tape, I don't think it's going to be putting you in a ditch at 150 or anything.

[boostspoon]

Agree with your dealer - the downforce generated from the trunk lip will cause an imbalance if you don't have the splitter mated. At lower speeds, you should still be okay and in control.

[David1]

It will be fine. Put it on. It doesn't add much downforce.

[AlpsRider]

Have any of you stuck your hand out of the window when you're going 145 mph? I have done it. It is a crazy amount of force. Don't take it lightly

Edit: Actually one reason that I think I'm going to get the official M Performance rear spoiler is because I don't trust all of the knock of brands to do aerodynamic testing. If they don't design it properly it could end up being an air brake.

[David1]

The window area is the most turbulent. At 150 with my arm and hand out the window I can still move it forward and back with not much effort.

[AlpsRider]

Originally Posted by David1

The window area is the most turbulent. At 150 with my arm and hand out the window I can still move it forward and back with not much effort.

Stick something out the window the size of the spoiler and try to hang on to it.

[DanG]

The spoiler is mainly cosmetic. The dealer is giving you BS. My M2 came with just the rear spoiler as port installed. It was part of the M Performance package. The splitters were not included in the package.

[AlpsRider]

Here is an article I found that explains in a simple way automobile aerodynamics and how spoilers, air dams and side skirts affect it.
https://www.carid.com/articles/will-...rodynamic.html

Edit:
Here is a video if you can't be bothered to read.

I get it, spoilers probably don't make much difference at 60 mph. Don't forget that where these cars are made in Germany people actually do drive 130+ MPH. I lived there, I've done it. Driving at those speeds for sometimes hours is something I'd never experienced until I lived there. I had a car with Pop up headlights. If I was racing someone I would turn off the headlights because it meant like 5 or 6 mph difference in top speed. That is what happens with aerodynamics at high speeds.

[boostspoon]

Originally Posted by AlpsRider

Stick something out the window the size of the spoiler and try to hang on to it.

LOL....yeah, a small m trunk lip spoiler = +10,000 aero dynamic points

[heavyD^2]

Originally Posted by DanG

The spoiler is mainly cosmetic. The dealer is giving you BS. My M2 came with just the rear spoiler as port installed. It was part of the M Performance package. The splitters were not included in the package.

Yeah the lip spoilers are more or less just cosmetic on these cars.

[chris719]

The trunk lid is not a really heavy duty part either. Nothing generating meaningful downforce would be attached to only a sheet metal body panel with 3M double sided tape.

[pruettfan]

A buddy of mine runs just the rear M carbon fiber spoiler on his M2, we run together on track quite a bit at speeds up to 114 and it doesn't seem to cause any issues. Personally I left mine alone because I didn't want to create a potential issue and because carbon fiber does not hold up well in the environment I live in.

[Tag]

Originally Posted by COChris

The dealer (parts dept) said BMW recommends for the pieces to be installed together to maintain aerodynamic balance.

Must be the skeptic in me, of the cynic , but when I hear shit like this my inside voice says (with South Park voice), "ohh, so instead of having it installed at port at a lower price the dealership can sell me the accessories for more $$$ and also charge for the install too? And being it's not a port installed option it doesn't get the full 4yr/50k mile warranty or show up on the cars build? Hell yeah, how do I sign up to for this fuckery?"

[COChris]

Originally Posted by Tag

Must be the skeptic in me, of the cynic , but when I hear shit like this my inside voice says (with South Park voice), "ohh, so instead of having it installed at port at a lower price the dealership can sell me the accessories for more $$$ and also charge for the install too? And being it's not a port installed option it doesn't get the full 4yr/50k mile warranty or show up on the cars build? Hell yeah, how do I sign up to for this fuckery?"

To the dealer's credit, they called me to make sure I got anything port installed that I wanted before it was too late.

[Robin_NL]

Originally Posted by pruettfan

A buddy of mine runs just the rear M carbon fiber spoiler on his M2, we run together on track quite a bit at speeds up to 114 and it doesn't seem to cause any issues.

This. This tiny rearspoilerlip is too small to cause a real measurable effect.


If we're talking the Moto GP Pace car spoiler/wing or an F40 rear wing, that's another story.

And even if it has an effect at high(cornering) speeds of <1% :

BMWs weight balance is about F51/49R or even worse irl.
So putting that lip on would theoretically make the balance shift a tiny bit from 51/49 to the even more 'godlike' 50/50 they are marketing

Cheers
Robin