Aerodynamics

[M5 TT]

Any one clued up on Aerodynamics??

1. Does increasing the size of the rear boot spoilers actually gain any down force??

2. After market Rear defuser create more down force?

3. Addition of a rear window spoiler do anything?

4. Front splitter type spoilers just for looks?

all in the hunt for more grip

[apexlocator]

Not M5 specific but:

1 and 3. The only significant rear downforce you can get is probably from a rear 2d or 3d wing with, I'm guessing, at least 200mm risers and 70 inches wide.

4. You'll need to balance out with a front splitter that extends 4 to 5 inches out, chassis mounted (you need to be able to stand on this splitter). This is usually a custom job and many track peeps use Alumalite for this, 6 to 10mm thick. All of these CF offerings on market now are just for looks.

2. Rear diffusers are just to reduce drag and increase air velocity undercar, thus more downforce, but you'd need a massive one I think; more downforce in rear means larger splitter up front.

On the street you'd look like a poser, on track you'd be serious contention. This is my research into aero for my other track car; you need to go all out for effective aero.

[M5 TT]

Thanks for that. So basically you will look like a tool on the street with any aero changes that actually work.

ok that will do for me. wont be going that route.

I remember a single seater track day I did and was amazed at the massive grip aero gave at speed.

[apexlocator]

I think a significant increase in grip can come from just running the right tires....r compounds like r888r.

I run those in the rear and its night/day vs street tires.

[M5 TT]

that's my plan for summer, but currently around 3 degree C and wet. Not sure the R888Rs would like that much.

Think I might end up using winter (not snow) tyres and then R888r in summer. MPSS are rubbish when its this cold

[Flying Ace]

generally and theoretically, the answers are all "yes". But you got to balance it out with testing to achieve real aerodynamic gains.

Front splitters by themselves can increase understeer, but aid braking, for example, hence you balance it with dialing in suspension tweaks or additional aero else where. Rear wring theoretically increases rear traction, but increases drag, hence you balance it with its pitch and height. The rear "roof" or "window spoiler" and diffuser theoretically smooths out the air flow allow it to "break" at a later point behind the car. When tuned properly, the window one should work to increase the downforce on the rear trunk spoiler.

What am I saying here is that if you're buying a smattering of ebay motorsports parts here, and vorsteiner there, you're not getting tested parts that work together and it'll either be for nothing but show or be counterproductive to what you're trying to achieve.

Read this:

https://grassrootsmotorsports.com/ar...-aerodynamics/


If you built a fully functional aerodynamic kit, you're going to look ridiculous with huge vents, huge spoilers, recessed wheel wheels, flowing body panels that directs air around the car and panels riding 1 inch above the ground and 0.5 inch wheel well gap.

[M5 TT]

Good article

So basically when I add an after market rear spoiler and front splitter its more or less for looks alone.

I don't want any huge daft looking spoilers. So HUGE sticky tyres it is then

[Flying Ace]

Originally Posted by M5 TT

Good article

So basically when I add an after market rear spoiler and front splitter its more or less for looks alone.

I don't want any huge daft looking spoilers. So HUGE sticky tyres it is then

yeah to be honest, IMO, even if you buy the complete kit (like a Vorsteiner or M Performance), and even if the kit was "tuned" to work together, it's still for a street application, which means it just isn't going to give you the desired function you're after. It really is a cosmetic package.

Yeah, I know, I'm keenly aware I don't practice what I preach. I have a Vorsteiner spoiler on my trunk (though the prior owner installed it). But it's carbon fiber doe!

I think the kits that really works are the BMW Motorsports GT4 kits (not sure if they make it for the M5), but they have it for the M4
https://www.bmw-motorsport.com/en/to...mw-m4-gt4.html

There was a forum member a few years ago that converted his E92 M3 to a GT4 car, which is basically a street car series eligible car with limited aero and no power tweaks.

http://www.m3post.com/forums/showthread.php?t=358384

The next "official" level up is the GT3 cars. But those are literally fully built race car, and you can't just buy these body panels, and even if you get your hands on them, they won't fit on your street car without major modifications.
https://www.bmw-motorsport.com/en/to...-gt3-gtlm.html