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      08-22-2014, 02:18 AM   #1
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Aerodynamics & Rear Spoler

Went to HPDE event. At high speed on the straightaway had a feeling that rear was lifting... Has anybody experienced this?

Thinking about the rear spoiler (M3 type). Do you think it will help with aerodynamics and provide some downforce?

Also, looking at the aftermarket CSL-style trunks. Are they just for looks or do they provide some functional aerodynamics?
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      08-22-2014, 08:02 AM   #2
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How fast were you going?
I race a 335 and hit 155 - 160mph at Mid-Ohio on the back straight and had no issues with rear lift. We don't have anything on the trunk either, it's completely stock. Not even an M3 lip spoiler.
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      08-22-2014, 04:39 PM   #3
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Quote:
Originally Posted by TSM330i View Post
How fast were you going?
I race a 335 and hit 155 - 160mph at Mid-Ohio on the back straight and had no issues with rear lift. We don't have anything on the trunk either, it's completely stock. Not even an M3 lip spoiler.
About 140-145 mph. It didn't feel like a significant lift, but more like I can use some downforce in the rear.

Spoke with an another guy who has E90. He said he had experienced the lift, but not every time.
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      08-22-2014, 04:48 PM   #4
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I haven't had any issues with lift, but then again I never tracked before I installed my spoiler. I went from the M3 spoiler to BMW performance (preference). If you're close to Vegas and want to try out the M3 spoiler, let me know and it's yours.
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      08-22-2014, 04:54 PM   #5
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Does a little lip spoiler really help with aerodynamics? I thought it was solely for looks. Sorry, I'm a newb :/ Just trying to learn
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      08-22-2014, 05:08 PM   #6
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Yeah, I wonder too whether they are just for aesthetics or really help with aerodynamics...

Generally, I am not a fan of spoilers, but if they have a useful function, I'd go that way. Obviously, a huge wing is not an option, but M3 style indeed looks too small to make any difference. CSL-style seems interesting, but again, want to be sure before, I go on that route.

Has there been any comparison of the rear spoilers?
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      08-22-2014, 05:09 PM   #7
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Quote:
Originally Posted by Manny_World View Post
I haven't had any issues with lift, but then again I never tracked before I installed my spoiler. I went from the M3 spoiler to BMW performance (preference). If you're close to Vegas and want to try out the M3 spoiler, let me know and it's yours.
Manny, why do you prefer the Performance version?
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      08-22-2014, 05:11 PM   #8
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Quote:
Originally Posted by BMWTF? View Post
Yeah, I wonder too whether they are just for aesthetics or really help with aerodynamics...

Generally, I am not a fan of spoilers, but if they have a useful function, I'd go that way. Obviously, a huge wing is not an option, but M3 style indeed looks too small to make any difference. CSL-style seems is interesting, but again, want to be sure before, I go on that route.

Has there been any comparison of the rear spoilers?
Quote:
Originally Posted by Fantastico View Post
Does a little lip spoiler really help with aerodynamics? I thought it was solely for looks. Sorry, I'm a newb :/ Just trying to learn
To be honest, I don't believe the M3 spoiler provided much if any down force. I did notice a change at higher speeds with the Performance spoiler FWIW.
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      08-22-2014, 05:19 PM   #9
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Quote:
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Manny, why do you prefer the Performance version?
I like the style, higher kicked, carbon fiber, and functional without drawing too much attention like a wing.
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      08-25-2014, 05:50 PM   #10
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Thanks Manny!

Anyone else has any feedback?
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      08-25-2014, 11:39 PM   #11
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Quote:
Originally Posted by TSM330i View Post
How fast were you going?
I race a 335 and hit 155 - 160mph at Mid-Ohio on the back straight and had no issues with rear lift. We don't have anything on the trunk either, it's completely stock. Not even an M3 lip spoiler.
THIS was the only feedback you guys needed in this thread. A REAL race car driver in an e9X without aero going significantly fast on a real race track did not notice any lift in the rear from lack of aero.

Yet the discussion continues about what sort of aero for the duration of the thread.

Sad.
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      08-26-2014, 12:10 AM   #12
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Oem M-tech....looks sweet but I'm biased.
I don't think these cars are in need of downforce at the speeds they reach....but I drive a 328 x-drive....maybe the rear wheel drive tt crowd pushing 400hp+ can chime in on this.
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      08-26-2014, 01:38 AM   #13
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Quote:
Originally Posted by The HACK View Post
THIS was the only feedback you guys needed in this thread. A REAL race car driver in an e9X without aero going significantly fast on a real race track did not notice any lift in the rear from lack of aero.

Yet the discussion continues about what sort of aero for the duration of the thread.

Sad.
Easy, forum friend. No need to be a forum police. The topic is not closed yet. Peace out.

Manny's opinion is valued and appreciated, I still need more feedback. The other person, whom I spoke with, and who also does experience the lift, is a 4+ year HPDE Group A driver. So, it is 1:1 at this point.
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      08-26-2014, 07:18 AM   #14
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Quote:
Originally Posted by The HACK View Post
THIS was the only feedback you guys needed in this thread. A REAL race car driver in an e9X without aero going significantly fast on a real race track did not notice any lift in the rear from lack of aero.

Yet the discussion continues about what sort of aero for the duration of the thread.

Sad.
Agreed 100%

OP, if the rear feels floaty, and you have the original subframe bushings, get those changed for M3 or aftermarket bushings.
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      08-26-2014, 09:51 AM   #15
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Quote:
Originally Posted by BMWTF? View Post
Easy, forum friend. No need to be a forum police. The topic is not closed yet. Peace out.

Manny's opinion is valued and appreciated, I still need more feedback. The other person, whom I spoke with, and who also does experience the lift, is a 4+ year HPDE Group A driver. So, it is 1:1 at this point.
The HACK has a ton of suspension and tracking experience, so he does have a valid point.

HPDE are completely different than racing.
I have 8 years of HPDE experience and over two years of racing experience. It's night and day different when you're coming down from 155 - 160 to out brake the car you're over taking into a corner to really understand the stability of the rear. I've never felt anything floaty or disconnected with the rear of the race car. I'm not sure how the guy you spoke to sometimes has the lift and sometimes doesn't.

You may want to check the rake of your suspension. You may be getting a little more downforce on the front of your car if it's too low.

In no way should you be feeling light in the rear at the speeds you're going. The factory limits our cars to 155mph. I highly doubt BMW would take their cars on the Autobahn and give them the okay if they're floaty in the rear.

TBH: I highly doubt the small lip spoiler (or even the larger one) will do much of anything at the speeds you're doing. Obviously, you see most race cars have huge wings in order to get downforce at lower speeds.
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      08-26-2014, 11:26 AM   #16
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Quote:
Originally Posted by TSM330i View Post
The HACK has a ton of suspension and tracking experience, so he does have a valid point.

HPDE are completely different than racing.
I have 8 years of HPDE experience and over two years of racing experience. It's night and day different when you're coming down from 155 - 160 to out brake the car you're over taking into a corner to really understand the stability of the rear. I've never felt anything floaty or disconnected with the rear of the race car. I'm not sure how the guy you spoke to sometimes has the lift and sometimes doesn't.

You may want to check the rake of your suspension. You may be getting a little more downforce on the front of your car if it's too low.

In no way should you be feeling light in the rear at the speeds you're going. The factory limits our cars to 155mph. I highly doubt BMW would take their cars on the Autobahn and give them the okay if they're floaty in the rear.

TBH: I highly doubt the small lip spoiler (or even the larger one) will do much of anything at the speeds you're doing. Obviously, you see most race cars have huge wings in order to get downforce at lower speeds.
There are valid points in in this post/thread. Rake of your suspension and bushings could be a factor. Your honesty in the last portion is completely true. I mentioned changing spoilers I notice a change at higher speeds (nothing drastic), which is what the OP was asking for. As you mentioned, huge wings are for downforce at lower speeds. Think the OP is going more for sports car feel than race car.
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      Yesterday, 11:40 AM   #17
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I think a rear spoiler looks bad-ss on this car. I would get it for the way it looks. I've long contemplated getting the factory carbon fiber lip spoiler put on my MZ4 Coupe.

But I wouldn't be putting it on for downforce reasons. It doesn't create enough and I don't currently lack for rear grip...I lack front end grip in high speed corners. So a spoiler in the rear will look great, maybe reduce what little aerodynamic lift is there at extreme speeds, but for what it is, let me just be honest...Unless I go to an APR type wing in the rear I am not going to see any significant result, and at that point its only going to exacerbate my front end problem at WSIR and Auto Club Speedway where at 120+ in a turn, there isn't enough front end grip to keep the car going where I want it to go exactly.

But I would LOVE to pick up one and install it.

Let's face it. You're probably not experiencing lift in the rear. You're probably experiencing INSTABILITY in the rear resulting from the rear wheels trying to twist itself loose at speed (the E9X 335 does not lack for torque), or lack of damper control in the rear which is common on BMW chassis and more likely the cause. And in turn project that into a WANT to have a spoiler. There's nothing wrong with that. I fully understand.

But you're fixing the wrong thing IMO. The spoiler isn't going to fix your problem with the rear end instability at speed. Stiffer springs and better REBOUND will. At ~3,600+ lbs with driver, each rear wheel has at least 900lbs, and the rear axle is seeing 1,800lbs of weight pushing it down. For it to actually have lift, there need to be significant aerodynamic force pushing it up.

I doubt it's aero. If you're on OEM rear shocks, it's probably time to replace them. If you're on adjustable rear shocks, increase the rebound in the rear and see what happens. I think what you're feeling is the springs releasing their energy because the rear shocks can't keep them contained.
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      Yesterday, 12:50 PM   #18
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Quote:
Originally Posted by StealYourFace View Post
Agreed 100%

OP, if the rear feels floaty, and you have the original subframe bushings, get those changed for M3 or aftermarket bushings.
Quote:
Originally Posted by TSM330i View Post
The HACK has a ton of suspension and tracking experience, so he does have a valid point.

HPDE are completely different than racing.
I have 8 years of HPDE experience and over two years of racing experience. It's night and day different when you're coming down from 155 - 160 to out brake the car you're over taking into a corner to really understand the stability of the rear. I've never felt anything floaty or disconnected with the rear of the race car. I'm not sure how the guy you spoke to sometimes has the lift and sometimes doesn't.

You may want to check the rake of your suspension. You may be getting a little more downforce on the front of your car if it's too low.

In no way should you be feeling light in the rear at the speeds you're going. The factory limits our cars to 155mph. I highly doubt BMW would take their cars on the Autobahn and give them the okay if they're floaty in the rear.

TBH: I highly doubt the small lip spoiler (or even the larger one) will do much of anything at the speeds you're doing. Obviously, you see most race cars have huge wings in order to get downforce at lower speeds.
Quote:
Originally Posted by Manny_World View Post
There are valid points in in this post/thread. Rake of your suspension and bushings could be a factor. Your honesty in the last portion is completely true. I mentioned changing spoilers I notice a change at higher speeds (nothing drastic), which is what the OP was asking for. As you mentioned, huge wings are for downforce at lower speeds. Think the OP is going more for sports car feel than race car.
Quote:
Originally Posted by The HACK View Post
I think a rear spoiler looks bad-ss on this car. I would get it for the way it looks. I've long contemplated getting the factory carbon fiber lip spoiler put on my MZ4 Coupe.

But I wouldn't be putting it on for downforce reasons. It doesn't create enough and I don't currently lack for rear grip...I lack front end grip in high speed corners. So a spoiler in the rear will look great, maybe reduce what little aerodynamic lift is there at extreme speeds, but for what it is, let me just be honest...Unless I go to an APR type wing in the rear I am not going to see any significant result, and at that point its only going to exacerbate my front end problem at WSIR and Auto Club Speedway where at 120+ in a turn, there isn't enough front end grip to keep the car going where I want it to go exactly.

But I would LOVE to pick up one and install it.

Let's face it. You're probably not experiencing lift in the rear. You're probably experiencing INSTABILITY in the rear resulting from the rear wheels trying to twist itself loose at speed (the E9X 335 does not lack for torque), or lack of damper control in the rear which is common on BMW chassis and more likely the cause. And in turn project that into a WANT to have a spoiler. There's nothing wrong with that. I fully understand.

But you're fixing the wrong thing IMO. The spoiler isn't going to fix your problem with the rear end instability at speed. Stiffer springs and better REBOUND will. At ~3,600+ lbs with driver, each rear wheel has at least 900lbs, and the rear axle is seeing 1,800lbs of weight pushing it down. For it to actually have lift, there need to be significant aerodynamic force pushing it up.

I doubt it's aero. If you're on OEM rear shocks, it's probably time to replace them. If you're on adjustable rear shocks, increase the rebound in the rear and see what happens. I think what you're feeling is the springs releasing their energy because the rear shocks can't keep them contained.
Thank you very much gentlemen. I see your points, as it most likely has nothing to do with aerodynamics. I will be looking into suspension optimizations. This is great feedback I was looking for. Very much appreciate it.
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      Yesterday, 06:48 PM   #19
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Quote:
Originally Posted by The HACK View Post
I think a rear spoiler looks bad-ss on this car. I would get it for the way it looks. I've long contemplated getting the factory carbon fiber lip spoiler put on my MZ4 Coupe.

But I wouldn't be putting it on for downforce reasons. It doesn't create enough and I don't currently lack for rear grip...I lack front end grip in high speed corners. So a spoiler in the rear will look great, maybe reduce what little aerodynamic lift is there at extreme speeds, but for what it is, let me just be honest...Unless I go to an APR type wing in the rear I am not going to see any significant result, and at that point its only going to exacerbate my front end problem at WSIR and Auto Club Speedway where at 120+ in a turn, there isn't enough front end grip to keep the car going where I want it to go exactly.

But I would LOVE to pick up one and install it.

Let's face it. You're probably not experiencing lift in the rear. You're probably experiencing INSTABILITY in the rear resulting from the rear wheels trying to twist itself loose at speed (the E9X 335 does not lack for torque), or lack of damper control in the rear which is common on BMW chassis and more likely the cause. And in turn project that into a WANT to have a spoiler. There's nothing wrong with that. I fully understand.

But you're fixing the wrong thing IMO. The spoiler isn't going to fix your problem with the rear end instability at speed. Stiffer springs and better REBOUND will. At ~3,600+ lbs with driver, each rear wheel has at least 900lbs, and the rear axle is seeing 1,800lbs of weight pushing it down. For it to actually have lift, there need to be significant aerodynamic force pushing it up.

I doubt it's aero. If you're on OEM rear shocks, it's probably time to replace them. If you're on adjustable rear shocks, increase the rebound in the rear and see what happens. I think what you're feeling is the springs releasing their energy because the rear shocks can't keep them contained.
Couldn't have said it better myself. The only time you might experience that lift in the rear is braking from high speeds, which is a result of having stock shocks/springs and not being able to control compression. That was a main problem I was facing when tracking my car without the rear wing and no BBK. The problem worsened when I got a rear BBK w/o a wing because it would lift and then lock up, haha.

As people have said, the little lip spoiler will do absolutely nothing to help this experience you are feeling. Better suspension will help you solve the issue.
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