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      03-25-2016, 08:53 PM   #1
Ryan13
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Brake Duct flap removal

Read all the threads/discussion on the flaps riveted to the outlet of the brake ducts. Is there a consensus on what they are there for? Aerodynamics or just blocking flow??

I had the front bumper and front wheels off, thought about it for a while, read some more, thought about some more, then ripped them off. They seem like they were either added after the fact (i.e. some BMW engineer uncovered something in testing and it was too costly to retool) or they were designed to be removed for some reason. I drove the car around the neighborhood without the bumper on, flaps removed...I noticed that as the tire rotated, dirt/sand was being thrown into the ducts. Perhap said BMW engineer discovered the opening was too wide and was allowing water, dirt, rocks to be thrown forward.

Anyhow, too late, they are gone now. Just curious if anyone discovered the real purpose.
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      03-26-2016, 01:19 AM   #2
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I think you're correct about sand/dirt getting in so they shut them off. I'm often cleaning sand out of the ducts with the flaps still in place. It's just an inherently bad design for brake cooling how it blows air straight onto the tyre and while not being ducted into the caliper area.
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      03-26-2016, 10:11 AM   #3
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Quote:
Originally Posted by Digs View Post
I think you're correct about sand/dirt getting in so they shut them off. I'm often cleaning sand out of the ducts with the flaps still in place. It's just an inherently bad design for brake cooling how it blows air straight onto the tyre and while not being ducted into the caliper area.
Well...I would assumed that if it were directed toward the caliper area, same reasoning applies - that your calipers would get sand blasted with sand/dirt. For a street car, I don't think you would want the potential of getting sand/dirt trapped in between your rotors and pads
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      03-26-2016, 10:36 AM   #4
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The ducts are there to pressurize the wheel well (aero), not for brake cooling.
And yes flaps were added because of dirt & gravel being slung from the tires.

I'm going to close them off entirely when I add proper brake cooling ducting.
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      03-29-2016, 07:06 AM   #5
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I am going to re-route those puppies… actually, i am going to ditch the right one, and re-route the other. Ill be chucking an extra oil cooler on the right one.
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      05-20-2016, 08:10 AM   #6
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Besides wheel well aero, could it have some front downforce effect?
Decreasing the gap might increase the pressure?
(I'm no engineer, just a shot in the dark?)

I've left mine stock and will be doing the brake ducts from the centre piece like Dubsesd had.

Oh and there is a thread like this already on the z4 forum:
http://www.z4-forum.com/forum/viewtopic.php?t=35339
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      05-20-2016, 02:01 PM   #7
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Evidently someone removed the flaps from my bumper at some point. I didn't know they were supposed to have flaps there, but did notice I get a good bit of small gravel in the ducts. Ya'll think it is worth putting them back?

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      05-21-2016, 12:40 PM   #8
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I have no flaps, and no evidence that there ever were any.
Maybe they were added after 02/2006?
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      05-21-2016, 12:48 PM   #9
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Quote:
Originally Posted by StickMon View Post
I have no flaps, and no evidence that there ever were any.
Maybe they were added after 02/2006?
Yes, I believe they were added or at least modified larger.
There is no functional benefit other than stopping throw back off of the tires.(cosmetic)
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      07-24-2016, 06:48 PM   #10
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Quote:
Originally Posted by Vanne View Post
I am going to re-route those puppies… actually, i am going to ditch the right one, and re-route the other. Ill be chucking an extra oil cooler on the right one.
Redirecting the stock vent is my thought as well. If you can add an opening inward of the stock opening( in the lower grill) as demonstrated in THIS brake duct thread and get a duct to the rotor from there; I'm considering removing the black inset (inlet) and fabricating a collection duct to direct the air flow first toward the center of the vehicle, then pick up a flex hose as demonstrated in the noted thread above. That way the stock opening can be used.
I have not had the bumper off to assess plausibility yet. I hope to yet this summer. I have some broken plastic under the driver side nose of the car I want to replace anyway.
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      07-25-2016, 10:02 PM   #11
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I snapped off the flaps and have not looked back. I presume at 145mph, there must be some cooling effect, but perhaps that's all in my head. It certainly didn't help the Hawk HPS pads I cooked within the first hour this past weekend. I know they are street...$170 for all four corners was worth a try. Picked up PF08s today.

Maybe if the car could get to 200mph, there would be some aerodynamics at play. At 145mph for 3-4 seconds, I can't see how there could be any negative effects.

For a potential positive. There were some spectators in the tower a couple of weeks ago. The rain was coming down so hard, we had to run with lights on, wipers full blast, and take some turns on the rain line. The guys in the tower came up to me in the paddock and asked if I was running any kind of special tire...said no, just PSS like most everyone else. They said it looked like a cloud when I went by, especially out the front wheel wells and a rooster tail out the back. One guy took a picture that I'm still trying to get. So...maybe the extra air flow helps with some water displacement.
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      07-25-2016, 10:09 PM   #12
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Quote:
Originally Posted by Bossdog View Post
Redirecting the stock vent is my thought as well. If you can add an opening inward of the stock opening( in the lower grill) as demonstrated in THIS brake duct thread and get a duct to the rotor from there; I'm considering removing the black inset (inlet) and fabricating a collection duct to direct the air flow first toward the center of the vehicle, then pick up a flex hose as demonstrated in the noted thread above. That way the stock opening can be used.
I have not had the bumper off to assess plausibility yet. I hope to yet this summer. I have some broken plastic under the driver side nose of the car I want to replace anyway.
I plan to get to this in a couple of weeks, will let you know how it goes.
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      07-25-2016, 10:13 PM   #13
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Quote:
Originally Posted by Ryan13 View Post
I snapped off the flaps and have not looked back. I presume at 145mph, there must be some cooling effect, but perhaps that's all in my head. It certainly didn't help the Hawk HPS pads I cooked within the first hour this past weekend. I know they are street...$170 for all four corners was worth a try. Picked up PF08s today.

Maybe if the car could get to 200mph, there would be some aerodynamics at play. At 145mph for 3-4 seconds, I can't see how there could be any negative effects.

For a potential positive. There were some spectators in the tower a couple of weeks ago. The rain was coming down so hard, we had to run with lights on, wipers full blast, and take some turns on the rain line. The guys in the tower came up to me in the paddock and asked if I was running any kind of special tire...said no, just PSS like most everyone else. They said it looked like a cloud when I went by, especially out the front wheel wells and a rooster tail out the back. One guy took a picture that I'm still trying to get. So...maybe the extra air flow helps with some water displacement.
The ducts don't provide any cooling.
They are intended to pressurize the wheel well to help with aero dynamics down the side of the car.
The flaps were added purely for cosmetic purpose to help limit the amount of dirt and muck thrown off the wheels from getting in there.
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      07-26-2016, 07:10 PM   #14
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Quote:
Originally Posted by Ryan13 View Post
I snapped off the flaps and have not looked back. I presume at 145mph, there must be some cooling effect, but perhaps that's all in my head. It certainly didn't help the Hawk HPS pads I cooked within the first hour this past weekend. I know they are street...$170 for all four corners was worth a try. Picked up PF08s today.
You have some real Brass Balls my friend! 145 mph and you thought "what the heck, I'll try some street pads cause their cheap"

That's how a 20-something crashed his Cobalt SS into my brand New Boss 302 in 2012. Remember, you not only put your car and well being at risk, you are putting others safety and property at risk as well!
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      12-17-2016, 09:21 AM   #15
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I recently purchased a 2006 Z4 M Roadster. I am accumulating an amazing amount of brake dust which I'm constantly wiping out of the wheel well. I was directed to get some Akebono Euro pads or the FTW. What I want is more braking power, less heat, less fade. And it would really be nice to have less of that sticky black brake dust forming all around my wheel well.

I will soon be doing my first autocross and hopefully graduate to HIDE. Can I have my cake and eat it too? Are there ceramic brake options with these give me more stopping power and less brake dust. ARE PF08 strictly for track use.

If anyone can impart some knowledge on this subject and give me some brands and options to get the most out of my car, but keeping in mind that I will be driving it on the street probably five thousand miles a year.
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      12-17-2016, 09:22 AM   #16
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I did want to add that I just bought a set of Bridgestone re - 71, so I have the tires to meet my needs for right now
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      12-17-2016, 11:41 AM   #17
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Quote:
Originally Posted by JJZ4MR View Post
I recently purchased a 2006 Z4 M Roadster. I am accumulating an amazing amount of brake dust which I'm constantly wiping out of the wheel well. I was directed to get some Akebono Euro pads or the FTW. What I want is more braking power, less heat, less fade. And it would really be nice to have less of that sticky black brake dust forming all around my wheel well.

I will soon be doing my first autocross and hopefully graduate to HIDE. Can I have my cake and eat it too? Are there ceramic brake options with these give me more stopping power and less brake dust. ARE PF08 strictly for track use.

If anyone can impart some knowledge on this subject and give me some brands and options to get the most out of my car, but keeping in mind that I will be driving it on the street probably five thousand miles a year.
PFC08 are track pads designed for endurance and I can attest to how good they are in that capacity. They really shine in lap after lap of hard braking and hi temps. That being said they're noisey as hell as a street pad and they do not work well until they get some heat in them.
I'd look for a different compound for autox. You don't need nearly the same braking characteristics. When it comes to brake pads there's always a trade-off somewhere.

A lot of Autox drivers run Hawk pads but again depends on how aggressive you go before they create a crap ton of dust and noise. Stock pads served me well when I ran solo.

Last edited by longress; 12-17-2016 at 11:48 AM..
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      05-29-2017, 02:31 PM   #18
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Quote:
Originally Posted by longress View Post
PFC08 are track pads designed for endurance and I can attest to how good they are in that capacity. They really shine in lap after lap of hard braking and hi temps. That being said they're noisey as hell as a street pad and they do not work well until they get some heat in them.
I'd look for a different compound for autox. You don't need nearly the same braking characteristics. When it comes to brake pads there's always a trade-off somewhere.

A lot of Autox drivers run Hawk pads but again depends on how aggressive you go before they create a crap ton of dust and noise. Stock pads served me well when I ran solo.
Wow- very different from my experience, pasted below from a recent post:
Okay - did the Drivers School last weekend with the PFC 08 pads.
In short, I thought they were great.

I drove them on the street for a few days before the school. Did some bedding right after installing them. I thought the stopping action was great (better than stock) under heavy braking, and it only got better as they got warm- then it was truly impressive. They dust a bit (especially under repeated, heavy braking - like for bedding), but it washes off easily.

On the track, I was really impressed, too. They were so much better and different than OEM brakes that I spent the first session adapting to them. The initial bite is substantial, and the braking effectiveness is markedly more than OEM. So I had to learn to brake much later to enter each turn at my desired speed. I didn't notice much warm-up required to get to full effectivness- they were good from the start.
I think I experienced a bit of fade at the end of my 4th session, after several pretty fast laps. When it happened, there seemed to be reduced response to initial pedal pressure (which surprised me), but by increasing the pressure (quite a bit), they were effective again. I'm wondering whether opening up the front brake duct openings would help for my next track day.

I've driven several hundred miles since the track day with the PFC 08s still on. Even in morning commutes with the temps in the 40s, they were plenty good (at least as good as OEM) from the first application. There is a bit of a "groan" sound (like OEM but more pronounced) when braking, and occasionally squeaking when braking at very low speeds (barely moving).
I'm a little concerned with preserving my rotor life, or I'd just leave the 08s on until the next drivers school in September. The braking (even in cool weather) is great, the noise is minimal, and the dust is no worse than OEM, maybe a little better. As it is, I'll put the Z compound pads on in the next few weeks when I find some time.

I'll update again then to report on the Z compound.

Meanwhile- anybody have a positive change from opening up the brake ducts (removing the riveted-in panels that block half of the opening on the front of the wheel well liners)?

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