Brake Ducts

[Bimmer-Bob]

So I understand that 135i's (and 128i's with M-Sport Package) came from the factory with brake ducts (see #4 in this diagram). My question is, where does this duct end?

I recently fitted the Performance front bumper on my non-M-Sport 128i. If I wanted to, I could add the Performance cooling package, which adds ducting from the Performance bumper to the above mentioned air ducts, but then what? Where do those ducts lead to exactly? Would I need different wheel well liners or anything?

[Ginger_Extract]

It just shoots out of the middle of the wheel liner. 100% non-functional. The only useful element is that with 135i models, it has a channel that directs air to the factory oil cooler.

[Bimmer-Bob]

Originally Posted by Ginger_Extract

It just shoots out of the middle of the wheel liner. 100% non-functional.

Really? That's disappointing. Why would BMW bother with completely useless ducting (and even require the use of the Performance ducting on the Performance bumper)?

I mean, I wasn't expecting racecar-level brake ducts, but I guess I was hoping for something better than the completely absent ducting on my car.

[Solo_M_Tech]

That " Non functional ducting" actually helps reduce wheel well temps by force evacuating the air in that area. Since the area in the wheel well is a low pressure area, the air tends to linger, and heat up. If you modify the backing plates by bending them back, or cutting and welding "scoops" on the back so it can catch some of that air, it drastically helps. You can go full race car and route ducting all the way to the backing plate with hose, but that's unneeded in 90% of situations.

[dcaron9999]

When I went with wider front wheels (8.5x18 versus stock 7.5x18), air passage was blocked even more, and it made my brake ventilation worse. Air from the front fender could no longer reach the rotors and calipers. Air only only hit the tire tread and did nothing at all for brake cooling.

I tried bending the stock E82 dust shields, then tried F30 dust shields, and finally gave in and routed flexible aircraft grade hose from stock ducts in the bumper, to my stock E82 dust shields. Also installed some Ti heat shields between pistons and brake pads.

The brake fade has been reduced on the track, but not completely eliminated. Then again, my 135i makes about 440 ft-lbs of torque, has a 3.46 final drive Quiafe LSD, and front 255/35R18 ZII SS tires have way more grip than 214/40R18 stock RunFlats. More more heat is generated in the stock Brembo calipers, and my pistons and dust boots are toast after 3 years of lapping/HPDE events...

[Bimmer-Bob]

Originally Posted by ApexResistance

That " Non functional ducting" actually helps reduce wheel well temps by force evacuating the air in that area. Since the area in the wheel well is a low pressure area, the air tends to linger, and heat up. If you modify the backing plates by bending them back, or cutting and welding "scoops" on the back so it can catch some of that air, it drastically helps. You can go full race car and route ducting all the way to the backing plate with hose, but that's unneeded in 90% of situations.

If I added this brake ducting, my plan would be to do so in conjunction with F30 backing plates. I just don't see how the air gets from these ducts to the wheel well? The liner seems like it blocks ventilation off pretty well. Are the 135i wheel well liners different? Will try to snap a pic of mine when I get home.

[Solo_M_Tech]

Originally Posted by Bimmer-Bob

If I added this brake ducting, my plan would be to do so in conjunction with F30 backing plates. I just don't see how the air gets from these ducts to the wheel well? The liner seems like it blocks ventilation off pretty well. Are the 135i wheel well liners different? Will try to snap a pic of mine when I get home.

I think they are. I have a nice 3X4" hole where the air is directed straight into the wheel wells from the front bumper. I modified my backing plates to protrude past the edge of the wheel to catch some of that air. I can get a picture tomorrow.

[Solo_M_Tech]

Originally Posted by dcaron9999

When I went with wider front wheels (8.5x18 versus stock 7.5x18), air passage was blocked even more, and it made my brake ventilation worse. Air from the front fender could no longer reach the rotors and calipers. Air only only hit the tire tread and did nothing at all for brake cooling.

I tried bending the stock E82 dust shields, then tried F30 dust shields, and finally gave in and routed flexible aircraft grade hose from stock ducts in the bumper, to my stock E82 dust shields. Also installed some Ti heat shields between pistons and brake pads.

The brake fade has been reduced on the track, but not completely eliminated. Then again, my 135i makes about 440 ft-lbs of torque, has a 3.46 final drive Quiafe LSD, and front 255/35R18 ZII SS tires have way more grip than 214/40R18 stock RunFlats. More more heat is generated in the stock Brembo calipers, and my pistons and dust boots are toast after 3 years of lapping/HPDE events...

I haven't had any major issues with brake fade yet. I have tracked my car for a year now with 32 laps of the Nurburgring under my belt ( with this car) and so far, nothing crazy. The stock brakes lasted one lap of the Nurburgring before they were toast. The Hawk HP+ and BMWP rotors lasted almost 6 months, but the rotors warped. Now Im running the EBC yellow stuff-R compound with StopTech Slotted rotors and they have had zero issues. Brake Fluid was the first weak link in the system.

[Bimmer-Bob]

Originally Posted by ApexResistance

I think they are. I have a nice 3X4" hole where the air is directed straight into the wheel wells from the front bumper. I modified my backing plates to protrude past the edge of the wheel to catch some of that air. I can get a picture tomorrow.

From what I can see on RealOEM (here) and cross-checking product photos on ECS Tuning's site, that 3x4" hole is only on the right side and is described by BMW as an air duct for the engine oil cooler.

It doesn't really make sense to me why an oil cooler duct would be in the right wheel well...where do you guys keep your oil coolers?

Also, you're saying you have that cutout in both wheel wells? That what I would expect, if they are indeed part of the brake ducting...

[Solo_M_Tech]

As you can see, my driver and passenger side air ducts that feed from the lower grill sections feed directly to the brakes. You can see the inner lip of the wheel in the photo. This is on both sides. This is 100% stock. Not modified.

[Bimmer-Bob]

Originally Posted by ApexResistance

As you can see, my driver and passenger side air ducts that feed from the lower grill sections feed directly to the brakes. You can see the inner lip of the wheel in the photo. This is on both sides. This is 100% stock. Not modified.

Thanks. So looking from the wheel well side, it's not that there is a cut-out, but the air is coming up from underneath the liner?

[Solo_M_Tech]

Originally Posted by Bimmer-Bob

From what I can see on RealOEM (here) and cross-checking product photos on ECS Tuning's site, that 3x4" hole is only on the right side and is described by BMW as an air duct for the engine oil cooler.

It doesn't really make sense to me why an oil cooler duct would be in the right wheel well...where do you guys keep your oil coolers?

Also, you're saying you have that cutout in both wheel wells? That what I would expect, if they are indeed part of the brake ducting...

See my post above. And on the 135i, the factory oil cooler is located in the passenger side wheel well. That's the stock location.

[Bimmer-Bob]

Originally Posted by ApexResistance

See my post above. And on the 135i, the factory oil cooler is located in the passenger side wheel well. That's the stock location.

Okay, I think I got it. Thanks a lot for the pics. At first I was looking for something like the oil cooler cutout.

It looks like it should be pretty effective at generating airflow, assuming there was a way to direct that airflow to the brakes (i.e., F30 backing plates).

[Solo_M_Tech]

Originally Posted by Bimmer-Bob

Okay, I think I got it. Thanks a lot for the pics. At first I was looking for something like the oil cooler cutout.

It looks like it should be pretty effective at generating airflow, assuming there was a way to direct that airflow to the brakes (i.e., F30 backing plates).

That or like I said, Moddify your stock backing plates. It's easy to do, just grab and bend back. They will drastically improve flow.

[dcaron9999]

The thing with brake fade is that it will vary immensely from one driver to the next ...

Consider this: the power that your stock versus tuned engine makes. The grip of the tires you use, the layout of the track you drive on most often (long stretches will cool your brakes better between hard braking zones). Do you drag your brakes (beginner to intermediate level driver), or use them hard and quickly (advanced drivers)? Do you cool down your brakes after each lapping session (no use of the brake pedal on the last lap before returning to pitlane)? What temperature range do your brake pads handle?

These will all have an effect on brake fade, brake pad longevity, and even brake noise to a certain extent.