[earthpounder]

The vague highway steering feel of the second gen X3, especially the 28i, was brought up in several past threads. Possible solutions discussed were: added weight to the front end, air dams, splitters, and vortex generators.

I had problems with steering wander on my 2014 X3 28i. It seemed like the front end was being blown around by crosswinds. Having to constantly correct the steering was tiring and annoying. As a cheap solution, I tried adding airtabs (vortex generators) to the leading edge of the undertray. The theory is that these devices somehow reduce the pressure under front end, to create a down force. The improvement was much better than I expected. The car is now much more steady at highway speed!

Did anyone else try any mods, and did they work?

[Barbera335]

Lol, sounds like a placebo affect to me.

[Bufalo]

I just pop the car into sport mode and the steering is fine on the highway. I mean, I drive the car in sport mode for everything, but I do notice that if I happen to get on the highway in normal/comfort (after a fill up on a road trip) that it's less precise than I expect. Still, it's never what I'd consider "a problem."

[earthpounder]

Here is the street view of my car with the vortex generators. As you can see, they are not really visible unless you're looking for them. At $3 a pop they are probably the lowest cost performance mod you could try, if you would like to improve your highway driving enjoyment. By the way, I have a graduate degree in engineering, and I worked for the USAF for many years. Vortex generators are well known to aeronautics and race car experts.

[rirrgang]

At what speed do these become effective?
Since installing Non-Run-Flats my X3 is perfect on the hiway. I mean a night and day perfect.

[TheCoolX3]

What did you use to put these on?

[earthpounder]

Before I put on the VGs, the car felt like it was getting unstable around 50 mph and got worse at higher speeds. Now it feels much more "planted" at 50 and higher, with less tendency to wander.

I got my VGs from Raneys Truck Parts, (they are very popular with truckers, to improve fuel economy.) They come with a high strength peel-and-stick adhesive attached. One issue I had was the surface I attached them to is slightly curved. I had to heat the VGs up with a hair dryer and put a small bend in them so they would fit flush.

Why do they work? Not really sure - the aerodynamics under a vehicle are complicated by something called "ground effects" which are tricky to account for. What is known is that the VGs should help to keep the air flow attached to the surface behind them (the undertray.) Attached airflow lowers the pressure on that surface. Lowered pressure results in a net downforce. A mere 1 psi pressure reduction over a 3 by 3 foot undertray could produce a downforce of 1,296 pounds!

[TheCoolX3]

Why the hell not! Ill give it a try, my X3 is lowered so it will take a prying eye to see them! Thanks!

[Wgosma]

...take your car to the nearest wind tunnel and get it tested, report back with data on the reduced drag and increased downforce numbers.

[earthpounder]

Not a bad idea to get wind tunnel data, if I could. I'm actually looking at measuring downforce using a vehicle road height sensor. The idea is to measure the front suspension deflection at various speeds. With and without the vortex generators. I'll post here if get any data.

[x3sm]

I hate the steering play on the highway. I installed 285/40/19 in the front and still not stable on highway, crosswinds are throwing me around.

[TheCoolX3]

I have 245s on the front and ever since I've lowered it and stiffened the coilovers the steering on the highway has gotten so much better. Its not a fight to keep the car straight going 100 anymore. It is not great but it is significantly better.

Originally Posted by x3sm

I hate the steering play on the highway. I installed 285/40/19 in the front and still not stable on highway, crosswinds are throwing me around.

[Opie55]

Funny that I have never noticed these vortex generators before this post, and I just sat next to a semi at a stop light that had a vertical row of about 20 of them on the trailing edge of the cab bodywork.

[Wgosma]

Originally Posted by Opie55

Funny that I have never noticed these vortex generators before this post, and I just sat next to a semi at a stop light that had a vertical row of about 20 of them on the trailing edge of the cab bodywork.

Originally Posted by Opie55

Funny that I have never noticed these vortex generators before this post, and I just sat next to a semi at a stop light that had a vertical row of about 20 of them on the trailing edge of the cab bodywork.

I believe they were initially / commonly used on airplane wings to create an airflow pattern that reduces drag, and provides greater lift.
F-1 race cars use them underneath the chassis/body., I'm not sure if the goal is increased downforce or simply less wind resistance...

[subieworx]

From and aerodynamics perspective and from someone who builds race cars this is comical.

[335iAP]

I don't think these would work, but I find the steering on the highway too twitchy and it'd be cool to have a way to make it need a little less correction

[MSportTune2]

I have a sDrive 20i LCI with electronic damping suspension. When at high speed on the highway, I switch to sports mode and the steering and damping tightens up. The ride is solid and stable. No issue at all. If in Comfort mode, depending on the road surface, it can be a bit bouncy but switching to comfort mode usually cures that. Car tracks just as well in either mode. Even with crosswinds, it's a little unsettling and still tracks well.

[335iAP]

Originally Posted by MSportTune2

I have a sDrive 20i LCI with electronic damping suspension. When at high speed on the highway, I switch to sports mode and the steering and damping tightens up. The ride is solid and stable. No issue at all. If in Comfort mode, depending on the road surface, it can be a bit bouncy but switching to comfort mode usually cures that. Car tracks just as well in either mode. Even with crosswinds, it's a little unsettling and still tracks well.

Problem with that (at least for me) is that sport mode prevents you from upshifting past 6th gear, which seems like a waste on the highway when I'm just cruising.

[Bufalo]

if you switch to manual shift and use the paddles, you can upshift to 7th and 8th and have sport response in the tallest gears.

[335iAP]

Originally Posted by Bufalo

if you switch to manual shift and use the paddles, you can upshift to 7th and 8th and have sport response in the tallest gears.

Does yours not eventually shift back down? That's what mine does.

[Bufalo]

Nope, if I click the shifter over to the left, into M/S, and use the paddles to shift up into 8th, it stays there until I shift down or move the leverl back over to D or come to a stop without remembering to shift myself. It stays in whatever gear I've selected - IF I have the lever over in M/S.

If you leave it in D, yes it will go back to automatic mode after twenty seconds or so.

[najnad]

1. I think a lot of the vagueness some people feel with the steering, esp at speed, with the F25 is due to the run-flat tires and/or improper tire pressures. Ensure all tires are at their proper pressures and if possible, get some good non-run flat tires.

2. You can have just sport steering enabled without switching the transmission to sport mode, if you have the separate switch next to the stick. When you put that switch into "Sport" (not Sport+) you are given the opportunity to adjust the settings and you can have it just for chassis and not drivetrain which will tighten up the steering (and suspension if you have EDC).