[PunsGalore]

Hi all,

I am wondering if ordering air suspension on the 25' X5 xDrive40i would be worth it? Air suspensions have always scared me a little, but open to hearing your thoughts! Will most likely go without due to cost savings and the extra piece of mind

Thanks

[tooloud10]

I prefer the 2-axle air suspension on my X5 because I do longer trips and the ride quality is great. Some people prefer a sportier ride but I'm not hot rodding this thing around.

[GordoCLM]

I haven't tried the standard suspension, but I had the air suspension on my 45e for 2 years, and now I have the M Adaptive Pro on my M60i, and I couldn't be happier with the change. It's a more sporty driving experience, firm but not uncomfortable at all. In fact, the air suspension could be uncomfortable on roundabouts due to body roll.

[LuckyBrand]

If I was a big traveler or highway driver it would definitely be a nice option. We didn't get it on ours due to we like a sportier ride and to be honest it rides really nice anyways on 22s and adaptive. Even in sport it rides really nice to us. We had an X7 loaner recently with air and on the highway that thing was butter.

If you can find both on a lot to try out that would be your best bet. Also consider how long you may keep the vehicle as many say long term the air suspensions can be problematic..

[PunsGalore]

Ok, I think I'll pass.. not carving up canyon roads but would rather a sporty ride than feeling like its a motorhome suspension - not a big highway driver either. Thanks for all your help!

[TurtleBoy]

It all depends on what type of ride you are looking for. If you want the most comfortable with some sportiness when desired then get the air suspension.

There should be zero concerns about costs in the future. Anything can break at anytime but odds are against it, just enjoy their vehicle.

[TurtleBoy]

Originally Posted by PunsGalore

Ok, I think I'll pass.. not carving up canyon roads but would rather a sporty ride than feeling like its a motorhome suspension - not a big highway driver either. Thanks for all your help!

You probably should try and test drive one as suspension fee; is a personal perception/preference. Anything someone says about suspension fee; should be taken with a grain of salt. On e person's sportiness is another's harshness just like one's floaty is another's comfortable.

[Dixie21]

I've had both in both V8 and 6 cyl variants. I currently have M-Adaptive in my M60i and I enjoy it a lot more than I thought I would. Most of my commute to work is highway so I swore by air suspension. Yes, air is smoother on the highway, but the M-Adaptive isn't exactly choppy. With that being said, I do prefer air suspension because I it does stiffen up nicely in sport mode along with reducing the ride height. You can also lower the vehicle when parked which makes it look awesome. I completely understand how stupid that sounds, but it looks really good with spacers and lowered when parked haha

[avi8tir]

Originally Posted by PunsGalore

Ok, I think I'll pass.. not carving up canyon roads but would rather a sporty ride than feeling like its a motorhome suspension - not a big highway driver either. Thanks for all your help!

Don't knock it before you try it. The air suspension is awesome. Even in comfort, the ride is solid, and sporty.

I live in an area where the roads suck and absolutely love the air suspension. I had an F90 M5 Comp before this and I hated driving it around because of the roads. And, the air suspension can get firm at the push of a button. I do almost zero highway driving and would choose the air suspension again considering the area I live in.

[jad03060]

Just because the vehicle is sprung with air does not automatically mean that it is floaty. That is primarily a function of how the shocks are tuned, not the springs. To keep from bottoming out on a bump, the final spring rate between a steel spring and an air spring needs to be about the same at full compression or it couldn’t hold the vehicle up…it’s just that a steel spring is likely a tit stiffer on initial, small impacts than an air suspension which is about as progressive as you can make a spring. A steel spring can only be wound to approximate a progressive spring rate.

Where you live, and the quality of the roads could sway you one way or the other…air springs will absorb smaller bumps better than a steel spring. Keep in mind that the tires are also part of the vehicle’s overall spring rate, so shorter sidewalls on larger wheels will tend to transmit more of the impact to the chassis than a smaller wheel.

[BlkGS]

Originally Posted by jad03060

Just because the vehicle is sprung with air does not automatically mean that it is floaty. That is primarily a function of how the shocks are tuned, not the springs. To keep from bottoming out on a bump, the final spring rate between a steel spring and an air spring needs to be about the same at full compression or it couldn’t hold the vehicle up…it’s just that a steel spring is likely a tit stiffer on initial, small impacts than an air suspension which is about as progressive as you can make a spring. A steel spring can only be wound to approximate a progressive spring rate.

Where you live, and the quality of the roads could sway you one way or the other…air springs will absorb smaller bumps better than a steel spring. Keep in mind that the tires are also part of the vehicle’s overall spring rate, so shorter sidewalls on larger wheels will tend to transmit more of the impact to the chassis than a smaller wheel.

The bigger problem with air springs is their spring rate drops as their ride height does. So if you want to drive sporty, air springs the more you lower the worse they are for the job. They mitigate this using more aggressive shock rates, but at the end of the day, air springs aren't sporty.

Air springs all leak eventually. Probably not within a 3 year lease or a 4 year ownership, but at year 6 or 8 or 10 or whatever they'll eventually leak and need replaced, steel springs don't leak and fail.

[TurtleBoy]

Originally Posted by BlkGS

The bigger problem with air springs is their spring rate drops as their ride height does. So if you want to drive sporty, air springs the more you lower the worse they are for the job. They mitigate this using more aggressive shock rates, but at the end of the day, air springs aren't sporty.

All a matter of perception. The air suspension can be very sporty when lowered, depends on who is driving.

[BlkGS]

Originally Posted by TurtleBoy

All a matter of perception. The air suspension can be very sporty when lowered, depends on who is driving.

It will never be as sporty as a steel spring setup. It simply lacks the spring rate at lower ride heights.

[TurtleBoy]

Originally Posted by BlkGS

It will never be as sporty as a steel spring setup. It simply lacks the spring rate at lower ride heights.

That is not the away the air suspension works as it is progressive. The spring rate actually increases as the ride is lowered. That is one of the reasons why Sport mode lowers the vehicle.

[BlkGS]

Originally Posted by TurtleBoy

That is not the away the air suspension works as it is progressive. The spring rate actually increases as the ride is lowered. That is one of the reasons why Sport mode lowers the vehicle.

That's not how air springs work. It's like an air mattress, if you fill it up less, it's softer and doesn't fill up all the way. If you fill it up all the way, the mattress is taller, and stiffer.

You cannot make a volume of air stiffer when it's at a lower pressure. That's not how air pressure works.

[TurtleBoy]

Originally Posted by BlkGS

That's not how air springs work. It's like an air mattress, if you fill it up less, it's softer and doesn't fill up all the way. If you fill it up all the way, the mattress is taller, and stiffer.

You cannot make a volume of air stiffer when it's at a lower pressure. That's not how air pressure works.

No, that is not how they work. As mentioned, they are progressive so the less air the higher the spring rate/stiffer they become.

[BlkGS]

Originally Posted by TurtleBoy

No, that is not how they work. As mentioned, they are progressive so the less air the higher the spring rate/stiffer they become.

Alright then, explain how they work? Because that would be the exact opposite of how every other air spring ever used works, and defies physics.

There may be a clever way to make it work. An embedded steel spring that sets a minimum spring rate for example. Maybe multiple chambers that can hold different pressure levels. But a standard air bag spring has a higher spring rate the more air you put in it as the vehicle raises.

[TurtleBoy]

Originally Posted by BlkGS

Alright then, explain how they work? Because that would be the exact opposite of how every other air spring ever used works, and defies physics.

There may be a clever way to make it work. An embedded steel spring that sets a minimum spring rate for example. Maybe multiple chambers that can hold different pressure levels. But a standard air bag spring has a higher spring rate the more air you put in it as the vehicle raises.

No, actually I think all air springs operate that way, at least the ones I have seen. The less air the stiffer they become. This may help you. https://www.motortrend.com/how-to/1506-air-suspension-how-it-works/

[vinibabs]

I have the MSport standard springs on my M50i.

Combined with the 22's, potholes feel terrible in the car. Air suspension is worth it IMO. (Chicago is where I drive)

I feel like I get bounced around over expansion gaps, etc.

[MotoWPK]

Originally Posted by BlkGS

Alright then, explain how they work? Because that would be the exact opposite of how every other air spring ever used works, and defies physics.

There may be a clever way to make it work. An embedded steel spring that sets a minimum spring rate for example. Maybe multiple chambers that can hold different pressure levels. But a standard air bag spring has a higher spring rate the more air you put in it as the vehicle raises.

The spring effect of an air spring is the result of compression of the trapped air volume resulting in a pressure rise (on compression, a pressure reduction on rebound). When the vehicle is lowered, the volume of the trapped air volume is reduced, therefore, for any given deflection of the suspension, the corresponding volume change caused by that deflection will be a greater proportion of the trapped air volume resulting in a greater pressure rise (on compression). Greater pressure rise, greater spring effect or increased spring rate.

From data I've been able to glean of the X5's air suspension, I've calculated the 20 mm reduced ride height in sport will result in an increased spring rate on the order 15% to 20%.

Your statement; "But a standard air bag spring has a higher spring rate the more air you put in it as the vehicle raises." implies there is a change in spring rate due to the volume of air in the spring, but this is incorrect. It is not the volume of air in the spring, but the relative change in volume for a given spring deflection; i.e. the higher the ratio of 'volume change due to deflection' divided by 'the original volume', the greater the pressure rise due to that deflection.

Also, and I don't know that this is what you were implying, but there is a fairly common misconception that the higher ride height is due to an increase in pressure in the spring. In reality, the pressure is unchanged, being what is needed to offset the weight of the vehicle, which does not change with ride height. The ride height changes because of a change in air volume.

[jad03060]

As the vehicle rides lower, the total volume available to compress gets smaller, so as it continues to get compressed, the pressure rises more with a smaller increment of height change.

The biggest advantage to air suspension is their progressive spring rate curve that can only be approximated with a steel spring and the softer initial impact.

FWIW, steel springs can fail as well, and the higher the load and the bumpier the roads, fatigue which causes their spring rate to change. At least with an air spring…it stays the same until it dies, not continually, slowly degrading over distance traveled with a steel spring.

Which you prefer, fine by me, and not all brands and models function the same. There are some characteristics that will be similar depending on the implementation, but lots of opportunities to tweak it.

[BeEmVee]

Originally Posted by PunsGalore

Hi all,

I am wondering if ordering air suspension on the 25' X5 xDrive40i would be worth it? Air suspensions have always scared me a little, but open to hearing your thoughts! Will most likely go without due to cost savings and the extra piece of mind

Thanks

Not sure if you’re aware, but you will only be able to select the standard design in the 40i and not M Sport if you opt for the air suspension. Just something to weigh aesthetics vs features.