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BMW M5 F90 (2018+) General Forums F90 M5 General Forum    Why no active anti-roll bars and rear steering on M5?

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      07-31-2018, 08:34 PM   #1
visualguy
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Why no active anti-roll bars and rear steering on M5?

Does anyone have any insight into the reasons BMW never offers active anti-roll bars (ARS - Active Roll Stabilization) and rear wheel steering (IAS - Integral Active Steering) on the M5? They do offer these on some other 5-series cars, such as the M550i.

Porsche offers these as options on some of their sports cars, so these can't be inherently bad for sporty driving, or weigh too much, or such thing...

Aren't active roll bars superior to passive ones in achieving a better balance between comfort and grip when the car isn't turning and roll stabilization and grip when the car is turning?

I started thinking about this when noticing that they offer the base M5 with softer anti-roll bars, and the M5 Competition with stiffer anti-roll bars. Wouldn't having active anti-roll bars instead be better?

Any suspension experts here? I'm wondering why BMW's and Porsche's philosophies diverge on this.
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      07-31-2018, 11:17 PM   #2
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Originally Posted by visualguy View Post
Does anyone have any insight into the reasons BMW never offers active anti-roll bars (ARS - Active Roll Stabilization) and rear wheel steering (IAS - Integral Active Steering) on the M5? They do offer these on some other 5-series cars, such as the M550i.

Porsche offers these as options on some of their sports cars, so these can't be inherently bad for sporty driving, or weigh too much, or such thing...

Aren't active roll bars superior to passive ones in achieving a better balance between comfort and grip when the car isn't turning and roll stabilization and grip when the car is turning?

I started thinking about this when noticing that they offer the base M5 with softer anti-roll bars, and the M5 Competition with stiffer anti-roll bars. Wouldn't having active anti-roll bars instead be better?

Any suspension experts here? I'm wondering why BMW's and Porsche's philosophies diverge on this.
For active steering I believe its the tradeoff of extra weight. The Porsche actually needs it. It weighs quite a bit more.

Their philosophy right now is that were at a time when their engineering abilities can outperform the advantage of less weight.

The active roll bars are the same thing with the weight. I loved having that on a Cayenne Turbo, but this isnt a Cayenne Turbo. Those extra mechanicals and the weight associated with them also gave driving it an artificial feel. The BMW is more engaging and more fun or predictable as a result.
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      07-31-2018, 11:57 PM   #3
visualguy
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Originally Posted by M5speed View Post
For active steering I believe its the tradeoff of extra weight. The Porsche actually needs it. It weighs quite a bit more.

Their philosophy right now is that were at a time when their engineering abilities can outperform the advantage of less weight.

The active roll bars are the same thing with the weight. I loved having that on a Cayenne Turbo, but this isnt a Cayenne Turbo. Those extra mechanicals and the weight associated with them also gave driving it an artificial feel. The BMW is more engaging and more fun or predictable as a result.
Porsche offers these features even on the 911, not just their bigger cars. The benefits seem very compelling. Take a look at this:

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      08-01-2018, 06:44 AM   #4
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Originally Posted by visualguy View Post
Quote:
Originally Posted by M5speed View Post
For active steering I believe its the tradeoff of extra weight. The Porsche actually needs it. It weighs quite a bit more.

Their philosophy right now is that were at a time when their engineering abilities can outperform the advantage of less weight.

The active roll bars are the same thing with the weight. I loved having that on a Cayenne Turbo, but this isnt a Cayenne Turbo. Those extra mechanicals and the weight associated with them also gave driving it an artificial feel. The BMW is more engaging and more fun or predictable as a result.
Porsche offers these features even on the 911, not just their bigger cars. The benefits seem very compelling. Take a look at this:

After test driving both, the difference really did seem negligible. To me the Panamera seemed bulky, big from behind the wheel, similar to an RS7 in size with better handling. The 911 turbo s seemed too small. Handling though was the biggest strong point on both. But for an extra 100 grand??? The price went from $120k to $200-$229k. It seems with the extra hardware came an almost unbelievable price tag.

If the M5 hadn't come along, I was seriously still considering the Panamera turbo, but the wife is getting '19 Cayenne Turbo with the active roll bars. You'd be surprised though at how many people buy Porches and dont choose that option. I had asked. The sales guy mentioned usually only gear-heads were the ones getting it.

If they do make such a difference, then my first thoughts are they decided to go for more of a traditional approach and save the $$$.
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      08-01-2018, 11:23 AM   #5
visualguy
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I don't think it's $$$ because these features are only $3,600 on the M550i, which is about the price of the full leather on the M5...
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      08-01-2018, 12:27 PM   #6
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I see your point then.
Either way, in 2wd mode, Ive found my own version of rear wheel steering - by going ass out sideways around turns.

Maybe thats why.
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      08-01-2018, 01:00 PM   #7
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The M5 doesn't need any of these features. The chassis is so well balanced and well tuned, it would just complexity without much benefit. The active torque vectoring and 4WD the car has, coped to the tricky rear and front diff, already do the trick. Rear steering although great can remove feel, and the same is true for active roll bars.

Another possibility is that BMW simply left it out of this gen to find something to add on the next
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      08-01-2018, 02:01 PM   #8
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Quote:
Originally Posted by CarlosM4 View Post
The M5 doesn't need any of these features. The chassis is so well balanced and well tuned, it would just complexity without much benefit. The active torque vectoring and 4WD the car has, coped to the tricky rear and front diff, already do the trick. Rear steering although great can remove feel, and the same is true for active roll bars.

Another possibility is that BMW simply left it out of this gen to find something to add on the next
Not sure about the feel part - the Porsche with these features seems to feel great...

Regarding not needing it in the M5... There's always a trade-off with passive sway bars. If you make them stiff, you sacrifice comfort and grip on rough roads when going straight. If you make them softer, you sacrifice handling in turns. BMW ended up offering two flavors of the M5 with different levels of stiffness for the sway bars, each of them with its own sacrifices. Instead, why not have active sway bars which enable you to have the best of both and avoid the sacrifices?

Rear-wheel steering is of course another feature that you can't really replace in some other way.

I wish journalists asked these types of questions when interviewing people from the M division, but they never ask such questions for some reason...
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