torsional rigidity?

[gee-m-w]

BMW has been touting lots of features about the new M3. I haven't heard a word about chassis stiffness, as measured by torsional rigidity. The car is clearly lighter, but it may not be stiffer over the outgoing model. Do we have any data or claims?

[swamp2]

Originally Posted by gee-m-w

BMW has been touting lots of features about the new M3. I haven't heard a word about chassis stiffness, as measured by torsional rigidity. The car is clearly lighter, but it may not be stiffer over the outgoing model. Do we have any data or claims?

It nearly always (if not always) progresses with a new chassis and consequently improves handling.

There is a list here. But some of the data looks flawed i.e. E46 compared to E30 M3, as well as incorrect units on some figures. No M cars are listed except the E30 M3. M cars also are always more stiff torsionally than their non-M counterparts due to increased chassis bracing, typically either on the body "pan" area or on suspension mounting points. Stiffer subframes could contribute as well.

[gee-m-w]

I thought this car has no rear subframe. I think the Roundel article mentioned they just bolted the axle right onto the car.

[BlackLight]

Originally Posted by gee-m-w

I thought this car has no rear subframe. I think the Roundel article mentioned they just bolted the axle right onto the car.

I'm not sure that is possible.
What the article said was that the rear subframe was ridgidly bolted to the chassis, vs flexible connectors in other 3/4 series.

[Needsdecaf]

Originally Posted by BlackLight

I'm not sure that is possible.
What the article said was that the rear subframe was ridgidly bolted to the chassis, vs flexible connectors in other 3/4 series.

Correct, I believe quote also stated that "because of this, the subframe also acts as a chassis stiffening brace". Paraphrasing.

[Jason]

Per our official info thread: http://f80.bimmerpost.com/forums/sho...d.php?t=923203

"Rear axle subframe bolted directly to body structure (bolted joints between the axle subframe and the body sills, without use of elastic rubber elements)."

[JoeFromPA]

The f30 is stiffer than the e90 to a notable degree, so I'd expect it here as well.

In regards to the rear diff, to confirm: The diff is mounted to the subframe via flexible bushing. The subframe is directly mounted to the chassis with no vibration-absorbing bushings, and supposedly this acts a very nice stiffening to the rear of the vehicle.

[Needsdecaf]

Originally Posted by JoeFromPA

The f30 is stiffer than the e90 to a notable degree, so I'd expect it here as well.

In regards to the rear diff, to confirm: The diff is mounted to the subframe via flexible bushing. The subframe is directly mounted to the chassis with no vibration-absorbing bushings, and supposedly this acts a very nice stiffening to the rear of the vehicle.

Sounded familiar to me, so I looked up where I had read this. You and I must have been recently reading Satch's article in Roundel:

"But wait: suppose - said the M engineers as they designed the current M5 and M6 - we mounted the carrier assembly directly to the body? Would that not stiffen the chassis? And then, with this cradle assembly secure, we could isolate the differential within this structure by the means of some kinelastic bushings that would securely hold it in place, minimizing noise and vibration from the active M Differential. That's another page from the M5 book of handling; the result is a chassis so stiff that M GmbH VP Albert Bierman says 'we can say now that the body is actually part of the car's suspension.'"

[JoeFromPA]

Originally Posted by Needsdecaf

Sounded familiar to me, so I looked up where I had read this. You and I must have been recently reading Satch's article in Roundel:

"But wait: suppose - said the M engineers as they designed the current M5 and M6 - we mounted the carrier assembly directly to the body? Would that not stiffen the chassis? And then, with this cradle assembly secure, we could isolate the differential within this structure by the means of some kinelastic bushings that would securely hold it in place, minimizing noise and vibration from the active M Differential. That's another page from the M5 book of handling; the result is a chassis so stiff that M GmbH VP Albert Bierman says 'we can say now that the body is actually part of the car's suspension.'"

Good ol Satch. I vascillate between absolutely loving the man and his writing and rolling my eyes at him.

[Needsdecaf]

Originally Posted by JoeFromPA

Good ol Satch. I vascillate between absolutely loving the man and his writing and rolling my eyes at him.

He CAN be pretty thick at times....

[JoeFromPA]

Btw, I find the rigidity of the f30 - even in 328xi trim - to be one of the absolute unsung heroic parts of the most recent 3-series. That chassis is significantly stiffer than my e39 m5, for example, to the point where I really had a hard time detecting any body flex. "Bank vault" comes to mind.

It also feels a lot better than my e60's chassis, a lot more responsive.

IDK, just really excited to see what M did with the chassis of the f30. Before recent years and more and more M3 owners becoming power-chasers and quarter mile lovers, M's magic was always in chassis, suspension, steering, braking, and cooling as well as fun-to-drive engines. I think that's where their expertise still is....

[Needsdecaf]

Originally Posted by JoeFromPA

Btw, I find the rigidity of the f30 - even in 328xi trim - to be one of the absolute unsung heroic parts of the most recent 3-series. That chassis is significantly stiffer than my e39 m5, for example, to the point where I really had a hard time detecting any body flex. "Bank vault" comes to mind.

It also feels a lot better than my e60's chassis, a lot more responsive.

IDK, just really excited to see what M did with the chassis of the f30. Before recent years and more and more M3 owners becoming power-chasers and quarter mile lovers, M's magic was always in chassis, suspension, steering, braking, and cooling as well as fun-to-drive engines. I think that's where their expertise still is....

I am also really excited. I think this car is going to rival a 911 in terms of handling response.

I definitely moan the loss of the sound of the S65. But willing to give that up for better chassis and much better interior.

[JoeFromPA]

Sound to me is the #1 thing that gets you excited as you approach a vehicle, and the #1 thing that loses interest over-time. Granted, I've never owned an S65. But I've owned an S62, including with a tubi rumore exhaust.

So I guess to me I don't dread going to an inline six turbo which I've heard plenty of good sounding motors with that setup.

[Needsdecaf]

Originally Posted by JoeFromPA

Sound to me is the #1 thing that gets you excited as you approach a vehicle, and the #1 thing that loses interest over-time. Granted, I've never owned an S65. But I've owned an S62, including with a tubi rumore exhaust.

So I guess to me I don't dread going to an inline six turbo which I've heard plenty of good sounding motors with that setup.

Not sure I agree there. My Acura MDX with VTEC has a pretty fun intake stonk when the intake flap opens up at 4,500 RPM. I have yet to tire of whacking that bad boy open and I've owned it for over 6 years. And that's just a silly Honda V6.

The S65's intake is pretty special. The S55 should be less so, but I don't see it as a deal breaker.

[GregW / Oregon]

Some eyewash, but no data:

[JoeFromPA]

Yep, intelligent people are known to disagree. I'm assuming you are intelligent; I'm assuming I am too.

I owned a 2006 Honda civic SI I put almost 120k miles on. Loved the cam changeover at 5800 rpms but it wasn't necessarily something magical to me. My s62/e39 m5 sounds great but by 5000 rpms things are moving so quickly my senses can't fully comprehend the sound the machine is making

[Wolfinwolfsclothing]

Originally Posted by Needsdecaf

I am also really excited. I think this car is going to rival a 911 in terms of handling response.

I definitely moan the loss of the sound of the S65. But willing to give that up for better chassis and much better interior.

Don't see it matching the 991 or rivaling it in any way. There isn't a better car out there than the 991 in terms of chassis response and suspension set up/geometry. Only car that comes close is the 458 Italia and that's a big maybe. And that's putting the 458 vs a base/991S. The GT3 in sure is in another ball game altogether from everything.

I too would rather have handling over speed, but too many M drivers have turned to wanting pure outright speed rather than handling. The new m5/6 handle unlike an M car and are basically numb sleighs. Sad when merc and Audi are beating the m5 handily in compares and the panamera is also a much better drivers car. I just hope they can dial it up a little more handling wise over the e9x m3 which was good. I worry about BMWS eps and truly want to see a real weight figure.

[Needsdecaf]

Originally Posted by JoeFromPA

Yep, intelligent people are known to disagree. I'm assuming you are intelligent; I'm assuming I am too.

I owned a 2006 Honda civic SI I put almost 120k miles on. Loved the cam changeover at 5800 rpms but it wasn't necessarily something magical to me. My s62/e39 m5 sounds great but by 5000 rpms things are moving so quickly my senses can't fully comprehend the sound the machine is making

Lol, that's probably it. The MDX is so slow that the sound is the only thing getting me excited.

[Needsdecaf]

Originally Posted by Wolfinwolfsclothing

Don't see it matching the 991 or rivaling it in any way. There isn't a better car out there than the 991 in terms of chassis response and suspension set up/geometry. Only car that comes close is the 458 Italia and that's a big maybe. And that's putting the 458 vs a base/991S. The GT3 in sure is in another ball game altogether from everything.

I too would rather have handling over speed, but too many M drivers have turned to wanting pure outright speed rather than handling. The new m5/6 handle unlike an M car and are basically numb sleighs. Sad when merc and Audi are beating the m5 handily in compares and the panamera is also a much better drivers car. I just hope they can dial it up a little more handling wise over the e9x m3 which was good. I worry about BMWS eps and truly want to see a real weight figure.

We shall see, but I disagree. I think it WILL equal the 991. Don't forget, the 991 has EPS as well, and the M Engineers have been gunning to make this the best EPS on the market. I have a feeling they will have succeeded.

Then again, I could be all wet.


As far as weight goes, the figure is there in black and white.

[Wolfinwolfsclothing]

Originally Posted by Needsdecaf

We shall see, but I disagree. I think it WILL equal the 991. Don't forget, the 991 has EPS as well, and the M Engineers have been gunning to make this the best EPS on the market. I have a feeling they will have succeeded.

Then again, I could be all wet.


As far as weight goes, the figure is there in black and white.

I still don't see it happening especially when porsche is the absolute standard and just raised the bar even higher with the GT3 which is flat out the best eps and doubtful it will be matched any time soon. But as far an handling response, the 911 is simply untouchable at this point and only beaten by higher range 911s. When the m3 wins two best drivers car comparos and car of the year like the 911 has, then we can talk. Don't see that happening in the slightest.
Also lets see what the m3 can get on the ring. 991S ran 7:37, simply don't see the m3 coming within 10 sec on that which is an awfully long time on that track.

[GregW / Oregon]

Originally Posted by Wolfinwolfsclothing

Don't see it matching the 991 or rivaling it in any way. There isn't a better car out there than the 991 in terms of chassis response and suspension set up/geometry. Only car that comes close is the 458 Italia and that's a big maybe. And that's putting the 458 vs a base/991S.

I thought the general feeling was the Cayman was actually better than the 911 as far as handling?

[gee-m-w]

Originally Posted by JoeFromPA

Yep, intelligent people are known to disagree. I'm assuming you are intelligent; I'm assuming I am too.

You just went Dunning Kruger on us.

http://en.wikipedia.org/wiki/Dunning...3Kruger_effect