Quote:
Originally Posted by Max Well
Quote:
Originally Posted by mfurse
Like putting running shoes on a hippo ... a carbon roof on an SUV is hardly going to make a difference to the already high centre of gravity is it now?
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Would disagree. It is exactly on the higher platform SUV/SAV where it should have the most relative improvement (certainly when compared with the smaller coupes and sedans where they are already low and therefore have a shorter lever arm length for the moment calculation). And your analogy seems upside down, for running shoes would be the tires? Perhaps a better one would be comparing two camels, one carrying a heavy cargo load and rider, and the other one walking behind without any load up top. Seems intuitively obvious the one without the load would have better maneuverability and stability during fast runs on uneven surfaces. For a more detailed discussion - https://x3.xbimmers.com/forums/showthread.php?t=1564722
Quote:
Originally Posted by mfurse
Agree a solid roof would be lighter on any car but the M3 was genuinely lighter than its contemporaries all up and the carbon roof was standard to assist in achieving that goal (as well as it being marketing of course - not sure how many mortals could feel the difference the roof makes in the M3).
The X3 M has been unfortunately engineered to be heavier than all its contemporaries. That seems like a massive oversight to me from BMW to enter a category for the first time with a good looking SUV, proper M engineering and end up heavier than nearly everyone - even the Merc GLC63S which is equiped with more cylinders, air suspension and is more plush in general.
All that weight means needing a suspension setup to contain the mass riding up high and rather predictably that has spoiled the ride somewhat. Reducing over 2000 kg's worth of SUV by single digits removing the sunroof... like I said ... hardly worth it in reality but each to their own.
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Not trying to dissect your discussion, but the actual DIN numbers don't support it's 'heavier than all its contemporaries', and the differences that are there are subtle c/w total vehicle weight (less than 150 lbs) - https://x3.xbimmers.com/forums/showthread.php?t=1624835 . Especially considering the ones that are slightly lower offer far less cargo volume, even to the point of making them unattractive comparisons to the X3M and SVR on that point alone.
And as discussed in the CFRP thread, removing the sunroof is not removing 'by single digits' (even if you are discussing in metric terms), and because that weight is at the very top of the vehicle, it adds the most to the upper moment (length of arm x weight). And suspect this is the reason BMW deletes the sunroof when one orders the M Driver's package and increased speed limiter from 155 mph to 177 mph (more stable platform providing a lower CG and SSF to further reduce rollover potential).
One can make the argument that a Driver wouldn't be able to notice this upper weight difference (and many have written such over the years), but until formal testing is done in SUV/SAV vehicles (and doubt it will be), we won't know if the CG and SSF (and skidpad and cones times) improve, and if so, to what extent. Personally, that would be interesting to see purely from a Physics/Engineering standpoint, but given that these 'trucks' shouldn't be performance-oriented in the first place, doubt it'll ever happen. 
Apologies to Imran for going off-topic to his thread. |
I guess I wasn't going for the overly literal meaning of the hippo quote - more a hippo is a big animal and giving it performance shoes wouldn't make it go quicker
Point taken though - removing weight from the roof would do something but in the greater scheme of things it's so little gain for, as you say, such a heavy "truck" that is difficult to make performance oriented in the first place.
I guess I should be happy we live in times that you can choose to buy an M car in pretty much any size, format and weight you like!