Torsional stiffness or lack thereof, some numbers

Dino D

Dino D

Zorg Guru (V)
British Zeds
Joined
Mar 28, 2014
Points
176
Location
Kent
Model of Z
2.8 Manual
Came across some stats here, big list of most cars: http://blogs.youwheel.com/2014/04/25/car-body-torsional-rigidity-a-comprehensive-list/

Some highlights:
All values’ unit is in Nm/deg.
BMW E36 Z3 5,600
BMW E46 Sedan (w/folding seats) 13,000
BMW E46 Sedan (w/o folding seats) 18,000
BMW E85 Z4 16,000
BMW E85 Z4 Coupe 32,000
BMW E85 Z4 M 16,000
BMW E85 Z4 M Coupe 32,000

A Z4 is nearly 3 times stiffer than a Z3 and as stiff as an e46 M3.
Guess you have an answer there as to which car benefits from strut braces or not!

Mazda MX-5 (NA 1st-gen, NB 2nd-gen) 6000
Mazda MX-5 (NC 3rd-gen) 8800
Audi TT Roadster Mk1 10,000
 
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Dino D said:
Came across some stats here, big list of most cars: http://blogs.youwheel.com/2014/04/25/car-body-torsional-rigidity-a-comprehensive-list/

Some highlights:
All values’ unit is in Nm/deg.
BMW E36 Z3 5,600
BMW E46 Sedan (w/folding seats) 13,000
BMW E46 Sedan (w/o folding seats) 18,000
BMW E85 Z4 16,000
BMW E85 Z4 Coupe 32,000
BMW E85 Z4 M 16,000
BMW E85 Z4 M Coupe 32,000

A Z4 is nearly 3 times stiffer than a Z3 and as stiff as an e46 M3.
Guess you have an answer there as to which car benefits from strut braces or not!
Click to expand...
Interesting numbers. Amazed at the difference between the Z3 & Z4.
 
Dino D said:
Came across some stats here, big list of most cars: http://blogs.youwheel.com/2014/04/25/car-body-torsional-rigidity-a-comprehensive-list/

Some highlights:
All values’ unit is in Nm/deg.
BMW E36 Z3 5,600
BMW E46 Sedan (w/folding seats) 13,000
BMW E46 Sedan (w/o folding seats) 18,000
BMW E85 Z4 16,000
BMW E85 Z4 Coupe 32,000
BMW E85 Z4 M 16,000
BMW E85 Z4 M Coupe 32,000

A Z4 is nearly 3 times stiffer than a Z3 and as stiff as an e46 M3.
Guess you have an answer there as to which car benefits from strut braces or not!
Click to expand...
Interesting info, thanks.
 
5harp3y said:
thats what a decade of material and chassis tech can do!
Click to expand...

Unfortunately it's speaks more about lazy engineering by BMW.
The MK1 Audi TT is double as stiff...

I've added the MX5 up here too and even that manages to beat the Z3 but not much. Poor show by BMW but I still love mine to bits.
Anyone can drive a properly stiff car but it takes hair on your chest to handle a wobbly Z3 (or so I like to think anyway!)
 
5th from bottom on that link, wouldn't swap my baby though.
 
I crapped myself a few times on spirited Dutch runs nearly going through fences and in to canals in my M44 trying to keep up with the big boys who had sorted their undercarriage.
 
The mx5 is miles better to drive than the z3 too

But the z3 had a heavy engine up front and a heavy rear end too. Makes for quite a wobbly car.
 
So I'm not an expert on torsional stiffness but the numbers do sum up what the car feels like. Is this measured solely in the chassis or do things like upgraded suspension that will improve all round handling also improve the torsional stiffness numbers?
 
it's an old car, just like my old bikes! left miles behind by modern technology
BUT, it's full of "character"

Hell, BMW say they will no longer be producing cars with internal combustion engines within the next 8 years! then it will be really old lol
 
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We are basically driving a wobbly jelly compared to a lot of other cars, not too many on that list lower than the Z3, makes perfect sense why the hardtop makes such a difference to the handling characteristics of the car.
 
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