Where to find torsional rigidity values?

[clowesy]

Anybody out there have any idea where I can find some reliable values for the torsional rigidity of any coupe or saloon vs its convertible sibling? There are plenty of figures for various cars all over the internet but nothing reliable I can quote for a university report. I've checked quite a few manufacturer launch packs, spec sheets and so on but found nothing. Any ideas?

[TooMany2cvs]

clowesy said:

Anybody out there have any idea where I can find some reliable values for the torsional rigidity of any coupe or saloon vs its convertible sibling? There are plenty of figures for various cars all over the internet but nothing reliable I can quote for a university report. I've checked quite a few manufacturer launch packs, spec sheets and so on but found nothing. Any ideas?

It's not the kind of information they generally shove in press-packs, unless they think they've got something to shout about and want to sell the car as a bit "techie".

Mebbe ring the importer and ask to speak to somebody in technical customer service? If they don't have it, then you're going to be out of luck short of getting hold of a bodyshell and a torsional-testing rig...

[MintSprint]

clowesy said:

...reliable values for the torsional rigidity of any coupe or saloon vs its convertible sibling?

I would be nothing short of astonished if you could find manufacturer's figures for a direct comparison between convertible and coupe/saloon versions of the same car.

They're hardly going to tell people voluntarily that they'll be paying a large premium for the privilege of driving something with a much floppier chassis.

[GetCarter]

clowesy said:

Anybody out there have any idea where I can find some reliable values for the torsional rigidity of any coupe or saloon vs its convertible sibling?

I'll just ask the wife...

[davebem]

Here are some figures compiled from another forum that maybe of some use. If found them when I was researching why alfa romeo 159s are so heavy! The Alfas could be used for your report as they are based on the same platform.

Alfa 159 - 31.400Nm/degree
Alfa Brera - 28,000 Nm/deg
Alfa Spider - 13,000 Nm/deg
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28.100 Nm/degree
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati QP - 18.000 nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19.600 Nm/deg
Ford Focus 5d 17.900 Nm/deg

Edited by davebem on Tuesday 18th November 20:32

[clowesy]

Thanks for that. I've seen various lists on different forums but I can't really quote figures from a forum unless they themselves have a credible source. I have however just found a review on here of from 2006 of the Z4 M coupe which reveals figures for the torsional rigidity vs the original convertible which should be alright. I also seem to remember an old a Top Gear episode where Hammond drives an Aston Martin convertible of some description (DB9 perhaps) and compares it to the coupe so I'm trying to find that.

[MintSprint]

davebem said:

Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg

BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Convertible 10,500 Nm/deg

BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg

Audi TT Coupe: 19,000 Nm/deg
Audi TT: 10,000 Nm/deg

Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg

Edited down to relevant pairs... that's interesting!

And I know it's hardly a big enough sample to be representative, but there's not that much variation in the comparative differences: broadly speaking, it suggests that the convertible version is typically around half as stiff as the coupe/saloon? That's actually even worse than I was expecting...

Some of the data is a bit questionable, though: why is the Lotus Elise 111S 1000 Nm/deg stiffer than a standard Elise, when they have identical chassis?

[Megaflow]

There is some very questionable data in that list. McLaren F1 vs Ferrari F50, both carbon fibre, one with a roof and one without, but the Ferrari is over twice as stiff as the McLaren?

Apparently an Alfa Spider and BMW Z4 are nearly as stiff as an F1. The Buggati Veyron is 50% stiffer than the next car in the list, which is Rolls Royce.

Edited by Megaflow on Tuesday 18th November 20:49

[clowesy]

Just found that Koenigsegg list figures for the Agera R on their website as 65,000Nm/degree which is just phenomenal.

[Debaser]

davebem said:

Here are some figures compiled from another forum that maybe of some use. If found them when I was researching why alfa romeo 159s are so heavy! The Alfas could be used for your report as they are based on the same platform.

Alfa 159 - 31.400Nm/degree
Alfa Brera - 28,000 Nm/deg
Alfa Spider - 13,000 Nm/deg
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28.100 Nm/degree
Lambo Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati QP - 18.000 nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19.600 Nm/deg
Ford Focus 5d 17.900 Nm/deg

Edited by davebem on Tuesday 18th November 20:32

A few of those don't look right to me.

[Swanny87]

TooMany2cvs said:

It's not the kind of information they generally shove in press-packs, unless they think they've got something to shout about and want to sell the car as a bit "techie".

Mebbe ring the importer and ask to speak to somebody in technical customer service? If they don't have it, then you're going to be out of luck short of getting hold of a bodyshell and a torsional-testing rig...

Do you mean to say that there are testing facilities where the manufacturers send pre-prod body shells and twist the living st out of them on a fk off big rotisserie device? I thought it would have been calculated in some form of CAD/CAM software.

[Debaser]

Swanny87 said:

Do you mean to say that there are testing facilities where the manufacturers send pre-prod body shells and twist the living st out of them on a fk off big rotisserie device? I thought it would have been calculated in some form of CAD/CAM software.

They'll need to correlate the CAE results somehow.

[Swanny87]

Debaser said:

Swanny87 said:

Do you mean to say that there are testing facilities where the manufacturers send pre-prod body shells and twist the living st out of them on a fk off big rotisserie device? I thought it would have been calculated in some form of CAD/CAM software.

They'll need to correlate the CAE results somehow.

Then the only sensible question that can follow is are there any videos of such testing? Before people jump the gun; I've already had a google and could only find: a video of some new jeeps going up a ramp, some blokes jumping up and down on a metal girder supported by wood...

[Sway]

Fairly sure it's part of the Australian Type Approval test, which should be available publicly...

Only say this as the figures for my GTM came from a chap who imported one and had to pay for it to be tested.

[mcford]

If you're compiling statistics from different sources you need to know if you're comparing like for like. Are these values just for the body or are they for a body with glass fitted?