Stiffness matters :~

[MGJohn]

for both sexes ...



How stiff is your'n....?
..

[T84]

Is this just for droptops?

[renrut]

I think the point is that chopping the roof off will always end in a compromise in stiffness. I give it maybe 5 mins before someone is harping on about how you don't want too much stiffness or that their roofless wonder is actually stiffer than the roofed variety without mentioning it has about 100kg of bracing bars added...

[EDLT]

Clearly it doesn't matter, because most people seem to think that the Mk1 MX5 is better to drive than the current one. So its about as relevant as hp/litre or torque/weight or any other statistic that only exists for the sake of internet arguments.

[Daston]

my car is just as stiff as a roofed version......oh wait space frame chassis :P

[5lab]

stiffness (fnarr) is more of an issue these days as cars generally have stiffer, shorter suspension travel, which in turn puts more loads through the chassis of the car. I'd be willing to be my na mx5 has more bodyroll then a new fiesta (say), and probably has less need to be stiff as a result?

[MGJohn]

5lab said:

stiffness (fnarr) is more of an issue these days as cars generally have stiffer, shorter suspension travel, which in turn puts more loads through the chassis of the car. I'd be willing to be my na mx5 has more bodyroll then a new fiesta (say), and probably has less need to be stiff as a result?

That is certainly true of my MG ZS. If I jack up the car using a front jacking point, as soon as I've got a front wheel clear of the ground after a few pumps on the jack handle, I notice there's daylight under the rear tyre too. Checking the door opening and shutting shows nil flexing ~ I find that kind of thing reassuring.

The shorter and stiffer suspension travel on my ZS is of course a large part of the reasons this otherwise quite ordinary production car handles so well.
..
.
Of course stiffness matters ... stands to reason,,,,
..

[rufusgti]

It is interesting seeing the differences in those cars. But notice they are all purpose built roadsters. designed not to have a structural roof. I'd really like to see the difference in stiffness between both these cars and convertibles that have been designed based on a standard body type. Like m3 cab/hardtop, mk4 golf cab, talbot samba cab, saab cabs. i think some of those would be interesting.

[The Wookie]

rufusgti said:

It is interesting seeing the differences in those cars. But notice they are all purpose built roadsters. designed not to have a structural roof. I'd really like to see the difference in stiffness between both these cars and convertibles that have been designed based on a standard body type. Like m3 cab/hardtop, mk4 golf cab, talbot samba cab, saab cabs. i think some of those would be interesting.

Something that may interest you is the quoted figure I've found for the Z4 Coupe is 32,000 Nm/deg, compared to the convertible's 14,500.

So the coupe version has double the stiffness.

Despite the unfair comparison against convertibles, that 24,000Nm/degree figure for the ZT is fairly impressive by itself for that era.... I'm guessing, instead of a calibrated machine, Longbridge measured it using the industry standard test of weighing an apprentice and getting him to hang off a 10 foot scaffolding pole attached across the back axle, and measuring the deflection with a spirit level

Edited by The Wookie on Monday 20th December 14:42

[John D.]

Cor! Look how stiff my Elise is

[CaptainSlow]

This graphic is a repost that gets trotted out everytime there is a MX5 v MG(T)F debate. You can guess which side posts it.

[kambites]

Correct me if I'm wrong, but isn't absolute stiffness rather irrelevant? Surely it's stiffness to weight ratio that's important?

I think that's why the mk1 MX5 doesn't feel particularly floppy compared to the mk3.

Edited by kambites on Monday 20th December 14:55

[Petrolhead_Rich]

That Chart looks awfully bias towards Rovers, Loving the way the ZT saloon is compared to a load of roadsters

[Gizmo!]

Love that comment that the MGF "remains competitive even now"... when it's 10% less stiff than the MX5 Mk3?

Wonder if the Mk1 MX5 was the earlier one or the later model with standard rear strut...

[kambites]

Petrolhead_Rich said:

That Chart looks awfully bias towards Rovers, Loving the way the ZT saloon is compared to a load of roadsters

Apart from the odd inclusion of the saloon, I don't see how it's particularly biased. Or do you just mean it has a lot of them?

Edited by kambites on Monday 20th December 14:56

[wolves_wanderer]

Well my RX8 is stiffer than a 996 Porsche 911 Turbo, a Ford GT and an Aston Martin Vanquish so it must be better than all of them.

A VW Phaeton is stiffer than the RX8, so better

http://www.pro-touring.com/showthread.php?55201-To...


Edit, and an MG ZT

Edited by wolves_wanderer on Monday 20th December 14:56

[Chris71]

MGJohn said:

MG stuff

Always thought my ZS felt pretty stiff structurally for an ordinary road car.

Try a proper racer though, with a decent spaceframe or better still a carbon fibre tub, and the it makes the best road cars feel like the mutant offspring of a mk1 MX5 and a blancmange.

[otolith]

For context, someone has compiled a list here:

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

[The Wookie]

This might also interest some of you

http://www.germancarforum.com/test-data/12334-list...

Although I can't speak for the validity of all of them, most noticeably in the flaccidity stakes, the Dodge Viper coupe is second only to the ladder frame chassis Dodge Durango SUV and the franky comical Lambo Countach...

Edited by The Wookie on Monday 20th December 14:59

[Munter]

Petrolhead_Rich said:

That Chart looks awfully bias towards Rovers, Loving the way the ZT saloon is compared to a load of roadsters

Did you read the text put in for the saloon? You might want to....

Also we should consider when comparing the MX5 against the MGF on that chart, that most MK1 MX5s have more stiffening than the release model which I presume is the one on the chart.