GTS - are the targa and buttresses structural?

I would imagine a GTS gets some rigidity from the top, but nothing in comparison to a GTB.
I doubt the buttresses help when the top is off.

 

A very interesting question, which I have tried to find an answer to in the past when I was trying to prove sufficient roll-over protection when I was trying to register the GTS for a HPDE event. I was unsuccessful in finding proof.

Since then, I have learned that the US-spec 308s has additional reinforcement in the A, B and C pillars as schematically shown in Ferrari Factory publication 267/83 (Safety plus Safety – Ulteriore Sicurrezza) although the publication doesn’t describe the type of reinforcement. US Federal safety specs were higher than Europe’s at the time, so presumably there were US Federal standards that Ferrari had to prove that they met…

However, your question seems to be about torsional rigidity, which pillar reinforcement wouldn’t directly address. I have to defer to others about frame design changes to provide greater torsional rigidity. I doubt there is any, but personally I have never found my GTS to be that soft; certainly suspension and bushing changes would have a more noticeable effect. In contrast, my 1987 BMW 325i convertible clearly has substantial reinforcement (huge door sills which are frame members) over its hardtop siblings.

 

The GTS has a structural reinforcement in each door sill, which sill is notably "higher" than the one of the GTB: about one inch and a half. There is a - longitudinal - "bump" just behind the silver door sill plate on the GTS, which does not exist on the GTB: it is flat.

As I have already written, I have a February 25th, 1989 GTS; and an April 4th, 1989 GTB. The difference in rigidity between the two is very substancial, believe me. You don't even need to drive the cars back to back to register it.
There is no doubt that a 328 GTB is not comparable in any measure to a sportscar of today; but between the 328 GTB and the 328 GTS, and as far as we are talking purely about the driving machine, the GTB is a much better car.

My GTS is here for driving with the top off, when the weather allows. But I carefully plan every trip with the GTB in advance, selecting the nicest roads and twisties, simply because the car is so much more enjoyable to drive.
Both have their plus and minus, otherwise I wouldn't have kept both. But the GTB is the better driving machine, "hands off" (no pun intended)

Rgds

 

I've had both and agree with nerofer. The B is a much better driver overall, except when you want a little wind in your hair. I'm guessing even with the additional reinforcements on the GTS, the pop top leads to a lot of flex within the chassis. The B just doesn't have it and thus has a lot less creaks and noises.

I bet the 328 cab is a lot worse than a typical GTS.

 

In my opinion, from an engineering perspective, the 3x8's rigid, tight-fitting targa top should meaningfully increase torsional rigidity. The windshield header and the roll hoop are 36 inches above the floor structure. There is a lever-arm effect from clamping the two together at that height. If there is x ft-lb of torsional force between the front and back of the cockpit floor, the targa has to bear just a third of that force to resist it. It can't be as stiff as a GTB, but it should clearly help. Not an expert, and have no proof... it would be cool for someone with some strain gauges to bear this out!

 

I won't re-open an endless debate...but: the GTB is not only stiffer, it is sharper: it seems more precise; it's really different. I won't enter the debate again; suffice to say that someone who has driven both will agree
(But, to be worthwile, the test should involve two variants of the same model: 308 GTB carb vs 308 GTS carb; two valve injected GTB vs two valve injected GTS, etc...and same market-version: US vs US, Euro vs Euro, etc)

 

Interesting. I have never looked there on a GTB and am surprised to learn that the "bump" is not there. A substantial difference. As I measure it on a US 308 GTS, the "bump" / door frame rail is well over 2" above the silver door sill plate.

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Yep, that's the one I was talking about. It's an additional stiffening tube that doesn't exist on the GTB. This is also part of the reason why GTSs are heavier than GTBs.
If you remember it...there was a thread many years ago on this very forum about a German guy who bought a damaged 328 GTS, and rebuilt it as a track car, but after cutting the roll-over pillar and windshield frame, then welding a GTB roof. So he had the stiffening at the bottom of the "torque box", and at the top. The car can be seen rather often in pics, it's green overall (and has 308 front fenders with the grills behind the headlight pods).
Rgds

 

GTS lacks stiffness, you don't need to go on an handling track to learn that, as it's clear in the every day usual driving too. The GTB is a much better car, but the GTS is a spider: that's a big plus.

This said, I by far prefer the GTB

ciao

 

The lack of stiffness didn't seem to dampen Villeneuve's enjoyment of the GTS so I doubt it would ever have a chance of dampening mine (I hope you'll excuse my argumentum ad verecundiam )

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As said by Alberto above, anyone, and I mean anyone, having an opportunity to drive both will know that the GTB is a much better car. It is so obvious that you would know after less than a mile.
As for the choice between the two, to each his own...I have had both side to side in the garage for seven years now.
Rgds

 

+1
You just have to drive along a bad surfade road ant you will hear the rooof rattle and the squeaks from the body. This doesn't mean the car cannot go fast on a track: it just has much less stiffness, but it works very well the same. The GTS is a great car, but the GTB is better.

But the GTS is a spider, and if you ask your wife which she prefers, the answer will always be "GTS"

ciao

 

I understood you both the first time & I don't dispute it. I'm just offering a balancing light hearted counterpoint that, maybe just maybe, points to a bigger truth

 

The GTS is unfortunately very flexible. The targa top adds nothing to rigidity. Try driving with a finger in the gap between the rear edge of the top and the body, and you can feel this gap opening and closing constantly with road bumps.

 

But, but...Gilles Villeneuve was just not a "normal" individual, was he? Someone from another world...
Rgds

 

He did not come from this planet!

 

Coming from a past of owning a 60's era Triumph as well as both a Fiat and Alfa Spider I know all about "flexible". I have only ridden in a GTB once, a '78 with plenty of squeaks and rattles. I drive my GTS all the time on rough roads with my hand spanning across the A pillar and the targa and really am amazed at how little movement I can sense between the two. I'm not trying to say the S is as rigid as the B but these cars are 30-40 years old now and to have a valid and quantifiable comparison all of the other contributors would have to be equal. That includes tires, shocks, springs, bushings, mounts, alignment and probably a couple of other factors I'm missing. All I know is that for an open top Spider the GTS is pretty amazing stacked up against it's contemporary rivals from the 60's (because face it, it is a 1960's design)

 

Except the Lotus Elan.

 

That was a unique design.

http://images.lotuselan.net/lel/22606/0/032.JPG

 

See my avatar!

That's a Spyder chassis +2 with a Zetec engine, but it illustrates the concept nicely

 

^^^ The two pins are the only thing that could be considered structural in the attachment of the targa, but both being on the same edge do nothing for rigidity.

 

The targa body is much more rigid than the cabriolet, of course.

It's like to compare the stiffness of a shoe box without the cap and one with a cap long the half of the box

Ciao