Does the targa top provide chassis stiffness?

[RedWings]

Targa top stiffness - real numbers ?

So the targa top adds stiffness... yea no shit, of course
I do pay attention when I drive and do notice the difference
(thats a rude response coming from a fellow Primer)

Anyways, the point of my original topic is to ask :

Does anyone have REAL engineering numbers on the difference in torsional values when the targa top is on and off?

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[pgilliam1]

Does the targa top provide chassis stiffness? Yes. If you can't feel the chassis flex with the targa off you're not paying attention.

 

[Hapa88]

I asked this exact question this past weekend during an AutoX event. The difference is amazing. The car felt so sloppy and very boat like with the roof removed. I have in car videos of each run, but I'm too lazy to upload them. Trust me, the difference is very noticeable, especially if you're pushing the car.

 

[nsx200416]

i noticed a vibration this past weekend when driving with top off, i am not suprised. top is only off when cruising or showing off

 

[Caustic]

If anyone doubts the chassis flex in an NSX-T, there is a simple test to give you an idea of what is really going on.

With the top on, drive down a bumpy road. While going over the worst parts, put your index finger on the crack between the connection of the top with the windshield (by your driver side window). This is the connection where the pin of the top drives into the top of the windshield. Don't put your finger between the two, just on it. You will easily feel the car flexing as the gap between the windshield and the top contracts and expands.

The same can be done on the rear side of the top. What is astonishing is how much more flex is going on there...

With the top off, it is obvious that there will be more flex. I have read on prime that the amount of flex for an NSX-T is 1/16". I call shenanigans on that number, it is absolutely more than that.


A couple of things about this though. After 6 years of ownership, I never noticed the flex with the top on until I moved to a city that has notoriously hideous roads.

I did the "finger" test before and after the STMPO RSTB was installed. The bar made a difference.

 

[BATMANs]

Compared to a coupe it still flexes and makes noise on or off.

I just can't stand that.

The rx7/rx8 have this space saving sunroof that tilts up and slides out instead of inside the roof.

That's what the NSX should have came with so it retained the rigidness and safety of a coupe but had an option of an open roof.

 

[RedWings]

I did the "finger" test before and after the STMPO RSTB was installed. The bar made a difference.

Caustic, I completely agree, the STMPO RSTB stiffness factor is a definite improvement to higher speed cornering, driveway ingress and egress, average driving with and without the top on, etc. Probably the single best mod that you can do to an NSX-T to improve chassis, etc. I have also done the "finger" test and agree that the declination is greater than 1/8" under certain conditions.

Batman - asthetically the sunroof sticking out doesn't work for me on the NSX, have driven an RX8 with that sunroof setup and recall it being a solid platform.

 

[Aaron94T]

That's what the NSX should have came with so it retained the rigidness and safety of a coupe but had an option of an open roof.

A sun roof can not be compared to a targa. I have 3 cars with sunroofs and I never use them as all they do is make noise and wind. Open, they add nothing to the driving experience.

As for the top making a difference when installed I would say it is nominal as it is just using pins. It obviously stops the car from twisting into the space the targa takes up but it is not attached to the car. As a comparison the supra uses 4 screws to install the targa which takes much longer but provides more noticeable rigidity.

 

[BATMANs]

A sun roof can not be compared to a targa. I have 3 cars with sunroofs and I never use them as all they do is make noise and wind. Open, they add nothing to the driving experience.

As for the top making a difference when installed I would say it is nominal as it is just using pins. It obviously stops the car from twisting into the space the targa takes up but it is not attached to the car. As a comparison the supra uses 4 screws to install the targa which takes much longer but provides more noticeable rigidity.

Year ago I met up with Petit Racing and the driver preferred the Touring model with the sunroof over the model without the sunroof which was lighter and had more head room. When he was asked why his response was that the FD sunroof angle of tilt provided downforce at speeds. In some cases where the track would come outta alignment on occasion.

I didn't have any issue with the FC/FD/FE sunroofs making noise at speed limits. It's only when I was breaking the speed limit when it was an issue.

Another benefit I loved about those sunroofs was that it was great for letting the heat out as opposed to just cracking the windows.