How to reduce flex?

[Cody@LoveFab]

Every stock Targa I've driven on the street, the steering wheel shakes around like crazy anytime the car travels over a series of ruts. Every Targa with our bars installed has a perfect stationary steering wheel. Perhaps my interpretation of "cowl shake" is different than yours.

 

[TURBO2GO]

Every stock Targa I've driven on the street, the steering wheel shakes around like crazy anytime the car travels over a series of ruts. Every Targa with our bars installed has a perfect stationary steering wheel. Perhaps my interpretation of "cowl shake" is different than yours.

The only time the steering wheel shakes in my car when I go over bumps is when the Targa is off... and that has happened whether it was OEM or braced with quite a bit of welded bracing. When the Targa top is back on, and you essentially "join" the A and B, the shake goes away. That's why I am saying the only way I see how cowl shake can be eliminated is to join the A and B up top. If you are saying your bars are eliminating shake when the targa is off, that is a new and a good thing.

 

[Papalazarou]

Sorry to resurrect an old thread, but I just wondered if anything's changed on the chassis reinforcement front? Any new products?
Reference the elimination of cowl shake. I'm also in the camp, that as much as I'd like to believe that chassis bars can stop cowl shake, I can't see how this is possible without either a roll cage or a proper roof.
With that in mind, would it not be possible to make a kit that does away with the traditional roof 'pin' fixings, and bolt the roof straight to the A & B pillars?

Cheers.

 

[silver2002]

I am under the impression that the "shake" was designed in to feel the road. I even think I read that somewhere.
Mine had the shake the day I got it in 05 [with only seven thousand miles on it ].

 

[greenberet]

The "shake" was described in the May 2014 issue of Car and Driver (see here), in which they compared a 2005 NSX-T to a 2013 Porsche Boxter. Here's what they wrote:

“With every new model, carmakers brag about a percentage increase in structural rigidity. If you've ever thought that these numbers were pulled out of thin air, drive an old car. The NSX's aluminum structure is nowhere near as solid as the Boxster's steel foundation. We might be more forgiving if the 3123-pound NSX weighed less than the 3035-pound Boxster, but in the NSX, the steering column shakes, the dashboard quivers, and the A-pillars flutter when the tires are on anything other than smooth pavement. Although this doesn't seem to affect handling, it cheapens the experience and reminds us that the NSX was engineered in the 1980s, when almost every car was even more flaccid.

… the [Boxter's] structure doesn't shiver like a wet dog.”

 

[Papalazarou]

The "shake" was described in the May 2014 issue of Car and Driver (see here), in which they compared a 2005 NSX-T to a 2013 Porsche Boxter. Here's what they wrote:

“With every new model, carmakers brag about a percentage increase in structural rigidity. If you've ever thought that these numbers were pulled out of thin air, drive an old car. The NSX's aluminum structure is nowhere near as solid as the Boxster's steel foundation. We might be more forgiving if the 3123-pound NSX weighed less than the 3035-pound Boxster, but in the NSX, the steering column shakes, the dashboard quivers, and the A-pillars flutter when the tires are on anything other than smooth pavement. Although this doesn't seem to affect handling, it cheapens the experience and reminds us that the NSX was engineered in the 1980s, when almost every car was even more flaccid.

… the [Boxter's] structure doesn't shiver like a wet dog.”

I thought that was a pretty weak article really. Sure the steering shakes over bumps and there is some movement for the A pillar. But the dashboard definitely doesn't quiver. But on the whole, content and accuracy is always the first casualty in these kind of reviews.
So back to the question; what options really work to reduce chassis flex? Can a rear tower brace really reduce cowl shake?

Cheers.

 

[2000NSXT]

I have installed the NSX-R chassis braces from SOS and although the flex is still there, I feel that it is about 30-40% less than before (on the same rough roads), making the car more enjoyable to drive with the top off now. The rear brace may also help a bit, but like some said, the flex will not completely go unless the A & B pillars are joined by a bar of some sort.

Oh! and Car&Driver is the worst auto magazine out there ... those jokers should know better than to test a older T-top car with the top removed with a ground-up built latest Boxster!

 

[Papalazarou]

I have installed the NSX-R chassis braces from SOS and although the flex is still there, I feel that it is about 30-40% less than before (on the same rough roads), making the car more enjoyable to drive with the top off now. The rear brace may also help a bit, but like some said, the flex will not completely go unless the A & B pillars are joined by a bar of some sort.

Oh! and Car&Driver is the worst auto magazine out there ... those jokers should know better than to test a older T-top car with the top removed with a ground-up built latest Boxster!

Agree on all counts. Firstly, regarding the type R chassis reinforcement. I had this on my previous targa and it helped a lot. I was just wondering whether there was any advantage in fitting heavier duty aftermarket bars?
Second, what I never understand with magazine articles is how they seem to get the information consistently wrong. Surely they are factual publications? And if they do not check their facts or sensationalise the experience, they may as well not write at all.

Cheers.

 

[greenberet]

Despite the factual errors car magazine articles unfortunately almost always have, I assume the author did drive a 2005 NSX-T and a 2013 Boxter back to back and then described his impressions of the cars' rigidity. Perhaps sensationalized in the vein of Jeremy Clarkson to make the article more titillating to read but his subjective impression was that the NSX-T is a lot less rigid than the Boxter. As 2000NSXT stated above, he finds his car more enjoyable to drive with the NSX-R front chassis braces installed because they make the chassis more rigid. Our NSX was king of the hill in terms of chassis rigidity when it came out but whether we like it or not, in the meantime other cars have knocked it from its throne on that measure.

I replaced OEM NSX-R front chassis braces with LoveFab's front chassis braces and my impression is that they further increased the chassis' rigidity up front. I can't comment on LoveFab's rear chassis brace because I haven't received it yet.

I can understand how front chassis braces stiffen the chassis at the front. Ditto the rear. I'd guess that they increase flex in the middle of the car, though. When a wheel goes over a bump, force is imparted to the chassis. If the chassis is flexible, it will absorb the energy locally and not pass it on to the rest of the car. If the chassis is rigid, the whole car will tilt. If you put chassis braces on the front, you decrease the amount of energy the front of the chassis will absorb and as a result, increase the amount of force that gets transmitted back into the rest of the car. Over a given bump, more energy will get passed to the middle of the chassis so without additional bracing, I'd expect the side sills will flex more than they did before.

How that impacts various shakes will depend on what causes them. If a shaking steering wheel and A pillar movement are caused by movement in the main frame rails at the front of the car, a front chassis brace should reduce that. A rear chassis brace should reduce how much the B pillars move relative to each other and any chassis creaks back there. If the frame rails are tied together tightly front and rear, I wonder how much the side sills themselves really bend and flex. My hunch is that they're pretty solid so probably not very much. But that's just a guess.

 

[jaffaz32]

Am i correct in thinking the front wheels are also designed to move slightly back and forth?

Also that TI Dave, Source 1 have developed kits to eliminate this? i have Dave's installed. Could this be what your feeling?

 

[jond]

The "shake" was described in the May 2014 issue of Car and Driver (see here)

That was written by a Porsche fan-boy.
The NSX is a supercar. A Boxster is a girls car.
Give me a break.

 

[TURBO2GO]

Guys there is no brace, no bar, nothing available that will get rid of this on the targa. As some may know I track my NSX and am pretty safety concious, so I have for we'll over 2 years now been looking into various types of roll bars, cages, materials, designs and talked to many fabricators. I've taken the car's interior apart examined and measured the thickness of materials, then shown that to fabricators and engineers. The bottom half of the car is extremely rigid. In fact, several race car builders that have looked at my NSX for cage work have stated that it is one of the stiffest cars they have ever seen, and that they "wished" the other cars they work on including more modern ones had that sort of rigidity. But the car is essentially relying entirely on the floor pan. The top must be tied together. I will add that although the coupe has this, it's still not as stiff as you'd think. Even the coup can use extra support.

I've come up with a design to tie the A and B together up top. It is a wide flat bar that attaches the two together. It still allows operation of the targa roof, but in place, it creates a T-Top rather than a full targa top. It goes down the center. This is the missing leg that will allow the tripod to stand. It is the missing component from the front and rear halves if you will. Any extra bracing currently available that tie the back half tighter or the front half tighter only place more pressure on the missing "leg" if you will. This will tie that together.

The front part will fit between the visors and allow visor operation, the rear will eliminate the dome light. Which can just be redesigned to go elsewhere. I am working with several competent fabricators on this right now. I posted a photo earlier on the Facebook page of what the car looks like with all the trim removed so you can see what you are dealing with.

 

[Papalazarou]

Guys there is no brace, no bar, nothing available that will get rid of this on the targa. As some may know I track my NSX and am pretty safety concious, so I have for we'll over 2 years now been looking into various types of roll bars, cages, materials, designs and talked to many fabricators. I've taken the car's interior apart examined and measured the thickness of materials, then shown that to fabricators and engineers. The bottom half of the car is extremely rigid. In fact, several race car builders that have looked at my NSX for cage work have stated that it is one of the stiffest cars they have ever seen, and that they "wished" the other cars they work on including more modern ones had that sort of rigidity. But the car is essentially relying entirely on the floor pan. The top must be tied together. I will add that although the coupe has this, it's still not as stiff as you'd think. Even the coup can use extra support.

I've come up with a design to tie the A and B together up top. It is a wide flat bar that attaches the two together. It still allows operation of the targa roof, but in place, it creates a T-Top rather than a full targa top. It goes down the center. This is the missing leg that will allow the tripod to stand. It is the missing component from the front and rear halves if you will. Any extra bracing currently available that tie the back half tighter or the front half tighter only place more pressure on the missing "leg" if you will. This will tie that together.

The front part will fit between the visors and allow visor operation, the rear will eliminate the dome light. Which can just be redesigned to go elsewhere. I am working with several competent fabricators on this right now. I posted a photo earlier on the Facebook page of what the car looks like with all the trim removed so you can see what you are dealing with.

Sounds great. I'd thought of a few alternatives but this sounds like a great option. Reference shoring up the back and the front thus putting more emphasis onto the middle of the car. I agree. However, in my experience, front chassis bars do stop the wheel tramp you get on bumpy roads when cornering hard.
Anyway, please post a link to your FB page, so we can take a look.

Cheers.

 

[TURBO2GO]

nsxprime facebook page not mine. Its not of the bar... but lots of photos of the B with all panels removed.

 

[Osiris_x11]

Believe it or not — a safety harness-bar secured with 4 hard-points in rear cabin, stiffens up the NSX quite a bit. Couple that with some beefy front-chassis bars and large(r) diameter engine-compartment brace, you'll be quite surprised.

FWIW, a late-model 911 Targa (993, 996, 997) has noticeably less structural rigidity than an NSX-T...

 

[TURBO2GO]

Believe it or not — a safety harness-bar secured with 4 hard-points in rear cabin, stiffens up the NSX quite a bit. Couple that with some beefy front-chassis bars and large(r) diameter engine-compartment brace, you'll be quite surprised.

FWIW, a late-model 911 Targa (993, 996, 997) has noticeably less structural rigidity than an NSX-T...

I think the NSX is actually quite a stiff car, but it can certainly be improved. I have everything you're taking about. A welded chromoly rear triangle brace, 2 front braces, the harness bar attached at 4 points. The car still will twist a bit on driveways and the steering will still wiggle slightly. Fact is.... The car is still two pieces. A rear half, and a front half.... Connected only at the floor. Tying the A and the B together up top will be tremendous.

 

[Papalazarou]

Any movement on this?

Cheers.