Interesting observation. I recently replaced my '88 Verts stock sway bars with Suspension Techniqes. Also, a while back I inherited a set of S5 T2 sway bars.

Seeing T2 sway bars being offered as an upgrade, this evening out of curiosity I decided to compare thickness with my micrometer since they were both loss in my garage. I honestly checked each several times to insure accuracy.

Results:

S5 TII front sway bar - .91 inches
S4 Vert front sway bar - .95 inches

Now, does this mean that thinner S5 TIIsway bars are an upgrade?

Hmmmmmmmmmmmmm.

Now wondering if I indeed "upgraded" when I installed my Suspension Techniqes.

Hmmmmmmmmmmmmmm

 

interesting, not suprising considering the need to keep body flex down on the vert anyway possible. They probably beefed the sway bar up a tad to help out.

 

Yeah - they beefed up the sway bar, strengthened the sills and included additional plating under the chassis to make the vert more rigid. This is common with convertibles which suffer from "scuttle shake" which is caused by a loss in rigidity from having no roof. This extra metalwork adds to the weight though.....

 

I believe they may be the same size as the S4 TII though.

 

so do you know the size of the suspension tech swaybars? did you measure those too?

 

When I get a chance, I'll measure my S4 TII to see how it compares to the Vert. As you see below, the Suspension Techniques is indeed a stiffer bar. Additional information found:

ANTI-SWAY BARS
Company Name Adjustable Diameter Front Diameter Rear
EIBACH no 1.125" 0.70"

--------------------------------------------------------------------------------

MAZDASPEED no 0.94" 0.62"

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RACING BEAT no 1.125" 0.625"

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SUSPENSION TECHNIQUES front 2-way adjustable
1.0625" - 1.125" 0.75"

--------------------------------------------------------------------------------

TRAK PRO no 1.125" 0.75"

 

yeah that's an interesting observation- I hope they are thicker than stock vert bars...

 

outer diameter does not take into account material type nor thickness of material, which are factors that would also increase 'stiffness'

edit: in regards to stock v. aftermarket

 

they are all steel right?

 

John,
The part number for the TII and NA S5 front bar is FC02-34-151. They use a 24 mm bar.

As an aside, does anyone know what the FC18-34-151 bar is? Infini part?

Getting back on track, the rear bar for the S5 convertible is part number FC01-28-151, and it’s 12 mm. The rear bar for all other S5 coupes is part number FC02-28-151, and they are 14 mm. Of course, you’ve got an S4, and I don’t have an S4 parts microfiche. According to my notes, the S4 convertible uses the same sized bars as the S5.

 

So, assuming the material used on all stock sway bars are the same, you have a stiffer vs. coup sway bar up front and a more flexible sway bar vs. coup on the Verts. Boy, that being the case, I'd love for some Mazda engineer to expain the logic behind that.

I have a S4 TII, so sometime between now and next weekend I'll measure and report to confirm.

Interesting................

 

You’d need to know the spring rates to have the complete picture, and the vert springs are "interesting". The S5 TII, GXL, and GTU-S (not to be confused with the GTU) all use part number FB44-34-021 on the right front and FB67-34-011 on the left front. The rear springs are FC01-28-011. On the S5 vert, the front springs used for the sport suspension are reversed. The sport spring for the coupe’s front left is mounted on the right for the vert, and the right front spring, is mounted on the left front of the vert. The rear springs for the vert are vert specific.

If the rear springs on a vert springs have a higher rear spring rate (and I think they should), along with not letting the car sag, that would increases oversteer. Dropping the swaybar rate would reduce oversteer. Maybe it evens out the handling, while not letting the rear sag.

Of course if that's not it, the explanation would be very interesting.

 

so i have an S5 NA. are the TII swaybars thicker? and are the s5 vert swaybars even thicker than the TII's ?

 

All US spec S5 coupes use the same sway bars (Infini IV's have larger bars). The verts have a smaller rear sway bar, but they also have different rear springs. Typically people change bars because they don't like the way their car handles. Larger isn't always better, neither is smaller, it depends on what you're trying to change. Oversteer? Understeer? Camber changes?

 

my car understeers.

 

Increase the front tire pressure, or lower the rear tire pressure, or increase the rear spring rate, or decrease the front spring rate, or go with a smaller front sway bar, or go with a larger rear sway bar.

That's a lot of stuff, but assuming the tires are good, I'd start with adjusting the pressures.

 

Where did u get the sway bars? Website?