2 Bolt vs 4 Bolt Strut Tower Brace

[chuck07]

I am looking at strut tower braces and trying to find the difference in 2 and 4 bolt (4 and 8 total) braces. I would imagine that the 4 bolt would provide more rigidity, but there are enough of the 'high end' ones with 2 bolts that I am thinking that the difference is negligible.

Has anybody switched between a 2 bolt to a 4 bolt?

I am putting this on my 07 V6 vert. DD with potentially light-hearted autocross in the future.

 

[SlowJim]

Why not just go to a junkyard and get one off a GT for like $20?

 

[csamsh]

I doubt anyone would notice a difference. The chassis is already pretty rigid

 

[Mike Rousch]

I doubt anyone would notice a difference. The chassis is already pretty rigid

Exactly, Complete waste of money.

 

[frank s]

I have experience with both the 2-4 and 4-8 strut braces on a 2006 convertible: summary, on that car they did make a perceptible difference.

The 2-4 bar reduced cowl shake by 40%, over a nasty piece of pavement very local to me. I used the single-bar brace available at the time, paid about eighty dollars to a fellow who took it off a coupe because "it was a complete waste of money". My experience proved him wrong.

Later on, on the same car, I had an opportunity to get a Shelby two-bar 4-8 item for an irresistible price. Before installing it I did a before-after test over the vicious pavement: removing the bar reverted to the same intolerable cowl shake at original.

Installing the two-bar 4-8 setup reduced the cowl shake by eighty percent. I went on to to a before-after-before test and confirmed my observations. When I sold that car, I took the 4-8 bar off and put it on my next Mustang.

Summary: the 2-4 single bar made a perceptible difference; the 4-8 double bar made even more difference, on a 2006 convertible. Worth it to me because I tested and knew it made a difference. If I'd never tested, I might have gone through life saying, "a complete waste of money",

I have read of tests wherein the installation was completed, then the nuts on one side loosened ever-so-slightly, and the void around the loose nuts filled with modelling clay. After a test on a rough section, there was visual evidence the nuts had moved lateral to the car's direction of travel. Sounds like a valid test, to me.

 

[chuck07]

Summary: the 2-4 single bar made a perceptible difference; the 4-8 double bar made even more difference, on a 2006 convertible. Worth it to me because I tested and knew it made a difference. If I'd never tested, I might have gone through life saying, "a complete waste of money",

I have read of tests wherein the installation was completed, then the nuts on one side loosened ever-so-slightly, and the void around the loose nuts filled with modelling clay. After a test on a rough section, there was visual evidence the nuts had moved lateral to the car's direction of travel. Sounds like a valid test, to me.

Thanks. The price difference doesn't seem too much since I am looking at used ones. Nice to see it makes a noticeable difference in convertibles.

 

[Norm Peterson]

Summary: the 2-4 single bar made a perceptible difference; the 4-8 double bar made even more difference, on a 2006 convertible. Worth it to me because I tested and knew it made a difference. If I'd never tested, I might have gone through life saying, "a complete waste of money",

Certainly for a convertible, your experience makes complete sense. The 4/8 configuration almost certainly takes better advantage of however much bending stiffness the STB has than the 2/4 can. It's still mostly a NVH mod, and cowl shake is really a vibration mode. Clamp the displacement of that mode off between two other points on the structure that are moving relative to each other and that mode goes away (or runs off to become a higher and less annoying frequency in some other location, perhaps).

Tying the strut tower tops together with a basic 2-point STB does force them to stay (more or less) the same distance apart under heavy braking and the impact from hitting bumps with the front wheels. Better than without anyway. And it at least forces them to move the same amount laterally under cornering loads (same-ish, if any joint slippage is present), which probably helps the camber situation for the more heavily loaded outside tire in a corner more than it hurts the inside tire's camber . . . theoretically. Realistically, the magnitudes of these slight changes in your tires' operating camber are going to be too small for most people to notice having only an uncalibrated SOTP for instrumentation.


A while back, meaning maybe 2003-ish, I happened to notice that mid-level Buicks actually came with STBs as OE . . . and you just knew they weren't there for performance reasons.


Norm

 

[claudermilk]

I can't say for certain how much effect a STB has on the S197 as mine came with the OEM one in the Brembo package. I would have added one anyway, so it saved me buying that mod.

That said, I did add STBs (front and back over time) to my old '95 Probe GT. Those strut towers were fairly close to the firewall, yet there was a perceptible improvement in steering response. The S197 strut towers are much further away from the firewall than that FWD car, so I would think there is more opportunity for flex. I am hearing that even the guys putting the Steeda STB on their 2nd gen Fusions are seeing improvement, and that car's strut towers are practically adjacent to the firewall.

It is a subtle change, but going from a U layout to a D layout cannot hurt stability.