I've got a Spoon one (which I got dirt cheap as the guy had no idea what it was worth ) and IMO it does make a difference.

 

Depends if it's hollow box-section or solid bar I suppose.

I was thinking of making one myself but then I saw the underneath of an S in the Hel thread, the x-bone chassis looks mighty enough as it is or am I missing something?
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As you get closer to the centre of the x bone, the rigidity will be massive, however, the closer you get to the ends of the bone, there will be some flex. I don't think this flex would be great enough to be noticed by an ordinary joe.

Honda didn't mess much up when it came to designing this car and I can't imagine torsional rigidity would be one of those things (especially as the went down the x-bone route) so in this case, I'd leave what is there, there.

... They wouldn't put a crap piece of u shaped metal there if that wasn't what they thought was needed, I would have thought?
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The car in standard trim is good, of course, but any road car is a compromise between performance and comfort, so almost every part can be improved to suit the particular needs of the driver. If Honda got everything spot on for everyone, why are there any tuning parts at all for the S2000. Indeed, why did they see the need to revise the suspension etc. over the years and why does Mugen exist???

I can say with confidence that every modification to my car has improved performance, albeit at the expense of comfort, lower braces included.

 

There's a brace at the top as well, don't forget. It doesn't sound like Honda got it right; it sounds like Honda designed the car and then in final testing decided there was too much rear flex and bolted on some braces as a much cheaper solution than beefing up the chassis. Maybe they tried a stiffer lower brace, but concluded that it was too stiff for most drivers. But then that's the point of mods: to make the car suit you.

I have all four, but the rear lower was the one that made a big difference. The fronts made a subtle difference, and replacing the rear upper was a complete waste of time and money.

 

I believe the geo guru guy at Centre of Gravity reckons the rear lower brace is important - reading a post about that was what convinced me to get one.........

 

Rear lower bar is a must, primarily for the reason Dembo says. There's one there anyway.

As is the front lower.

Front upper is bling - mine is coming off.

Is an aftermarket one worth it? Well all things are done to a cost when it comes to OEM, and some of the 6 point ones look like a good idea to me.

 

Hmmm, I may take some convincing Martin.....such as a passenger ride in the beast this Friday? (purely for research purposes of course)

I believe there's a bit of a queue forming lol

Re: braces the best one is the front upper, AKA the leaning over support for people like me with bad backs

 

I have a Cusco rear lower, and noticed more positive feel at the limit. However my brace is steel bar which I imagine would make more difference than Aluminium.

 

Mugen exists to exploit the wealthy/stupid/both into parting ways with their cash for a product that says 'Mugen' on it.

Going back to the car, the front is very strong/stiff. Any strengthening needs to be done at the rear of the car.

Shigeru Uehara said those words and he designed the car in the first place!

 

I agree.

I have a front lower Spoon and Cusco lower rear. i noticed a big difference after fitting the front. Shrper turn in and postive steering.

The differenace after the fitting the rear was negligible but as Lovegroova suggests, its not expensive so why not.

 

The cheap eBay one seems to be a similar design to the Cusco one, the Tegiwa one looks like a box section piece of metal.