My initial thoughts are less sway bar, but I'm still learning this whole B Street thing. I think the large bar is a lot for the street tires.

What does your caster look like?

 

Are we really on 'street tires'? The 245/255 is only a tick behind the STR tire size and the tires are the same. The limit is that the bar only affects roll and front/rear roll bias by stiffening the front. STR can affect pitch and roll with adjustments at both ends.

That could make shocks important. Looking at SoloStorm output last weekend there was one section were there were left/right transitions at the rate of 7 every 10 seconds. But what that shock should look like and if it would still be reasonable on car that is also street driven.

 

Are we really on 'street tires'? The 245/255 is only a tick behind the STR tire size and the tires are the same. The limit is that the bar only affects roll and front/rear roll bias by stiffening the front. STR can affect pitch and roll with adjustments at both ends.

That could make shocks important. Looking at SoloStorm output last weekend there was one section were there were left/right transitions at the rate of 7 every 10 seconds. But what that shock should look like and if it would still be reasonable on car that is also street driven.
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Nobody in STR is running a bar that large though. People used to stuff things like 275 wide Hoosiers on stock S2000 tires, and that's what those large bars were made for. Like you said, changing your roll bar stiffness is effectively changing your cars balance. In a perfect world, you probably wouldn't run any sway bar at all, and would tune your car with spring rates, but we happen to be in a class where that isn't possible. We put as much tire (grip) on the front of the car as possible, and then the rear end becomes loose. That's where the beefy front sway bar comes in to play. With the 245/255 combo, you are increasing front contact patch by 14% and rear by only 4%, so it's going to become loose. So you stiffen the front to balance it out. If you are pushing, you went too far, unless there are gains to be made in front grip via camber, toe, caster, or *shock*.

But on the subject of shocks, it's my personal opinion that the stock shocks are the last thing you should invest in for an S2000 in B Street. After all, a car from our region made it to 2nd in nationals last year on stock shocks with over 100,000 miles on them. On top of that, the cost of a shocks that are worth investing in, are equal to the cost of every other B Street mod combined. Until you are that fast, there are better places to spend your money.

 

My caster is not as good as I would like. It is set at max with -2 camber and is 5.9 right side and 5.7 left side

 

My caster is not as good as I would like. It is set at max with -2 camber and is 5.9 right side and 5.7 left side
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I'm curious to the impact of caster on all of this. The research I've done has been all over the map on this subject, from maxing it out as you have for the sake of camber, to set it in the middle and leave it alone. I'm currently in the tinkering with garage alignments phase, so I can feel all the differences, and I think I might just have to turn that bolt one of these days to see what it does. If you have toe plates, you may want to turn it back about 30 degrees, re-set your toe to 0, and see how it does. I don't know what my caster is in degrees, but it's pretty close to the middle setting based on the eccentric bolt. I'm debating increasing it to about 45 degrees on each side and seeing what happens (talking eccentric bolt rotation), but I still have room to go more on camber bolts, so I'm going to do that first.

 

It depends. If your stock like I am I run 5-6psi differential typically. I'm running RS3V2s 225/255 all stock bars, shocks, etc and I run 35F/30R with .5 degrees of camber up front, 0 toe and 1 degree left and 2 degree right in the rear with 1/8" toe in. All my adjusters were frozen when I went to get an alignment .

You run a higher front pressure to improve responsiveness, but how much depends on how smooth your surfaces are. I keep the rear pressure low for stability. If I were to run 35psi in the rear I would be spinning out XD.

I imagine with a bigger front bar you could get away with higher rear pressures or you would use the higher pressures to improve rotation.


David Certainly our wheels are not as wide as the STR wheels. With stock wheels you are getting some pinching of the tires on the front which you wouldn't get in STR.

 

I'll save you some time, agrivation, and money; get the 245s and skip the 225 phase.

 

Are we really on 'street tires'? The 245/255 is only a tick behind the STR tire size and the tires are the same. The limit is that the bar only affects roll and front/rear roll bias by stiffening the front. STR can affect pitch and roll with adjustments at both ends.

That could make shocks important. Looking at SoloStorm output last weekend there was one section were there were left/right transitions at the rate of 7 every 10 seconds. But what that shock should look like and if it would still be reasonable on car that is also street driven.
[/quote]


Nobody in STR is running a bar that large though. People used to stuff things like 275 wide Hoosiers on stock S2000 tires, and that's what those large bars were made for. Like you said, changing your roll bar stiffness is effectively changing your cars balance. In a perfect world, you probably wouldn't run any sway bar at all, and would tune your car with spring rates, but we happen to be in a class where that isn't possible. We put as much tire (grip) on the front of the car as possible, and then the rear end becomes loose. That's where the beefy front sway bar comes in to play. With the 245/255 combo, you are increasing front contact patch by 14% and rear by only 4%, so it's going to become loose. So you stiffen the front to balance it out. If you are pushing, you went too far, unless there are gains to be made in front grip via camber, toe, caster, or *shock*.

But on the subject of shocks, it's my personal opinion that the stock shocks are the last thing you should invest in for an S2000 in B Street. After all, a car from our region made it to 2nd in nationals last year on stock shocks with over 100,000 miles on them. On top of that, the cost of a shocks that are worth investing in, are equal to the cost of every other B Street mod combined. Until you are that fast, there are better places to spend your money.
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This is one (rather complicated on a Dallara) example of a decoupled suspension. When both wheels move together over a bump the use the center spring/shock. When they move in opposite directions in roll or one wheel bump they slide the casting the rods are connected to; the black cylinders on its side contain additional springs and shocks for roll.

There are other simpler setups with two shock/springs and simple rods. There are also systems with an extra spring/shock to control pitch.

Our system of individual wheel springs is a bit of a kludge that is simple to implement but means a big increase in wheel rate to control roll and pitch and complicated interactions.

The difference between a 7" wheel and 9" wheel is significant, but not that significant. You finished 4th on Sunday, 2.1 seconds off the win. The B/Street win was 1.9 seconds behind the STR win. Within both classes the win was determined by less than 2/10ths of a second. It is a difference...but not that great a difference.

Note that the winning B/Street did have aftermarket shocks (it was last year's 2nd place finisher on OEM shocks), but that was its first outing on them. Shocks are quite complicated and I don't think we have a good handle on what would work best. I think a few drivers may have figured it out...but figuring out the shock valving doesn't make you Sebastian Vettel or the rest of the car an F1 Mercedes. While they may have finished 5th instead of 10th, they may never have had their success in tuning recognized with a win.

We don't have enough data acquisition to answer the camber question. Well, we probably do in front...the most possible in B/Street isn't enough. It is the rear where the question exists. To my eye I can't imagine a street car designed to work correctly on highways has enough Ackermann for the tight turns on an autocross course. It is adjustable on an oval track late model or modified.

The track cars with big wings and front splitters need stiff springs to keep them from bottoming. However, too stiff a spring reduces grip. Fortunately for B/Street we just need to figure out the front bar and shocks.

 

What is the definitive evidence that the 245/40 is faster than the 245/40, especially with the RE71r? Note that the top A/Street S2000 at the Nationals in 2014 was a 225/255 RS3 setup.

 

He would need to have a OEM '07 rear bar in BStreet. That's going to be a 311 lb/in bar.