Hi Rich,
Need a codriver in 2008 for some National events?
Actually it remains to be seen if the 2008 Viper is even going to be allowed to run in Stock class. I'm going to guess that the regular '08 makes it in but the ACR gets pushed to ASP, as happened with the previous ACR. But we won't know for a little while, for your sakes I hope it does, for my sake (I have an '04), I hope it doesn't.
The SRT-10's presence in SS is tenuous and I think the Maxcy's almost spoiled my plans by doing quite well last year.
As for the front bar. From what I've seen thus far the Viper understeers a bit steady-state in stock form, even with a good alignment. At first glance, more front bar would seem the wrong thing, and if you only ever ran on stock tires, it would be.
As we move from 275 front and 345 rear street tires to 315 front and 345 rear race tires, we are doing two things, both of which will necessitate more front roll stiffness.
The first thing is we're increasing the size of the front tires a lot (40mm) relative to stock. This is going to increase front grip relative to rear, which is seeing no width increase. More front grip = shift towards oversteer. A little bit of oversteer is ok, especially in autocross, but we don't want it to get out of hand. A good range of adjustability is key to be able to keep the car working well on a variety of surfaces - asphalt, concrete, HPT, etc. I don't really know how much front bar is going to be the right amount; the beauty of the 1.25" Speedway-style bars is you can change the center section from a soda-can .095" wall thickness all the way up to 1.25" solid, or even larger OD centers in extreme cases. I'm going to guess the Viper will end up wanting something around a .250" wall (what I plan to start with), but I don't know much about the stock bar rates yet so it's hard to say. With a Speedway-style bar, for less than $100 you can shift your adjustment range stiffer or softer to suit. Lot better than having to buy a whole 'nother bar.
I know the stock 10" wheels aren't ideal for a 315 but a 285 really throws off the diameters, and IMO is too little tire for a car of this weight (at an autox anyway).
The second thing is these R-comps are adding a lot of lateral grip relative to stock. The result of this is the car will be transfering a lot more weight to the outside in the corners. This means the inside rear corner will have a lot less load (and available grip) mid-corner than the car had stock. The result of this increased grip means the diff is going to have a much harder job when we get on the gas, and the car is going to want to spin the inside tire a lot more than it did on the stock tires.
By increasing front roll stiffness relative to the rear with a stiffer front swaybar, we are making the front tires do more of the "work" in the corner. More scientifically, we are changing the lateral load transfer distribution such that in a corner, the front sees a higher percentage of the total lateral load transfer. Increasing load transfer % in the front means we are decreasing it in the rear (for a given lateral g), which means we will have more weight on the inside rear tire, which means the diff won't have to work as hard. Or ideally, not at all.
The crap diff is a real weakness in this car, too bad Dodge couldn't give us a clutch-type (the Corvette unit works great) or some sort of preloaded Torsen. Oh well. Two of the three people that actually read this far are saying to themselves "why don't you just get some Motons and a better diff" but of course, these aren't allowed by the rules - in Stock class we have a very limited toolset to "fix" our cars with, so we have to do the best we can with what we have.
If everything goes well we'll have a car that turns AND puts power down out of corners without smoking the inside rear tire, which is really frustrating. I used to autocross a Stock-class Honda S2000 which has a Torsen (Quaife-like) diff and is notorious for this. Later I autocrossed with good success a slightly modified Nissan 240sx with its stock (crap) viscous diff, which has characteristics similar to the Viper diff.
I hope you choose to stick it out and run Super Stock in 2008. In my opinion it is the toughest class in all of the SCCA, part of why I chose to run there. If all this lateral load mumbo jumbo sounds interesting to you and you'd like to learn more, Herb Adams'
Chassis Engineering is a nice accessible text that explains it well.
