Like many out there who built the custom 'worlds' car last year, let alone people brand new to the platform, when I got the 8.2 and threw the stock setup on I was quite disappointed to say the least--the car rolled all over the place in the corners and the rear washed out constantly. My first reaction was to throw my old rc8b w/ worlds setup on it--this gave me my old car back, basically, but I really wanted to understand what was going on with the direction the team had taken and what things like the lower d-plate and custom holes Maifield drilled in his shock tower were doing. After all, they're running a "lower d-plate" to "lower the roll center", but then they raise it more than they lower it by going down to a custom hole on the tower, so the explanation of "it lowers the roll center, this equals more traction" just wasn't making sense.
Over the past month, I've done a lot of track testing and analysis of what the new direction the team has taken with the rear, specifically Maifield's setup changes from the neobuggy article about his nats car that many of us had been doing for a while. In addition, I measured the heck out of the car with a pair of calipers and then plugged everything into Performance Trends Suspension Analyzer, examined the roll center changes and the changes to camber rise when the car is squatted and rolled. This helped me understand what had caused the changes I had experienced on the track. It also made it quite obvious that there is some misconception about what is actually causing the "more traction" in the rear of the car with the changes the team has done -- that's not to say the team doesn't know what they're doing, I wholeheartedly believe that they do, but what is said on the internet and what works its way back to the club racers isn't always 100% accurate.
Let's compare the book setup geometry to to Maifield's nats geometry. The main differences in play here are inside hole on the aluminum rear hubs, the custom "one lower" drilled camber hole on the tower, and the lower d-plate that lowers the rear hing pins down 1mm. Note that Maifield ran his car at 30mm, but in order to compare just the changes and make roll centers come out comparable, I had to set both cars to 29mm in the rear. Also note that I had to multiply all figures by 10 to get the software to take them since it was designed to get angry if you put numbers in that were out of range and the software was designed for full size cars.
Stock
Maifield 2012 Nats
The first thing you should notice is that Maifield's roll center is HIGHER than the book setup, even with the lower d-plate mod. This is due to the inner camber link mount being lowered. This means that his setup, even with the lower d-plate, has less roll than a stock setup. If you only get the d-plate mod, then you're going the OPPOSITE direction that Maifield is going in terms of ROLL CENTER. This is the danger of following trends.
Now lets look at what happens when both of these setups go into a corner.
Stock
Maifield 2012 Nats
What should be abundantly obvious now is that Maifield's setup has much more camber gain. How much? Maifield has 2.17 degrees more camber gain in the example chassis roll above, giving his outside tire more contact patch in this specific situation (note that his outside tire is more straight up and down.) It is my belief that this camber gain is the key to keeping the rear in play in corners--after going to the drilled hole on the tower, I noticed a dramatic increase in my ability to power through the apex and corner exit where I previously rotated and waited for the rear to hook back up to put the power down. It showed up in my lap times as well.
Summary
The book setup has a lower roll center than Maifield's setup, even though Maifield has a lower d-plate. Obviously just going for the lowest roll center isn't the ticket. Maifield's setup has WAY more camber gain. My thoughts on this, having come from building the "worlds rc8b" last year, is that they have moved from the lower hole on the hub to the upper hole, and down on the tower (two holes) for the camber link in order to sweep the upper/lower control arms upwards towards the wheels, putting the suspension further into the "camber rise" curve when at normal ride height, causing more camber gain in the corners. In their latest mod, you will find the front caster blocks have their mounting hole for the lower arm moved upwards (so I hear, I have not measured myself,) perhaps continuing this trend in the front of the car--only time will tell.
Lower D-Plate Mod
As far as the d-plate is concerned, I don't run the lower d-plate mod. There's two reasons: I don't feel my roll center needs to be any lower--I feel that I need to run at least the 2.6 sway bar. If I was hanging around the 2.5 all the time and still couldn't get enough chassis roll, then I might. The other reason is that using the stock d-plate gives LESS camber gain on squat, yet provides MORE camber gain on roll. It's not much of a difference, to roll center or camber gain--the 1mm difference is pretty small, smaller than any other adjustment done to the rear. I'm not a fan of it, but to each his own. Maifield runs it, and he could easily run circles around me. I can't explain it. Do what ya like
Wayne