Hey guys! New to the forums here but have been playing Forza since the very first one came out on the original X-Box, haha. I"ve looked around for the help I need but just don’t find the answeres so I figured I’d come talk to y’all experts. I consider myself a fairly good tuner, never mess with the leader board cars unless it’s something of my interest (Mainly stick to what is actually out at the racetrack). Stuck in college right now so don’t have anything better to do but sit around and mess with Forza until I graduate and start up a shop. ANYWAYS, I can’t quite get a grasp on the gearing I guess it is, or maybe suspension. All of my cars run the goofy suspension set up (positive camber, soft and hard springs, tall height, etc.) For the most part when I come across another car built like mine I can walk all over them, but then someone else shows up in the same car, no goofy suspension, and hooks good and pulls me the whole time. Specifically the '02 Camaro. I’ve had fastest 1/4 mile passes into the 8.5X’s, but no consistency whatsoever. And still get beat. What exactly do I need to be building towards in my tune? I try to set everything up as to where it looks good in the benchmark, and then test it and smooth out the gearing and traction issues and what not. Just don’t see why I put hours and hours into different tunes with no better results. I run with NO traction control, stability control, and manual with the clutch. Just stumped 
If you can, please post your build/tune and I can provide you with some feedback, or we can pm if you prefer. Outside of the build/tune, it is all about the launch and shifting timing. My '02 is sitting at S776 with a 8.533 in the 1/4, 2-car.
Just ran the 1/4, 4 times to check consistency and got a 8.550, 8.650, 8.550, 8.538… so, if the time is not consistent one could get a wide spread. I believe you are at 8.583 w/S776 (probably same build as mine), and, based on what you described tune should not be that off from what I probably have…so…u should be able to improve. Good luck!