So, there have been more than a few posts on here regarding my foolish endeavors prepping my Grand National for SCCA autocross competition. Some regard it as silliness, most others think it’s pretty badass. I’m having fun with it, though, and that’s all that really matters.
That, and results. Is what I’m doing working? How do you tell?
You tell with data. You collect data, and you analyze it, and the data will tell you if what you are doing is working or not. Without data, I’m just talking out of my ass.
So I got some data, then overlaid it on this video:
This is telemetry collected using superimposed on a video feed from my Go-Pro. If you watch the little g-meter in the bottom left, you’ll see the car hit 1.1g lateral acceleration, not in a crazy offset, but a sustained turn.
1.1g. Sideways. In a 1987 Buick Grand National.
Granted, this was at the Wilmington Air Park in Ohio, which is concrete. This car would not be able to do that on asphalt. Or would it?
That one was on asphalt, on a really cold day. It hit 1.0g. I’m happy with it.
What put the car over the top? What made this possible? Tires.
Big, beefy, sticky BFGoodrich Rival S tires. In 275/35R18. The biggest I could fit under the car without cutting it up.
What made getting this much rubber underneath a car that came with 215mm wide tires originally? Careful measurement and custom offset wheels. I aquired a set of Weld RT-S71B forged wheels for these meats. Getting them on the car and balanced required on-car balancing, since these rims are lug-centric. Weld can also only manufacture to a half-inch on the offsets. These wheels needed 1/4″ spacers on all four corners to truly get them to not hit stuff.
The results are remarkable. I’m at the point now where I finally feel I’m in need of a bigger front swaybar. You see, the car is rolling a bit too much now and putting too much load on the outside front tire. It likely always has, but now I can prove it:
This photo was captured by the people at autoxpix.com, and shows quite clearly the wheel attempting to escape the bead of the tire during the 1.1g turn in the first video. I’ll attempt to compensate for this with more front tire pressure moving forward, but a better front anti-sway bar is going to be the real fix. Anti-sway bars don’t just make the car roll less in turns, the extra roll resistance actually transfers load from the outside wheel to the inside wheel, allowing the inside tire to handle more of work.
I don’t know when I’ll be able to get that done, I need to treat my property for termites soon, and that costs about the same as the swaybar I need. Oh, the woes of being a grownup.