Tele-Caster

I know that bit above about weighing wheels seems **** at best or like a bunch of Internet B.S. at worst.

But I really AM that **** about the static and rotational weight of a tire / wheel package because that influences everything else that is going to come next in prepping the car, from how much power I'm going to need, to how much swept braking area I'm going to need, to how much rebound dampening I want in the shocks and struts. I need to know what the stock OEM wheel weight is, to have a baseline to compare other wheel and tire combinations to, and I need their weights to make a comparison and use some old-fashioned "slide rule maths" to make educated parts choices as the prep unfolds.

I also weighed the car -how much it weighed in total, and how much weight as a percentage was carried on the front and rear axles. I needed to know that to have a basis for comparison after mods are made, in order to determine spring rates, anti-sway bar rates and front to rear bar bias, and so on.

I needed to know whether the engine was healthy enough to race on, so it got compression and leak-down testing. Once deemed to have more a little life left in it, the next step was to dyno it OEM with all maintenance up to date -again, to have a basis for comparison so I could apply math to the problem of maximizing the car's potential.

Think about the carpenter's mantra of "measure twice, cut once" and that's the gist.

I did a whole lot of "measuring twice" so that I would only have to "cut once".

But the first hurdle really was deciding what to do about wheels and tires. The whole car was built around the tire and wheel choices made. Add 10, 20 or even 40 pounds of overall rotating mass in the wheel and tire combo, and I need to make different choices about engine mods just to keep acceleration close to stock and I need a little to a lot more brake just to maintain OEM stopping performance. Any increase in static and dynamic weight at the wheels, tires, and brakes is going to affect shock and strut valving, too, with the expectation being that increase in unsprung weight is going to likely require more rebound damping than I might otherwise want.

The prep process for me went in the order that I listed with chassis stiffening coming after tires and wheels because whether any of this is done or not, or how much and what kind is done, influences the choice of spring rate, anti-sway bar rate and front to rear bias, and shock / strut valving, as well as what I want for final alignment settings. Adding a roll bar, for example, can shift the front / rear weight bias of the car, which impacts its understeer and oversteer, so anti-sway bar bias is going to be different for me in a stiffened car than one that isn't. A strut brace generally affects turn-in response, and that affects my choice in sway bar rates and front / rear bias. So for me, doing suspension and then doing chassis stiffening would have me doing suspension twice. Rear axle comes before engine because if I can re-gear, I might not need much in the way of power increase to get all the power on the ground my tires can use and if I do elect for more power, the qear ratio will effect what I want for a power curve and upper rpm limit. In my case, I couldn't re-gear and stay in class, and that, too, effected what I wanted the power delivery of the engine to be like.

But for me, it all starts with tires and wheels. That decision sets the stage for everything else that follows.

And that's why I am **** enough to weigh what's on the car and weigh choices because their weight has an effect on all of the prep that follows, from how much power I need to accelerate them, to how much brake I need to slow them, to how much rebound damping I need to keep them planted on the ground. Once that decision is made, changing one's mind can be a really, really expensive proposition, because the rest of the car, in a sense, is tuned to the tires -at least, that's how I've always done it in autocross.

Wider isn't necessarily better. For autocross, I'd rather have a car that'll pull .87 lateral G at 60 mph and .82 at 120 than one that will pull .85 at 60 and .89 at 120, because I'm going to spend a fair bit of time at 60 or less and none at 120. Past experience is an influence here, too. I was most competitive when campaigning a Porsche 924S at the same race weight as my current Mustang running on 215 / 60 -15 Pirelli P-6000's or Michelin Pilots of the same size. Every now and then, I could post faster times than folks with more powerful cars running wider rubber, and when I couldn't, it wasn't because I brought the wrong car to the race, but because I didn't have my schnitzit wired tight in hitting my marks on corner entry, apex, power out, set up for the next "gate," and so on.

Tires need to be sticky, but they don't necessarily need to be big for what I'm doing, and the more dialed in the chassis and suspension is, so that weight transfer is as minimal as possible, the "less big" they need to be, in my experience.

Tele-Caster

If they're what I think they are, they're indeed the lightest 17's I came across but they're still not as light as my OEM V6 wheels. If they're what I think they are, I recall them weighing a tick under 20 pounds each, bare. It's not an insignificant difference for what I'm doing.

I may have to wind up using them,eventually, because of SCCA Solo rules on tire availability. I think I'll be good for the upcoming season, but after that, I'm probably going to have to change.

Which means that I'm going to have to do something different with shocks and struts and brakes, too, as my whole car is basically set up on the tires and wheels I've chosen to run on, because of the impact they have on everything else that comes after.

PNYXPRESS

Sounds like we have similar goals with our cars.

But I am starting with lightening up the car as much as possible, as high up as possible. Then chassis stiffness and handling, then braking, then adding power.

Tele-Caster

That's a good way to begin, for sure! Where adding power improves vehicle performance in acceleration and top speed, dropping weight can do that plus improve braking performance, lateral grip, and transient response, among other things. That's kind of a foundational mod, because of the effect that weight reduction has on other performance parameters and definitely the one I would have done first, too, if the rules I'm following allowed for it.

Unfortunately, they don't.

About the only things thst I can do and remain class compliant are to ditch the Mach 460 sound system and swap the driver and front passenger seats for aftermarket units that wiegh at least 25 pounds each including associated bracketry.

PNYXPRESS

Haha. Well I'm putting on a carbon fiber roof panel that will be painted body color so it won't be noticeable. That will eliminate 20+ poinds from the extreme top of the car.

BabyGT

Is that something pre made or something you are fabricating?

PNYXPRESS

I have to mold it and then lay the carbon. No one makes one that I know of.

I already did my cowl for the new edge cause I was tired of it cracking.
I got a uncracked cowl for the SN95 that I am gonna mold up also.

BabyGT

Sweet, if you decide to make a few or one comes out not quite to your satisfaction for the new edge and the sn95 let me know.....

PNYXPRESS

I can do that. I still have the mold for the new edge.

BabyGT

Okay let me know what you would want for them.