Nissan Maxima?? (Page 2 of 2)

You're thinking like a drag racer, and this isn't drag racing. You are also "fine" with the straight line speed. But that straight line speed is a function of a couple things.
Drag vs Horse power. For a given Horse power (at peak), your car will only go so fast based on its drag (with gearing to have the maximum HP at the peak RPM). to go faster you need more Hp.

But how fast you get to top speed is acceleration. Your car will accelerate fast with lower gearing, or less weight, or more Hp. To do that you have to 1. shift to a lower gear and run up to redline, 2. change out your rear end to get a lower drive ratio, or 3. bigger engine, 4. use smaller tires. (one of those is easy to do, but hard on the car, another is easy and helps in other ways, and the third/fourth is expensive). If you have 5 gears to use and they are lower, you can optimize your engine speed to use max power in every place on the track. Why do you think bicycles have gone from 1 to 3 to 5 to 8 to 12 to 18, to 30 speed gearing???? to maximize the limited Hp of the human body!.

Having a big grippy tire in the corners is awesome, but this is about compromise of cornering speed vs acceleration, braking and straight line speed. And at some point you'll have more tire than you need. I'll bet you won't loose that much cornering speed with a 225/40, vs a 255/40. But you'll gain in other areas.

Weight, there is a rough rule of thumb that says 1 lbs of wheel weight is worth 2x lbs of body weight.
The real thing to understand is not so much the weight, but the inertia of the wheel. Interia, or the moment of Inertia (see wikipedia here: http://en.wikipedia.org/wiki/List_of_moments_of_inertia ) for a wheel like element is I= mr^2 (that's mass * radius squared). So the further the mass is away from the axle of the wheel, the more it increases the inertia.

lets assume that all of the 59 lbs of the 17" (diameter) tire/wheel is in the tread (which is not, so this is overly stated). The sidewall height is 255*40% (255mm*0.40=102 mm or 4") so the radius is 17/2 + 4 = 12.5". Square that = 156.25 in2, times 59 lbs = 9219 lbsinch2 (pounds inch squared).

The 20 lbs 225/40/15" tire plus 15 lbs rim =35 lbs. same calculations = 4235 lbsin2.  So there is less stored energy each wheel (that was only one wheel calculation). Now that's not as big a deal as car weight, but it can make a difference.

Yes, look at the spring perch for the front Maxima, if its the same as the late 200sx its a 6" dia spring, kind of big. The 4 Runner rear is a 6" spring also. and there are some other springs that will fit that also., just have to take a tape measure to the JY.

Mack,

This is some really good stuff, I suppose more research is needed and serious consideration warranted for a smaller/lighter wheel tire combo, time to search Craigslist again. Thanks, for the much appreciated input.

Two of the idea's you mentioned, we could so, namely shed more weight and smaller/lighter wheel tire combo, the others would take us over the $500 cap.