Yes, the rims are different sizes, but the outside diameter of the tires should be about the same between stock 17s and 18s. This means the distance between the fender to the tires should be the same regardless the rim size is 17 or 18, stock.

Now that you got me really curious, I went to measure the car. From the edge of fender to the center of wheel is 14 inches front, 15 inches rear.

 

mines is ~13 3/4" front and ~14 1/2 rear

 

Do you know if the car was ever lowered?

 

ocdavid

i have not seen any indication that the length (height) of the rear springs changed with the 2004.5+ models. spring rate and unloaded length being different measures all together. they would, however, have different loaded height.

some math....
some basic assumptions are made to simplify the calculations, so is not exact, but i think will illustrate the point regardless.

the weight of the z is listed on nissan's website as between 3188 and 3299 lbs depending on the model. so let's use 3250lb as an example.
the weight distribution is also listed as 53% front 47% rear. so the rear weight will be 0.47 x 3250 = 1527 lb
that rear weight divided evenly between each rear wheel. 1527 divided by 2 = 763lb

at static spring compression
763 lbs would compress the 2003-2004 rear spring: 763lb div by 342lb/in = 2.23 inch
763 lbs would compress the 2004.5+ rear spring: 763lb div by 427lb/in = 1.79 inch

assuming the unloaded length between the two OEM suspensions is the same.
when loaded the 2003-2004 rear will sit 2.23 - 1.79 = 0.44 inch lower than a 2004.5+

make sense?

EDIT: i also agree with above posters. the springs will not settle, they may sag after many many years, but not settle in the immediate term. also the "perception" that larger rims look more lowered as there is more metal to see and less black tire. the black of the tire gives the illusion of more wheel gap.

pp

 

$155 for an acid wash? Just take a bottle of vinegar and add it to your bucket of suds when you wash your car next time. It won't harm the paint or anything, and it'll take the water stains out.

 

4000,

Thanks for the info. yeah, this guy was asking for that price, but I thought to myself, what can i do with $155??? 7 1/2 lapdances in vegas,VIP room at the crazy horse 2, twelve cases of Newcastle, External Disk Dives, or a new headunit for the stock "Z" radio(+$100), OMG the list goes on and on...

I will take your advice on the vinegar + soap soultion. Thanks!!!

 

Palepony,

Thanks for the breakdown of this. It makes a lot of sense having someone who has done his research on suspensions. looks like I am going to buy some wheels, and some sort of suspension upgrade. Thanks for posting, puts my mind at ease.