I've been looking at a set of 17" rims, but I have a question .. if I got them, then how much would the height of my ride be raised? 2 inches? would I need to get a set of lowering springs to keep the height? I think it would look weird with my bodykit being higher off the ground

 

when I got my 17 it really dosent look like it went higher at all, it actually looks nicer because it fills the whole wheel well

 

i dont think it will make a huge difference to the height, if you go for low profile tyres the diameter of the wheel wont change much and they do fill the arches much better. my car is stock height on 17's.

 

Actually, your hieght shouldnt change at all. If you do things the correct way and go with the right size tire your ride will be just the same distance from the ground as if it were stock. If you get a tire that has a larger diameter than the stock ones, your speedometer and odometer will be off. The sticky in this section has a link that will show you what im talking about. Its the first link in there, the one thats like miata.com or something.

 

all depends on outer diameter of the wheel (rim+tire)

How to calculate outer diameter:
-------------------------------------
stock tire size is 205 / 50 R15.

205 is width of the tire, in mm
50 - is profile height % (procentage of width)
R15 - outer diameter of the rim

1. calculating profile height
width / 100 * profile height %
205 / 100 * 50 = 102.5 mm (or 102.5 / 25.4 = 4.04 inch)
so profile height is 4.04 inch

2. calculating outer diameter of the wheel
outer diameter = profile height + rim outer diameter + profile height
outer diameter = 4.04 + 15 + 4.04 = 23.08

So, outer diameter of stock wheel is 23.08 inch.

So if you keep outer diameter of your wheel around 23 inch you will be ok (no change in riding height and no change in speedo measurement (sp) )

So lets see, outer diameters of some tire sizes:

205/45 R16 = 23.3"
205/50 R16 = 24"
205/45 R17 = 24.2"
205/40 R17 = 23.5"


If you want to calculate how ride height will change you need:
1. calculate outer diameter of stock wheel and wheel you want to install
let's say:
A=outer diameter of stock wheel, which is 23.08"
B=outer diameter of aftermarket wheel, let's choose 205/50 R16 = 24"

so ride height change will be:
ride height change = B/2 - A/2 = 24/2 - 23.08/2 = 12-11.54= 0.46 inch

if this number is positive, then riding height will be increased on 0.46" (as we calculated it)
if number is negative - riding height will be decreased on that number.


If you have any questions - ask. I hope you understand my English.

 

u can look at my pics in the pic forum. id say it sits higher, but if u didnt own the car, u wouldnt know.

 

Dmitry that was very helpful!
thanks smile.gif

so with 205/40/17 i will have a difference in my speedo? anything to worry about? 23.5" vs 23.08" stock


23.5/2 - 23.08/2 = and an increased ride height of .21"?

 

It won't be a difference, you probably will not notice it at all.


Calculating speedo measurements change
============================

A - outer diameter of stock wheel
B - outer diameter of aftermarket wheel

Coefficient of change (Z) will be:
Z = B/A

So, your actual speed will be:
Actual speed = Speedo measurement * Z

*no metter is your speedo in mph or kph.

For example:
if you use 205/40 R17 (outer diam = 23.5"), (stock is 23,08")

Z= 23.5 / 23.08 = 1.018

So if your speed will show 60 mph your actual speed will be:
60 mph * 1.018 = 61.08 mph

 

For speed it would have to be the radius, so multiplythat # by pi, pi is about 3.142858.

 

Circuit lenght = 2 * radius * Pi = diameter * Pi.

You don't need to calculate circuit lengh to know how will speedo measurements be changed. Cause you are manipulating with diameter ratios. It would be the same.

. . . .B * Pi . . .B
Z = -------- = ---
. . . .A * Pi . . A


BTW, Pi = 3,1415926535897932384626433832795