Originally Posted by Yoshimura

If you keep same tires, all this is useless.

For same ET and same tire width, tire will be at exact same location no matter the wheel width.

Originally Posted by Mark P

Thanks for saying it so politely.

Originally Posted by Yoshimura

Sorry. English is not my native language.

Originally Posted by alpinestaraudi

Thanks Mark. I had a handle on the basics but this is very in depth. Thanks for taking the time to help a newbie!

Originally Posted by Mark P

Also FYI my OEM 20x8.5 ET33 peelers fit on an SQ5. LarryV has them

Originally Posted by JBDinTX

Yes. My offset is 25. I am also from north Texas (callisburg). This winter was brutal. Here is a pic

Originally Posted by Mark P

As nicely as I can say it, you really need to know the exact specs of what you have, and how changes in Width and ET will affect the wheels placement so you know what you'll end up with, long before you consider buying a different wheel and having it powder coated. That's a big undertaking if you don't even know how it will end up, when you're entire reason for doing it is based on that.

So here are the details...

Offset is the measurement (in millimeters) from the centerline of the wheel to the hub mating surface. [Assuming the spoke arrangement doesn't move...] the more positive the value, the less material exists on the wheel by the hub, and the wheel moves inward (towards suspension parts). Conversely, the more negative the value, the more material exists on the wheel by the hub, and the wheel moves outward.

So for a given width wheel, the change in ET directly dictates how much the outer edge and inner edge of the wheel moves. An ET10 wheel sticks out 20mm more than an otherwise identical ET30 wheel.

But once you start changing widths, now you need to take that into consideration. ET is measured from the centerline of a wheel. So if you keep the same ET, and only change width, the wheel will grow/shrink both inwards and outwards each by 1/2 the change. Thus for a given ET, going from a 7" wide to an 8" wide wheel will grow 0.5" inward and 0.5" outward.

If you are changing both ET and Width, you need to apply both changes to get the result. It may be mentally easier to first consider the wheel growing by width, then account for the ET difference.

Thus going from:
19x8 ET39
to:
20x9 ET40

Looking first at the width change of 1", your wheel will grow 1/2" inwards and 1/2" outwards. Then apply the ET change of +1mm will then move that result 1mm inward. So basically the net result is the wheel will be 1/2" further outwards than what you have now. Does that result in something you'd be happy with? If so, go with that.

Alternatively if you went with that same wheel, but otherwise an ET25, that would push the wheel out an additional 15mm (0.6"), for a total change of about 1.1" further out than your current setup. Is that what you want? It seems you don't have S-Line (or rather you don't have 20"/255 OEM wheels/tires), and therefore don't have the wider paint-protecting plastic fender extensions, so I might be hesitant to suggest adding that much width to your wheel. For reference, the S-Line/20" OEM wheel is 20x8.5 ET33, which compared to your original wheel would be 0.25"+6mm= ~0.5" further outward wheel. So if you went with the ET25, you'd be another 0.6" further outward than S-line/20" setup.


http://www.tirerack.com/wheels/tech/...jsp?techid=101

I created this previously to compare various wheels to the wheels that were coming standard on my S-line/20" (blue). You can use that to see how some of the others compare to each other as well:



Hope this helps!

Originally Posted by AngryQ5

this was the best explaination!!!!!!

great i know et now!!!!

was afraid to ask but i know now!!!