We're all familiar with this, right? ................................................
https://www.s2ki.com/forums/index.php?showtopic=48572

Basically, even though the OEM SO2s are labelled "225", we've been ordering "245" when it comes to non OEM replacements so that we keep the tread width more or less the same. (Please read the above link for the rest of the details).

I have 2 stacks of OEM 16" rims sitting in my garage. One stack has the OEM SO2 tires mounted on them. The other stack has Michelin Pilot Alpin mud & snow tires mounted on them. These Michelins are the EXACT same sizing as the SO2s. Now, based on what we've been told about the weird SO2 rear sizing, I expected the 2 stacks to be different in height or at least the same. Well, to my surprise, the Michelin stack is TALLER!



This struck me with some curiosity, so I did a more isolated comparison:


Here are the two "225s" side by side. Note that overall, they are about the same width, EXCEPT ........................................

Notice that the width of the "footprint" on the SO2 is wider and this is why we've been getting "245" in non-OEM tires. The SO2 tread is more "square" at the edges, thereby putting down more rubber ...................... about the same rubber as a "245".

Now, here are the front "205s":

To my surprise, the width (and footprint) of the SO2s are NARROWER. The difference in height of the two stacks is NOT from the rear tires (as one might expect) but because of the difference in the front tires.

 

Very interesting.

 

The real difference is the contact patch and not the section width. You hit the nail on the head. If you just stack them side to side they are going to be close. If you look at the contact patch it will not be close. The front tires on the S02 are actually a little narrower than some of the other tires as well.

 

My thought exactly.

 

So, do you think that replacing the fronts with 225 width (increasing the contact patch) may contribute to the much talked about "oversteer problem"? I would think a 225/245 stagger would be great for the car, but maybe that is too much front tire for a 245 rear.

 

This may not answer you directly but let's look at what Honda did on the AP2. They went with a 245 on the rear and bumped up the front to 215. I guess if you were to tow the "company line", this would be "ideal". Somehow, I doubt that another 10mm up front is going to dramatically change things. In fact, I've seen a few owners running 225/245 on 16s and they have not indicated anything detrimental.

Also keep in mind that many owners have gone to 225/255 on 17s.

 

Please note that the michellins sidewalls buldge more than the SO2's that is the reason why you will see the height difference.

 

This may be one way to look at it, although it is wrong. The bead width of the Michelin is exactly the same and thus the "bulge" is exactly the same. It's just that the Michelin (or most other non-OEM tire) does not have the same "blocky" sidewall construction as the OEM SO2. The sidewall of non OEM tires begin to "curl" toward the tread sooner (a more rounded transition between the sidewall and the tread) while the OEM tire takes a sharper transition, waiting longer before taking the turn to make the tread. It is this difference that gives the "optical impression" that the sidewall "bulges" when in fact, it doesn't.