EMan 928

I was looking at the site last night and saw that Porsche used the 245/45/16 tire size for both the 8" and 9" wheels (before the GTS wheels). I have the 9x16 D90's on one of my cars and the 245/45/16's look a little narrow to me. what do you think? Is the 245/45/16 the correct tire for both a 8" and 9" wheel?

edfishjr

An 8" wheel is about the smallest you want to use with a 245 tire. A 9" wheel will provide very good support (good transient response) for a 245. On the other hand, you can definitely go bigger, 255 or 265 on a 9" wheel (if available) is fine and will usually provide more ultimate grip, especially with a modern, ultra-high performance summer tire with stiff sidewalls. You can even go 275, but I wouldn't recommend it for a street car where good transient response is a key component to driving enjoyment. This all assumes you can get a proper aspect ratio to keep the total diameter close to keep from creating problems with gearing, CG height or rake.

I autocross a different make car with 275/35-18 BFGoodrich Rivals on an 8.5" wheel. This is considered an "over-tired" combination, but the increase in ultimate grip over a 255/40-17 on an 8.5" is considerable, at the expense of transient response. It works only because the Rival has a very stiff sidewall and the aspect ratio is less, meaning a shorter sidewall.

In a 16" diameter, you are now really constrained, as there are few options for high-performance tires these days.

James Bailey

the 245 recommended rim width is 7.5 to 9 inches, tire width of the bulge of the sidewall is the 245mm when fitted on an 8 inch rim...note that tread width is more like 9.5 inch depending on the tire.
The nominal "size" noted on a tire is NOT tread width but section or bulge width and each tire maker decides what width rim is used for their measurement. So many variables

FredR

The stock S4 rear wheel has an 8 inch rim and was kitted with a 245x45x16 so I think you can assume it works just fine. A 9 inch rim will also take such a section and wider if you can find one of a suitable diameter without screwing up the final gear ratio [as other options inevitably seem to do].

Guess it all depends on what you are happy with.

Regards

Fred

EMan 928

Thanks for the responses. Looks like Porsche kitted the 245/45 with the 9" D90 rim as well as the 8" S4 wheel. To me the tire just looks weird on the 9" D90 rim...the look where the rim is actually wider than the tire. Does anyone have a GT with these D90 wheels and the 245/45/16 tires? Be curious if your tire sits the same on the rim as mine.

James Bailey

that look is because a 9 inch rim is measured at 9 inches where the tire bead sits on the rim and NOT the overall width from wheel lip to wheel lip. Design 90s being a cast wheel have thick lips to add strength which also adds width. And as mentioned your tread width will vary from one brand to another on the same nominal 245. So you may have the look and reality that the sidewalls splay out to mount on a rim which is wider than the actual tread width but it actually will handle better that way

terry gt

What Santa said . I have 245 on my D90 9" rims and they do look narrow . However there are very few tires in that 16" size range to choose from , and if you go wider you may end up with a taller tire which will effect the gearing

worf928

245 is correct - as far as OE fitment is concerned - for the D90 rim.

EMan 928

Thanks, guys. I appreciate the confirmation. Like I said, it just looks strange.

worf928

<sarcasm>
This is yet another way in which the 928 was ahead of its time. Today the kids call this look "stance" but they would probably prefer to stretch a 225 onto the 9"...
</sarcasm>