PHIL928

I just bought a set of these What tires do you run on them?

FiveElements

I agree. Even with a 275 size tire, the car breaks loose easily, especially with mild upgrades to intake and exhaust.

FiveElements

I went with 225/40/18 front 265/35/18 rear, but the tires are a bit stretched on the rim, especially on the 8" fronts. I'm wondering about rub with a 245 front though. Let me know if you do try that size.

A 275 or 285 would probably be fine in the back. Lots of space there and I have no spacers.

I really like these rims. They are light, modern looking, BBS quality and an actual Porsche part rather than aftermarket.

vsteinh

Hello,
I finally bought slightly different wheels - also because of the helpfull comments of you guys.
Now I got:
7,5 x 17 ET 65
9 x 17 ET 55
Can you tell me what the best/biggest size for the tires is?
Thanks again for your help. I'm getting close....

CardinalCar

Where did you find your wheels in the end? I'm trying to find a proper set as well.

Those are the correct sizes for the GTS OEM wheels. Tire sizes from the factory were

225-45/17 (Front)
255-40/17 (Rear)

...but whether those are "best" or not is more of a debate. Regardless of what you put on, you'll want something which is close to the total diameter of the whole package. Figuring that out isn't difficult but requires a few steps.

What you need is the rim diameter plus two-times the sidewall height.

The sidewall height can be calculated in inches as follows:

(Section Width) * (Sidewall %) / 25.4

So for the tire sizes above:

Front: 225 * 45% = 101.25 / 25.4 = 3.99"
Rear: 255 * 40% = 102 / 25.4 = 4.02"

Therefore total diameter for each:

Front: 17" + (2 * 3.99") = 25"
Rear: 17" + (2 * 4.02") = 25"

So, for example, a 235/40 on that front rim gives a total diameter of 24.4", which is 97.6% of the original diameter.

Probably close enough not to matter, assuming the width fits under the fenders, but I wouldn't want to see it much farther away from the original size.

vsteinh

Following you advice, I would take
Front: on the 7.5x17: 235/40/17. -2.28%
Rear: on the 9x17: 265/40/17. +1.28%
Do you think they would fit on the wheel - and in the wheel house?
Thanks

Rod Handsfield

Use this handy tire size and circumference calculator
http://www.csgnetwork.com/tiresizescalc.html

FiveElements

The 235/40/17 should be okay. The size of the front will obviously not effect your drive ratio, MPG or speedometer. I'd run a 275/40/17 rear. It should fit well, be the more available and look a bit more aggressive.

vsteinh

Hello I checked several sources and I believe a 275 tire on a 9" rim is not possible. Even if I loved to...
Besides this, the combination 235/40/17 and 265/40/17 seems not to be possible to
order.
Nevertheless the combination 235/45/17 and 265/40/17 is possible. Both tires are slightly higher than the original sized tires. 25.33 and 25.35 inch. I hope this is not a big issue.

Besides this I found the Bridgestone Potensa RE760 Sport tires. Do you have any experiense this these tires?
Thanks
Volkmar

jcorenman

Certainly possible, but to what advantage over the 225/45-17 and 255/40-17 that Porsche used on these wheels? From some of the comments, you would think that Porsche was a bunch of dummies. They weren't, generally, but different folks make decisions for different reasons.

Personally, I am not convinced that fitting wider tires on the same width rims always buys you anything (except maybe looks). More rubber, yes, but a wider tire on the same rim also rolls more, and won't handle as crisply. It all depends on what's important to you.

Using the Tirerack spec's for the Bridgestone RE760's that you mentioned, a 7.5" rim is the minimum width recommended for a 235/45. If you went with the 225/45 then 7.5" is the reference width, with a range of 7-8.5". Being in the middle of the fitment range is good, I think.

Same with the rears, the 265/40 puts the 9" rim at the minimum of the range, while it is the reference width for the 255/40.

The larger diameter is not a big deal, your speedo will read a bit mph low and you will have effectively stretched the gear ratio a few percent. S4's are already geared pretty tall, but it is a relatively small effect.

Personally we have stuck with the 225/45-17 and 255/40-17 sizes that Porsche used for those wheels (we have two sets, for the S4 and the GTS). Our GT is on 235 & 265, but on wider 18" rims.

FiveElements

I have a 9" rear rims and the 265/35/18 tires are fairly stretched on them. Unless you are a race car driver on the street and want your sidewall very tight, you can certainly run a 275/35/18 tire. The factory tire for that exact rim on my 9" Panamera is a 275/45/18 size. It will not slip or be of any more poor traction with those tiny 225 front tires anyway. One of the best setups is a 9" front and 9.5" rear rim for a 928.

http://www.ebay.com/itm/Porsche-Pana...54aab7&vxp=mtr

88bender

Hi Guys

I read so much about which rims I can put on my 928S.
I would like to put 17" or 18" tops - which rims are the best fit and wont effect the ride and handling?
PLEASE HELP ME

Thanks

Vilhuer

Yes it is possible. Each tire manufacturer has its own limits. As mentioned Tirerack.com has tech specs for many of them.

Lucas Peiris

hey could you elaborate on the et47 being bad im looking at some with 7.5x17 et52 and 9x17 et47 rear