mweaver444

I have a 2017 C4S Coupe with 245/35ZR20 (front) and 305/30ZR20 (rear) on the vehicle right now. I am not sure the exact rim size, but they are OEM rims. From what I can find online it looks like it could be (based on wheel size.com):
8.5jx20ET49 and 11.5jx20ET56
or
9jx20ET51 and 12jx20ET63

I found a set of used winters that I would like to purchase, but I am not sure if they will fit correctly. They are:
8.5jx19H2 ET56 (front) and 11jx19H2 ET48 with 235/40R19 (front) and 295/35R19 (rear).

Will these work on my car? Any guidance would be greatly appreciated. I'm new to the site, but not to Porsche. This wheel and tire thing isn't my strong suit.

Thanks! Mike

NiteJav

If you have RAS aka rear axle steer PCCB's (ceramic brakes) you will need to use 20's as 19's will likely foul with the RAS components or the ceramics. Otherwise that setup will work.

Any awd 991 is considered a wide body or medium body if you consider the Turbo body (fender based air scoops to be the 'true' wide body)

OEM 991.2 is 8.5jx20ET49 and 11.5jx20ET56

The 19's at the front will be 7mm closer inboard at the rim level, worst case scenario a 5mm spacer up front would get you very close to oem. The narrower tire brings the tire only 2mm closer inboard.
Those 19's at the rear will stick out about 2mm more at the rim level or about 3mm more at the tire level. (All in very acceptable range)

The front offset is a little strange, the rear is almost dead on.

The typical size/offsets for 19's for a 991.2
Front - 8.5 x 19 ET 50 - 235/40 R 19
Rear - 11 x 19 ET 56 - 295/35 R 19
https://www.suncoastparts.com/produc...91G219WWS.html

mweaver444

Huge thanks! No RAS or PCCBs on it so seems like a winner! Much appreciated and next level knowledge!

mweaver444

As a side note, the winters I found are OEM Porsche as well. THe offsets on the front do seem weird. Again, sincere thanks!

mweaver444

@NiteJav Is it possible to tell if TPMS is already installed? They are OEM rims, but already have the tires mounted. Just trying to understand exactly what I am buying.

mc3456

I had a 2017 C4S Cabriolet and just used my OEM RS Spyder wheels with stock size Michelin Alpins as my Winter rims and a set of HRE P101s (pictured) as my Summer rims.

Porsche does make a barely narrower set for winter, but frankly it is just a money grab. There is zero difference in performance by sizing down only 10mm front and back. I kept my Alpins (used only 400 miles in total) in case I get another 991.2, but that is looking much less likely now given the dearth of good cars on the market.

If you are near Boston, I can offer you mine for a very good price. They were only used about for 5 days of actual driving as I ended up storing my car from November - April for the 2 years I owned it. Needless to say, the tires are basically brand new.

mweaver444

Great idea and thanks for sharing! Car looks great too!

NiteJav

Most TPMS sensors have a metal valve stem (silver or black are the two typical colors) similar to the image below. (the porsche sensors look entirely different then the image below but the valve stem is the same)



Keep in mind there is a difference in TPMS sensors from 991.1 to 991.2. So if the prior owner was using this on a 991.1 there could be a problem. (frequencies are different)
If they were using it on a 991.2 you should be in good shape. Also find out what the date codes are on the tires, anything 2015 or older is probably not usable even if the tread depth is good. https://www.tirerack.com/tires/tiret....jsp?techid=11
Anything over 10 years is very dangerous, for me personally 7 years is about my limit.