These are 8.5 X 19 ET54 235/35 ZR19s on the front and 11X19 ET51 285/30 ZR19s with a 24mm spacer on the rear. I think they look very nice on this '93 GTS but anything larger would be too much...

 

We are talking about street use and offsets.
Don't know why anyone would run 305's up front for the street. Heck, I only ran the 275's of DE days way back when.
Track car ran 305's up front and 335's in the rear on 18X12" wheels. But that won't work on a 928 unless highly modified.
We do see the effects of larger and sticky tires on the 928. Rip out of the sway bar mounts.

 

Andy, regardless of the offset discussion and all, you'll need to dump those tires and put the rubber bands on it to get the diameter down. The shoulder on a J rim is something like 15mm, total diameter therefore somewhere in the 21+ neighborhood. So ~~3.5"/2, or less than 2" from new tread to rim edge. Ok for riding on rails, not so good for anything that includes hard impacts, like potholes and even casual road construction.

There just isn't room in the front wheelwell for much more than 25.7" tires on wheels that wide, especially if you stretch to 275's. You'll be rubbing before full lock, worse when suspension is compressed I predict. The Pana original tires are too big diameter IIRC to even mount with wheels straight ahead. So if your economic calcs didn't include new tires, they should. Goes for any Pana wheels, really.

 

...but it DOES remind me a bit of a DONK

 

As the world looks at larger and larger wheel diameters as standard, getting wider performance 17" tires is getting a ittle tougher at least in the Mich Pilot family. There are enough cars that still use 255's in the market that they are in production, but I forsee that soon the 17" sizes will slowly fall away as the wider 16" sizes have over the last decade. The Honda Pilot DD has 18" wheels, and wider tires than the rear of the 928 has right now. So looking ahead, 18" wheels are probably in our future if they aren't already on our cars. Meanwhile, the ride on the 17" wheels with the Mich Pilots is great. No teeth rattling, not as much worry about tire and wheel damage on less-than-stellar roads. The Panamera comes with several different wheel options, and many here have gone that route. Maybe find a set of similar 18" and know that they will be OK on fitment.

 

There was a local guy here in Salt Lake who had 19's on his 928. I didn't think it looked good at all on the car. They were nice wheels and all but it didn't look right, it reminded me of a matchbox car.

Don't do it, I think 18's are the max for me.

Andy

83 Euro

 

yes, on the street there are no adverse effects with 275s up front.. it fits the car perfectly, doesnt rub, and you can go full lock with no issues.

yes to make 305s work , its a stretch, but depending on the manufacturer.

sway bar mounts dont break unless they have been pre-torn by hitting a birm. OR, i suppose you have the wrong spring and shock combination.

the new chassis ive been running has not tweeked or hurt the swaybar in 54 race days with no mods at all. about 80% of full stiff setting of the sway bar (devek)..... thats with slicks and DOT race ruubber, and at the track. no street driving will ever come close to those kind of forces.

that looks very nice.