IceCold4x4

So I'd like to run 245/45r17 on all 4 corners what wheel offset would make this possible? Or a 245/40r18 if that makes finding a wheel easier.

davek9

First the year of the car will make a difference, and also wheel and tire sizes are the topic of many threads, please search the topic under this forum

FredR

If you want the system to function as Porsche intended it you need wheels with ET65 up front to maintain the NSR [negative scrub radius] that Porsche designed into the system- this is nothing to do with the size of rubber carried but it just so happens that a good offset also helps wider rubber fitment but not many rims have such offset and therein lies the problem of availability, The rears are less critical but ideally around ET55. To carry a 245 section the rim width needs to be in the range 7.5 inch to 9 inch with the optimal size rim being a 8.5 inch for this section size.

IceCold4x4

I did search and didn't seem to find anyone running a square 245 setup.

So sounds like an et60 17x8 would be the size that should work at all 4 corners? That should be fun to find....

FredR

Quite a few folks have run 245's all round on 16 inch wheels but supply options for 245x45x16 are now extremely limited. If you run the same size section front and rear the car will tend more towards oversteer compared to stock setups that experience noticeable understeer by design.

GeorgeM

https://rennlist.com/forums/parts-ma...for-928-a.html

IceCold4x4

Mainly looking to be able to rotate tires evenly as this car is pretty much going to be a daily driver and trip car and those sizes seem easy to find if a flat is encountered. While also giving improvements in tore tech and traction. Want to run Michelin Pilot Super Sports as I loved them on my s60r.

FredR

I personally think the concept of rotating tyres is an outdated concept for high performance cars and given the wear patterns are different front to rear it makes little sense to me to rotate them but it would be interesting to know what the brains trust thinks about this concept. For your needs a set of GTS wheels [Cup 1 or Cup 2] with 235x45x17 on the fronts and 265x35x17 would be perfect.

I have run Michelin PS2's and loved them - same for Pirelli and Continental. Over here I can only get 4 years out of a set and by then the heat has trashed them. Indeed the local police recently introduced legislation limiting tyre life to 4 years from date of manufacture to try and prevent some of the horrific wipe outs we see in this part of the world. On our track days a few years ago we found that on a 60 second autocross lap each year of service consistently increased lap times by 1 second per year of use.

terry gt

I run a 245/45/17 on the front with a 8 inch rim 56mm offset , rolled fender lips
rear should be a 275/40/17 , to make the car balanced

IceCold4x4

So I found a set of 18x8 5x130 bore 71.58 et 57. From searching over the past day or so it appears that fitment will work with a 245/40r18 at all 4. They also have a 18x9 et43 would that allow for a 265 in the rear? Or would I be better running an 18x10 et 65?

Petza914

I run those exact wheels on my 928 Spyder but in the silver finish. They were the closest think I could find to the TechArt Formula style that I love on the 928 in an acceptable offset (the TechArts have a 911 front offset).

I'm running
Front - 18x8 - offset 57 with Nitto Invo 235/40-18
Rear - 18x10 - offset 65 with Nitto Invo 295/35-18 and 15mm spacer

...but my rear bodywork is much wider than stock because of the convertible conversion on my car.

My front fender lips are rolled and I don't have any issues with rubbing or contact, even with mid-corner suspension movement.

Good luck getting them in the US though - CMS doesn't distribute to any wheel dealers here in the States. I had to use a division of the Company I work for to buy them in Italy and ship them over with some of the paper handling machines I sell, but here are a few different angles so you can see what they look like with the 928 body lines (or at least 928 convertible body lines) in case you're able to work out how to get them here.

IceCold4x4

That's awesome, glad to hear confirmation. And see pictures Do you think there'd be a problem stepping up to a 245 in the front?

Petza914

I selected my tire sizes based on trying to be very close to the proper rolling circumferences of the OEM sizes and based on what width tires should be used on what width wheels. Below is a chart that shows the idea and possible tire section widths based on wheel widths.



On an 8" wide wheel, 245 is pushing it and outside the ideal range. On my rears I went a little outside the range too and it doesn't seem to cause an issue with the way the tire sits on the road or with a rounded sidewall look, so I think performance wise the 245 would be fine, however, with these specific wheels and their offsets, that extra 5mm toward the outside might be just too much. Prior to these wheels, my car came with Carrera Lightweights that were
FRONT 225/40 ZR18 mounted on 8Jx18 ET 50 wheel
REAR 285/30 R18 mounted on a 10Jx18 ET65 wheel

Prior to rolling the front fender lips I actually had the tire catch one turning into my neighborhood on the mid-corner bump. It puckered the lip a little, but didn't go beyond and into the fender portion, buy you can see that with that setup I was 7mm further out on the wheel, even with a slightly narrower tire. I like the look of the lower than stock ride height and haven't had any contact again, but I'm probably maxed out on stance. With 245s you'd probably need to run the higher stock ride height and/or roll the fender lips. Here's are a couple more shots so you can see the wheel and tire relative to the fender.