Larger Tires

[Ric Garwood]

I have a 2003 Cabriolet with 18 inch stock rims.  225/40 front (25.1 inch tall) and 285/30 rear (24.7 inch tall).  I would like to upsize slightly to 235/40 front (25.4 inch tall), and 295/35 rear (26.1 inch tall).  I looks to me that I will not have any clearance problems, but this is my first Porsche, so I wanted to get advice.  As it is now, rear tires look a little small.  Plus I read somewhere that Porsche speedos read lower than actual.  Thanks.

[judgejon]

My memory is that the 285 is an all-season tire, and the 295 is a summer only, not M&S rated.  
Look for tire sizes on inside of gas flap. 

[Ric Garwood]

OK, Thanks.  Can someone confirm that adding front 1/2 inch width and 1/4 inch height will clear without rubbing when turning?  And that adding rear 1/2 inch width and 1.4 inch height will clear?  Actually one half those numbers in/out and top/bottom.

[Loren]

Front: 235/40ZR x 18

Rear: 295/30ZR x 18

 

These worked fine on my car (MY99 996 Coupe). My front wheels were 8" not the stock 7.5".

I do not think you can go any wider on the front and very little on the rear.

[Ric Garwood]

THANKS.  I would like rear 295/35 so they are taller than front tires.  There appears to be plenty of room for extra height.

[judgejon]

I don’t intend to start the “tire wars” up again, but I ran on Michelin PS2’s year round.  It’s not a winter tire, not m+s rated, but rated aa and great in wet weather.    295/30 on the back. 

Edited September 26, 2020 by judgejon
Additional info

[Ric Garwood]

That settles it.  Keep the 225/40 on front and go to 295/30 on rear.  Then they will be almost the same height.  Front 25.1 inch and rear 25.0 inch.  Thanks for the comments.

[JTT]

I apologize for being late to the party.  I am running PS2s in 295/30-18 on my C2 Cab, lowered on B8s and H&R springs.  No clearance issues.  That said, I wouldn’t do it again.  The 295 on a 10” wheel is a bit too much.  I noticed the extra sidewall flex almost immediately when pushing the car on corner entry (yes, mine are N spec).  I’ll definitely go back to 285 on next change.  If you have 11” wheels, 295s should be great.  You may not notice, but this was my experience.

[Ric Garwood]

Wow, 295 is only 1/4 inch wider inside and outside, but it is 1/2 inch taller.  So I guess there is more flexibility.  I mostly went with the 295 to get the rear tire the same height as the front tire.  Thanks for the info.