There are a couple of good calculators at http://www.1010tires.com/tech.asp

BTW, if they didn't send what you ordered (245 v. 235) return them.

 

Here is a pic

 

Very nice - I like the way they fit. What type of wheels and what are the widths and offsets. Thanks.

 

you are correct! More grip in front means a balance toward oversteer in the rear.

The issue will likely not be noticeable. If it is, adjustments can be made to tore pressure, and that should balance things out. vs spec, Slightly more pressure = slightly less grip. Slightly less pressure - slightly more grip. So - if there is an issue with understeer/oversteer balance, it can be resolved with a lb or two more pressure up front, and a lb or two less pressure in back.

Personally, I wouldn't bother...

 

This is incorrect. The aspect ratio is a ratio of the sidewall to width. The width is 10mm wider, therefore the tire sidewalls will be taller.

Tire measurements are given in mm and ratios. 245/35/19 is a 245mm wide tire whose sidewalls are 35% of the width, with an inner diameter of 19". If OEM fitment was 235/35/19, then you should only change values that result in the same height of the tire, or rolling circumference. Your new 245/35/19 tire is 26" tall, while the OEM tire was 25.7" tall. This might not seem like much on the front tires, but it would cause a significant speedo error on the rears.

IMO, stick with the engineers at Porsche and put the right size tires on.

 

it is worth being incorrect to have you make your second post in more than 4 months

 

Thanks to all for your help and insightfull comments!

 

Wheels are Vorsteiner V-308s with standard offset.

 

Yeah, I can't believe how long it took you to be incorrect. I've just been waiting and watching your every move, with my fingers poised over the keyboard itching to correct you.

OR...

It was useful information, and NOT criticism, that you AND the OP could use.

 

No problem...wasn't taken as criticism...it is comforting to know that you are out there ready to pounce

 

OK. Group hug everyone. I was jsut looking for some insight. Didn't mean to start a "mine's bigger" thread.

Thanks everyone that posted. I have had the wheels/rims mounted for about 24 hours (that is a whole other story) and so far I cannot decern an appreciable difference. Then again, I haven't really pushed the car either.

 

No issues here. I was only clarifying an issue for you. I realize I've only posted here a few times, but that doesn't mean I am inexperienced with these cars. Far from it.

You may not feel a difference, but it is there, by definition. It's one of those details that an insurance adjuster would notice, say, if you were to careen off the road due to excessive understeer and wreck your car. "Why did you put non-OEM tires in the front?" they would ask... just sayin'