frankfast

I just purchased a set of 18" Carrera 3 wheels (off an '08) for my '01 996 C4 Cab. The tire profiles for the 996 and 997 on 18" wheels are slightly different. I've been advised that I need 5mm spacers on the front but which profile tires should I use - '01 or '08 or doesn't it matter?

RallyJon

225/40 F 265/35 R

frankfast

That's the size indicated for an '01 with 18" wheels. Do you know the reason for not using the size indicated for an '08 (235/40 front and 265/40 rear)? That is the size originally mounted to the wheels I just purchased.

TTJunkie

You want to be careful here. Your offsets and suspension components are different. You also have to worry about your AWD differential and the PASM/ABS computers. Modifying tires requires a lot of calculation. That said, increasing 10mm from stock won't make any difference. But if you're going to play with tire sizes, you might as well maximize traction. Just remember to allow for tolerence lock-to-lock and under compression and keep front-to-rear diameters within a few tenths of an inch.

gota911

What is the wheel width and offset for the front and rear?

RallyJon

265/40-18 is full inch larger diameter than 265/35-18. The 997's transmission ratios are lower to compensate. Your gearing will be 4% taller with the 997 tire size.

Are you looking for an excuse to keep the 997 rubber, rather than spend big bucks to put the correct size tires on? You probably won't hurt anything.

frankfast

I have to buy tires in any case. I just wanted to know whether I should go with the standard '01 fitment or the standard '08 fitment. By changing to the later, I didn't know if the car would respond adversly. It doesn't look like there is much difference. More rubber in the front and the car slightly higher in the back. It will be more agressive than the 17" wheels that came with the car.

gota911

Everything else being equal, taller side walls will give you a little softer ride but there will also be a little more flex of the side walls when cornering.

ivangene

TTIWWOP !

OH, post offsets and widths...... and is your car C2/C4?

frankfast

Car is a C4. Came stock with 7" and 9" by 17" wheels with 55mm offsets front and rear. The new wheels are 8" and 10" by 18" with 57 and 58mm offset. I was told to add a 5mm spacer at the front wheels by a company that should know.

ivangene

LINK

try this really cool interactive comparison tool...

be sure to read the results down at the bottom of the page - not sure I got the link right... cant pull it up from work

frankfast

Can't pull it up either.

RallyJon

Taller, softer sidewalls are not more aggressive. You want more sidewall (flex) and worse gearing in the name of getting more rake for a "more aggressive" look? Sorry, don't get it. Maybe you should have just gone for 19s? 18s are so last decade anyway.