((( Tire Help )))

KaiMeN::S · #1 (**permalink**) 02-14-2007, 07:42 AM

Hey everybody,

I am getting a new set of wheels, specs:

20x8.5 front
20x10 rear

I was wondering what would be the best set of tire size for my setup.

Was thinking on 245/30/20 front and 285/25/20 rears.

Any thoughts?

**beez** · #2 (**permalink**) 02-14-2007, 02:34 PM

If N-spec tires come in those sizes, then they'd be good - you need to be very careful with these in that they need to be within 3% of the overall diameter of each other front to back, and within 3% of the same overall diameter of the stock tires you are replacing. Take a look at the "specs"pages for the tires (Michelin PS2s for instance) at TireRack.com. You might need to go to 295s in the back to get the correct diameter. If you don't stay within those diameters, you'll have trouble with your electronics like PSM and ABS working correctly... and you want those to work correctly.

brad

**jim@tirerack** · #3 (**permalink**) 02-14-2007, 03:13 PM

We would recommend 245/30R20 front and either 265/30R20 or 275/30R20 rear. Both of these application will work fine on the car. If I can help with the specific tires let me know.

KaiMeN::S · #4 (**permalink**) 02-14-2007, 11:16 PM

Quote:

Originally Posted by jim@tirerack

We would recommend 245/30R20 front and either 265/30R20 or 275/30R20 rear. Both of these application will work fine on the car. If I can help with the specific tires let me know.

265 or 275 sounds small. Isn't something ike 285 better?

its a 20x10 rear.

**beez** · #5 (**permalink**) 02-15-2007, 12:15 AM

Quote:

Originally Posted by KaiMeN::S

265 or 275 sounds small. Isn't something ike 285 better?

its a 20x10 rear.

It depends a lot on your rim width, and again you're also hemmed-in a little by having to be within 3% of your overall OEM diameter.

For instance, on the tires...

The OEM specs for 19" PS2s is:
front - 235/35-19 - overall diameter=25.5"
rear - 265/35-19 - overall diameter=26.3"

If you have 18s, the diameters are 25.3"/26.3" respectively.

For the 20" you have:
front - 245/30-20 - overall diameter=25.8" - a good match
rear - 285/30-20 - overall diameter=26.9" - a good match
rear (alternate) 295/25-20 - overall diameter=25.8" - a good match - except that 295 would probably be just a little too wide to use on the 10" wide rim you have - 295 would be better used on a 10.5" or 11" rim. 285 is best used on a 9.5" to 10.5" rim. A 295 tire on a 10" rim might give you a little too much sidewall flex, imo.

I don't see a 275/30-20 PS2 on Tirerack - only a 275/40, which is waaaay too tall.

You should do this math on any tire you'll likely use on the new rims... I'm assuming you have the offsets figured out. Staying within the 3% tolerance for the overall diameter is very important if you want your electronics to work properly... and I would recommend staying with the brands and models of tires that are Porsche N-spec for the car. If you're not sure what N-spec is, do a search and you'll find it - there's been plenty of earlier threads on the topic.

brad

KaiMeN::S · #6 (**permalink**) 02-15-2007, 12:47 AM

Thanks Brad.

**Santa Fe** · #7 (**permalink**) 02-15-2007, 12:54 AM

N-spec tires - http://www.caymanclub.net/reviews/sh...uct=37&cat=all

**jim@tirerack** · #8 (**permalink**) 03-07-2007, 07:28 PM

You have to keep the diameters close to stock front and rear. If not the anti lock brakes can be affected. The 245/30R20 and the 275/30R20 would do that.