turbosjedi

I noticed the other day that my left front tire is a tad low. I hit it with the gauge, and it reads 12 pounds. So I inflate it to the proper pressure, and head to me local tire store. I say, Dude, the left front tire has a leak in it. I hand them the keys, and I sit down to read my bible, Redbook. Dude comes back and says...dude, you are down to the secondary rubber, we can't fix it. I said, OK, then slap a new Michelin sport on it, and I am good to go....he says, no, we have to replace all four tires because they are worn down, and because the car is all wheel drive, got to replace all four...This is news to me...I owned an all wheel drive Porsche before this one....and I never heard about the four new tire thing. Since the manual for the car is at home....I dawdle on over to the dealer....Explain to the Porsche SA problem, he looks at it....says...wow dude, you need four new tires and an alignment. Because our local dealer is a strong supporter of our local chapter of the PCA....I agree to order the tires from him, as well as an alignment....He says...got to order the tires, so I will call you when they come in...I take off, and about five minutes later, my SA calls...dude, you have the wrong set of tires on that car...and the ones on the back are the wrong size....I say....Dude, how can they be the "wrong" tires....Well. because they don't have an "N" code that means Porsche approved.....And the back tires are supposed to be a 295/30/R18...and yours are the 295/35/R18.....So I am now completely flummoxed....Why would there not be the correct tires/sizes on a CPO car? The tires were brand new when I bought the car last August. Why would you care if your tires have an "N" code or not? And if anyone out there has a 2005 TT "S," what the hell are you running for shoes on your car?

SSST

Dude. The N spec is Porsche specific and was created due to all the weight on the rear tires. Higher weight ratings and stiffer side walls to control all that weight swinging around back there.

mmporsche

Factory sizes are 225/40 18 and 295/30 18. It is very important to match the diameter of the fronts and rears on an all wheel drive P car. I wonder if this led to premature wear and damage to your diff? The N rating has been discussed before here so do some searching to formulate your own opinion. Being that it is a CPO car I would definitely review your paperwork if you do in fact have issues caused by the incorrect tires being on the car.

turbosjedi

thanks guys. I just shake my head at the whole damn business. A CPO car with the wrong tires/sizes...just unbelievable.

mmporsche

Just to be clear, I am not sure the difference between a 30 and 35 series tire is enough of a difference to cause any problems. I am sure others on RL with much more knowledge will chime in very soon so hang tight.

turbo4 me

I am surprised it didn't trigger your PSM. A while back I replaced my rears, left the fronts in place. On the way home went through a sharp corner and the PSM triggered- that will get your attention.

Back to the tire store I went for 2 fronts-

JG 996T

CPO car should have had N spec tires. Go back to dealer that sold you the car.

adam_

Dude, you are being scammed with the 'all 4 tires' thing. Total scam.

The difference between 100% and 0% is 8mm of tread. 0.3 inches. Given then you are NOT at 0% on the old tires the likely difference is not enough to matter.

Dealers and tire stores have found this is the new scare tactic to sell more tires!


(PSM will trigger with brand new tires that have not yet had the mold release worn off...you bought new fronts for that? )

Oh, it is a violation of CPO policy to sell a car with non-N spec tires.

(It kills me when people think "Its a Porsche dealer and a CPO- they'd never cut any corners, they have so much reputation at risk".... see how that works out now, they will deny it I bet!)

turbosjedi

I am going to try to contact the area rep tomorrow and see what we can do. I appreciate the help....dudes...

nick49

CPO states that all tires have to be the same brand, model, speed rating, specification code and age. If the tread depth is less than 4 mm they must be replaced with N rated tires.

The AWD cars are very touchy when mixing brands and old with new. Aside from triggering PSM and slipsiding a bit when brand new, uneven matches can cause several issues of instability and quirky handling. I've experienced this first hand and even went to my alignment guy looking for answers. I fit new rears of one brand that should have been compatible with my 50% PS2 fronts. I even looked at diameter charts, compared revs/mile, physically measures the worn fronts and everything looked good. It was not and actually scary to drive. I then got new fronts that exactly matched the rears in rev/mile and amazingly the car was transformed into handling better than ever in my nearly year and a half of ownership.

Going on 11 years of Boxster ownership, and having my 996 C2 for 7 years, mixing up anything and everything never presented a problem. The AWD is totally different. I don't believe anything I read or hear and have to experience it first hand. That I have.

2K7TTMIA

The CPO coverage better get you some free proper tires!

turbosjedi

So the update....The car's tires were within spec when it was sold, so the CPO does not demand a change of tire. I could argue that the size is wrong, but the tires have almost 8k on them, and it looks bleak to get anything done. The dealer certainly is not going to help me out, so I am just going to eat it and see if anything improves with the correct size, and a correct alignment. Lesson learned here, was stated earlier, just because it is a CPO, does not mean it is a perfect car. Plus, I learned something with the N spec tires. I really appreciate the input guys, thank you so much.

Kevinmacd

Let me just say this the P stabilty control is sensitive to not having all four tires within a spec. If 1, 2 or three are worn, putting on a new tire will cause the stabilty control to kick in when making some fun corners. With that said you really don't need to use N spec tires, there are others out there that work very well. You can use Hankooks, Nittos, TYokohamas, Sumitomos etc, as some have professed on this board work well. I have the Hankooks and they are a nice performer for regular street driving. Yes those sizes on your car are not the stock size! The N spec are approved tires by Porsche, but keep in mind that the N spec only means the tires meet the total perfomance specified by Porsche. Non N spec tires are safe but just might not give your the extra .001 sec on a course!