fast1

The tires on my 981S need to be replaced, and my desire was to replace my Pirellis with Michelin PS4S. Strangely enough the 20" PS4S are approved by Porsche and have the N designation, but the 19" tires aren't approved. Unfortunately Porsche doesn't offer a reason as to why a tire is not approved; it's just a pass/fail process. Although I've learned a little about performance tires over the decades, I'm certainly not an expert. So I typically default to the factory tire experts with respect to their recommendations, but if I don't buy the Michelins I really don't see a tire that appeals to me.
Bottom line is why would a 20" tire be approved but a 19" tire fail?

vracer

I looked at TireRack a few days ago, and if I remember correctly, either the 19 or the 20 listed the fronts and rears manufactured in different countries. Is that the difference??? Just not tested by Porsche??? Michelin just didn't pay the fee to Porsche to get the designation on both sizes???

fast1

Bizarre enough to be correct. Other than size, the 19" and 20" tires should be identical.

badabing

It just depends whether or not the tire manufacturer agreed to have their tires tested by Porsche or not.

I bet if the specific tire is not contemplated for an OE fitment then the manufacture is much less inclined to bother with the testing process.

I own several p-cars and like you I always tried to use N spec tires.

However this past season I tried out a few sets of non approved Conti Extreme Contact on my track only 987.2 Cayman S and I'm happy to report they performed just as well if not better than the previous tire which was N approved.

If they can perform on track pushed to the limit i wouldn't think twice about running them on the street.

storii

If the PS4s in a particular size(s) are N rated, I wouldn't think twice about mounting the same tires in different sizes without the N mark. As a matter of fact, I'm currently running the PS4s in 245/35/20 in front and 275/35/20 in rear on my 981 BS. These sizes are not N rated but it doesn't bother me at all. If Porsche tested a particular tire in a particular size and was happy enough with it to grant the N badge, other sizes of the same model should be just as good as long as fitment is within reason.

GregWormald

I've heard that the N spec tyres are actually different from the plain ones as they are often modified for autobahn speeds in the wet.

vracer

I hate, (refuse) to say how fast I went in the rain when picking up a new bimmer in Munich.

Kitc2246

The "N" isn't a pass fail but whether or not Porsche has official tested and endorsed the tire as an OEM. I'm guessing they pay Porsche for the testing and "N" designation. I'd recommend at least price comparing with Tire Rack. Their price includes two years of road hazard. I use one of their recommended local installers. Make sure you print the install price or you will pay more. Any N Spec tire for a Porsche is going to have a high speed rating, but that doesn't mean a non-N spec tire can't have the same or even higher speed rating. Porsche Pilot Sport 4S is a replacement tire for my 2009 Boxster. See the Tire Test in Tire Rack. The 4S are excellent in the rain.

2009 Boxster PDK wSport/Sport+

il pirata

As Kitc2246 stated it's whether Porsche tested the tire with the Manufacture or not. They do not test every possible combination of tires. Since my first Porsche in 1973 by and large I have had tires without the N designation without issues. If you research the tires in details it will be hard to find a difference in published specifications (speed rating, UTOG, etc etc).

Here is what Tire Rack says about N spec:

https://www.tirerack.com/tires/tiret....jsp?techid=26

I have never seen a test done with N spec tire set and a non N spec tire set with same car same car, conditions, etc. but my guess is you would have to be Walter Rohrl to know the difference....maybe.

I do have N spec PS4S on my 2016 Spyder because the price from dealer was less than Tire Rack and the installation cost was much less the indy tire shop, plus the tech who does the work will not mess the wheel up. Huge fan of the tire for street use.

You did not say what year your 981 S is, but for the 2016 model there are 19" N spec tires available. The UTOG mileage is pretty low though for these, frankly I would go for the RE71R if you want to go all in for performance or the Extreme Contact Sport if you a longer lasting tire that still delivers great handling. BTW the PS4S listed in the link below are not matching, the front is a the standard "ECO" version and the rear a Mercedes version. Not sure why Tire Rack would even try to sell this combo. The Michelin site does not list the rear PS4S as available for the 981 S.

https://www.tirerack.com/tires/TireSearchResults.jsp?tireIndex=0&autoMake=Porsche&autoYear=2016&autoMod el=Boxster+S&autoModClar=&frontWidth=235%2F&frontRatio=40&frontDiameter= 19&frontSortCode=57261&rearWidth=265%2F&rearRatio=40&rearDiameter=19&rea rSortCode=57648

Scooby921

It's not that Porsche tests the tire and Michelin "gets" to put an "N" on the sidewall. It's that Porsche has chosen that tire (model and size) to be an OEM option. Thus they've worked with Michelin to fine-tune the compounds used in the tire to achieve Porsche's goals for the vehicle. The "N" means that tire is a slightly different rubber compound than the basic "non-N" tire. This also means an N1 is a little different from an N0. They are all going to be different from a Mercedes or Ferrari or BMW spec and designation on the same tire. The N-spec Pilot Sport Cup 2 for the GT3 or GT4 is a slightly different compound than the M-spec of the same tire for the AMG GTR.

This is why you might find a 20" tire with an N spec, but not a 19" tire of the same model. Only one of the two is/was used as an OEM tire option on a Porsche vehicle somewhere around the globe.

As for needing to Walter Rohrl...not quite. Though it is a whole lot easier when you have access to an OEM vehicle dynamics facility and have the ability to test back-to-back. A Ford vehicle dynamics engineer told me they tested the N-spec Pirelli PZero for the Mustang. Better maximum lateral acceleration and improved steering feel over the non-spec compound, but the N-spec doesn't like cold temps and water. Below 50°F and wet and they skate. Ford opted for a different tire spec to make the car safer at lower temps before [smart] people install winter tires.

vracer

[QUOTE=Scooby921;15665504. A Ford vehicle dynamics engineer told me they tested the N-spec Pirelli PZero for the Mustang. Better maximum lateral acceleration and improved steering feel over the non-spec compound, but the N-spec doesn't like cold temps and water. Below 50°F and wet and they skate. Ford opted for a different tire spec to make the car safer at lower temps.[/QUOTE]

Thanx, Scooby; I think that's the first time I have read a direct source quote like that.

Code

Bingo. I went to a Michelin performance tire seminar where they said exactly what you just posted.

daylorb

How did you like the Conti? Really appealing considering the sizable price difference. Tempted to try them when my 4S wear out.

fast1

I had previously read the N designation meaning at the Tire Rack site. Here is an excerpt from their long N explanation which is puzzling: "Using tires that are not N-specific is not recommended ...." I have a 2013 981BS. If you go to the Tire Rack site and search by make and model for a 2013 981BS, Michelin PS4S along with some other tires is listed for 19" wheels. So if you are to believe Tire Rack's N spec guidance, they are listing a tire which is not recommended. 20" Michelin PS4S for a 2013 981BS do have the N rating. Why would Tire Rack list a tire which by their own definition is not recommended?

Drew_K