Higher N always better for tires?

My rears are close to the wear bars, and I just picked up a screw in one. Rears are 295/30-18 Michelin PS2 "N2" and the fronts are 225/40-18 PS2s but not N rated. The fronts have about 7/32nds so are fine. Looking at Tirerack, they have three versions of the 295/30-18 PS2: N2 (with a lower weight capacity), N3 and N4. The Porsche tire guide only lists up to the N3 for that size, so I have no idea what application the N4 is even for. An older post says "get the highest N that's offered," so should I get the N4s even though the N3s are the latest recommended in that size for 996s?

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Ideally all 4 tires want to be N rated and believe it or not the same N number. How important is this? Well, here's what happened to me and why I think it may be more important than many owners think: Briefly, my Turbo required new rear tires. Dealer parts manager told me he may not be able to get same tires -- the same N number -- and to keep the same N number the front tires might have to be replaced as well. Before I could object he told me since my Turbo was covered by CPO warranty if he couldn't find the same N tires as the fronts Porsche would buy new front tires that matched the new rear tires. My point is that if Porsche feels so strongly about this that it would buy new front tires even though they were perfectly servicable (and still are with 24K miles on them later) just to ensure all 4 tires not only are the same brand and model of tire but also have the same N number that there might be something to this. Sure, it could be that the number of tires Porsche has to replace is very small and it is willing to do this to pull in the suckers. But maybe not. Anyhow, parts manager did find the right rear tires so there was no need to replace the front tires. Sincerely, Macster.

My understanding is that the higher numbers in the N-spec tires are later revisions of the tire. I'm sure the changes between N2 and N3 are subtle, but they are different. I've also heard what Macster said - you should match all four tires.

To complicate your search even more, not only should the N spec be the same front and rear, but you should also check the sidewall on each tire for the build date. Preferable to have the same build date (year/month) on the fronts and rears as pairs, but also front to rear (as much as possible). Over time, even same size and spec tires have formula variances. Best situation is four same spec and same build year/month. This is VERY hard to do when only purchasing two tires at a time. But if you only need rears, why by 4.

Higher Ns are newer tires which is generally going to be better than older tires. N testing is expensive, and only done when the manufacturer has made some improvements to the tire; a lower N rather implies they're are an old/obsolete technological revision. Also, tires have limited shelf life and a lower N has probably been sitting around a while longer than the higher N. Mixing N revisions is akin to mixing different brands/models of tires and the lawyers say shouldn't be done due to slight differences in grip potentially unbalancing the car unpredictably in different conditions and result in lawsuits. In real-world terms? I think you'd be hard pressed to tell the difference without instrumentation. Ideally, though, you won't bother with N-rated tires at all, since N is purely marketing and not the least bit necessary. You can get better tires than PS2 for cheaper that just haven't paid Porsche obscene amounts of money to test them. http://www.tirerack.com/tires/tirete...jsp?techid=26&

Interestingly, the N3 225/40-18 fronts are not XL, are light weight, and have a low load rating. Probably soft sidewalls for the light front end. There are no N4 225/40-18 fronts. I'm still curious just what application the N4 295/30-18 PS2 rears are for. Maybe GT3 with the 235/40-18 fronts?

For those that don't know, "N" rating means the tires are speced and approved by Porsche. There may be subtile differences such as the aspect ratio, tread pattern adjustments, compliance or stiffness of the casing, etc. These tires should work very well on your P car and not cause any handling or braking issues. When in doubt, and not willing to experiment, get an "N" tire. This does not mean a non "N" tire will not work, or even not work extremely well. It just means it was not tested, approved and speced by Porsche. If you run a non spec tire you can not hold Porsche responsible if your car develops tire related handling or braking issues. Personally, I have run several non spec tires and found some superior as far as road noise and handling to the "N" spec tires. I guess it depends on your comfort level with experimentation. I'm one that seems to always prefer non conformaty and always taking the road less traveled.

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It's not that it won't work, it's that it is isn't designed for the car. The load that our cars carry in the rear versus front is dramatically different than other 50/50 cars so the N tires address that issue. For the street? I'm sure you could use and tire (non N rated) that you want but the performance with not be the same nor will it stand up the same way. It's not the fronts I worry about it, it's the rears.

Have you been happy with the performance of the non rated fronts? P car owners are famous for modifications to improve the performance of their cars, many of which would not be Porsche approved. I would not be very concerned about buying new rears that don,t match the fronts .Buy a pair which allows you to buy a matching front set at a later date if you notice a problem.

Given the wear rate, I will replace the rears only now, then all four should be worn out at about the same time. The "correct" N3 version is out of stock anyway. Good point that the N4 is likely to be more recently manufactured than the N2. The N2s on the car now have dates of 2708 and 2907, so they're not exactly ancient. Edit: Update from Damon--the N3s are gone forever. All N4 now in that size.

There is an 'N' article in the current issue of Total 911 that may shed some light for you.

This is more important than many realize. Particularly critical for the AWD cars as differing tires can affect the car's ability to sense slippage, etc. One of our club members tried to go cheap recently on his 996Turbo (despite what the tire guy told him) and wound up scared of the way the car handled on a trip--it was scary above 65 mph). He returned to the tire dealer who was good enough to straighten things out for him. Here's what happens when you go really cheap and put retreads on your 911:

All is explained in the Porsche brochure on N Spec Tires. You can download it here