Understanding Porsche N spec Approval when Choosing Tires

July 25, 2008

For those of you that have been long-term readers you’ll remember a post I did some time ago where I offered my research services to answer any Porsche related question. That post, “I’m not a Porsche Expert, but I Play one on the Internet” continues to generate a number of questions and I want to do my best to keep answering them for you.

In my opinion, it’s a win-win situation. You get great content to help research a specific Porsche topic and during my research I learn even more about Porsche Cars, Products and LifeStyle. Please feel free to keep sending your questions in by simply commenting on this article or any other on the site (I see them all.) If I don’t answer them directly, here on the web-site, I will email you back personally whenever possible.

Today’s question has to do with finding the right tire for your Porsche. More specifically:

“What does it mean for a tire to have a Porsche N spec approval?”

A Porsche N spec approved tire is one that has passed a series of difficult and diverse test designed by Porsche engineers to ensure maximum performance and safety under a wide range of driving conditions. To qualify for this approval and “to be an Original Equipment tire provider on a Porsche vehicle or be approved by Porsche for the replacement market requires the joint product development efforts of the tire engineers working alongside the Porsche vehicle engineers.” In some instances specific tires will only be approved for specific Porsche applications or models.

Tires may be specified for a particular vehicle or range of vehicles and must successfully pass the tire company’s laboratory tests to assure that they would be capable of adequately supporting the Porsche vehicle while allowing it to reach its top speed on the German Autobahn. Additional laboratory, test track and race track tests are conducted to confirm that the prototype tires meet Porsche’s noise, hydroplaning and handling requirements. Prototype tires will also be evaluated to assess their high-speed durability, uniformity and serviceability. Upon test completion, the tires will be released for production.

Let’s look at some of the tests required by Porsche for N spec approval:

SPEED: The tire must be capable of safely handling the Porsche vehicle at any speed while allowing it to reach its top speed on a track or the German Autobahn.
NOISE: As tires continue to grow in size and width, noise suppression becomes more and more important. Generally speaking, Porsche performance tires are low profile and very soft. This makes it even more difficult to manage road noise. You can rest assured that those tires with a Porsche N spec approval will be as quiet as possible.
HYDROPLANING: The focus in recent radial tire development for Porsche vehicles has primarily included optimum handling on dry surfaces and the safest possible behavior on wet surfaces, even at high speeds. Tires developed by various manufacturers, in concert with Porsche, offer a specific set of wet grip properties which few, if any, other automobile manufacturers demand in equal measure from the tires they use on their vehicles.
HANDLING: I’m not sure this particular heading requires any additional explanation. Your tires provide the grip that keeps your Porsche “stuck” to the road. Poor tire construction, soft sidewall, tires that are too firm, etc. all these things will lead to reduced handling and possible safety concerns that can be avoided by choosing a Porsche N spec tire.

Once a tire has been approved by Porsche it is branded with the N spec approval. The N-specification brandings include: N-0 (N-zero), N-1, N-2, N-3 or N-4. These markings on a tire’s sidewall clearly identify them as approved by Porsche for their vehicles. The N-0 marking is assigned to the first approved version of a tire design. As that design is refined externally or internally, the later significant evolutions will result in a new generation of the tire to be branded with N-1, N-2, N-3, etc., in succession. When a completely new tire design is approved, it receives the N-0 branding and the succession begins again.

It is important to note that certain tire manufacturers may produce the exact same tire in name, size and speed rating as those that have the N spec approval. However, if they are not branded with the N spec approval than it is very likely that they do not adhere to the same rigid production and quality requirements demanded by Porsche.

According to a recent Porsche owner’s manuals, if you do run Porsche N spec approved tires on your car, it is always recommend that your tires be replaced in pairs (one axle at a time.) In the event of tire damage such as cuts, punctures, cracks or sidewall bulges that cause a single tire to be replaced for safety reasons, the remaining matching tire on that axle must not exceed 30 percent wear. If the remaining tire has more than 30 percent wear from new, it should also be replaced. Handling inconsistencies may result if this is not done.

Here’s a list of some of the more popular Porsche N spec approved tires:

There are many, many more tires, than those listed above, that are Porsche N spec approved. If you are researching tires, one of your best bets is to check out The Tire Rack as you can look up your vehicle by make, model and year. The resulting list of tires will provide you with various information including whether the tire is a Porsche N spec approved one.

As a conflicting and interesting end to this post, I recently replaced the tires on my 1997 Porsche 993 C4S. After days of research I ended up selecting a tire that was NOT Porsche N spec approved. At the end of the day I received an excellent tire that performs as well, if not better, than the N spec approved tires the car was originally equipped with. Here’s a review of the Sumitomo HTR Z III tires I chose.

Don’t forget, if you have more questions you would like researched and answered, please ask below or by sending me an email to ask at 993C4S dot com.

Written by 993C4S · Filed Under Advice, Tires and Wheels | Leave a Comment

Review of the Sumitomo HTR Z III for Porsche DE Events

May 14, 2008

On Monday I posted about choosing the right tire for your Porsche (any Posche). Specifically, I discussed how the new Sumitomo HTR Z III contradict the concept of having to pay (or over pay) for quality. My review was based on 1500 miles or so of ordinary and spirited street driving. Today’s post is a review, compliments of John D. (Founder of Rennlist and PCA DE Instructor) of the Sumitomo HTR Z IIIs on the track as compared to Michellin, Toyo, Dunlop and BF Goodrich Ultra High Performance street tires. I want to emphasize that this review is a comparison of high performance STREET tires to other high performance STREET tires. While the Sumitomo is a great STREET tire, it would not be fair to compare it to a purpose built/designed track/racing tire.

Here is what John had to say:

I run in the Instructors group (RED) - and the first session out was slow, to see what the tires would do and to break them in (they had less than 100 miles on them before I hit the track - not advised.) I think I was the perfect HWFM (Hey Wait For Me) Racing ombudsman during the break in.. OK…

Fast forward to the next day (3 sessions later).. Temps were about 60 degrees F in the afternoon. Tire pressures were set at 33/37 COLD (post track session - these were 36/41). Observations…??

For a street tire the HTR Z IIIs outperformed my previous Michelans, Toyos, Dunlops, BFG tires. They have a stiffer sidewall than the HTR ZIIs (by a whole lot - which is why I didn’t like the ZIIs on the track).

Performance of the ZIIIs are as follows (rated 1-10 compared to the tires above):

Feedback - 8

Traction - 8.5

Braking - 9

“Looseness” in the corners - 9

Predictability - 9.5

Ability to control - 9.5

“Hot” laps - 8.5

I imagine I killed the life of these tires on the second day by - oh - about 5,000 miles - BUT - they are great tires to run to the limit.

For everyday use? Good. They will flat-spot over night - so it may take a mile or two to run them out. (I agree with John on this and have noticed it myself).

In wet weather/rain? Absolutely fine.. Back it down a notch - and they grip as well as any ultra-high-performance tire. Maybe better…

Sumitomo is a Great Tire for your Porsche

As you can see from John’s review above, these tires perform extremely well. I don’t make it a habit of plugging products on my site (I do it occasionally when something is worthwhile) but these Sumitomos are that good. Factor in the cost (or lack there of) and you would be crazy not to get a set for your Porsche next time you need new tires. I don’t know how long before Sumitomo raises their prices, but based on the number of people I personally know who have purchased these tires, it may not be long.

Do you run these tires? Do you agree with my review from Monday? What about John’s review above? I would love to hear your thoughts.

Thanks again to John D for allowing me to post his review here. If you have a minute don’t forget to check out John’s charitable organization Rennwish.

Written by 993C4S · Filed Under Tires and Wheels | 4 Comments

Choosing the Right Tire for your Porsche

May 12, 2008

When I purchased my 1997 Porsche 993 C4S the odometer read 24,000 miles. From the service history I could see that it had four new tires installed (Continental ContiSportContact 2s) less than 4,000 miles ago. This basically matched up with the information from my PPI and with my visual inspection upon receipt of the car.

Enjoying the car as much as I do, I clocked more than 6000 miles last season (including a great trip to Prince Edward Island). This meant the tires now had 10,000 miles on them and the rear tires were starting to feel a little worn. It was very subtle at first, a little chirp around a tight corner or a quick spin on a fast start. Given these signs I decided to start shopping for new tires.

The first place I started was the 993 forum on Rennlist (RL). As a quick aside, if you haven’t been to Rennlist, and you own a Porsche (any type of Porsche), you owe it to yourself to check it out. The recommendations and opinions on RL were varied, to say the least. Like me, a lot of people felt strongly that you get what you pay for and therefore the more expensive tires must be the best. Thankfully, especially grateful was my bank account, I/they were wrong.

Tire Choices for a Porsche 993

Back in January I posted this article “Tire Choices for a Porsche 993.” As you can see I had listed the following tires as my choices:

Bridgestone Potenza S-02
Continental ContiSportContact 2
Pirelli PZero Rosso
Michelin Pilot Sport Rib

I even went on to mention the following two tires as cheaper alternatives but I was going to shy away from them as I felt “you get what you pay for.”

Sumitomo HTR Z II
BFGoodrich g-Force T/A KDW 2

As I said, turns out I was wrong. When push came to shove and it was time to pull the trigger to purchase the new tires for my Porsche, I did one last round of research. What I found was this thread which pushed me over the edge.

Sumitomo HTR Z III for Porsche

You see, when I was researching, the Sumitomo HTR Z III wasn’t on the list (just the HTR Z II). It seems that with the HTR Z III, Sumitomo made some significant improvements. So, without wasting any more time, I went online to The Tire Rack and ordered four (4) new tires all for $700 delivered. That’s a cost savings of almost 45% to my original choice of the Michelin Pilot Sport Rib.

My 993 was scheduled to visit the shop for a spring check-up, 30k service and brake bleed so I opted to have the tires delivered directly to them. After seeing the wear pattern on my old tires I decided to do a four-wheel alignment (they were cupping a little on the interior front edges) along with a hi-speed balance. This way, not only am I starting with a matched set of four new shoes, but I know they alignment and balance is correct. Assuming I keep the proper air-pressure and don’t play too hard, I should get some significant wear from these tires.

First Impressions

Since picking the car up I have turned almost 1500 miles on the new tires, each one with a huge smile on my face. The Sumitomo HTR Z IIIsare as advertised. They are very sticky, with a firm/stiff sidewall that handle great for daily driving (spirited or otherwise). I have not yet used them on the track or in the rain so I can’t comment on that aspect. However, for driving on back roads, highways and anywhere else, I am most pleased. They stick as good, if not better, than any tire I have driven in the past. They seem to blend well with my stock suspension and absorb the bumps and pot holes quite well. I can’t comment on road noise as I usually have the windows open or the revs too high to hear.

All in all, I am extremely pleased with these tires and would recommend them highly to anyone, for any modern Porsche, regardless of budget. We all know that there are lots and lots of modifications to do to our Porsches. So, if you can get a great bang for the buck with this tire, why not turn around and roll the money into another mod!! Keep sliding down that slippery slope.

Written by 993C4S · Filed Under Tires and Wheels | 1 Comment