N rated Tyres

[burrow01]

Hi

Agreed that a good TC system will allow exactly the amount of power that the tyres can handle. But this will vary dependent on the tyres fitted - Slicks or P6000's would have different levels of power handling []

My point was that the uber powerful Mercs and Audis are generally speed limited to 155mph, and have extensive traction control systems, which, according to most comparisons, are not as sensitive as those used by Porsche (or are pushed harder). From this I am deducing (incorrectly maybe) that these cars are less sensitive to their tyres than Porsches, especially as they are mostly saloons rather than out and out sports cars

Pete

 

[Hilux]

I think a good traction control system (like a good ABS system) puts more not less load on the tyres as it manages the power to keep the tyres at their maximum traction point rather than letting them spin wildly

I agree completely.

you can turn it off and therefore the tyres have to be safe in that condition.

Good point.

An M5 weighs a lot more than a 944, do BMW insist on N rated tyres?

Edited to add that its the load rating and speed rating thats important. Note that the speed rating is only for 10 mins at that speed with the correct load rating on each wheel. I bet the load rating for a 911 rear tyre is a lot more than for a front tyre.

 

[Fen]

Having just recently taken some tyres from Black Circles to my local KwikFit for fitting to the hearse I can confirm it needs some form of heavy duty tyre. Of course Black Circles knew that and had supplied them, but KwikFit called Dunlop technical to check as it wasn't clear from the sidewall. I also noticed that there is a BMW specific model of Michelin Pilot Primacy (I was going to buy them until I read on BMW Land that people like the Dunlop 9000 just as much and it's 2/3 the price) alongside the regular ones that would also fit the car acceptably.

What does that mean? At the very least that there is a BMW specific Primacy, but that the non-BMW one is also OK, at least on a 530d.

 

[sawood12]

The 155mph speed limiter on many German cars has nothing to do with the capability of the tyres to handle the weight and power of the car. It's simply pandering to the liberal greenies that are so politically strong in Germany. In anycase I think these cars can be de-restricted pretty easily to unleash their full potential. If they needed to restrict the cars to 155mph for safety reasons then they would have done it through gearing rather than easily defeated electronic governing.

In any case Porsche don't insist on using N rated tyres - in fact there are many older models that no longer have current N rated tyres available for them - 968 for example. They will run perfectly safely on normal non-N rated tyres. All Porsche have done is to develop a tyre with specific characteristics that suit their cars better than the one-size fits all std tyres which should, in theory and in the right hands, allow the driver to get that little bit more from their car. It's purely upto the driver to decide if they want to put N rated tyres on their car - there is little or no price difference so it's not as if Porsche or the tyre manufacturer is getting any more profit out of the sale of these tyres.

 

[burrow01]

Hi

I agree to a certain extent about the "green" credentials of the 155mph limit, but it was agreed by the major German manufacturers to avoid a speed war as engines became more powerful. It means that they don't have to develop items, specifically brakes, suspension, tyres and ride heights etc, that can handle the higher speeds, thus enabling them to retain the saloon car ride comfort and NVH characteristics along with very high power outputs.

You can have the engines de-restricted, but this applies mainly to either non standard / uprated or "Sports" versions of the cars, rather than the normal versions, and these typically have harder suspension, lower ride heights and better tyres, bigger brakes etc.

I agree that the N rating of a tyre means that it is more suitable for the type of Porsche that it is approved for, rather than the generic version, and should be considered a recommendation rather than a cast iron rule - lots of track dayers are using R type compounds and tyres that are not N rated, but for normal road use, I'm happy to go with the Porsche recommendation as it is available

Coincidentially I had new tyres fitted today - removing the Fulda's and Federals that the car came with.... I was just going to have the fronts done, and the tyre fitter started muttering about insurance - is this an urban myth, are there any known cases of insurance claims being refused due to non-fitment of N rated tyres?

They found a nail in one of the rears anyway - so now I'm N rated all round []

Pete

Pete

 

[Diver944]

I have to take a few things as Gospel:

1. Porsche make fantastic cars, and develop/test them to the highest standards there can be for a road car.

2. The only thing in contact with the road on that car is the tyres.

3. If Porsche go to all that effort to test and help a manufacturer specify a particular tyre for my particular model then I am going to make full use of all their input and fit the correct N rated tyre to my car.

After saying all that, I do not believe there is a current N rated tyre that has currently been tested on a 944 so for a 944 I personally would not choose N rated over and above any other tyre.

BTW P6000s are king []

 

[burrow01]

Agree with everything apart from the P6000's []

Pete

 

[sawood12]

I agree, there is no point in specifically going for an N rated tyre for a 944, but i'm sure it will not do any harm whatsoever.

The N rating is all about maximising performance and not about better safety so you will not be penalised by your insurance company for not fitting N rated tyres on any Porsche model. Not all tyre manufacturers offer an N rated tyre and Porsche cannot tell you not to fit a certain manufacturers tyre as it would be anti-competitive and therefore illegal so there is no way an insurance company should specify thier use - if they do i'd go with another insurance company.

 

[mik_ok]

Partnerships between car and tyre manufacturers is (as stated by others) far from unique to Porsche.

Toyo do a TVR-specific version of the T1-S. Ferrari have specific tyres for certain models. Lotus worked with Goodyear on unique tyres for the Esprit, and changed their concept along the way from "hard platform, compliant tyres" to "soft platform, hard tyres" (or the other way about?), so tyres that work well on the earlier cars don't on the later ones (and vice versa). I'm not an expert on the model, and that change may have occured along with a change in tyre size too (?).

It's a win/win for the above parties ~ car manufacturer reduces their development time, has a level of control over the tyre manufacturer, and can negotiate some good prices. They don't need to compromise handling traits to take account of four or five tyres that may potentially be purchased.

Tyre manufacturer gets the marketting Kudos of "chosen by (insert manufacturer of choice here)" and a nice little "known" market. I'm sure this allows them to better predict the market demands of that particular tyre and optimise their manufacturing schedule accordingly.

I decided to ignore N-Ratings on the 944 as no tyre was ever specifically developed for it. Tyre design has moved on a lot over the last few years, and maybe TyreX that was released last year (and therefore unavailable when the car was designed) works perfectly with the chassis (?).

Many folks have changed to 17" (or even 18") wheels with different tyre sizes to OEM, so you've already "lost" the factory setup. To accept "N-Rating" as the correct option for a 944 with 50/50 front/rear weight balance, when said tyres have been optimised to suit a 911 with 33/67 seems questionable.

 

[Hilux]

Many folks have changed to 17" (or even 18") wheels with different tyre sizes to OEM, so you've already "lost" the factory setup. To accept "N-Rating" as the correct option for a 944 with 50/50 front/rear weight balance, when said tyres have been optimised to suit a 911 with 33/67 seems questionable.

IMO spot on and well put. I agree in particular with the 911 scenario. Unless you get an N rated tyre specific to the 944 its all irrelevant I consider. I do however consider that the load rating (which is normally not considered) is crucial. How many people out ther looked at this aspect before they bought []

 

[sawood12]

Not neccessarily so. The N rating is not only homologated for 911's but also Boxters and I guess Caymens now which have pretty near perfect weight distribution. Let's not all assume that the purpose of the N rating is to correct deficiencies in the chassis performance i.e. the N rating is nothing to to with compensating for screwy weight distribution - just the opposite. The tyre characteristics are just one of thousands of parameters design engineers can fiddle with to achieve a set up that they want to go to production with. It is rediculous to assume that after investing many millions of whatever currency is involved to develop a chassis and suspension set up that it will work just as effectively irrespective of the tyres you fit. This is where the N rating comes in as a benchmark - Porsche have developed the N rating with the tyre manufacturer and has probably made just as many tweaks to the chassis as the tyre manufacturer has made to their tyre to get the right compromise.

 

[Fen]

But surely you don't think a Birdgestone N3 rated tyre will drive exactly the same as a Michelin N3 rated tyre? That being the case the chassis absolutley does have to work with a range of tyres.

 

[burrow01]

Hi Fen

Agree with your statement, but each manufacturers N version of the tyre should work better on the specific model of Porsche that it is rated for over the non N Rated?
Maybe this is a test that should be performed - back to back testing of the N rated vs the non N rated version of the same tyre on the same car?
Quick question, are any N rated tyres still available for the 944? what were the original tyres that were rated?

Pete

 

[Fen]

I agree, but I expect there may well be less difference between some N-rated and non N-rated tyres of the same model than between N-rated versions of different tyre brands. I don't know what a tyre needs to comply with to be N-rated, but I suspect it's a set of construction parameters that some models are already close to or maybe even completely compliant with. Conversely I'd espect some tyres are significantly different and making an N-rated version compromises the original design immensely. What would be interesting is to know what exactly N-rating is in terms of construction. I guess it may even just be that the tyre has passed a set of specific tests in which case it would possibly have little bearing on actual performance (if it needs to reach a minimum threshold for sidewall stiffness for example, some tyres could significantly exceed that and some just scrape through but both be N-rated apparently the same).

 

[944Turbo]

I have used N rated Michelins as per the 968, N-2 and N-3 Bridgestone SO2 (very worn Pirrelli N rated for a trackday) and my favourite tyre so far on the 944T is Dunlop SP9000 They are slightly less grippy than the N rateds but the break away is much much nicer.
This was not a direct comparison as I was going from worn to new each time.
When the 'N tyres' broke away (on track- direct provocation on corners with big run off) I failed to catch them at least half the time, I never experienced it on the road, the limits are high, but it was very tricky to catch .
I find the SP9000 much more predictable and can play with them more. I have only only done one (wet) trackday on them so dont know what happens when you get very silly, but they seem to allow a small drift angle before taking up a slight sideways stance where they grip again (unless you really give them a big bootfull in 1st [])
I have 17x9 and 17x7.5 wheels 255 and 225

 

[sawood12]

Well the article I read was charting the process that Dunlop was going through with Porsche on their N rated tyre. It described a programme of significant track tests on places like the Nurburgring and other specific testing facilities over a period of several months. The resulting tyre, even though it visually looks the same as the non-N rated tyre was constructed in a completely different way, specifically it was made up from 5 ply's intead of 3, had a Kevlar bead instead of steel and a shallower tread depth. There are other differences that Dunlop were not willing to detail in the article for obvious reasons. This doesn't sound to me like a process of the tyre company throwing Porsche a few tyres and saying "try those on for size guv" and getting an N rating - it sounds like a far more involved process that results in a completely different tyre. I'm sure Porsche must choose one of the tyre manufacturers as a 'Launch' company to develop the initial characteristics, then Porsche will work with the following manufacturers to emulate similar characteristics across different manufacturers' N rated tyres. However for commercial reasons i'm sure Porsche wont be able to simply pass on the 'recipe' for the construction of the tyre from one manufacturer to the other hence the reason for an individual development process for each tyre manufacturer that wants to off an N rated tyre.

 

[Fen]

That there is extensive development isn't a surprise. My point was not so much what is involved in getting N-rating but that now Dunlop have it their tyre will not have the same characteristics as Pirelli's N-rated tyre of the same size.

 

[944Turbo]

I also read that article and have not tried the SP sport Maxx a version of which is N rated, there was something in the article that put me off, cant recall exactly what now though - will have to try and dig it out for a re-read,
Tony

 

[Hilux]

My point was not so much what is involved in getting N-rating but that now Dunlop have it their tyre will not have the same characteristics as Pirelli's N-rated tyre of the same size.

Thats my argument also. Porsche will spec a specific N rating with a manufacturer as recommended for the particular model. Buying another N rated tyre doent mean its the same, ergo there isnt therefore an N rated tyre specific for the 944 so its a bit irrelevant IMO.

I CAN however see the justification with new models where the tyre is still in manufacture.

 

[dlknight]

[] Crikey started a right old discussion off didn't I [8|]

As far as I am aware the porsche N rating for tyres is mentioned in the 944 workshop manual, so I felt by its inclusion in such a publication that this was indeed a valid tyre specification system for the 944. As Scott pointed out above Boxsters and Caymens have near 50/50 weight distribution as well as the 944. I'm not aware of Porsche ever saying "this tyre is only N-rated for a 911" or either "this tyre is only N-rated for a Boxster".

Maybe we should ask Porsche ? [8|]

Seriously all IMHO [8D] I almost bought some non N-rated Bridgestones from Johnsons tyres but managed to get 2 x Continental Sport Contac 2 N2 off ebay for less than the price of one Bridgestone []

Regards

Dave K.