"N" rating on tyres
Discussion
later N's just mean a later tyre. Personally i think its a total load of absolute nonsense, you would be better checking the pressures, temperature and tread depth than worry about this spec, however the OPC would make you feel as if you've broken the 11th commandment.
Front and rear tyres come up at different times anyway and depend on your geometry, its total *ollocks.
Off now to run for cover....
Front and rear tyres come up at different times anyway and depend on your geometry, its total *ollocks.
Off now to run for cover....
porsche4life said:
later N's just mean a later tyre. Personally i think its a total load of absolute nonsense, you would be better checking the pressures, temperature and tread depth than worry about this spec, however the OPC would make you feel as if you've broken the 11th commandment.
Front and rear tyres come up at different times anyway and depend on your geometry, its total *ollocks.
Off now to run for cover....
I wouldn't dismiss it that readily - I have had a bad personal experience of mixing n numbers axle to axle and a friend has just had a very nasty experience on his 964 which I believe is related to n numbers.
Will eat my hat..... would only believe if Walter Rohl said it himself after 7 pints of Bavarians finest without the Porsche lawyer present.
How can u be sure the nasty experience has got anything at all to do with N tyres.. (I have had a wide variation of N's over the years) OPC love to point it out, i tell them i will have worn the tyres out before i would notice and i catch up the N's next time, once there were no N's at all, again picked up by OPC, would never have noticed otherwise, totally ignored their pleas of Porsche designed etc, you are compromising this and that....
no chance
The fact i was down to 2mm on the inside edge of the rears was a much more significant issue.
How can u be sure the nasty experience has got anything at all to do with N tyres.. (I have had a wide variation of N's over the years) OPC love to point it out, i tell them i will have worn the tyres out before i would notice and i catch up the N's next time, once there were no N's at all, again picked up by OPC, would never have noticed otherwise, totally ignored their pleas of Porsche designed etc, you are compromising this and that....
no chance
The fact i was down to 2mm on the inside edge of the rears was a much more significant issue.
porsche4life said:
Will eat my hat..... would only believe if Walter Rohl said it himself after 7 pints of Bavarians finest without the Porsche lawyer present.
How can u be sure the nasty experience has got anything at all to do with N tyres.. (I have had a wide variation of N's over the years) OPC love to point it out, i tell them i will have worn the tyres out before i would notice and i catch up the N's next time, once there were no N's at all, again picked up by OPC, would never have noticed otherwise, totally ignored their pleas of Porsche designed etc, you are compromising this and that....
well, how about the fact that I swapped the rear tyres for another set with an identical "n" numbers to those on the front and all was sorted again?...is that proof enough for you or shall I call Walter Rohrl (to be honest it'll be hassle for me - I'll need to call Stig Blomqvist first to get Walter's number and Stig's a little busy at the moment, but is in the UK over Christmas...unless you want to call Walter yourself for the proof
) However, what I will concede is that I ran my last 911 on Continentals which had no "n" numbers - i.e. technically non-Porsche approved. The tyre and compound is identical to the n rated ones that Porsche use. The car drove perfectly well.
its all circumstantial - you can simply have a bad tyre... actually vesuvius got me thinking, if you put aftermarket brake pads in, is that a crime ? also i am looking to change the Porsche approved PCCB's cos their crap will i have to mention that as well - oh dear this could get expensive.
As for Walter, as i said, we would need to catch him at the beer festival ( on his own)....
As for Walter, as i said, we would need to catch him at the beer festival ( on his own)....
Actually forgot ot mention this one: OPC pointed out that i had different N's front to rear.... guess who supplied and fitted the last set of tyres.... yes a Porsche approved tyre fitter........ and no they never mentioned it and i never checked.
Slightly intrigued by what problems you were experiencing...
Slightly intrigued by what problems you were experiencing...
I was under the impression it was ok to mix N rated tyres front to back, but not on the same axle, ie side to side (Obviously in an ideal world they would be the same) . Having discussed the issue of N rated tyres with my local tyre fitters, it would appear it is not the compounds that differ but the contruction. The main differences are sidewall stiffness and carcass measurement, thus a 285 N rated tyre will often have a wider tread section than a non N rated 285 and also benefit from a much stiffer sidewall.
I questioned my tyre fitters after having new Michelin Pilot Sports fitted to my 330 Diesel Sport. The tyres that came off were also MPS in the correct size. However when they were removed, the fitter said they were an Audi fitment and not the recommended BMW fitting.
The difference on driving the car with the correct BMW fitment tyres was vast, the car rode better, the turn in was a lot more linear and progressive (compared with the Audi fitment which were a lot more pointy and made the car feel very nervous and tramline a lot, although they felt like they had more outright grip)
What may seem like a scam to the more cynical amongst us, is (IMHO) just Porsche getting tyre manufacturers to engineer tyres to suit our cars with their "engines in the wrong place" as Mr Clarkson says
I questioned my tyre fitters after having new Michelin Pilot Sports fitted to my 330 Diesel Sport. The tyres that came off were also MPS in the correct size. However when they were removed, the fitter said they were an Audi fitment and not the recommended BMW fitting.
The difference on driving the car with the correct BMW fitment tyres was vast, the car rode better, the turn in was a lot more linear and progressive (compared with the Audi fitment which were a lot more pointy and made the car feel very nervous and tramline a lot, although they felt like they had more outright grip)
What may seem like a scam to the more cynical amongst us, is (IMHO) just Porsche getting tyre manufacturers to engineer tyres to suit our cars with their "engines in the wrong place" as Mr Clarkson says
Sounds fair enough, but these tyres are not specified for each individual car are they? Not all of us have the engine in the wrong place (your words, not mine ) and the age and style of use may vary considerably, so I find it hard to believe that Porsche can specify a 'one size fits all' approval rating to get this fine tuning of the handling you mention.
) and the age and style of use may vary considerably, so I find it hard to believe that Porsche can specify a 'one size fits all' approval rating to get this fine tuning of the handling you mention.MartinD said:
well, how about the fact that I swapped the rear tyres for another set with an identical "n" numbers to those on the front and all was sorted again?...is that proof enough ...................
All 6 tyres were same make/model/type/age ? if not it doesn't prove anything
Of course!!!!!
By kind permission of Maurice Piper, Porsche Club GB 993 Register Secretary:
The Dreaded N Specification
Many people have difficulty with this when choosing replacement tyres, so this article sets out the position specific to the 993, although many aspects affect other models.
The N Specification is a Porsche system of approved tyres, first introduced in the 1988 Model Year – it means that Porsche have worked with the manufacturer to produce an optimal road tyre for a particular model and wheel size combination, and tested it to their satisfaction at the time. Whenever this process is performed for an individual set of approved tyres, the N spec number will increase. Often this will coincide with a model change, but can certainly occur within a model’s lifetime, and thus a bewildering chart of approved wheel and tyre combinations (for summer and winter use) is produced and published every year in Christophorus, the Porsche company magazine. Importantly, Porsche recommendation is matching brand, type and correct N spec ALL ROUND …..
For the 993 the variables come down to 16”, 17” and 18” wheels, wide or narrow body, and manufacturers Bridgestone, Continental, Dunlop, Michelin, Pirelli, Toyo and Yokohama. Not all manufacturers produce (or did produce) all sizes, and, being in England, we generally ignore the winter recommendations, which are aimed towards use on packed snow. This may be a consideration for some users, of course! 16” wheels are also a rarity here, so I’ll skip those.
The last list for 993 was produced for MY 1998 and, strictly speaking, these are the highest N specs for the particular tyres that should be fitted to 993s – manufacturers do continue to produce the same sizes in multiple N specs, although sometimes you have to search hard to get the correct one. Higher (and some lower) N spec tyres will not have been tested on the 993, although they may work well. Sometimes manufacturers produce identical size / models with and without the N rating. The N spec tyre will be different in some way, compound, tread grooves, whatever, but it may not be apparent.
So here’s the list by model and fitment – ‘summer’ use only !
Carrera Coupe 2/4, Cabriolet, Targa, Carrera S
17” x 7” 205/50
17” x 9” 255/40
S02 N3, Sport Contact N1, SP Sport 8000 N0, MXX3 N1, Proxes F1-S N0
Pirelli special case : Direcionale N2 Front, Asimmetrico N2 Rear (this combination seem no longer available, Dec 05)
Carrera Coupe 2/4, Cabriolet, RS
18” x 8” 225/40
18” x 10” 265/35
Sport Contact N1, Pilot Sport SX N0, Asimmetrico N2 or N3
Carrera S, 4S and TT
18” x 8” 225/40
18” x 10” 285/30
S02 N2, Asimmetrico N2
Porsche did not do all this testing for fun – if you want your car to handle the way the factory intended, there are good guidelines here to follow. If you change sizes at all, you (are on your own and) need to be aware of the change in the ratio of front to rear rolling diameters, because a significant change will screw up the ABS and/or the 4WD. The logical calculation of rolling diameter from the tyre section / profile is not accurate in this regard, so be warned, you may need to check with the manufacturer. FYI, the calculation for rolling diameter is Wheel Diameter (in mm) + Section*Profile*2, so for a 225/40 18, it becomes 18*2.54 + 225*40%*2, giving a logical RD of 637.2. As an example, an actual figure for a Bridgestone S02 in that size is 642.62 ....
People often ask about fitting 285/30 x 18s on the rear of narrow bodied cars (Kylies!) ... it may well require 'rolling' the wing edges, and only gives you understeer anyway … Don't assume bigger is better! Another thing, pre-96 cars need a steering rack brace fitted to run 18 inch wheels, while they are not recommended for Targa at all (Not quite as simple as that, check for details).
That’s pretty well it! HTH, cheers, Maurice
___________________________
Maurice Piper
993 Register Secretary
The Dreaded N Specification
Many people have difficulty with this when choosing replacement tyres, so this article sets out the position specific to the 993, although many aspects affect other models.
The N Specification is a Porsche system of approved tyres, first introduced in the 1988 Model Year – it means that Porsche have worked with the manufacturer to produce an optimal road tyre for a particular model and wheel size combination, and tested it to their satisfaction at the time. Whenever this process is performed for an individual set of approved tyres, the N spec number will increase. Often this will coincide with a model change, but can certainly occur within a model’s lifetime, and thus a bewildering chart of approved wheel and tyre combinations (for summer and winter use) is produced and published every year in Christophorus, the Porsche company magazine. Importantly, Porsche recommendation is matching brand, type and correct N spec ALL ROUND …..
For the 993 the variables come down to 16”, 17” and 18” wheels, wide or narrow body, and manufacturers Bridgestone, Continental, Dunlop, Michelin, Pirelli, Toyo and Yokohama. Not all manufacturers produce (or did produce) all sizes, and, being in England, we generally ignore the winter recommendations, which are aimed towards use on packed snow. This may be a consideration for some users, of course! 16” wheels are also a rarity here, so I’ll skip those.
The last list for 993 was produced for MY 1998 and, strictly speaking, these are the highest N specs for the particular tyres that should be fitted to 993s – manufacturers do continue to produce the same sizes in multiple N specs, although sometimes you have to search hard to get the correct one. Higher (and some lower) N spec tyres will not have been tested on the 993, although they may work well. Sometimes manufacturers produce identical size / models with and without the N rating. The N spec tyre will be different in some way, compound, tread grooves, whatever, but it may not be apparent.
So here’s the list by model and fitment – ‘summer’ use only !
Carrera Coupe 2/4, Cabriolet, Targa, Carrera S
17” x 7” 205/50
17” x 9” 255/40
S02 N3, Sport Contact N1, SP Sport 8000 N0, MXX3 N1, Proxes F1-S N0
Pirelli special case : Direcionale N2 Front, Asimmetrico N2 Rear (this combination seem no longer available, Dec 05)
Carrera Coupe 2/4, Cabriolet, RS
18” x 8” 225/40
18” x 10” 265/35
Sport Contact N1, Pilot Sport SX N0, Asimmetrico N2 or N3
Carrera S, 4S and TT
18” x 8” 225/40
18” x 10” 285/30
S02 N2, Asimmetrico N2
Porsche did not do all this testing for fun – if you want your car to handle the way the factory intended, there are good guidelines here to follow. If you change sizes at all, you (are on your own and) need to be aware of the change in the ratio of front to rear rolling diameters, because a significant change will screw up the ABS and/or the 4WD. The logical calculation of rolling diameter from the tyre section / profile is not accurate in this regard, so be warned, you may need to check with the manufacturer. FYI, the calculation for rolling diameter is Wheel Diameter (in mm) + Section*Profile*2, so for a 225/40 18, it becomes 18*2.54 + 225*40%*2, giving a logical RD of 637.2. As an example, an actual figure for a Bridgestone S02 in that size is 642.62 ....
People often ask about fitting 285/30 x 18s on the rear of narrow bodied cars (Kylies!) ... it may well require 'rolling' the wing edges, and only gives you understeer anyway … Don't assume bigger is better! Another thing, pre-96 cars need a steering rack brace fitted to run 18 inch wheels, while they are not recommended for Targa at all (Not quite as simple as that, check for details).
That’s pretty well it! HTH, cheers, Maurice
___________________________
Maurice Piper
993 Register Secretary
Paul968 said:
Sounds fair enough, but these tyres are not specified for each individual car are they?
Paul, May I suggest you do a little research b4 sounding off to the PH world ..
The whole N program is based on approving specific tyres for specific models, and for every available wheel and tyre combination for every model since 1988 ....
HTh, cheers, Maurice
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