Discussion
Just read this on another forum,posted by a chap shown around the Pirelli factory in Carlisle,proof as it were that N rated tyres are slightly different in quality and in some cases compound.
Credit given to the original poster as follows,
I hope its of interest.
"The first point of significance was that all the tyres are manufactured using the same process, on the same machines with the same operators. The critical difference between OEM tyres and "general" (Pirelli terminology), is that during the final inspection process there are two tolerance limits.
Let me explain that amongst other checks, the actual grading of the tyre is based on three particular criteria, these are, concentricity, radiality, balance.
The inspection stage is done by inflating the tyres and running them against a huge steel roller to simulate road use. They are then scanned with a laser to look measure the above elements. Then they are graded according to the results, OEM, G (general), Junk/Scrap. The OEM requirements are much tougher than the general requirements in terms of the three main criteria, so thats where the cream of the tyres go.
I asked about Porsche in particular and the N ratings, the N rated tyres are OEM, and so are within the tightest tolerance settings when compared the the G tyres. This doesn't mean that non N rated tyres are no good, but they are definitely not to the same standard as N rated.
Another key point is that the tyres are, or can be made with slight variations for different OEM's. So as an example we discussed, the plant manufactures P Zero's for Porsche, Audi and JLR. The base chemical compounds for each of these OEM's varies slightly, usually tweaked to add more or less silica to impact the the grip or economy (more silica equals softer compound, more grip, less economy, less silica the opposite). These slight variations are all kept within a tolerance specified by headquarters in Turin, so no great variations, but variation all the same.
When taking the above into account, you can then realise that if buying non N rated tyres (G), you could actually be buying P Zero's with different, or a mix of compounds, for example one may have been made on the Porsche line, two others made on the JLR line and one other on the Audi line. So not all P Zero's, PS2's, Potenzas are equal. To be sure to get the best quality tyre made to the tightest tolerances with the correct Porsche compound then you have to buy the N rated tyre.
When I asked about the different requirements of different OEM's, he was very quick to say Porsche is the most demanding customer with the toughest requirements. This is also taking into account the tyres they produce for Lotus, McClaren, AM as well as the above mentioned OEM's"
Credit given to the original poster as follows,
I hope its of interest.
"The first point of significance was that all the tyres are manufactured using the same process, on the same machines with the same operators. The critical difference between OEM tyres and "general" (Pirelli terminology), is that during the final inspection process there are two tolerance limits.
Let me explain that amongst other checks, the actual grading of the tyre is based on three particular criteria, these are, concentricity, radiality, balance.
The inspection stage is done by inflating the tyres and running them against a huge steel roller to simulate road use. They are then scanned with a laser to look measure the above elements. Then they are graded according to the results, OEM, G (general), Junk/Scrap. The OEM requirements are much tougher than the general requirements in terms of the three main criteria, so thats where the cream of the tyres go.
I asked about Porsche in particular and the N ratings, the N rated tyres are OEM, and so are within the tightest tolerance settings when compared the the G tyres. This doesn't mean that non N rated tyres are no good, but they are definitely not to the same standard as N rated.
Another key point is that the tyres are, or can be made with slight variations for different OEM's. So as an example we discussed, the plant manufactures P Zero's for Porsche, Audi and JLR. The base chemical compounds for each of these OEM's varies slightly, usually tweaked to add more or less silica to impact the the grip or economy (more silica equals softer compound, more grip, less economy, less silica the opposite). These slight variations are all kept within a tolerance specified by headquarters in Turin, so no great variations, but variation all the same.
When taking the above into account, you can then realise that if buying non N rated tyres (G), you could actually be buying P Zero's with different, or a mix of compounds, for example one may have been made on the Porsche line, two others made on the JLR line and one other on the Audi line. So not all P Zero's, PS2's, Potenzas are equal. To be sure to get the best quality tyre made to the tightest tolerances with the correct Porsche compound then you have to buy the N rated tyre.
When I asked about the different requirements of different OEM's, he was very quick to say Porsche is the most demanding customer with the toughest requirements. This is also taking into account the tyres they produce for Lotus, McClaren, AM as well as the above mentioned OEM's"
Gary11 said:
When taking the above into account, you can then realise that if buying non N rated tyres (G), you could actually be buying P Zero's with different, or a mix of compounds, for example one may have been made on the Porsche line, two others made on the JLR line and one other on the Audi line. So not all P Zero's, PS2's, Potenzas are equal. To be sure to get the best quality tyre made to the tightest tolerances with the correct Porsche compound then you have to buy the N rated tyre.
Or you just buy Michelin Pilot Supersports, all made to the exact same (very high) standard 
Edit - Oh, apart from some CGT sizes which owners have forced Porsche to stick an N stamp on - does anyone believe that Michelin are doing anything whatsoever different for this new MPSS N rated CGT tyre - bearing in mind they will sell a miniscule amount ?
Edited by TB993tt on Friday 13th December 10:10
That's a very interesting post.
However, this bit confuses me:
I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
However, this bit confuses me:
Gary11 said:
JThey are then scanned with a laser to look measure the above elements. Then they are graded according to the results, OEM, G (general), Junk/Scrap. The OEM requirements are much tougher than the general requirements in terms of the three main criteria, so thats where the cream of the tyres go.
Manufacturer (OEM) ratings (N for Porsche, J for Jaguar, M for Mercedes, A for Audi and R for Audi R8 - there may be others too) are part of the markings molded into the sidewall during the manufacturing process, not stamped on afterwards.I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
blade7 said:
I bought 4 18" Michelins for my 944T recently, there wasn't a lot of price difference between the N rated and standard tyres.
Just musing in that Porsche never approved 18" wheels on a 944T only 17" & that only with geo changes & 968 castor blocks. So N rated has even less relevance on a 944.thegoose said:
I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
That was my thought too when reading the OP.tr7v8 said:
blade7 said:
I bought 4 18" Michelins for my 944T recently, there wasn't a lot of price difference between the N rated and standard tyres.
Just musing in that Porsche never approved 18" wheels on a 944T only 17" & that only with geo changes & 968 castor blocks. So N rated has even less relevance on a 944.
. ArrowSC said:
thegoose said:
I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
That was my thought too when reading the OP.Wozy68 said:
And mine
I take the point that may well be an "assumption" by the original author,but find the factual content more interesting TBH. Perhaps we need to ascertain at what point the designation is applied,it is not beyond the realms of possibility for this to be annealed after inspection if indeed they are individually inspected by manual(human) means,surely its an assumption that a failed N could be a passed G?I wouldn't take that as a given.
G
You've got it there Marcus. It's clearly b
ks.
Bert
ks.Bert
thegoose said:
That's a very interesting post.
However, this bit confuses me:
I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
However, this bit confuses me:
Gary11 said:
JThey are then scanned with a laser to look measure the above elements. Then they are graded according to the results, OEM, G (general), Junk/Scrap. The OEM requirements are much tougher than the general requirements in terms of the three main criteria, so thats where the cream of the tyres go.
Manufacturer (OEM) ratings (N for Porsche, J for Jaguar, M for Mercedes, A for Audi and R for Audi R8 - there may be others too) are part of the markings molded into the sidewall during the manufacturing process, not stamped on afterwards.I can understand there being a different "recipe" for each OEM but I can't see that the batches of manufactured tyres are tested and if they fail the OEM spec they could still be OK (G for general) - that would mean removing the molded in markings.
I'm in the fortunate position to have access to some equipment that should be able to determine differences between the tyres (silica compounds). Is this worth pursuing?
I should be able to determine surface energy characteristics (IGC), surface area of the base compound (BET), silica/elemental make up / content (SEM/EDX). If we had access to the raw materials, particle size would also be an interesting key quality attribute to understand
Samples of each tyre would be required N vs. non N, same brand and model. I would also throw a third sample into the mix e.g a winter tyre to show whether the above techniques are discriminatory. Samples should be blinded to not introduce bias.
This would however not determine any differences in manufacturing tolerances for shape/sphericity etc.
I should be able to determine surface energy characteristics (IGC), surface area of the base compound (BET), silica/elemental make up / content (SEM/EDX). If we had access to the raw materials, particle size would also be an interesting key quality attribute to understand
Samples of each tyre would be required N vs. non N, same brand and model. I would also throw a third sample into the mix e.g a winter tyre to show whether the above techniques are discriminatory. Samples should be blinded to not introduce bias.
This would however not determine any differences in manufacturing tolerances for shape/sphericity etc.
Edited by Gouki on Sunday 15th December 01:08
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