Tyre availability, size and fitment

[911Time]

The Porsche tyre approval situation isn't very straightforward, especially as depending on its age & wheel size, each model of 911 can potentially have a different tyre 'officially' approved.

When I bought my 991 Carrera 4S, the Michelin Pilot Sport 4S (PS4S) was still a relatively new tyre and had only received Porsche approval for the wide body/Carrera 4S cars (as Sponge said) but that's no longer the case.

Gonesailing is right - there is now a Porsche approved N0 rated version of the Michelin Pilot Sport 4S (PS4S) suitable for the 991 GTS whether it's 2 wheel-drive OR 4 wheel-drive. In fact according to the Porsche document 'Overview Summer Tyres Current Vehicles' the Michelin PS4S tyres are now approved for ALL versions of the 991 with 20" wheels, whether narrow-body or wide-body (with the exception of the GT3, R, GT3 RS and GT2 RS).

So, whether you decide on buying a 991 GTS in 2 or 4 wheel-drive you CAN choose Michelin PS4S tyres.

BUT - without wishing to throw a spanner in the works after all that explanation, for some reason according to the EU tyre label data, the Porsche approved N0 version of the PS4S doesn't seem to offer as high a classification for Wet Grip as the non-approved version! :dont know:

For example:

The Porsche approved N0 rated Michelin Pilot Sport 4S tyres for the GTS or 4 GTS, in size 245/35 ZR 20 (95Y) XL and 305/30 ZR20 (103Y) XL have been classified on the EU Tyre label as 'E' for Rolling Resistance and 'B' for Wet Grip (the higher the rating the better).

The Non-approved version of the Michelin Pilot Sport 4S in the same size is classified as 'C' for Rolling Resistance and 'A' for Wet Grip!!

So, to recap: Whether you buy a 991.1 GTS with 2 wheel-drive or 4 wheel-drive you CAN fit the Michelin PS4S tyres, which a lot of people (including myself) think are far superior to the Pirelli P-Zeros (especially in the wet).

If you buy through an OPC and want to maintain the Porsche Extended Warranty then fit a set of N0 approved ones or if not you could choose to fit the 'standard' version, for the further potential improvement in wet grip, detailed above.

Hope that helps clarify everything tyre wise on a 991 GTS/4 GTS and other 991 variants listed (but not on any other model, age, wheel-size, colour etc, where the whole discussion will have to start again....) :lol: :lol:

 

[spongebob squarepants]

Hi Sarlim,

To Clarify

The Porsche tyre approval situation isn't very straightforward, especially as depending on its age & wheel size, each model of 911 can potentially have a different tyre 'officially' approved.

When I bought my 991 Carrera 4S, the Michelin Pilot Sport 4S (PS4S) was still a relatively new tyre and had only received Porsche approval for the wide body/Carrera 4S cars (as Sponge said) but that's no longer the case.

Gonesailing is right - there is now a Porsche approved N0 rated version of the Michelin Pilot Sport 4S (PS4S) suitable for the 991 GTS whether it's 2 wheel-drive OR 4 wheel-drive. In fact according to the Porsche document 'Overview Summer Tyres Current Vehicles' the Michelin PS4S tyres are now approved for ALL versions of the 991 with 20" wheels, whether narrow-body or wide-body (with the exception of the GT3, R, GT3 RS and GT2 RS).

So, whether you decide on buying a 991 GTS in 2 or 4 wheel-drive you CAN choose Michelin PS4S tyres.

BUT - without wishing to throw a spanner in the works after all that explanation, for some reason according to the EU tyre label data, the Porsche approved N0 version of the PS4S doesn't seem to offer as high a classification for Wet Grip as the non-approved version! :dont know:

For example:

The Porsche approved N0 rated Michelin Pilot Sport 4S tyres for the GTS or 4 GTS, in size 245/35 ZR 20 (95Y) XL and 305/30 ZR20 (103Y) XL have been classified on the EU Tyre label as 'E' for Rolling Resistance and 'B' for Wet Grip (the higher the rating the better).

The Non-approved version of the Michelin Pilot Sport 4S in the same size is classified as 'C' for Rolling Resistance and 'A' for Wet Grip!!

So, to recap: Whether you buy a 991.1 GTS with 2 wheel-drive or 4 wheel-drive you CAN fit the Michelin PS4S tyres, which a lot of people (including myself) think are far superior to the Pirelli P-Zeros (especially in the wet).

If you buy through an OPC and want to maintain the Porsche Extended Warranty then fit a set of N0 approved ones or if not you could choose to fit the 'standard' version, for the further potential improvement in wet grip, detailed above.

Hope that helps clarify everything tyre wise on a 991 GTS/4 GTS and other 991 variants listed (but not on any other model, age, wheel-size, colour etc, where the whole discussion will have to start again....) :lol: :lol:

The problem on the narrow body is the 295 rears, The size is still not available, unless that has changed?

 

[MJA911]

The problem on the narrow body is the 295 rears, The size is still not available, unless that has changed?

No, it hasn't changed, put PS4S non N rated on mine 2 weeks ago because of the unavailability of n rated 295 rears. Shame but impressed with the generic PS4S, the Pirellis they replaced had gone hard, quite a difference. OP, as detailed previously, you'll have no problem on a GTS getting n rated PS4S for it as they're available for 305 rears.

As for your 2wd/4wd conundrum, having had both in 997 form, I found the difference subtle and comes down to whether you prefer a slightly more planted feel of 4wd you'll be familiar with or a slightly more agile feel. In bad weather I guess the 4wd is safer overall, although on standing water it doesn't help as a friend recently found out in his 997 Turbo S. Haven't driven a 4wd 991, but my slim hipped 2wd 991 feels secure, especially with the new tyres :wink:

 

[911Time]

.....the 295 rears, The size is still not available, unless that has changed?

Just to be clear, the Michelin PS4S is available in 295/30 ZR20 (edited due to typo) but as you say Sponge that specific size isn't 'officially' approved: It's very odd and frankly I wonder whether it's a glitch, but then the PS4S 305/30 ZR20s are approved for the models I listed earlier.

As far as the OP, Sarlim is concerned: As MJA911 said, the 991 2 GTS or 4 GTS can both be fitted with Porsche approved N0 stamped 245/35 ZR20 and 305/30 ZR20 tyres, so there's no issue in him sourcing a Porsche approved Michelin PS4S for either model, if that's what the he wants/needs for warranty purposes OR the non-approved versions (if warranty isn't a consideration) for the reasons I mentioned previously.

 

[MJA911]

The rears are actually 295/30 (not 295/35), could be wrong but I think the reason this size is not n rated is because the PS4S is n rated for the 992 and there is no 295/30 tyre for those, the 'standard" R20 992 rear is 305 although most of them will have R21 wheels anyway.

 

[spongebob squarepants]

.....the 295 rears, The size is still not available, unless that has changed?

Just to be clear, the Michelin PS4S is available in 295/35 ZR20 but as you say Sponge that specific size isn't 'officially' approved: It's very odd and frankly I wonder whether it's a glitch, but then the PS4S 305/30 ZR20s are approved for the models I listed earlier.

As far as the OP, Sarlim is concerned: As MJA911 said, the 991 2 GTS or 4 GTS can both be fitted with Porsche approved N0 stamped 245/35 ZR20 and 305/30 ZR20 tyres, so there's no issue in him sourcing a Porsche approved Michelin PS4S for either model, if that's what the he wants/needs for warranty purposes OR the non-approved versions (if warranty isn't a consideration) for the reasons I mentioned previously.

:thumb: Sorry for the hijak, I'm still wondering will the N rated 305 Michelin's fit the 295 rim? And If so in the crazy Porsche warranty world would this still preclude them from the warranty :dont know:
I have to change my tyres soon, I'm not putting P zeros back on, so it seems madness your left with a choice on the 2S of either fitting P zeros or Sport techno's to get the Porsche warranty :roll:

 

[911Time]

:thumb: Sorry for the hijak, I'm still wondering will the N rated 305 Michelin's fit the 295 rim? And If so in the crazy Porsche warranty world would this still preclude them from the warranty :dont know:
I have to change my tyres soon, I'm not putting P zeros back on, so it seems madness your left with a choice on the 2S of either fitting P zeros or Sport techno's to get the Porsche warranty :roll:

The simple answer is Yes, the 305 section tyre WILL fit either the 11J rim, that normally carries a 295 (such as on on your car Sponge) or the 11.5J rim - there's only 10mm difference anyway between the tyre width and elsewhere in the range Porsche have no problem fitting 305s to 11J.

The question of whether that's acceptable to an independent Insurance agent providing the Porsche Extended Warranty is the grey area and I agree in this instance it makes no sense to limit owners whose cars came with 295s to an inferior or non-classified tyre.

Choosing an N0 rated 305 seems far more sensible and defensible to me but that's just my opinion - others are available :thumb:

 

[MJA911]

Putting 305 on my 11j rims was mentioned to me also, but not having warranty concerns I choose generic 295 over n rated 305 on the advise of the people setting my car up, I wanted to maintain balance and avoid understeer, also felt more comfortable with 295 on 11j. Could easily understand going with the 305 for warranty reasons though, but I would just check the 305/11j is OK and would pass the 111 check etc.

 

[911Time]

Putting 305 on my 11j rims was mentioned to me also, but not having warranty concerns I choose generic 295 over n rated 305 on the advise of the people setting my car up, I wanted to maintain balance and avoid understeer, also felt more comfortable with 295 on 11j. Could easily understand going with the 305 for warranty reasons though, but I would just check the 305/11j is OK and would pass the 111 check etc.

In your situ, without warranty concerns I'd favour the generic (non-approved) 295 tyre but mainly because it has a better EU wet grip rating than the approved one...

Whilst 305 is the maximum section width you should fit on an 11J rim, it's perfectly normal practice and given there is only 10mm difference in width any change in the contact patch will be so negligible over a 295 as to be insignificant regarding understeer.

As I mentioned earlier Porsche fit 305s on 11J elsewhere in the range so it's not like they're not comfortable doing it.

 

[MJA911]

I also apologise for the thread hijack, last one, just wanted to add that a 10mm width increase on the rears was regarded as significant enough by the people setting my car up, possibly the best known chassis tuner for our cars in the UK!

They were aiming for nice pointy feel, but still within OE geo settings thus protecting the tyres from unusual wear and didn't want fatter tyres on the rear affecting that. Can't complain at the outcome, it feels like a light, agile, 911 should to me, keener turn-in than previous 911s I've had. It's also the 3.4, another contributor to the 295 decision.

There's always been a lot of discussion about n-rated and I've always preferred to have them, but a person from Michelin told me that it can mean something as insignificant as the cosmetics on the tyre wall or as significant as a difference in the compound but unless you're deep in Michelin you'll not know what it is for a specific tyre. I leant on the expertise of others to go generic on these tyres, must say they do feel very good.

 

[spongebob squarepants]

Thanks chaps :thumb: There doesn't seem a conclusive answer lol, it's surprising how much wider and better the 305's look, bearing in mind they will fit and can't be worse than the P zeros I'm gonna do it....

I can't see how it can have such an effect on handling as the sport techno's (standard to the 2S) are 305's :dont know:

 

[MJA911]

Thanks chaps :thumb: There doesn't seem a conclusive answer lol, it's surprising how much wider and better the 305's look, bearing in mind they will fit and can't be worse than the P zeros I'm gonna do it....

I can't see how it can have such an effect on handling as the sport techno's (standard to the 2S) are 305's :dont know:

No, it wouldn't be huge as it's within spec and in itself it won't make a big difference, but just like with geo settings there is a range that can be worked with to affect the characteristics of how a car behaves, it's usually only apparent under some sort of load. Wider rear tyres means more grip at the rear which will encourage understeer, on my car we wanted to encourage front end grip (i.e turn in) through the geo backed up by the tyres. The Pirellis that came off were so bad on the fronts, that was the biggest contributor to how much better it feels now.

 

[911Time]

I also apologise for the thread hijack, last one, just wanted to add that a 10mm width increase on the rears was regarded as significant enough by the people setting my car up, possibly the best known chassis tuner for our cars in the UK!

They were aiming for nice pointy feel, but still within OE geo settings thus protecting the tyres from unusual wear and didn't want fatter tyres on the rear affecting that. Can't complain at the outcome, it feels like a light, agile, 911 should to me, keener turn-in than previous 911s I've had. It's also the 3.4, another contributor to the 295 decision.

There's always been a lot of discussion about n-rated and I've always preferred to have them, but a person from Michelin told me that it can mean something as insignificant as the cosmetics on the tyre wall or as significant as a difference in the compound but unless you're deep in Michelin you'll not know what it is for a specific tyre. I leant on the expertise of others to go generic on these tyres, must say they do feel very good.

First of all I'd like to apologise to Sarlim for continuing to digress into a discussion about tyres however, I think most would agree that the issue of tyre performance is pertinent to the nature of the thread, as the subject goes to the very heart of the matter i.e the availability of grip and its central importance in vehicle safety. I hope therefore that Sarlim won't mind this indulgence because the availability of suitable tyres, whether they are 'officially' approved, whether that actually provides a benefit in tyre performance (over the generic tyre) and whether tyres of X size can or could be fitted, is still relevant.

Thanks MJA for clarifying the advice that you received - I'm sure everyone knows who you're referring to and obviously they have considerable experience in chassis set-up, specialising in Porsche.

I'm a big advocate of companies like CG but presumably you didn't go there just to discuss a possible change of rear tyre size but to benefit from their very comprehensive chassis tuning, which would also include considerations such as tyre fitment, how you intended to use the vehicle and what you wanted to gain from the whole experience - I'm equally sure that if you changed to 305s they would simply have tweaked things a little to get the best from that set-up.

I agree that if you want to maintain the handling balance closest to how Porsche originally intended, then you should start with the set-up that the car came with - in your case that would be a 295 section rear tyre but it could be a 305 for someone else - in the absence of warranty considerations and the availability of Porsche approved tyres, that would be the ideal starting point. I wasn't recommending a change to 305 simply for the sake of change!

Optimising a car's chassis dynamics, is all about efficiently controlling the forces being fed into the chassis and creating a balance between the components, that provides the driver with vehicle control, predictability & safety. In the case of Motorsport, these improvements might cumulatively result in faster lap times but on the road, gains tend to be more subjective and harder to quantify beyond 'feel'. The degree to which they will be obvious afterwards, will largely depend upon how the car presented initially and how much improvement could be dialled in: Even brand new cars can be improved but the passage of years and miles tend to offer the greatest gains for older vehicles (no offence).

Unfortunately, whether on the road or track, there is no such thing as a 'perfect' chassis set-up, it's always trade-off because it's a bit of a moveable feast: The variables are always changing - unlike a circuit, no two journeys/days (conditions) are the same and even on the track things evolve - hence the need for practice sessions.

But I digress: My point was, that in my opinion when taken alone, an increase in width of 10mm from a 295 to a 305 section tyre on the standard 11J rim, where everything else remains the same, won't make sufficient difference to be noticeable to 'most' drivers on the road and whilst, strictly speaking, the fitment of a 305 section tyre on a vehicle intended to wear a 295 may be slightly sub-optimal, it's perfectly acceptable and within the bounds of what can safely be fitted to an 11J rim. More importantly, there are many other factors that will have a far greater effect upon the car's handling, including (but not limited to) the tyre compound/pressure (slip angle), the current geometry set-up, age/quality of the suspension components, age/quality of the bushes, occupancy, fuel load etc, etc than to worry about the effects of a change to 305.

I don't expect anyone to take my suggestions over what a Porsche specialist says but I'm not your average enthusiast/driver/contributor either. Just for the sake of explanation: At the age of 53 I've been working on cars for over 40 years (which makes me feel very old :sad, I'm a qualified Automotive Engineer, graduated top of my class for 3 years and was very fortunate to go on to work with Audi through the wonderful Group B rally years. Despite eventually leaving engineering as a day job, (to move up the business ladder), I maintained my contacts within the industry & motorsport, both professionally and personally and whilst I'm now old and decrepit, the passion still remains

Times may change but the fundamentals remain the same and personally I'd still have been happy to go from 295 to 305 on my own car (had that been necessary) and to accommodate the change with some slight tweaks if needed.

All that said, every day is still a school day, so I'm happy to tip my cap to a Porsche specialist if they actually said that changing from 295s to 305s was a no-no

 

[MJA911]

It wasn't a no-no Mark, just a choice made for my car in conjunction with the geo. I didn't give it much thought at the time, it sounded logical and with CG I tend to leave them to it, they sourced the tyres via the firm who is just round the corner from them.

 

[911Time]

It wasn't a no-no Mark, just a choice made for my car in conjunction with the geo. I didn't give it much thought at the time, it sounded logical and with CG I tend to leave them to it, they sourced the tyres via the firm who is just round the corner from them.

Thank you for clarifying MJA!! :thumb:

In either size, the Michelin PS4S is a very good tyre - glad you're enjoying the new chassis set-up!!

BTW I made a typo earlier in this thread regarding the 295 section tyre and typed 35% aspect ratio, instead of the 30% I intended.

In my defence, I'd refer you to my age/decrepit condition, as mentioned earlier