There is a rather lengthy piece on tyres in the 3.2 Register, Register News. For convenience, I have cut and pasted it below. I hope it is helpful:
Tyres - Overview
I asked fellow register member Richard Bernau to follow up on an interesting e-mail he submitted recently on tyres and tyre selection for the 3.2 Carrera. Richard is not a tyre expert, but like myself, tyres are a "˜pet' subject and I feel he has produced a well balanced and informative document for all to read and learn from.
My 3.2 Carrera Needs New Tyres!
Selecting the right tyres for your 3.2 Carrera is an important decision. Your safety, as well as driving enjoyment over the next years and thousands of miles will be affected by this decision. The information and opinion provided here and the advice and recommendations are just that "" hopefully helpful information and advice and MY opinions, MY recommendations. I hold no qualification as a tyre expert other than my personal experience. Ultimately you must ensure that you select tyres that match your vehicle...and the way you drive it!
How many tyres do I need?
This is a paraphrase from www.tirerack.com -
"˜Since tyres affect the performance of your vehicle, ideally all four tyres should be as identical as possible or handling problems may arise. If your tyres don' t match, it is possible that one end of your Porsche won' t respond as quickly or completely as the other, making it more difficult to control.'
Some folks would go further and have you believe that mixing and matching different tyres is a complete no go area and that to do so is to virtually guarantee a serious accident. I disagree. For a start, 3.2s have a different size tyre and different rim widths front and rear, so all things being equal the front and rear will behave differently anyway!
I know its stating the obvious, but the front and back of a 911 are, of course, not equal "" the front is lightly loaded and the rear heavily loaded. With different inputs of steering and throttle and in differing conditions your car will understeer or oversteer. Having different tyres front and rear will only change these characteristics to a degree. If the tyres are fairly closely matched the change in handling characteristics will not be great. Porsche designed your car with smaller front wheels and tyres in order to decrease the oversteer characteristics that are inherent in a rear engine design. Consider this example, using a tyre with slightly less grip on the front of your 911 will further decrease any tendency to oversteer. It will also increase understeer and may slightly decrease braking ability as a less grippy tyre may lock slightly more easily. So, not really a catastrophe, just something to be aware of.
I have from time to time run different front and rear tyres with no problem at all. One time, I even did a set of 10 laps at Oulton Park with mismatched tyres front and rear (I didn't have time to change to my track tyres and didn't want to miss out on my session!). Admittedly, not best practice but no real problems, just a slightly greater tendency to understeer as the front tyres had slightly less grip. This is exactly the same effect as might have been achieved by altering tyre pressures, running a bigger rear tyre or altering an anti-roll bar setting "" all perfectly normal methods that people use to tune the handling characteristics of a 911.
One thing I would not do is run different tyres on either side of the car. I think that the possible mismatch in grip and performance could have adverse consequences under severe or panic braking.
A further point to consider is relative tread depth. If your rear tyres only have a millimetre or two of tread left but your front tyres are new, for example, you are again effectively changing your handling balance "" particularly in the wet. Your car will become an oversteer meister!
Conclusion "" replacing just the front or rear tyres of your car is not necessarily a recipe for disaster, just beware that it may alter the handling balance of your car.
What is the right size for my 3.2?
Buying the correct tyre size can get complicated, if you decide to upgrade from your car's Original Equipment size. Most 3.2s run on 16 inch diameter Fuchs forged alloy wheels. The standard widths are 6 inch at the front and 7 inch at the rear. In 1989 the rear width increased to 8 inchs. A fairly common upgrade is to run "Turbo Fuchs" which are 7 and 8/9 inch wide respectively. Some 3.2s may alternatively have 15 inch diameter Fuchs or Teledials in 6, 7 or 8 inch widths.
The standard size front tyres on 16 x 6 are 205mm width with 55 series profile. On 16 x 7 (or 16 x 8 on 1989 cars) standard rear size is 225mm width with 50 profile.
Do you have any options? On the standard 6/7 inch rims, basically no. You cannot run a tyre wider than a 205 on a 6 inch rim or wider than 225 on a 7 inch rim. While it is physically possible to fit a bigger tyre on these rims there is no performance advantage on such a narrow rim. If you are lucky enough to have 8 inch rims at the rear you can run a 245/45 for a little extra width while retaining the same overall diameter and rolling circumference. All other things being equal this will reduce oversteer and increase understeer (which may or may not be desirable).
On Turbo Fuchs you have more options. On the front you can run the standard 205/55 "" which will be nicely stretched out on a 7 inch rim and will work much better than on a 6 "" or you can upsize to a 225/50 or a 225/45. The main benefit of the slightly wider tyre is, in my experience, under dry braking. The wider front track that the 7 inch rims provide makes a noticeable improvement in turn-in and front end, steady-state grip. The difference between the 205 and 225 in terms of turn-in or grip in a steady-state corner is not so great.
The 225/50 retains the same overall diameter as a 205/55 but you may run into clearance problems. All 911s are slightly different in this respect but most will experience a slight clearance or rubbing problem "" generally on the left hand side. On my car I had a slight rub on extreme right hand cornering even with the fenders rolled and with 0.75 degrees of negative camber. My ride height is also slightly lower than euro spec but not as low as say a classic race car. However, with 1.25 degrees of negative camber I have no problem. I suspect that a 225/45 tyre would help with clearance problems but this a rare tyre size that is not widely produced.
If you have 16 x 9 wheels for the rear, you can run a 245/45. If you choose to run 205 on the front you may find that a 225/50 gives a better handling balance. Some tyre makers may suggest that a 9 inch rim is too wide for a 225 tyre but I have found it works just fine. There is often very little difference in actual size between say a 225 and a 245 as tyre makers can vary the width of tyres by as much as ±10mm from the stated or nominal width. This is worth checking when considering new tyres. A 9 inch rim is wide enough to run a 255 or a 265 tyre, but there are, as far as I know, none available with a profile that would work for a 911.
Is Bigger Better?
A lot of 3.2 owners have purchased a set of 17 inch wheels to "update" the look of their cars. Quite apart from the aesthetic merits of such a change, does it offer a worthwhile performance improvement? I do not have 17 inch wheels so I cannot speak from personal experience. However, the vast majority of people who make the change to 17s swear that it is an improvement. This makes sense. If overall diameter remains the same as standard then the tyre sidewall must be smaller i.e. a lower profile tyre. A smaller sidewall normally means a stiffer sidewall and as this is a part of the cars suspension, you have effectively stiffened the overall spring rate of the car. It may make the ride of the car slightly more harsh as a consequence.
Perhaps of more importance is the question of the quality of the 17 inch wheel. The Fuchs wheel is a very strong and comparatively lightweight wheel. This is because it is forged rather than say pressure cast. It will not break. It may bend due to an impact - but it will not break. Aftermarket 17 inch wheels, such as the Cup replicas, are pressure cast and are less strong than Fuchs wheels. They also weigh a lot more. They may break "" and some have done just this when used on track. It is however rare and may be of no consequence to you if you do not plan on spending a lot of time on the track. The same reservation applies to Fuchs replicas which are also pressure cast in the same pattern and thickness as the stronger forged original. This is the reason why Cup replicas are so cheap unlike say a Fikse, HRE or some BBS wheels which are all modular wheels with forged centres. If you want to take your car on track days it may be best to stick to the well respected brands like BBS, Speedline, Ruf, Fikse, HRE or Fuchs.
I mentioned that 17 inch wheels will generally weigh more than Fuchs (as will larger 17 inch tyres). Why is this important? For everyday driving, it is probably not all that important, however, increased weight is generally bad, but heavier wheels and tyres means more un-sprung weight, which is twice (actually four times) as bad. Unless you are racing though, an increase in un-sprung weight will probably only be noticeable if you drive on particularly bumpy roads (i.e. most of the UK) or have a particularly worn out set of shock absorbers, in which case, you will notice a marked deterioration in ride quality.
The other size consideration, which I have mentioned above, is overall tyre diameter. As a rule of thumb, staying within a ±3% diameter change is desirable. A greater change in diameter will mean that your speedometer becomes inaccurate and that your gearing will change. For more information there are a number of online sources with tyre diameter calculators such as:
http://www.tirerack.com/tyres/tiretech/general/size.htm).
If you have 15 inch rims on your 3.2 and decide to run a modern low profile tyre such as 205/50 and 225/50 then you will make quite a change to your overall gearing. This lower gearing actually makes a noticeable improvement in acceleration and can have benefits in certain classes of racing "" your speedometer will however be inaccurate and optimistic.
So what tyres should I buy?
First, lets be clear, we drive 231hp cars from the 1980s. THEY ARE NOT PORSCHE GT1s OR MCLAREN F1s. We don' t need extra special tyres. Our cars are great but they are not that different in performance from plenty of modern sports cars - Audi TT, BMW 330 to name but two. Accordingly, I believe it is entirely unnecessary to use the latest and greatest tyres on our cars. If you want to, absolutely fine, go right ahead, but you certainly don' t have to.
Lets call the most expensive highest performance tyres " max performance" . When nothing but the best will do, these are the tyres that you want. In this category, I would include: Bridgestone Potenza SO2/SO3, Continental Contisport Contact II, Dunlop SP Sport 9000, Goodyear Eagle F1, Kumho Ecsta MX, Michelin Pilot Sport, Pirelli PZero, Toyo T1S and Yokohama AVS Sport. None of these tyres will disappoint in terms of performance. They may be noisy, they may be harsh riding, but they will grip. Some of these tyres are available in "N" spec but we will get to that a little later. Some may be slightly better in the wet and some slightly better in the dry. Without proper test conditions and experienced drivers though I would defy you to pick a great deal of difference between them with just the seat of your pants to guide you. The biggest difference you notice with a new set of tyres is that they are new.
New tyres will (almost always) out perform your old tyres especially in the wet because the tread blocks of old tyres get worn and feathered, they are no longer flat and the edges have little nicks out of them - result, less surface area, less grip. Also, old, heat cycled rubber is harder - result, less grip. The two benefits old tyres have is good heat dissipation and less squirm from tall tread blocks - probably only an advantage on the track.
The next level is " ultra-high performance" . These are still great tyres. Five years ago they may have been the very best you could buy but they have now been superceded or they may be just a small rung down from the manufacturer's max performance offerings drawing on much of the same technology. In this category I would include: Bridgestone SO1, Bridgestone RE730, Continental Contisport Contact I, Dunlop SP8000, Falken FK451, Fulda Extremo, Kumho Ecsta Supra 712, Michelin Pilot SXGT and Yokohama AVS ES100. Again, these are all great tyres, just not quite as good as the max performance. These tyres may be a little quieter and smoother riding than the max performance offerings. They will all have a much more modern construction and tread pattern than the tyres our cars came with. And that leads me to my next point. In 1984 the standard sport tyres for a 3.2 were (I believe) Pirelli P7s. Great in their day, but absolutely hopeless by today' s standards. Non-sport models may have got Pirelli P6s or something even more ghastly. Even the later 3.2s only got tyres like Bridgestone RE71s or P700z Pirellis - again very outdated compared to modern offerings. Tyres have improved enormously in the last 20 years and any of these ultra-high performance tyres will run rings around the 1980s offerings. Modern road tyres can sometimes pull over 1G on a skid pad - even racing slicks struggled to do this 20 years ago. Tread patterns are much better at dispersing standing water and tread compounds with silica and long chain carbons molecules have a much better wet weather and dry weather grip without sacrificing wear and longevity.
The next category would be "high performance" and in this category, I would include tyres like: Dunlop SP2000, Kumho Ecsta 711, Pirelli P7 (the new ones!) and Pirelli P6000. There are many, many others in this category but my knowledge kind of runs out at this level "" and you have to draw the line somewhere!
There is plenty of information on these tyres online. Try www.tirerack.com for user reviews and comparison tests on most of the above listed tyres.
Do I need "N" rated tyres?
This is an emotive point where people hold wildly differing opinions. Some will have you believe that if you do not fit N rated tyres to your Porsche then you will inevitably crash and die in a flaming wreck. I will let you know what I think later.
What are N rated tyres?
Just exactly what constitutes an N rated tyre is a bit of a mystery. The best way that it has been explained to me is that it is a Porsche approved tyre. Supposedly, Porsche has been involved in the development of the tyre and has made a tyre that is slightly different than a non-N rated tyre. I have heard of three specific characteristics attributed to N rated tyres. First, stiffer sidewalls meaning sharper response (and presumably a harsher ride). Secondly, lower noise for prolonged high speed autobahn cruising. Thirdly, that the tyre is wider than the spec or nominal width.
Lets have a think about whether these characteristics are enough to justify the extra cost of an N rated tyre. Think of this, an N-rated Contisport Contact I is a softer side-walled tyre than a non-N-rated SO2 or P-zero, it is also notoriously noisy when part worn. Is it a better tyre because it has an N-rating? Another data point, I had a set of Yokohama N-rated S1Zs "" very noisy and a good but not great tyre in terms of sidewall stiffness and response - hence I would rate them below the max performance category above. The next tyres on my car were non-N-rated SO2s and they outperformed the S1Zs in all respects. This almost certainly is a case of technology moving on as the SO2s were at that time the latest and greatest covers around, but it certainly shows that an N rating is simply one of many factors to consider when making your decision on what to buy.
I personally think that N ratings are not a whole lot more than a clever marketing gimmick to make you pay more for an essentially similar tyre with an N printed on the side. I do not doubt that Porsche has some involvement in the development of the N rated tyre and I admit that they might be slightly better, with a stiffer sidewall or less high speed noise or wider (for what that is worth unless you increase your rim width) but why pay a whole lot more for such dubious advantages that you in all likelihood won' t even notice? If you must buy N-rated, fine, but I don' t think you need to and you shouldn' t feel ashamed buying something else. Its your wallet that's being emptied.
I do understand the appeal of something that is Porsche approved but it is also worth bearing in mind that N ratings were never available when our cars were new and N-ratings are not designed for our cars in the first place.
For your information and in order to put forward a different view, I did find the following information on N ratings and what they mean but, as you see, it is somewhat contradictory:
"I contacted the factory last year regarding the Bridgestone SO-2s, as they were not on the list of official tire recommendations, thinking that this list might be outdated. I' m wondering: What is " N-spec?"
' Nx' (x = 0, 1, 2,...) is used to designate tyres built specifically to Porsche specs, determined by extensive testing. Any Porsche dealer will have a list of tyres that the factory recommends for a specific car and rim size. As I pointed out, the Bridgestone S-02 is not recommended for *16* inch wheels, but is OK to use with *17* inch wheels. N0, N1, N2, and N3 are currently used, but I have absolutely no idea what the significance of this differentiation is.
I just called the factory, this is what I learned: Back in 1985 the ' VR' was the highest speed rating, rated for speeds of 210 km/h and above. Of course, when considering that an S4 will do 270 km/h or more, this rating might not be sufficient. The powers that be (i.e. the government) then decided that you had to use specific tyres on specific cars (Porsche told me that this applies only in Germany and Australia). These tyres are specifically stated in the registration papers (or in an update list from Porsche). Failure to use these tyres will get you in big trouble with your insurance when something goes wrong, i.e. you might lose your coverage. It would also constitute a breach of traffic code regulations, i.e. you won' t pass TUV inspection. Anyway, to make sure you use the right tire, Porsche and the tire makers agreed on this extra designation. The letter ' N' was chosen arbitrarily (it just stands for ' Nummer' or ' Number' ). The numerals 0, 1, 2, etc. are used to designate updates within one series of tyres. Every time they change something in the construction, the value is increased by 1. N2 is therefore the third modification series.
ZR has since been superseded by WR and YR, which are rated at 270+ km/h and 300+ km/h, respectively. Still, speed rating is only one factor in determining whether a tire is suitable for a specific application, other factors include grip (wet and dry), tire noise, ride quality, etc. The N-spec will therefore be continued to be used.
An N-spec tire will have the same outward appearance (tread pattern, dimensions) as a ' regular' tire, but the rubber compound and carcass construction will be different. Porsche puts a lot of effort into testing tyres and getting the tire makers to produce tyres to their specs. They might be harder to find (depending on your location), wear faster and possibly cost more, but I use them - at speed, the last thing I want to worry about is tyres. Testing tyres is somewhat of an empirical science, depending on weather conditions (obviously) and the tester him or herself. For instance, Porsche (other makers might do the same) goes to the trouble of testing all the winter tyres for this year in New Zealand, where they find suitable conditions in June/July. Porsche continues to test tyres for all models, albeit more frequently for the current production cars. The current list for the 928 that Porsche was friendly enough to fax to me is designated ' 7/11' and dates from 02/20/1998.
Hope this helps. (Are you still awake?)
Best regards,
Thilo Corts
' 87 S4 auto mailto:corts@webx.de"
Further comments on N-ratings come from the highly respected Adrian Streather who is in the process of publishing a book on the 964 series.
"One thing I have learned is that the N rating does affect design of the tyres."
Which somewhat contradicts Mr Cort's comments and indeed Adrian's comments below:
"From my testing I have come to a conclusion which some will disagree with but I must state. "If you own a Porsche 911 then purchase Porsche recommended N rated tyres". I would also extend this to all model Porsches because the 944 is so much better with the Bridgestone SO2s fitted (pity about the lack of power). Whilst I cannot say what the N rating consists of I have worked out basically what it means. N0=Very High Performance Tyre low on comfort. N1 thru N4 shows lowering of high performance specifications and an increase in comfort (comfort being ride comfort). Remember these ratings are on standard set-up 911s. When you lower and stiffen the suspension these N ratings and the affect on your own 911 may not be as you expect."
Again, contradicts the above, and to be fair seems, more like an endorsement of SO2s.
I honestly believe that you are much better off simply doing your homework and buying a tyre at a price and of a performance level that you are comfortable with. In my experience, if you want the ultimate in dry performance, then R compound tyres will exceed the dry performance of any road tyre "" N rated or otherwise "" and wet performance depends more on the drivers skill and the ability to feel the "limit" of the tyre. Give me something nice and consistent with a progressive break-away and this tyre will do me just fine on the public highways. Unless there is standing water, I will also take the R compound tyre on the track every time.
How much should I Pay?
This might be blasphemy to the N rated brigade, but for road tyres, I don' t think you need to pay more than about £70-90 per tyre for a very good tyre. Conventional wisdom says buy a premium tyre from the premium brands. Get a top of the line tyre from Pirelli, Conti, Michelin, Bridgestone, Dunlop, Goodyear and you won' t go far wrong. Problem is you pay a premium price - I hear prices of GBP120-220 quoted on the 3.2 Titanic List.
I suggest you widen your search and open you minds to other possibilities. Tyre manufacturers such as Yokohama, Kumho, Toyo and Falken all make very good max performance or ultra-high performance tyres, they are just relatively unknown here in the UK and as such they are somewhat underpriced compared with the competition. Try the Toyo T1S. It is standard fit on TVRs now that the SO2 is unavailable. Any tyre that can keep the various TVRs on the road has to be good. It has in some tests been rated as the top (non-R compound) tyre you can buy. Try the Falken FK451 for an even better bargain. Maybe not quite a max performance tyre, but this is what I am currently using and I love them. They do everything well including looking good and a set of 4 is under £300 (for 225/50 and 245/45 "" standard sizes are even cheaper). Mine have had half a dozen track days and a trip to the Ring and they are wonderful. Very similar to the SO2s in grip and feel with slightly lower limits and slightly better wear characteristics. Also quieter. As others will testify, I don' t baby them. If that isn't cheap enough for you then I am told that the Fulda Extremo is even cheaper. Gemballa used these tyres on its 600hp 993 based twin turbo Extremo (http://www.fulda.co.uk/pages/porsche.htm) in 1999.
Where to buy from?
One of our own Simon at Essential Styling claims to offer good prices on most major brands, so try him (http://www.essentialstyling.com/). Another supplier, you can add to the list is Bracknell Tyre and Battery - they are reputed to be the cheapest in the UK and can get most brands to order.
Richard Bernau
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