Testing our tires!

A

Story of Unscientific
Tyre Testing

by
Adrian Streather RO Swiss-European Region TIPEC (SERTIPEC)

.

Introduction

This article
is all about tyre testing. The results are totally subjective and unscientific
however I hope that my efforts can provide just a little insight into tyre
selections.

One can only
get the best out of ones Porsche with the correct tyres for your needs fitted.
We all have different conditions in which we drive, we all drive differently and
very few tyres are great in every category. Porsche publish their
recommendations for summer and winter tyres every year in their magazine
Christophorus. They also issue Technical Service Bulletins but in recent years
Porsche seemed to have stopped doing this. The last one I have is dated 1995.
Various Auto Clubs around the world do similar things as do many of the
respected motoring magazines. I highly recommend that these publications be read
as well to ensure you have all the possible data. New tyres for a Porsche is an
expensive business and getting it right first time is the goal.

Test
vehicles

Porsche 911
(964) Carrera 4 rego AR5029

Porsche 944
(1985.5) rego AR23953

Togetherness

Tyres
tested

Note
one: I received no support from any of the tyre manufacturers.

Note
two: I have not and cannot comment on the aquaplaning abilities, or lack thereof
any of these tyres. The 944 has never been in the situation and the 911C4 does
not aquaplane. Not on me anyway. AWD and extra weight in the front which is not
present on most other Porsches.

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205/55ZR16
Bridgestone S01 tested on 911C4 only

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225/50ZR16
Bridgestone S01 tested on 911C4 only

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205/55ZR16
Bridgestone S02 tested on 911C4 and 944 front only

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225/50ZR16
Bridgestone S02 tested on 911C4 and 944 rear only

bullet

205/55R16
Michelin Alpin Pilot tested on 911C4 and 944 front only

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225/50R16
Michelin Alpin Pilot tested on 911C4 and 944 rear only

bullet

205/50R17
Yokohama A008P Assymetrics tested on 911C4 front only

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255/40R17
Yokohama AVS Assymetrics tested on 911C4 rear only

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205/50ZR17
Pirelli P7000 tested on 911C4 front only

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255/40ZR17
Pirelli P7000 tested on 911C4 rear only

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215/60R15
Pirelli 5000 tested on 944 only

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205/55VR16
Semperit tested on 944 front only

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225/50VR16
Goodyear Eagle VR50 tested on 944 rear only

Bridgestone S01

These were the
tyres that were installed on my 911C4 when purchased it. my C4 was completely
stock standard with standard original 1990 design wheels. 6JX16 on the front and
8JX16 on the rear. This was the first time I had used or driven on Bridgestone
tyres on a Porsche, previously I had been a Pirelli person. The S01 was the best
tyre I had ever driven on. In the dry the grip was excellent. In the wet the
grip was excellence and even in the snow after being caught out a couple of
times these S01s worked well past my expectations. The S01 certainly did nothing
to assist or reduce the inherent understeer of the 911C4 in standard set up but
my opinion on the S01s is that they are an excellent high performance tyre. On
criticism is that they did wear quickly, especially on the inside of the fronts
on the AWD C4. They were not what I would call noisy on the road, they were
smooth but when worn the C4 made you know that the tyres were worn.
Unfortunately S01s are no longer easily available. Some stock still remains here
in Europe but they are very hard to find. Some of the Tuning firms have stocks
of them for their modification programs but I have not found a tyre store with
stock.

The
911C4 with its original wheels and SO1s and Gail of course

Michelin Alpin Pilot

If you live in
Switzerland and want to drive in winter you need winter tyres. In fact if you
live anywhere that has a true winter climate you should not venture out without
winter tyres. The 911C4 was a complete mystery for myself in winter so this time
I went with the official Porsche winter tyre recommendations for 16 inch wheels
in winter.

So what can be
said about these tyres. They have a low speed rating, 190kph maximum. I have had
them up to 260kph just to see how they would go. Answer, not good.

These tyres
are brilliant in the snow and ice. Never felt safer. In the wet as long as the
road surface was cold, less than 7 degrees centigrade. No problems at all.
Unfortunately as the road surface warmed or the road was dry, the performance of
these tyres fell away rapidly. In the dry four wheel drifts are very common as
the understeer causes some concerns, to me anyway, when you push it a little
hard. As soon as spring arrives these tyres need to be removed and replaced. of
course only bad luck means its snows after you put your summer tyres on. These
tyres also wear very quickly in the dry so gentle driving is required before
they can be replaced.

Next winter I
shall wait to the last moment to replace them and I will get them off at the
first opportunity. To be completely fair though. These tyres are brilliant
winter tyres and they ensure safe driving with the 911C4 regardless of the
weather. I highly recommend them.

Now I also
tested these tyres on the 944. Just for fun. The 944 being RWD is severely
limited in use in the mountains. However I would still highly recommend these
tyres as winter tyres for the 944 should you be able to drive around in winter.
In the flat areas of the world I would see no major problems and the 944 and the
Michelins would make an excellent combination. I did not feel any major changes
in the balance of the 944, without power steering my 944 understeers anyway and
the 205/225 combination seemed to reduce this understeer as compared to the all
round 15 inch 215s previously installed.

Winter, what else can I say

Tread Comparison Between P7000s and the
Michelin Alpin

Bridgestone S02 Potenza

Well what can
one say about these tyres. The best tyre ever manufactured for a 16 inch wheel
and installed on any model Porsche. I have used these tyres on the 911C4 and the
944. They provide brilliant grip in dry and wet and even in the snow. Not that I
recommend anyone use them in the snow. I was forced to once on the 911C4 and
they handled the job very well. The SO2 is the first tyre that I have ever had
total 100% confidence in under all circumstances. I have pushed both Porsches
very hard wearing these tyres and never have I been let down by tyre or Porsche.
On a negative side, the SO2s tend to wear more quickly, they are quite expensive
and they do have a high road noise level. I still think they are brilliant and
safe tyres and well worth the purchase.

These tyres
are currently installed on the 944 and will remain installed until they wear out
or I sell the 944. The 205/55ZR16 front and 225/50ZR16 rear combination really
works on the 944. I have taken the 944 out in warm and dry conditions and wet
and cool conditions. I really drove it hard on some of the toughest high speed
and low speed corners through hairpin bends anyone can find anywhere in the
world. Real James Bond type roads. The uncomfortable and inherent understeer of
the non power steering equipped 944 was very nicely reduced. Never to oversteer
but I like a little bit of understeer. Many will say that these tyres are too
expensive for an old 944 but personally I feel they are worth every penny and
they allow the 944 owner/driver to extract a little bit more from the abilities
Porsche built into the 944. The road noise problem is reduced a little bit on
the 944 as compared to the 911C4. However this might be down to the fact that a
high speed the 944 makes more noise where as the 911 gets smoother as the speed
increases. Rear engined versus front engined I guess.

911C4 with the SO2s installed on 16 inch 993 Cup
Wheels

944
with the SO2s installed

215/60R15
Pirelli 5000
tested on 944 only. These were the tyres that the 944 was
purchased with. A Porsche delivered option at the time. Not a recommended choice
in my opinion. These tyres are too wide all round for a non power steering
equipped 944. They cause massive understeer and the 944 is difficult to manage.
Hurts the shoulders sometimes and under braking they also offer little control.
Not a very good wet road tyre either. Good grip in the dry once the understeer
is mastered but they get worse in the wet. Road noise level is okay but not my
ideal choice.

205/55VR16
Semperit
tested on 944 front only. These tyres are again not what I would
recommend. The 16 inch 205/225 combination is highly recommended on the 944 in
my opinion and is a huge improvement on the 215s all round, chalk and cheese
really but these Semperits are just to hard and inflexible and they squeal
easily under load. Good wearing tyre. Road noise level is good but again would
never be a tyre of choice.

225/50VR16
Goodyear Eagle VR50
tested on 944 rear only. Same comments as above not my
ideal tyre choice for a Porsche.

Yokohama A008P Assymetrics
and Yokohama AVS Assymetric Combination

These tyres in their
17 inch sizes are Porsche N0 rated. This combination works extremely well on the
911C4. 205s up front and 255 on the rear. I am not convinced that this
combination can be bettered for road use. Track use I would recommend 225s up
front but not for normal use. There is some evidence emerging that the stress
placed

911C4 with Yokos Installed

Pirelli P7000

I was hoping
to be able to write a glowing report on these tyres. Unfortunately I cannot. I
cannot write a negative report either. I would say these P7000s would be an
excellent high performance tyre on any auto type except a Porsche 911 (964) C4
or any other 911 for that matter, especially the C4s.

The P7000 17
inch version is not Porsche approved or N rated. They provide adequate to
slightly good performance on dry road of varying temperatures and good to very
good performance in the wet. Heating the tyres up does not really seem to make
much difference. You can see on my C4 that these tyres have been used because I
have nice brown rims on the side walls. They are much quieter than the
Bridgestone SO2s and they are quieter than the Yokos but where they need to
perform at their best, they do not. With my somewhat heavily modified suspension
on the C4 the P7000s still cause a four wheel drift which I did not have with
the Yokos. I have certain stretches of road which I can duplicate the same
conditions over and over again. Play with speeds and other parameters. I feel
that this gives me a quite good comparison between tyres. The P7000s just do not
perform to what I need or fell confident with. As I said they are good tyres, I
would certainly recommend them for autos like the Audi RS2, RS5, Audi TT etc but
not for the 911s. Balance is not one of the high points of these tyres. They are
also expensive so I would certainly look at other tyres anyway. One thing I have
learned is that the N rating does affect design of the tyres. With the Yokos I
had no wheel rub despite my efforts to cause it. The P7000s which are the same
technical size rub at full left lock when going backwards. This is caused by the
design of edge better the tread and sidewall. It is more vertical than the
Yokos.

911C4 with Pirellis Inside on the way home to be
installed

The P7000s Before Installation

Summary

From my
testing I have come to a conclusion which some with 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.

Final
Note

I also had a
couple of sets of Pirelli PZero Cs, given to me to test. Due to cost reasons and
not wanting to damage my 911 Turbo wheels more than necessary with all these
tyre changes I have decided not to personally test them. I have more than enough
evidence to make the following statement.

Pirelli PZero
C is a great track tyre, It is a great tyre to install on your Porsche to drive
to and from the track as well. They are great in the dry and not so good in the
wet on the track. They are not road tyres which will provide year round driving
pleasure because firstly they will wear out fairly quickly and they a really are
a superb high performance tyre. I have driven a 911 (964) Carrera RS shod with
these tyres and all I can say is awesome!!!. Pirelli have a brilliant tyre here
but I do not recommend them for normal road using Porsche owners. Please do not
mix up Pirelli PZero Cs with other forms of the Pirelli PZero Series.

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