July - September
Best grip thanks to modern tyres – even for classic
New tyre approval lists published following extensive tests with classic Porsche models
. Drivers of classic
With these tyre tests for classic sports cars,
The latest lists with the new tyres added this year can be downloaded from the Internet using this link:
Continue reading the following pages to find out how these tyre tests take place and what else need to be considered with respect to tyres for classic
As around two thirds of all
All these approvals are usually updated every two years through ongoing tests. The reason for all this effort is obvious: As the manufacturer,
However, special tyre approvals for new
Oldsters can be dashing too
To avoid dramatic errors, new tyre models are tested and processed for approval for all the older car models. The
Because tyre testing also means driving at the limit in a controlled manner. The disciplines of dry and wet handling are of paramount interest, while brake testing and aquaplaning tests round off the test program. The entire test program is aimed at precisely measuring how the tyres behave up to the limits. Every facet of behaviour, from the initial steering movement to the exit of the bend, is precisely analysed and logged for each set of tyres in the test. The car turning cleanly into the bend is just the first step towards approval. Well-controlled behaviour under high transverse acceleration is obligatory, and exiting bends must be mastered without any discontinuous loss of road adherence.
A harmonious performance is paramount
The tests always comprise several rounds on the test track, which is rich in curves, and precisely determined lap times are used for comparative purposes. A tyre must deliver performance at its limits in a predictable and balanced manner to obtain a good evaluation. The same applies understandably to the front and rear axles as this is only way to get good marks and the prospect of approval for the historic vehicle series.
The marking that turns tyres in a historically valuable dimension into
The corresponding number after the "N" is solely used to differentiate the approval series. Example: The first version of a tyre with the dimension 195/65 R 15 was approved with the mark N0 for the applicable
Keyword tyre ageing
This particularly critical aspect was also tested during the latest test series in summer 2014. This effect mainly plays a role when a vehicle with a long history is only rarely driven and spends more time standing than driving. The tyres visibly become more brittle, the traction and level of grip decrease. The word "undriveable" may not apply directly if such a tyre is just over five years old. But the capability for a smooth driving style, which may have characterised it at one point, decreases steadily with increasing age in all cases. If you take a look at the so-called DOT number on the tyre flank, you can quickly determine how old the tyre actually is. The number accompanying the letters DOT is always a four digit number, specifying the production week and year of the tyre, i.e. 1302 for week 13 in year 2002.
During the 2014 test program, tyre-testing expert Dieter Röscheisen evaluated a twelve year old tyre as very critical, particularly regarding wet handling: "The tyre was tested on a 1988 930
A completely different tone is struck in the test evaluation results regarding a new 185/70 R 15 tyre for the 1963
Just as an aside, this vintage
Approximately 300 tyres to choose from
The afore-mentioned and other new tyre qualities of tested and approved designs and matches are listed in detail on the
This is because not every new tyre developed and matched with a current model was continued to be manufactured for decades after the period during which it was produced as original equipment. Some types were simply discontinued, others are modified due to new regulations regarding the rubber compound recipes. This is, for instance, the case if specific chemical compounds used in tyre production are changed when more modern components come onto the market offering better grip and, simultaneously, less rolling resistance. The tyre manufacturers cannot let such developments pass them by.
Simply mounting the tyres of subsequent evolutionary stages without testing onto rims of older vehicles has not been successful in practice. There have been cases within the broad field of historic vehicles where the car has become almost uncontrollable when driving at the limits after it had been equipped with unspecified tyres. Really disastrous driving behaviour is not necessarily the immediate result. However, in the majority of cases, significantly unbalanced behaviour during steering and handling resulted. A particularly negative problem is when a tyre performs poorly under wet conditions. Just like all other drivers, the driver of an older
This is just one of the reasons why the new developments for older vehicles by the tyre industry are subjected to the
One of the manufacturer's tasks here is also to maintain a suitable stock: Tyres for models from the sixties and seventies are - due to the lack of demand - no longer manufactured in continuous mass production. Instead, a new series is produced from time to time when required. If suitably stored (cool and dark), the tyres only age slowly and slightly. This ensures that the quality is maintained, even after a few years.
Preventing ageing: Store tyres like good wine
A tyre starts to lose suppleness and grip after about five years. It does not, of course, become abruptly undriveable, but starts to appreciably lose balance over subsequent years. However, the effects of ageing can be slowed down if storage is implemented with care – in a similar manner to good wine: Tyres age less rapidly if stored in the dark at lower temperatures. If you can afford it and have the necessary space to do so, store a fresh set of tyres for your forthcoming pleasure tours in your cool cellar and park your vintage
If you don't want to or cannot change the tyres so frequently, you should pay attention to the following tips. Because, if the vehicle stands for too long in one place without greatly increased tyre pressure, so-called "flat spots" occur. It is therefore common practice to raise the air pressure up to the maximum permissible pressure for the rims, which is usually 4.5 bar, when storing cars. So-called tyre shoes or tyre pillows, obtainable from accessory dealers, are also useful in this case. These are concave supports made of rubber, plastic or wood placed under the wheels so that the car is parked with all four wheels in the hollows. The concave form distributes the tyre contact area over a significantly larger area and prevents the tyre from becoming square during the standing time due to flat spots.