TYRE TEST TIPS

Peter Davson-Galle, via email

I always enjoy reading local tyre tests and thank you for continuing to do them.

I do, however, have a few criticisms and suggestions for future ones.

The Conti tested was not the regular SC5, but the 5P (presumably the front axle one).

These are not the same tyre. The 5P is also in the process of being replaced by the SC6; surely this in worth a mention.

The Pirelli is not just any old P Zero, but the new P Zero PZ4. It is superior to the old P Zero and you don’t assist readers by not pointing out that this is the version. The confusion is exacerbated by the continued availability of the old P Zero in 235/35R19.

Confusion is also created by not noting that the PZ4 comes in two main versions. These versions are the L for luxury cars and the S for sports cars. From the look of your picture, you tested the PZ4S.

On reporting methodology, I think that your simple summation of rank by numbers is overly crude. Given your inevitable inability to hold variables constant or have corrections for them, I suggest that you take more seriously the idea of a ‘confidence window’. Roughly, the idea is that if two tyres perform closely, then one can’t be confident that one has a difference attributable to the tyre. At the very least, one should weight the individual test scores for result summation purposes in a way that reflects the extent of difference, not just rank order.

I hope that you do your wet tests prior to doing your dry tests. If not, then you have a flawed methodology owing to the different level of damage done to various tyres’ tread elements during dry testing. On wet testing – a simple circle test is limited as a guide to wet cornering performance.

Finally, why not take the two best wet braking tyres and two best wet cornering tyres, have JAX shave them to 3mm and retest in those disciplines? Of course they’ll do worse, but tyres cope with wear very differently and the performance order might well be reversed.

Good, quality suggestions, Peter – thank you. We are always trying to improve and evolve our tyre test so we’ll consider the practicality of your suggestions before the next one. We did wet testing last for all the tyres, partly on the basis that in the real world, your tread blocks are not going to be beautifully unworn – and optimal for wet weather performance – as they are new. We’ll also look to offer more insight into new tyre products in future tests, as well as weighing the tyres. We tested a ContiSportContact 5P this year but unfortunately it was named, incorrectly, as just the 5 in the test.