Conti calls new compound Black Chilli

Tread pattern shared with ordinary GP4000

After 2000miles cuts but no flats

Continental Grand Prix 4000S £34.95

When it first arrived on the UK market as a replacement for the much-loved GP3000, Continental’s GP4000 promised much, thanks to its Vectran anti-puncture belting and then-new tread compound. In the event, the tread was a huge disappointment, with early samples displaying a dire lack of wet weather grip. This was partly rectified in short order by changing the compound, but the tyre never convinced in the wet.

At the beginning of 2007 a new development from the German manufacturer promised to make the GP4000’s woes a thing of the past. By milling the carbon particles used as filler for the rubber polymer to a previously unheard-of level of fineness, Conti came up with a much more elastic tread compound that was claimed to offer more grip wet or dry, better mileage and even greater puncture resistance.

Traditionally, carbon soot, which adheres tenaciously to rubber and gives it the familiar black colour, has been the favoured filler. More recently, powdered silica, which forms a more elastic compound and permits the making of coloured tyres, has become popular. The new development involves the refinement of carbon soot particles by a factor of 10, down to the size range of around 10 nanometres. These are not carbon nanotubes as used in carbon fibre manufacture. Their size means that a greater density of filler to rubber can be achieved, thus improving the durability of the compound. At the same time, the smaller particles are better able to move relative to each other, ensuring that the compound is also more elastic and better able to conform to the road surface than that of a tyre filled with larger particles. Tactile impressions are of a much softer and stickier tread, which indents easily and deeply using a finger nail.

The result is a claimed a 30% improvement in both grip and rolling resistance over the black ASC compound used in Continental’s GP4000 clincher. Tread life is also claimed to be increased by around 5% thanks to the greater abrasion resistance of the compound.

For some reason, instead of coming up with an entirely new model called, perhaps, the GP5000, Conti stuck with the GP4000 label and added an S to denote the use of the new compound. The tread pattern is the same, and the tyre is currently on offer in the 23c format with more to follow. Virtually identical to the 4000 in appearance, the 4000S is a very different animal in practice. RCUK’s editor, writer Rich Land and Letourguide.com writer Dave Harmon have all put in some serious mileage in all conditions on the tyre, and the conclusion is universally favourable; not one puncture over perhaps 6000 miles, a good wear rate and, crucially considering the failings of the old tyre, almost incredible wet weather grip as was amply proven by RCUK’s ed. in the Dartmoor Classic. As for the claimed 30% reduction in rolling resistance, this probably translates to about 5% in practice, which is still worthwhile on its own. Let’s just say that with the 4000S, the great tyre promised by the 4000 has finally arrived.