Kraiburg Retreads for When the Going Gets Really Tough

Retreads working in one of the most extreme applications imaginable – is this possible? In conjunction with its Italian partner Ghelardini, retreading specialist Kraiburg has proven that it is possible to marry up these two apparent opposites, and highly successfully. One fact that demonstrates this is that today virtually 80 per cent of all retreaded tyres used in the marble quarries in Carrara, Italy, run on Kraiburg compounds. And the customers are more than satisfied with the performance of these retreaded tyres.

The marble is cut from the rock face into blocks weighing up to 60 tons. In the past, it took up to six days to chisel out a block of this size, whereas today it is cut out of the mountainside in a maximum of six hours. Whilst still on site, the blocks are then cut to size in just 20 minutes – a task that once took several hours of arduous labour, since marble is almost as difficult to cut through as its close relative granite.

Up until a few decades ago, the marble blocks were transported either on a type of wooden sled or by rail down into the valley. Today, trucks are used exclusively for this task. These trucks have to struggle up the narrow, extremely windy roads with gradients of over 30 per cent up to a maximum height of 800 metres above sea level, where they pick up their loads and transport these back down to sea level for further processing in Carrara. Perfectly functioning braking systems and extremely force-resistant tyres are vital under such conditions.

Due to the harshness of the application, Carrara is regarded globally as one of the most popular areas for testing new tyres. The tyres fitted on vehicles which constantly run downhill carrying heavy loads have to demonstrate what they are capable of on ground that is a mixture of broken marble stone/dust. The risk of mechanical damage and damage due to cracks and cuts is extremely high. Reason enough for Kraiburg to test its Kraiburg plus Premium Line, launched last year in Italy, this testing application.

In conjunction with its Italian retreading partner and Kraiburg plus exclusive distributor Ghelardini, who supplies most of the transport companies working in the quarry at Carrara with retreaded tyres, various vehicles were fitted with the tyres – initially with a very sobering result. “In the same way as numerous producers of new tyres and retreading material suppliers that have gone before, Kraiburg also first had to learn the hard way”, explains Holger Düx, who is the regional sales manager at Kraiburg, responsible for the Italian market.

Whereas average tyre performances on drive axles normally range between 18,000 and 25,000 km, Kraiburg’s tyres came to the end of their useful life after only 6,000 km. The diagnosis: massive chip and chunk problems. However, in spite of this initial set-back, both Ghelardini and Kraiburg persisted in their plans to offer an ideal compound for this extreme application. Accordingly, by working together with the Kraiburg product development and technical service departments, a solution was soon found and the tyres were changed over to an extremely chip and chunk resistant compound of the latest Premium Line generation, namely Kplus 30.

Haulage company Emanuele Defrancesco was selected to perform a comparative test. For this purpose, the two vehicles in the fleet (3-axle semi-trailer tractor and 4-axle 4WD dump truck) were fitted on the drive axle with retreaded tyres with the KDY3 profile and Kplus 30 compound as well as with the K46 profile in the standard compound. Premium new tyres in design DY were used as a reference. The vehicles were deployed in identical applications on a ramp with an average gradient of about 18 per cent up to a height of 500 m above sea level.

Test result – on par with new tyres thanks to Kraiburg
After about four months, it was possible to compare the results. The vehicles achieve on average (thanks to the optimum maintenance of air pressure checks, regular rotation by axle every 2,000 km) a final performance of around 26,000 to 28,000 km with different quality retreads. This value was also achieved by the Kraiburg standard compound and in some cases even exceeded on removing the tyres when they were down to 4 mm tread depth.

By contrast, the Kplus 30 compound exhibited absolutely uniform tyre wear, and an additional performance of 10 to 15 per cent was recorded, which in turn roughly corresponded to the performance of the reference tyre. Also in terms of mechanical damage, no difference was noticeable compared with the new tyre.

“At the outset, we were a little sceptical, since we have been working for many years almost exclusively with the world’s leading new tyre manufacturers. We were all the more surprised by the fact that Kraiburg tyres are – in terms of their performance and the price/benefit ratio – fully competitive”, states Emanuele Defrancesco. The chip and chunk resistance was also mentioned as a positive factor, along with the uniform tyre wear of the Kplus 30 tyres. And, what is more: “On account of the convincing set of results and the professional support from Ghelardini, we have decided to equip all of our vehicles in future with Kraiburg plus retreaded tyres at the corresponding axle positions. This will enable us to make savings of around 25 per cent.”

The fact that the tests with Emanuele Defrancesco are not a one-off is reflected by the fact that today almost 80 per cent of all the retreaded tyres deployed in the marble quarries in Carrara are produced using Kraiburg’s latest generation of compounds. Acknowledging the satisfaction on the part of the customers and the tyre dealers who market them, Bruno Codega, managing director of Codega Pneumatici based in Carrara, comments: “Today, we are glad that we didn’t allow ourselves to be disheartened by the initial difficulties that we encountered. In the end Kraiburg and Ghelardini have proven themselves to be absolutely reliable and fair partners. We have no problems whatsoever with Kraiburg retreads. My customers let me know immediately if something is wrong, so I should know.”