Last year, Michelin launched a new version of its EvoBib hybrid tyre range, dubbed as its flagship agricultural tyre for tractors in the 200hp to 300hp bracket. The new two-in-one tyre has been developed specifically for use with Central Tyre Inflation System (CTIS), and offers improved performance and wear characteristics.

We visited Michelin’s research and development facility in Ladoux, France, to find out more about the development of the EvoBib range.

Background

Traditionally, tractor tyres were designed for optimum traction and wear characteristics in the field, with less of a focus on the metrics we now use to judge performance. The demands required from today’s agricultural tyres are constantly increasing. Users now require larger sizes, increased load-carrying abilities and improved traction, while aiming to reduce ground pressure.

The majority of this is all largely achievable, until you include the fact these tyres need to have improved characteristics for large horsepower tractors and increased road speeds up to and above 50km/h, as well as being capable of spending longer on the road, as farms become more and more fragmented.

The introduction of IF and VF tyre technology has been a huge help in achieving the requirements outlined above. Taking this technology one step further, manufacturers are now pursuing hybrid-style VF tyres. Essentially, these are two-in-one VF tyres that have been designed for optimum performance in the field and on the road.

EvoBib

To no surprise, Michelin was front and centre in hybrid tyre development. In 2017, it showcased the first generation EvoBib, this was a tyre born out of the brand’s Ultraflex technology. At low pressures the contact patch increases, in turn increasing power transmission and reducing soil compaction. Meanwhile, at higher inflation pressures, the tyre is transformed, showing more favourable traits for road use, ie reduced contact patch, reduced rolling resistance and a central continuous band for constant road contact, increasing grip and reducing vibrations. The first generation EvoBib tyre was awarded a Gold innovation medal at Sima show 2017.

Skip forward to 2023 and seven years of field testing later, Michelin launched its latest generation (very high flexion) EvoBib tyre range, which claims design tweaks and performance improvements, as well as a wider range of sizes for modern tractors.

The new EvoBib is the first agri tyre on the market specifically developed for use with CTIS systems to aid its adaptive design for optimised performance on and off the road.

Michelin believes that modern inflation systems are key to fully optimising tyre technology and are something that it sees becoming much more common on high horsepower tractors in the not-so-distant future.

Although major leaps have been made with VF and IF tyre technology alone, Michelin believes integrating such technology with CTIS is the next step. In 2017 Michelin acquired German CTIS specialists, PTG to further enhance its portfolio and optimise its Ultraflex technology.

Tyre design

Visually, the latest EvoBib thread pattern differs quite a bit to the first generation. Particularly, the shape of the central blocks, which are now a different shape with chamfered front corners. Spacing of the central blocks and lugs has been increased.

During a presentation, Olivier Coulomb, who is responsible for Michelin off-road tyre development, explained that the improved central band of blocks offer key characteristics for road use, including improved comfort, grip and longevity. The cut in the outer lugs reduces friction when operating at field pressures as it effectively closes, forming a traditional continuous lug. Increasing the space between lugs and the design of the carcass was important in improving traction, comfort and self-cleaning characteristics.

“With the design and architecture of the EvoBib, we are able to increase the contact patch of the tyre by 47% by just reducing the pressures between road and field, double that of a VF AxioBib (24%). So, it’s obvious, the more you increase the footprint of the tyre in the field, the better it is in terms of soil compaction,” added Olivier.

Nicolas Reboul, OE director for agriculture tyres, outlined that differences did not stop there: “Not only is the design new but the compound is too. It has been developed specifically for this tyre to improve traction. From testing, we have achieved up to 15% more traction that our competitors and the same traction as a lug pattern VF tyre. The new compound also reduces rolling resistance and, therefore, helps reduce fuel consumption. Again, from testing we have recorded 7% greater fuel savings than our direct competitors.”

This translates to a 2l/hr saving compared with competitor hybrid tyres and a 1l/hr saving when compared to the AxioBib 2 using CTIS.

Test facility

The research and development facility in Ladoux, comprises 450ha in total, a large proportion of which is used for tyre testing. Not only does the facility include 20 test tracks (45km in total), but also dedicated areas for testing on wet and dry surfaces, noise tests and comfort, etc. There is also a large block of agricultural land for testing agricultural tyres. Here, Michelin performed a number of different exercises on the road and in the field to show the benefits of the EvoBib and importance of the correct tyre pressures.

Rolling resistance demonstration

First up was the measurement of rolling resistance at the optimum field and road pressures for the given axle loads. The manufacturer outlined that rolling resistance can be attributed to one third of heavy duty vehicles total fuel consumption. Therefore, reducing rolling resistance is important in order to reduce wear and fuel consumption.

A Fendt Vario 828 fitted with Fendt’s own VarioGrip CTIS system shod with EvoBib VF600/70 R30 (front) and EvoBib VF710/70 R42 (rear) tyres was used. The rear axle load totalled 12,800kg, which equated to 6,400kg per wheel. The front axle had a loading of 5,000kg, or 2,500kg per wheel. Two runs were carried out, one at optimum road pressure and the second at optimum field pressure. At the same forward speed both times, neutral was engaged and the distance travelled was recorded to establish the difference in rolling resistance. (See table 1). The result was a difference of 38m, or 23%, by just operating at the recommended road use inflation pressure.

Fuel consumption demonstration

The second EvoBib demonstration was carried out, this time in the field and focused on fuel consumption. The tractor in question was a Massey Ferguson 8S.265, equipped with a PTG CTIS system and EvoBib VF 710/70 R42 (rear) and VF 600/70 R30 (front) tyres.

In terms of axle loading, the rear totalled 9,200kg, which equated to 4,600kg per wheel. The front axle had a loading of 4,400kg, or 2,200kg per wheel. Using a loading system, a constant load of 7,900kg was pulled during each run (See table two). A difference in fuel consumption of 5.1l/ha was recorded, as the higher inflation pressures resulted reduced traction and increased slippage. The current EvoBib sizes available are:

Depending on usage, Michelin recommends the following:

Leaving CTIS aside, the demonstration clearly proved the importance of correct inflations pressures. In the field, the message is simple. Lower pressure – larger contact patch – more traction – reduced compaction. Regardless of the VF tyre used, there are a number of tangible benefits to using a CTIS system and establishing optimum pressures in-field and on-road, not just for one or the other tasks. However, Michelin believes that the new two-in-one EvoBib tyre combined with CTIS pushes these optimums further.

The tyre essentially transforms into a road tyre when inflated and a field tyre when deflated, with results nearing those achieved from its dedicated RoadBib and AxiobBib road and field flagship ranges.

Although targeted towards the larger 200hp-300hp tractor market, the range remains quite limited in terms of sizes – Michelin is currently working on expanding the range.