Using CupWheel tires is like driving on flat tires

An air-based caterpillar track. That’s the effect of the CupWheel tire construction from Galileo. The development of these special tires, featuring a bent sidewall, began twelve years ago. Initially, they developed a tire that could function without air pressure, used among other things in pivot irrigation systems.

In viticulture, on steep slopes, CupWheel tires are used as an alternative to caterpillar tractors. Over these twelve years, significant development took place, with a set of 710/70 R38 CW and 600/65 R28 CW tires as the latest product. ‘CW’ stands for CupWheel. This is also the first set of tires with this unique construction for heavy tractors.

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Goal of CupWheel tires

The purpose of the CupWheel tires is twofold: to achieve low ground pressure and high traction. Many lugs on the ground. With the right combination of weight and tire pressure, the 710/70 R38 tire puts four lugs on the ground.

A side benefit of the tire’s construction is its high lateral stability, compared to a conventional air tire at low pressure which wobbles more on the sides. The CupWheel is essentially very stiff in the sidewall to transfer enough traction, but the bending allows the tire to flatten extremely while remaining almost the same width.

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Caterpillar on air

The CupWheel tire is also known as a ‘tire caterpillar’. And that’s actually what it is. The tire size and tread pattern are like those of a normal tractor tire, but the special sidewall construction allows the tire to flatten enormously and roll over the ground like an air cushion. It behaves like a caterpillar track, supported not on wheels but entirely on air, resulting in even pressure distribution.

Wageningen University Research mounted 710/70 R38 CW rear and 600/65 R28 CW front tires on a Fendt 820 with a five-furrow reversible plow, to plow from above. The tire pressure was then 0.55 bar at the rear and 0.4 bar at the front. In clay soil, this worked excellently on both beet fields and wheat stubble, with no visible wheel slip. Note that on the same field, a tractor on standard air tires also managed well with the plow without excessive wheel slip.

A precise comparison of the CupWheel tire versus a normal air tire in terms of wheel slip related to traction has not yet been performed. However, the first impression from practical experience is positive in favor of the CupWheel tire. On the other hand, even though it’s barely visible and hard to measure, a CupWheel tire does have a few percent slip when pulled hard. The laws of physics dictate that a tire needs a certain wheel slip to transfer traction through friction in the contact area between tire and soil.

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Critical tire pressure

For optimal performance, the right tire pressure is critical. This applies to every tire, but it’s even more critical for the CupWheel tire. A tenth of a bar can make a difference. During the test, the tire pressure was therefore increased by 0.05 bar at some point.

According to Galileo specialists, it’s a known phenomenon that the tire becomes a bit more flexible over time, requiring a slight increase in tire pressure. The tire doesn’t warm up, but the carcass becomes a bit more flexible with use. The trick is to choose a tire pressure that keeps the rim just off the sidewall.

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Comfortable ride

The CupWheel is not a transport tire, but it’s quite suitable for road travel. Because the tire flattens extremely and the rim almost touches the sidewall, the tire pressure must be significantly increased for transport above 10 kilometers per hour. The tire table goes up to 1.2 bar, and at 40 kilometers per hour, the tire still has a carrying capacity of 5,800 kilograms. An Alliance VF 710/70 R38 is around 6,000 kg.

Comparison of tire tables shows that in terms of carrying capacity relative to tire pressure, the CupWheel tire is in the same range as a VF tire. In transport, the tire won’t have the comfort of a regular air tire, but the difference is relatively small. Compared to a caterpillar tractor, the CupWheel tire is a relief in terms of comfort.

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Further testing

The first impression of the CupWheel tire is promising, but more practical experience is needed for a definitive verdict. While there are initially no indications for concerns, the tire’s lifespan is a question that can only be answered by long-term practical use. So far, only above-ground plowing has been done with the CupWheel tire.

710 width is actually too wide to drive in the furrow. However, when a CupWheel tire drives through the furrow, a lot of loose soil will get into the deep fold on the side. Due to the extreme flattening, the tire will also push this soil out. Whether this is a potential issue will require more extensive practical experience.

The tires are not yet widely available for sale; they are currently part of a test series. The price indication for these tires is in the order of magnitude of the same size in the top segment of regular tractor tires.

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