Cooper Tires has updated its long-serving STT mud tyre, it’s called the STT Pro. Here are the key changes.

THE STT PRO OFFERS the usual advances seen in a new tyre; improved carcass strength, better cut and chip resistance and improved traction.  There’s a third ply for the Amor-Tek construction, and a new compound which is where a lot of the advances in tyre technology come from these days.  The compound includes silica, very often added to tyres to improve flexibility, reduce rolling resistance and improve wet-weather handling.

In the case of the STT Pro it is ‘chemically infused’ which sounds like a top-end dinner menu item, but it’s actually distinct from mechanical mixing.  Chemical infusion better mixes the silica with the rubber and other materials like carbon black that go to make up a tyre, which is by no means just plain rubber.  There’s also special anti-chip additives in the Pro.

The traction side of things is improved with small breaks in the tread blocks that trap air, helping to stop mud sticking.  There are ribs and groove walls to eject small objects such as stones.   An interesting development is a ‘flex groove’ which does what is says, permits greater tyre flex.  That’s good because it means the tyre can better adapt to the terrain, so there’s less bouncing and more traction. 

Cooper claim the STT is the “latest generation most advanced mud tyre” – readers new to 4WD should note that “mud tyre” is a term used for a tyre oriented more to offroad use than onroad, not just purely used for mud.  However, the STTs are quite liveable as an on-road, daily drive tyre and on previous vehicles this writer has run them successfully.

Kimberley VI

The STT Pros were tested in the Australian outback, and Cooper claim total test mileage to exceed 1,000,000km.  The size chart is below.


A good range of sizes, but there’s no 17″ tyre less than 265, eg a 245/70/17.

The STT Pro doesn’t look like it brings any radically new design features to the market, but rather appears to be an evolution and refinement of existing techniques and technologies.  If you’ve got a set, comment below.


  • Cooper say the STT Pro will last longer than the previous version (the SST) due to the silica, but declined to say how much longer.
  • Re tread design – “Tread design is considerably different [ to the previous version ]. Improvements in the tread design deliver more mud traction. One improvement in particular is Flex Groove around the tyre. This feature allows the tyre to flex which dampens the impact generated by inconsistent terrain. This is of particular relevance in dirt roads while driving at low pressures.”
  • Re price changes – “There is a price change for this. Pricing is already updated on our website. You can get pricing by clicking on the quote button in the product page:

 Discoverer STT RR WW

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  1. Currently running a set of ST MAXX which are about half worn now and have had a hard life but I have been considering a move up to the STTs. I have been told that their “on road” life isn’t as good as some of their competitors and if that’s true, maybe this new STT has addressed that issue too. Any thoughts or comments on that Robert?

    1. It would be hard to comment on relative tyre life especially with mud tyres as so much depends on how they are used. The STTs will certainly wear faster than the ST Maxx, as you get with any move to muddies, and they will cost more. My first question would be do you need the STTs? The modern all-terrain is very good now, as are modern vehicles, so there’s less need for aggressive tyres. Conversely, the modern muddie is now much more streetable than ever before, so they are definitely a daily drive option.

      I’ll ask Cooper if longevity has been improved.

      1. Depends on where you live and drive as well.

        When I lived in Queensland I found that aggressive A/T tyres such as BFG AT’s where fine, even for the occasional trips to places like Landcruiser Park. However, when I moved to Victoria I quickly found that the A/T tyres did not perform so well in the winter mud found in Victoria. They would quickly blockup with the wet clay that is everywhere in Victoria (Ordovician yellowy and grey stuff and the high country red stuff) in Winter.

        If I had the money to buy them and space to store them I would run 2 sets, MTs for winter and ATs (ie ST MAXX etc ) for summer ….

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