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NTRubicon 02-03-2016 09:43 PM

Cooper STT Pro Tyres

After running the stock Goodyear Wrangler Silent Armour tyres for nearly 40,000km over some very rough terrain, they ended up looking like this:
All five have looked like this for the last year, and aside from painting the sidewalls with tyre paint, they were just starting to look a bit ratty. Time for UPGRADES!

After looking around at the offerings in the AT market (Cooper ST Maxx, Mickey Thompson P3, Bridgestone Dueler, BFG AT KO2), I started looking at a few of the more aggressive packages: Goodyear Duratrac offers a decent 70/30 tread (this was a really close second choice - I just couldn't come at the 2 ply sidewall); BFG MT KO, and the Cooper STT Pro - the new kid on the block. All were roughly in the same price range, and I wasn't about to squabble over $20 a corner when the only thing you need to keep moving out here in remote NT is reliable (inflated) tyres.

Being a relatively stock Jeep, I needed to make sure of several aspects - that the tyres were going to fit the stock wheels, that they would fit within the wheel well, that there would be no/minimal rubbing. After reading through a LOT of forum posts on here, the 285/70R17 was identified as the way to move forward.

Considering the big change, my wife and I decided to take advantage of the time the wheels were off the car and get them sandblasted and powder coated to match the bullbar and sliders - texture black. As this undertaking required the removal of the TPMS units, new valve stems had to be sourced in a hurry. My local dealership wanted to sell me these TPMS units as a single item - at a cost of $192.38 EACH. Fortunately, Stuart Murchison was just a phonecall away, and a quick over the phone transaction had 5x valve stems in an airbag and on their way to my door for less than $100.

Here is the final product mounted on the wheel (white lettering to the inside) and ready to go back on the Jeep:

and leaving the showroom floor:

First impressions are as follows:

- there is the faint hum that is the trademark of the mud terrain tyre , but not much of it - there is not enough noise coming from them that the air conditioner fan can't block out.
- there is less feel at the steering level for where they are on the road, an expectation of anything with over 15mm of tread when compared to the previous tyres of <5mm tread
- there is the slightest change in gearing when driving between 60-80km/h where the transmission can hunt for the appropriate gear for a second or two longer than normal, but this was also expected due to the increase in rolling diameter.
- the rolling resistance is negligible at road pressures (currently running 34-36psi around town), though its possible the Jeep does slow down a little easier with engine braking than it did prior to.

Next post: Driveway dimensions and kitchen window admiring

NTRubicon 02-03-2016 09:58 PM

Driveway dimensions, fit and finish, and kitchen window admiring

The first few days, my wife got to break in the tyres driving some 100km of corrugated roads south of Alice Springs while I was out of town, and reported back with "they're really nice" "everyone else is jealous" and "they feel a bit splashy on the dirt road" followed by this picture:

Tyre pressures run on that occurrence were 25psi all round, and the 'splashy' feeling was likely due to the decreased pressures and operating speeds of likely around 100km/h on corrugations.

Back in the driveway, a good look around shows how the tyres sit in the wheel well. Please note: there is a Teraflex levelling kit installed and a Uneek4x4 bull bar attached (and the springs/shocks have had 40,000km of abuse), so dimensions may vary slightly for those that are completely stock and looking to fit these.

Things get a bit tighter for the spare, with added compression of the spare tyre rubber stoppers
very little room to move around the third brake light,
and even less room around the well space in the rear bumper - there is contact from the tyre at the lower right side on the rear bumper, but no vibration that I can see thus far.

Next Post: Flex and rub check

NTRubicon 02-03-2016 10:13 PM

Flex and Rub early testing

Time to check clearances and see how these go over some uneven ground! I took a quick trip down to a local levee bank which is just the right size to flex out the Jeep in both directions to see maximum compression and droop of stock suspension (pardon the shameless plug for my local 4wd club here.. and here):

What I found was that there was a clear finger widths clearance around all components at lock steering, and at full suspension compression while stationary. That being said, it is unlikely that the clearance would be there if the bump stops were struck in anger, and likely there would be some amount of rubbing at speed but this is yet to be tested fully - I'll report back once I have some more data.

I drove around a little on the rocks at road pressures and found the grip exceptional, there was good feel at the steering off road, and I felt as sure footed as a mountain goat.

Next post: Mud! early testing

NTRubicon 02-03-2016 10:33 PM


As luck would have it, some rain fell a few days ago, and the normally very dry area of central Australia became suddenly a muddy playground, and I was immediately drawn back to the same place where the rub testing took place.

Some fun was had. Please indulge me, as I don't get to see mud all that often. Even a little bit is exciting.

Early impressions are that these tyres do EXACTLY what they are designed for. What I took notice of while out playing in muddy puddles, was the excellent ejection of mud from the tread blocks, something I felt to take a closer look at. One can observe that between the sizeable tread blocks there is some impressed dimples. These appear to create a air pocket that prevents the mud from sticking between the blocks, and allows for great ejection of particulate matter. I found myself comparing them to the dimples in a high end Japanese sushi knife:

This made the explanation of the 30 foot rooster tails of mud I briefly saw in my rear view quite understandable, and even more enjoyable.

Apologies for not going deeper into the mud, but I will endeavour to find some deep mud and drive it until it stops me. I'm taking it slowly at the moment as I'm getting used to having grip again. I'll add more mud information as I collect it. For now its home to pressure wash the day away under the watchful supervision of the boss.

Coming soon: Off-road grip and slip, high speed bitumen and dirt review, 'bush bashing' trailblazing along tracks not driven for over 50 years, river rocks and sand, shale and s&*( your pants ascending/descending.

Snort 04-03-2016 07:01 PM

Great review nt. I will take an interest in further comments on wear ect.

samft 05-03-2016 12:12 PM

Keep the details coming!
theses look like really good tyres

Are they genuinely quiet on sealed roads? I'm impressed if they're barely louder than the A/C

LeighP 05-04-2016 06:51 PM

Been reading lots of good feedback on these tyres.....which will probably be my next set.

NTRubicon 05-04-2016 10:23 PM

I'll preempt my next instalment with a few questions answered hopefully before they are asked.

I've found the tyres rub the swaybar links on full flex while disconnected, not much but enough to hear it in the cabin on a quiet day with the windows down.

The road noise is a little more noticeable with a few thousand km on the tyres, but not much. I haven't got the nice smooth roads you all probably have around you, so my tyre noise is substituted somewhat with ambient road noise - but I'll try to capture some high quality iPhone video and put it up with some speed comparisons. I've taken the roof off recently and the road noise is not as bad as any other mud tyre I've heard on the road

One area of caution - weight. I've discovered that the spare is putting a minimal, but still unacceptable amount of pressure on the stock tailgate, and I'm taking steps to rectify this - by means of a rear bar with tyre carrier - I'm tossing up the hinge upgrade over the full rear carrier - the wife doesn't want me to burn $800 on a hinge upgrade and just get the full bumper mount instead - she's a keeper.. I'll ask questions about these in another topic.

I have sustained a gouge out of one of the tyre lugs about the size of my fingertip. Mulga wood is the hardest substance on the surface of the earth, and it will scoop out a lump of rubber faster than you can imagine - I'm just glad I caught the lug and not the space between lugs (1" off and I'd be telling a whole different story)

NTRubicon 09-04-2016 03:46 PM

3000km review

Early results are in, these are some tough tyres. They have had 3000km of mixed terrain (school/grocery run, highway km, dirt road km, 50km of dodging pointy sticks, loose rock/gravel, little bit of mud) and here are the updates on how the tread looks

A little bit of chipping around the edges, but generally unscathed. The road noise has gotten perhaps a tiny bit louder, but this may be just that I'm running roofless now and I'm noticing it a bit more. Generally I'm very happy with the way these tyres are handling everything I throw at them.

One incident after leading a group of five vehicles out bush, picking our way through 50km of overgrown trail (not really a trail, we were following a spot on a map that hadn't seen activity since the 1960s) I discovered a gouge out of one of the tyre lugs that was luckily positioned in the best possible place it could have occurred:
Suffice to say, I suffered a lot less damage than one of the other vehicles on the trip:

The weight of the spare has become a minor issue for my stock tyre carrier. The rear door has just started flex a little, and rather than wait for it to get dangerous, I have moved the spare inside and secured it to the luggage area. Fortunately I have no long distance trips planned for the short term, so I've got time to organise a bumper mount tyre carrier. Putting my pennies away for one of these:

Fuel economy over 3000km has gotten worse with the addition of larger, heavier mud tyres (as expected) and I'm averaging 1.5L/100km more - this could also be due to doing a lot more off road travel now with the more reliable grip too. I"m hedging my bets until I have 10,000km on them at least.

Next post: I'll try to upload some video to illustrate how these tyres are in various conditions.

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