Cooper S/T – RoadTraveler.net

April 2, 2012December 10, 2018

MPG, Fuel Economy, Tire Width, and Treads No. 1

Newer, detailed article, click here: Tread Matters

Will The Most Efficient Tires Please Drive Forward

It’s often stated that narrower, lighter, less aggressive tires are more efficient and will yield better fuel economy, but how much better? To properly compare apples and pears one must take care to reduce the variables that are always present during real-world tests. In this case I used the same vehicle, same gas pump, during similar weather conditions and time of day, calculated the odometer error, and used the same section of freeway. The GPS-confirmed road speed was 64-MPH and was maintained by cruise control. The tires were inflated to 35-PSI in all but the last test with the Dick Cepek F-C II treads where I goofed and only used 32-PSI. The F-C II tires performed so well I doubt they could have provided better economy with an extra 3-PSI.

Cooper S/T 255/85R16D on Toyota 4Runner, @ 15 PSI.

If you think the fuel economy numbers listed below are too high you are partly correct, the tests involved almost zero city driving. The variables of in-town driving are not repeatable and won’t yield consistent data. What these tests do show is the fuel economy potential of this vehicle and establishes a baseline against which other tests can be measured. For each test the modified 2006 4.7L V8 4Runner was fueled and then driven a few blocks to the same freeway onramp, onward to a specific exit, and then the route was reversed and terminated at the same gas pump where the engine was promptly turned off.

SXT & S:T 255:85 IMG_3028 — Dean SXT Mud Terrain & Cooper S/T, both 255/85R16. Two of the narrowest 255/85 tires made.

All the tires used were close to the same diameter, about 33-inches, and they were all mounted on Toyota FJ Cruiser TRD 16 x 7.5-inch aluminum wheels. Because of the slight differences I tire height, one corrected odometer reading of 56.76-miles was used for all the tests. Listed below with the figures are the weights of each tire/wheel combination.

Results:

Cooper S/T LT255/85R16D: 75-lb 3.027-gal. = 18.75 MPG

Maxxis Bighorn LT255/85R16D: 82-lb 3.017-gal. = 18.81 MPG

TreadWright Guard Dog LT285/75R16E: 87-lb 3.331-gal. = 17.04 MPG

Dick Cepek F-C II LT285/75R16D: 83-lb 3.121-gal. = 18.18 MPG

Bighorn, Guard Dog, S:T IMG_6515 — Maxxis Bighorn 255/85R16D, TreadWright Guard Dog 285/75R16E, Cooper S/T 255/85R16D

Commentary

I was a little surprised that the very narrow and light Coopers consumed more fuel than the heavier, more aggressive Maxxis Bighorns. Though when filling-up after the Cooper test the gas-pump didn’t stop normally and a little gas spit from the filler, possibly contributing to the lower reading. Longer distance tests would likely be more accurate, but this type of testing is very time consuming and expensive.

It was expected that the heavier, wider TreadWright Guard Dogs with their aggressive lug tread would use more fuel. The Cepek F-C II tires impressed me by splitting the difference and topping eighteen MPG!

IMG_0937 - Version 2 — Cooper S/T 255/85R16D, Dick Cepek F-C II 285/75R16D

Surely tread design, width, and weight all make a difference. My theory is that width and tread design have a larger impact on fuel economy than tire weight, at least when there is only a few pounds difference. There is five pounds separating the Maxxis Bighorn 255/85R16 and TreadWright 285/75R16, but I don’t think those additional few pounds account for the 1.77 mile-per-gallon difference. There is a seven pound difference between the Maxxis Bighorns and Cooper S/Ts, but the results for these two 255s were so close you could call it a tie.

Your mileage will vary.

March 12, 2012March 20, 2012

Traction Tire Preview Prelude

For several years I’ve been a fan of what are often called aggressive all-terrain tires. Labels and classifications can be difficult, sometimes neither descriptive nor adequate as there is much crossover, gray-area, and blurred lines with tread designs. These tires are not as open as a mud tire, but offer much more void than the typical all-terrain or all-season tire. Current examples include Mickey Thompson ATZ 4-rib, Dick Cepek F-C II, Cooper S/T Maxx, Goodyear DuraTrac, Dean SXT Mud Terrain/Cooper S/T, and the Toyo M55. These treads are also called traction or commercial traction designs.

Limited Terrain SUV Tires

When marketing types decided that utility vehicle was no longer an adequate description for 4WD utility wagons, the Sport Utility Vehicle (SUV) appeared, surged, then dominated the light-truck utility market. Lighter-duty all-terrain tires that offered less void and less traction became popular on the increasingly soft SUVs over the past two decades. It’s understandable that SUV tires became so road-biased, as invariably that’s where many log all their miles in their SUV trucks, but many of these conservative “all-terrain” treads would be more accurately described as all-season tires.

A Michelin all-season (cross terrain) — Michelin Cross Terrain SUV tire, properly labeled an all-season highway tire.

Despite the 4WD SUV becoming the modern on-highway station wagon for much of the U.S. if not most of North America, there are still those that want their 4WD wagons to be body-on-frame truck designs, shod with better, higher void traction tires. These folks include hunters, sportsmen, off-highway adventurers, people who live or work in rural areas, and those who travel in serve climates. For a variety of reasons a mud terrain tire may not be preferred (less MPG, longevity, and less traction on wet roads, with more noise) but a low void all-season tire labeled and masquerading as an all-terrain often doesn’t do the job either.

More void is desirable to absorb debris and let it escape. The wetter the material the more void you might want, and open, lug designs are typically louder, though modern tire design has reduced the noise penalty for some traction tires.

20051006-084347 — Toyo M55 & Multi-Mile TXR LT255/85R16D

What Size

I’ve never been a fan of needlessly wide tires, but wide tires have dominated the enthusiast 4×4 truck aftermarket for several years. Fat tires work well for some applications, but have many limitations for common usage, particularly on-pavement, where even the most active off-highway explorers travel thousands of miles each year. A slight correction seems to have occurred, where not every enthusiast 4×4 tire needs to be over 12-inches wide; 285 mm wide tires have caught on.

While I’m currently using and have accepted 285s, in my mind they are still a bit wide, roughly 11.5-inches depending on the tire—narrower tires track straighter and offer better MPG. Drivers are at least aware of fuel economy because of the cost of fuel, though I don’t see many people driving for fuel economy, bad habits are prevalent and it seems we’re often in a hurry.

The days of much narrower 33-inch enthusiasts tires like the LT255/85R16 are disappearing fast. Thankfully, if you don’t want such a tall tire, there are many 235–265 mm wide treads in the 31–32-inch range that can deliver better fuel economy.

ST 255 & FCII 285 — Great traction tires: LT255/85R16D Cooper S/T & LT285/75R16D Dick Cepek F-C II

Eighteen Inch 33s

Not knowing much about 18-inch tires or wheels, but owning a set of take-off eighteens, I studied the options and was pleasantly surprised to discover the LT275/70R18 size. This size is just slightly narrower than the common 285 mm treads in either a 16, 17, or 18-inch, but with a reasonable aspect ratio of 70 percent. Most 275/70R18s are 33.3-inches tall, very similar to the tall 255/85R16 size that I’ve loved for fifteen years.

Eighteen-inch wheels are two inches taller overall, so tire sidewalls are a full inch shorter at the bottom (the part we feel and drive on). Historically 255/85R16s were flexible and pleasant riding load-range D designs, though load-range E is becoming more common in a 255/85, but 275/70R18s are almost all load-range E rated. Not all load-range D or E tires are created equal, some are stiffer than others, but shorter load-range E sidewalls on a 275/70R18 are going to be stiffer in almost every application. Again, stiff sidewalls can be a positive or a negative, depending on your needs and preferences, refer to this Wheels, Tires, and Sidewalls article for more on this subject.

To be continued…

March 5, 2012March 5, 2012

LT255/85R16 Tire Delivery Part 2

With a bed and trailer full of tires & wheels I was off to see my tire guys for dismounting, mounting, and balancing so I could get my 4WDs off jack stands and rolling again. A few days later I loaded the bed of the Tundra with the Bighorns and Cooper S/T treads, as well as one old Multi-Mile Wild Country TXR so Brian would have a proper 255/85 spare.

Years ago the TXR was a big seller for the western tire chain Les Schwab. I really liked the void ratio of the TXR—not an A/T nor an M/T—and I purchased a few sets over several years. However, they were not the most rugged tire and tended to cause a steering wheel wobble. The last rig I ran the TXR on was my 2005 Wrangler, which was not as tolerant of their idiosyncrasies, so I moved on to better tires…and have yet to stop.

A load of LT255/85R16D tires, a Multi Mile TXR in the foreground.

I had a few goals for this little trip; deliver the tires, meet my new friend Brian, enjoy a country drive, and conduct a mileage test. After fueling at my local filling station and resetting the trip meter, it was time to roll with a goal of keeping my speed at 65 mph or less.

Through the cities and into the fertile Sierra Valley I drove. It cost, but one of the features I enjoy on the new Tundra is the satellite radio. There are a few stations I like, but I seem to listen to Outlaw Country often, Steve Earle came on singin’ Hillbilly Highway.

March 1, 2012March 5, 2012

LT255/85R16 Tire Delivery Part 1

Stranger Danger Online

The world may be full of dangerous people, and jokes about meeting people “on the internet” can ring true when you hear a horror story or two. However, there are lots of very honest, honorable, and friendly people in the world, and many of them are online—just like the rest of us.

Is Mr. 255/85 Selling His 255s?

I received a note from a guy named Brian asking specific questions about the LT255/85R16 tire size. After a few emails I decided he was a nice family man and agreed to sell him two sets tires, which I’d been contemplating selling for a while. These sets, one of Maxxis Bighorns and another the Cooper S/T, were used but still had about 14/32 of tread remaining.

I’ve been a user and advocate of the 255/85 size since purchasing my first set in 1998, but I have been using more 285s, mostly because there are many more tread choices. There just are not that many 255s made these days, and some of the better, tougher, and longer wearing designs don’t track well on my 4Runner, further limiting my options. The 255/85 is still a great size, I’ll likely never stop singing the praises of this 33×10″ tire, they’re still what I prefer running on my F350.

Cooper S/T 255/85R16D, Cooper S/T MAXX 275/70R18E, Dick Cepek F-C II 285/75R16D

By rural western standards Brian lived nearby, about 80 miles, but had a very busy work schedule that was going to prevent us from meeting for several weeks. I offered to deliver the tires if he paid for my fuel.

Tire Swap Fest

The Maxxis Bighorn 255/85 tires I sold were still mounted and being used on my F350. The Cooper S/T treads were mounted on a spare set of TRD FJ Cruiser wheels for the Mall Crawler. Selling these required lots of tire changing and even some tire purchases but it will take me a few posts to share the whole story. Imagine that, James buying and testing tires. Though buying and swappin’ tires is much easier and less expensive than swappin’ women—just sayin’.

Pulling the Maxxis Bighorns from the F350’s OE forged aluminum wheels meant I needed to fit something else. I robbed the set of Dick Cepek F-C II in LT285/75R16D from the Mall Crawlin’ 4Runner and ordered replacements…