Cooper Discoverer S/T Maxx

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The tread of the ST/Maxx isn't nearly as aggressive as a mud terrain tire. These are classified as "commercial traction" tires and have what is best described as an aggressive AT tread.

. . . I FEEL these tires are much CLOSER to a mud terrain than an all terrain. . . .

My best description is stated above and I stand by it. "Closer to" means "closer to", and ST Maxx's are noticeably closer to a KM2 than a Dynapro ATM or even a BFG AT. Especially when taking into consideration the less than average snow performance I have experienced.

 

[bijanjames]

Tread Wear Update:

-9,077 miles in one year and one month, Rotating Full Size Spare, Rotation every 3,750miles
-265/75r16
-Nissan Frontier Pro4x
-On road psi 35, off road psi 20
Tread depth new was 18/32nd, now 3 tires are at 15/32nd, the most recent one off the spare is at 16/32nd, and the one now on the spare is 14/32nd. The tire wear is very even on all the tires. Averaging 2,500 miles for every 1/32nd of an inch of tread wear lost, so we are looking at about 40,000 miles of tread life rotating 5 tires...Truck is not a daily driver, miles are mostly highway (Denver to Bozeman), and several off road trips (Moab, San Juans, Flat Tops). This is about what I expected for this tire, so not overly disappointing. They preform very well overall for what they were intended for.

 

[Redline]

285/75R17

I wish this tire came in 285/75-17 ---- all I have to pick from in that size are Nittos, Toyos, & KM2.

It does now

 

[Hilldweller]

It does now

Yeah. But now I have 16" wheels....

 

[bijanjames]

I have been very pleased with the performance of the Cooper ST Maxx, the only thing that was eating at me was my initial tire size choice. So I sold the 265/75r16's and purchased 255/85r16's. What held me back initially from doing this was front end clearance, but this was remedied by a 1/2" spacer and upper control arm on top of the ome springs. This size in the Maxx runs slightly smaller than other 255/85r16 tires (32.8"), so they fit very well. I can tell a difference in gear loss. Calculation takes me from a 3.69 to a 3.54, not bad, but noticeable. I gained 3/4" of clearance all around, which is nice, and went ahead and ordered a sixth matching wheel and tire to put under the truck, so I can do a six tire rotation. These should last a long long time...

 

[(none)]

I've tried searching... Anyone with 255/75r17s mind measuring their mounted height? Or does anyone know the actual height?

I'm curious because Cooper lists the 255/75s as having a smaller diameter than the 265/70s, which doesn't seem right. From another thread on here, the 255/80s measured about .5" taller than the Cooper listed size (32.8" listed, 33.3" measured), so I'm looking to see if the 75s are the same way.

 

[silverEx]

I've tried searching... Anyone with 255/75r17s mind measuring their mounted height? Or does anyone know the actual height?

I'm curious because Cooper lists the 255/75s as having a smaller diameter than the 265/70s, which doesn't seem right. From another thread on here, the 255/80s measured about .5" taller than the Cooper listed size (32.8" listed, 33.3" measured), so I'm looking to see if the 75s are the same way.

Some quick imprecise measurements on a worn tire are at or a little above 31" on a 7.5" FJ steel wheel. It was never a true 32" even when new, and definitely smaller than a 265/70. I'll try and get a better measurement on the spare for you

 

[(none)]

Some quick imprecise measurements on a worn tire are at or a little above 31" on a 7.5" FJ steel wheel. It was never a true 32" even when new, and definitely smaller than a 265/70. I'll try and get a better measurement on the spare for you

Thank you for the info. I've emailed Cooper as well, so I will post with what they reply with. Guess I need to measure how tall my 265/70s actually sit.

Looking around, I've seen everything from 30.5" overall (general grabbers) to 32.1" (Continentals) for the same size tires. I'm thinking the Cooper measurement difference is due to the 255/75s being C rated and about all of the other sizes being E rated.

 

[Redline]

I've tried searching... Anyone with 255/75r17s mind measuring their mounted height? Or does anyone know the actual height?

I'm curious because Cooper lists the 255/75s as having a smaller diameter than the 265/70s, which doesn't seem right. From another thread on here, the 255/80s measured about .5" taller than the Cooper listed size (32.8" listed, 33.3" measured), so I'm looking to see if the 75s are the same way.

Never had that 255/75/17 size in front of me....but my experience and measurments have shown that Copper's published tire data is quite accurate, meaning: inflated height on a specific width wheel, no load.

 

[(none)]

No reply from Cooper, but I did a quick measure of the height of my stock Dunlop 265/70r17s, they are right at 30.5" if not a touch below. So if the 255s are just over 31" mounted, I think I'd be good with that.

 

[(none)]

Well, another update: Received a reply from cooper:

"Thank You for your email. Your question or comment is very important to us at Cooper Tire. Please feel free to call me at 1-800-854-6288 and we will do our best to answer any questions you have. Please reference this email when you call.
These numbers are based on the actual calculation.

255/75R17 =32.05
265/70R17 = 31.60"

Take it for what it is.

 

[SilicaRich]

Well, another update: Received a reply from cooper:

"Thank You for your email. Your question or comment is very important to us at Cooper Tire. Please feel free to call me at 1-800-854-6288 and we will do our best to answer any questions you have. Please reference this email when you call.
These numbers are based on the actual calculation.

255/75R17 =32.05
265/70R17 = 31.60"

Take it for what it is.

Good to know their 255/75R17 size seems to be a true 32" tire. All other websites usually have it listed as 31.8"

 

[Webfoot]

These numbers are based on the actual calculation.

255/75R17 =32.05
265/70R17 = 31.60"

Good to know their 255/75R17 size seems to be a true 32" tire. All other websites usually have it listed as 31.8"

No, I believe that is all that is, a calculation. It's just the rounded down output of the basic tire size formula: dw + (2 r wt)/25.4

dw = nominal wheel diameter in inches
r = aspect ratio
wt = width of tire

I have the S/T Maxx LT255/75R17's myself and I think the billed diameter of 31.77" was accurate within my ability to measure when they were new.

 

[Kmrtnsn]

No reply from Cooper, but I did a quick measure of the height of my stock Dunlop 265/70r17s, they are right at 30.5" if not a touch below. So if the 255s are just over 31" mounted, I think I'd be good with that.

the size difference in diameter between a 255/75 and a 265/70 is. usually between .2 and .3 inches, depending on brand and whether the tire is an LT or a P Metric size. Generally the 265/70s run between 31.6 and 31.9 inches in diameter and the 255/75 between 31.7 and 32.1, making the "equivalent replacements requiring no speedometer adjustment/re-calibitration.

 

[silverEx]

Well, another update: Received a reply from cooper:

"Thank You for your email. Your question or comment is very important to us at Cooper Tire. Please feel free to call me at 1-800-854-6288 and we will do our best to answer any questions you have. Please reference this email when you call.
These numbers are based on the actual calculation.

255/75R17 =32.05
265/70R17 = 31.60"

Take it for what it is.

I just pulled of my low mile spare st maxx in LT255/75/17, and it measured right at 31.75" mounted on a 7.5 in wheel. I would say cooper's published numbers are accurate