Cooper ST's - 255/85/16

[Redline]

With the two previous posts in mind

When people talk about a wider tire having better lateral stability, I think often they are inferring that this added lateral stability is on pavement. I believe this is a point made in Scott's tire selection white paper which I generally agree with.

Is it likely that a substantially narrower tire like the 255/85 Cooper ST not only lacks lateral stability on pavement but off-highway as well? Is this commonly accepted?

I understand that track width can add or reduce sidehill/rollover stability, but I'm talking more about (side slip) lateral stability on much less extreme sidehills. I'm thinking it makes more difference than many of us have considered in the past.

Opinions?

Experience?

Science?

 

[p1michaud]

Lateral Stability

With the two previous posts in mind

Is it likely that a substantially narrower tire like the 255/85 Cooper ST not only lacks lateral stability on pavement but off-highway as well? Is this commonly accepted?

My experience is based on comparing the 255/85R16 Cooper ST's to the 32" x 11.5" MTR tires.

My opinion is that lateral stability off-highway is also affected on snowy and icy conditions. Can't comments for the dirt and rocks yet.

 

[R_Lefebvre]

Well, there's two parts to this.

Lateral "stiffness" and lateral traction.

The first, lateral stiffness, is affected by the sidewall stiffness, and overall sidewall height, as well as how a given tire is mounted on a wheel of a given width. The more the tire is pinched in on the rim, the less stability the sidewall will have for a given tire. You'll see on sports cars, the tires are often mounted on wheels wider than the tread. This stretches the tire out and increases sidewall stiffness.

I think the tires are fine for that. Certainly these 245/75/16 are much better than the 265/70/16 P-metric tires that were on these rims previously! I took those off ASAP because they were terrifyingly unstable.

Then we have lateral traction, which is just as it sounds. This is what I'm saying is lacking in this tire on snow.

Lateral traction is a double edged sword. You don't want too much lateral traction or risk having the truck roll. If given a choice, I'd rather skid than roll.

 

[Redline]

...SNIP

Then we have lateral traction, which is just as it sounds. This is what I'm saying is lacking in this tire on snow.

Lateral traction is a double edged sword. You don't want too much lateral traction or risk having the truck roll. If given a choice, I'd rather skid than roll.

This is what I was referring to in the questions I posed.

Lateral traction as opposed to sidewall stiffness/stability.

 

[Redline]

Dude:

How are you liking your Cooper STs?

How was the trip back to AZ? Noise better or not quiet enough?

Been in the dirt with them much?

Tires installed last night. I found an interesting place here in CA, kind of a cross between a chop shop and midnight tire sales... The owner was super cool and was very interested in the Tacoma, my travels and talking about Land Rovers. There were people coming in and out cash flying and about 8 guys working at once. I was in and out in less than 25 minutes.

I really like the ride with these Coopers, smooth ride and much quieter than the BFG's (at least to my ears.)

The Tacoma is once again very happy :wings:

 

[SEREvince]

First time ST's in snow

Snowed like crazy here yesterday. I'd say about 2'+ in the mountains. I loaded up my St. Bernard and took to the hills.

This was the first time I've had my Cooper ST's in any real snow and I was very impressed. I ventured on a completely untouched mountain road and they handled like a champ. Granted this was paved road underneath, but they churned through 2' of powder and never skipped a beat.

They are 285/75/16's Load Range D about 95% tread

The road is pretty typical mountain road. Plenty of switchbacks.
via Barcis

 

[Desertdude]

Dude:

How are you liking your Cooper STs?

How was the trip back to AZ? Noise better or not quiet enough?

Been in the dirt with them much?

I am so digging these tires! Nearly 8K miles so far - Quiet on the road, great traction in snow and on wet roads. Had the chance to do a bit of dirt too.

I am sold on these tires, thanks for the recommendation. :26_7_2:

 

[Redline]

Good to hear. You are going to accumulate the miles much faster than I.

 

[SOAZ]

One other note. The tires have worn very evenly, besides the chunking.
I had some really bad wheel wobbles at all four courners, but the left front seemed the worst.
I took it in for a free re-balance and they were way out of balance. Not the tires fault I'm going to say. The chunks will of course make the tire get out of balance, plus I prob threw a few weights over time.
One tire was 3.8 ounces out of balance. Ouch!

The best part is they ride like a dream again. Nice and smooth now.

 

[FLYFISHEXPERT]

Cooper Discoverer S/T VS. Dean Mud Terrain SXT

This is my first post here, thank you SOAZ for turning me on to this thread. Thank you to everybody that has been posting on this subject. All I can say is WOW. What a great body of knowledge you have going here.

I would like to see if there are any updates after everybody has been driving on these during the winter. Winter traction is very important to me here in South East Idaho.

I have a 98 4Runner and I will be purchasing new tires in the coming weeks and have decided on 265/75R16 instead of the 255/85R16 so I will not have to re-gear. I am currently running 245/75R16 Cooper Discoverer ATR’s. I have narrowed my decision down to the Discoverer S/T and the Dean SXT. It was mentioned in a previous post that the S/T and SXT use the same case. Does anybody know if the rubber used for the tread is the same between the two? Any reason I should choose one over the other?

Also, what size tires was everybody running prior to installing the 255/85’s and how many people changed their gears?

Thanks Again.

Beau

 

[R_Lefebvre]

I had my first off road excursion last weekend, and all I can say is the tires seemed to hold their own against everybody else who was running mudders. But, we weren't in deep mud. Mostly dirt, and swampy water on top of still frozen earth.

 

[SOAZ]

This is my first post here, thank you SOAZ for turning me on to this thread. Thank you to everybody that has been posting on this subject. All I can say is WOW. What a great body of knowledge you have going here.

I would like to see if there are any updates after everybody has been driving on these during the winter. Winter traction is very important to me here in South East Idaho.

I have a 98 4Runner and I will be purchasing new tires in the coming weeks and have decided on 265/75R16 instead of the 255/85R16 so I will not have to re-gear. I am currently running 245/75R16 Cooper Discoverer ATR’s. I have narrowed my decision down to the Discoverer S/T and the Dean SXT. It was mentioned in a previous post that the S/T and SXT use the same case. Does anybody know if the rubber used for the tread is the same between the two? Any reason I should choose one over the other?

Also, what size tires was everybody running prior to installing the 255/85’s and how many people changed their gears?

Thanks Again.

Beau

Welcome Beau!
I ran the 255's for the last year and a half without new gears. It was just fine as long as you don't try and hot rod around.
Maybe some other members in cooler climate can comment on the winter weather driving. :costumed-smiley-007

 

[xcmountain80]

Well I'm still on the fence. I'm not sure if I want those darn 255 BFG MT's.


Aaron

 

[Redline]

I can't comment on the tread durometer, but I would suggest you study the differences in the treads. I think the Cooper ST might have more void. They have a narrow open center channel (rain slow slush, mud). Also might be a bit louder.

Dean SXT is available from Les Schwab if that is important to you.

Redline

P.S. Welcome to the ExPo :safari-rig:

SNIP...

I have narrowed my decision down to the Discoverer S/T and the Dean SXT. It was mentioned in a previous post that the S/T and SXT use the same case. Does anybody know if the rubber used for the tread is the same between the two? Any reason I should choose one over the other?

Also, what size tires was everybody running prior to installing the 255/85’s and how many people changed their gears?

Thanks Again.

Beau

 

[ashooter]

Well I'm still on the fence. I'm not sure if I want those darn 255 BFG MT's.


Aaron

Ditto.

I LOVE the tread design of the Cooper, but it seems almost too skinny to put on my FJ80... I would like to like the Toyo M-55, but Redline has me a little spooked about that one, especially considering the $250/ea (or more) price tag... The BFG KM seems to have a lot of happy customers, but the tread seems overkill for the kind of driving I do.

When I get ready to actually spend money on a set of tires, I may just flip a dang coin!