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Discussion Starter #1
Sorry if this is a "dumb" question. I don't recall ever seeing an "outside" indication on a tire. These are a pair of new Kumho Solus TA71 for the front of my '08 STS RWD Northstar. They are nondirectional at least to my knowledge.
For what it's worth they are replacing a pair of Uniroyal TigerPaw that have developed "scallops" on the outside of the tread resulting in road noise as in a loud thump.
 

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Discussion Starter #2
Sorry if this is a "dumb" question. I don't recall ever seeing an "outside" indication on a tire. These are a pair of new Kumho Solus TA71 for the front of my '08 STS RWD Northstar. They are nondirectional at least to my knowledge.
For what it's worth they are replacing a pair of Uniroyal TigerPaw that have developed "scallops" on the outside of the tread resulting in road noise as in a loud thump.
572195
 

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Just guessing here, but do they (the tires) have a rim protector (extra rubber on the shoulder of the tire that helps keep the wheel rim from getting scrapped on a curb, etc.).
 

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That denotes an asymmetrical tread pattern. If you look at the tread, the outside will be different than the inside. The goal is to increase the tire's turning response without sacrificing all weather capabilities. There are summer tires like this also.

Asymmetrical tires are a big advantage over directional, these can be rotated to all four corners so they don't get that choppy tread wear like directional tires are prone to do.

Your Uniroyals developed the choppy tread from lack of rotation, almost 98% chance that is why. Rotate those new tires to the rear in about 6000 miles, and cross to the opposite sides when you do. The rear tires will go straight forward. Then in 6k miles, repeat. And keep repeating. If you do this, it will stop any choppy tire wear issues but not wheel alignment wear issues.
 

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As above, you'll probably see a difference in where grooving is located for anti-hydroplaning. They can be rotated from side to side, but before doing a front>back rotation, make sure your build has the same size rims & tires at all four corners. Many STS have wider rear wheels & tires, I forget the build code.
 

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Discussion Starter #7
572202


Here's a shot of the tread showing the asymmetrical pattern you mention. The two white lines go to the inside according to the "OUTSIDE" designation on the left sidewall.
I see some subtle differences in the tread now that you mention it. Is the "turning response" you mention at highway speed?
I'm under the impression that the tires can't be "rotated" as the fronts and rears are slightly different sizes. I believe the rears are P255/45R18 which measure slightly larger in diameter. I don't understand why GM would do this.
Thanks for your feedback. Much appreciated.
 

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View attachment 572202

Here's a shot of the tread showing the asymmetrical pattern you mention. The two white lines go to the inside according to the "OUTSIDE" designation on the left sidewall.
I see some subtle differences in the tread now that you mention it. Is the "turning response" you mention at highway speed?
I'm under the impression that the tires can't be "rotated" as the fronts and rears are slightly different sizes. I believe the rears are P255/45R18 which measure slightly larger in diameter. I don't understand why GM would do this.
Thanks for your feedback. Much appreciated.
Yes, turning response would be noticed as more responsive, the faster you are moving. Compared to a similar tire type without the asymmetrical tread pattern. So if you have the staggered fitment, (larger tread width on the back; again, for handling balance) you can still rotate. Just go right to left. This is important so you don't start the scalloped/choppy tread pattern.
 

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View attachment 572202

Here's a shot of the tread showing the asymmetrical pattern you mention. The two white lines go to the inside according to the "OUTSIDE" designation on the left sidewall.
I see some subtle differences in the tread now that you mention it. Is the "turning response" you mention at highway speed?
I'm under the impression that the tires can't be "rotated" as the fronts and rears are slightly different sizes. I believe the rears are P255/45R18 which measure slightly larger in diameter. I don't understand why GM would do this.
Thanks for your feedback. Much appreciated.
Interesting, there's a more pronounced difference between inside/outside on the Firestones on mine. Regarding the larger tires in the back, that was an option you could add when you ordered the car. It's a RWD car with an available V8 that made good power. Wider rear tires were a nice option for some tastes. I don't push mine because I have sportier options, but I do like the way the car looks from behind. Kind of a retro 60's/70's thing like a '76 Celica GT I had just out of HS. I put TA Radial 60's on the front, and 50's on the rear. American Racing slotted aluminum wheels, of course ;)
 

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Discussion Starter #11
I normally run about 30 PSI in the fronts on the STS. Now wondering if a bit higher PSI would also minimize wear on the outer tread. It already rides like a park bench in an earthquake so probably wouldn't be much worse.
 

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Without a compelling reason to do otherwise, most cars are best off using tires inflated to the specs on the door sticker. While the lower tire profile of our STS do provide better handling at the sacrifice of some "tire cushiness" the ride is most dependent on the suspension components and condition. That's why some folks paid dearly for the variable magnetic ride shocks. My last model style Buick LeSabre's stock suspension and big old balloon tires gave a much nicer ride, but couldn't out corner an STS.
 

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Interesting, there's a more pronounced difference between inside/outside on the Firestones on mine. Regarding the larger tires in the back, that was an option you could add when you ordered the car. It's a RWD car with an available V8 that made good power. Wider rear tires were a nice option for some tastes. I don't push mine because I have sportier options, but I do like the way the car looks from behind. Kind of a retro 60's/70's thing like a '76 Celica GT I had just out of HS. I put TA Radial 60's on the front, and 50's on the rear. American Racing slotted aluminum wheels, of course ;)
I work at Firestone. Which tires do you have on your STS? I like your car out of high school. I remember those Celicas well. So, what are your sportier car options now? I also have a 2000 WS6 6 speed car and the burnout machine, 1968 LeMans droptop. Yes I know off topic lol. The Trans Am has decidedly asymmetrical Potenza RE 760 Sport tires, awesome dry weather summer tires.
 

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STS recommended tire pressure is 30 PSI cold. Strange that the same era CTS with the SAME SIZE tires as the STS front tires (I am referring to the 18" 235-50-18s) recommends 35 PSI.
 

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Agreed, though I suspect the difference in tire pressure come from a whole series of small details like front or rear drive, engine and total weight, anticipated loading and driving styles, etc. (or they threw a dart at the Wheel of PSI)
 
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