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99 Seville STS, 08 STS4 N* 1SG F55
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Discussion Starter #1
So I took my STS on its first >50 mile roadtrip last weekend. I figured it would be good to check the tire pressure (I know: I should do it every week :thepan:). I checked the driver's door sticker and it says for 235-ZR-16 tires they should be at 30 PSI. Well, the Zs are long gone and she's wearing a nearly new set of BFG 235-R-16s. Is there a different pressure recommendation for non-Z rated tires? Also just curious as to people's results with tread life and gas mileage on these cars as related to tires - 30 PSI seems kinda low, I couldn't convince myself to go below 32. And one last thing - does the Z sticker on the door mean my car doesn't have a speed limiter?
 

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95 aurora + 97 seville sls
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The speed rating shouldnt effect the required pressure. I run h rated tires but I too felt like 30psi was low. Usually I run 36-38psi in the front and 32psi in the back. No treadwear problems here.
 

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1999 White Diamond STS
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Yea, 30 is pretty low IMO too. The tires usually sag a lot when that low.

I didn't know 99's had a Z tire option? I thought that was only the older K-body cars??
 

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02 STS
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The Z/W rated option was available upto late 2003...

and Yes any car with a Z or W door sticker does not have a speed limiter:thumbsup:
 

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White Diamond 2001 STS
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I also run a higher pressure, especially in the front. Usually 35-36 psi in the front and 31-32 psi in the rears. I DID have slightly uneven wear on my old Cadillac when using the recommended 30 psi front/rear. The front tires would wear on the edges (meaning underinflation).
 

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99 Seville STS, 08 STS4 N* 1SG F55
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Discussion Starter #6
The Z/W rated option was available upto late 2003...

and Yes any car with a Z or W door sticker does not have a speed limiter:thumbsup:
Thanks to all. I guess my alignment guy got some advice from you guys - I had the tires balanced and the car aligned a couple weeks ago. When I went to check the tire pressure they were all at 36, so I'm guessing they set them there when the balance was done. Felt a little wierd to bleed them down but I'll go pump 'em up again. While the PCM doesn't speed limit the car we have other speed limiters here in New England: short, crappy roads with lots of curves, resulting in a higher law enforcement density :thehand: since they have lots of places to hide. Were Z rated tires specific to the STS or are there STSs without Z-rated? And if so, why?
 

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02 STS
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. Were Z rated tires specific to the STS or are there STSs without Z-rated? And if so, why?
Yes you had to have a STS to have any chance at Z or W rated tire... No SLSs came with "unlimited" tires... Lots of STSs (maybe most) came with slower "H" rated tires. The lower rated tires last longer, ride smoother, and tends to be quieter... GM knew that only a handful of STS owner would ever push there cars over 120 MPH... and that the previous list might be more important to most owners...

So this was an option.
 

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99 Seville STS, 08 STS4 N* 1SG F55
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Discussion Starter #8
So I have an ultra-rare Light Bronzemist Metallic Z-Rated STS? :bouncy:

If only I didn't know that its out in the garage right now plotting when to eat the headgaskets... :hide:
 

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1999 White Diamond STS
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I guess so, as you can tell, I had no idea it was even an option for 98-03 cars, and I looked at a ton when I bought mine a few months ago. I have seen more then a few older STS and Eldo's with Z's though...

Very interesting Ur7x, probably thinking even less were ordered with that 'W' tire?
 

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W and Z cars would be about equally rare (or not rare) year by year... I don't know which year GM switched from "Z" rated tired to "W" rated tires... Both are rated at speeds faster them a stock STS can go so none of these cars were limited... As far as I know there was never a choice between Z, W and H ratings...it was "W or H" or "Z or H" does that make sense
 
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