I have a 1996 SW1, 150K. At 121K, I had 4 new tires installed, not the original P175/70R14 size, but the P185/65R14 size, as I was told the original size was "rare" and was unavailable at the tire shops I shopped at the time, and that this other size was a suitable substitute. These newest tires have an 80K treadware rating, but I can see now I'll be lucky if I make it halfway there. After only 29K of driving, they're pretty bald.
Here's my question: Is the proper inflation for these tires the same as that for the original size? In other words, is it the same 26psi rear and
30psi front as the sticker on the inside of the driver's door indicates? I've kept the tires at that inflation, and rotated them every 6K, but, as I say, they're balding, and perhaps a little moreso on the center of the tire, which would suggest overinflation, right?
...not so uncommon (tire size) on tirerack.com. I ran oversize tires also and ran the pressure slightly higher for occasional spirited driving. What's the UTQG (Uniform Tire Quality Grade) rating of your existing tires?
Here's an interesting link related to wear ratings and the UTQG:
Hi, Ethan, While I am no expert on tires, I certainly would not rely (for long) on the sticker placed on the car. The tire dealer or manufacturer would seem to me to be better sources for that information. Good luck!
I checked out the link you gave and looked around the website a bit. I have the Yokohama Avid Touring. The UTQG is 620 A B. I also skimmed through the owner reviews. It seems that a few of the owners--especially the ones who have driven over 30K on their tires--have experienced short tread life, same as I.
...no expert here either. IIRC, the sticker on the car has tire pressure numbers based on what the engineers calculated the right pressure was for those tires and the specific car. I'm sure they probably have a fairly complex calcuation of what types of ratings/charteristics they want in a tire first, then they shop, sometimes they have a tire specifically made for them, then they get the tires, test them, play with the numbers and somewhere in the long journey they give us the sticker with the right numbres when the car hits production...
The sticker has always been ground zero for me to start with.
The numbers cast into the side of the tire are max pressure that tire will handle based on the engineers at the tire manufacturer, not a recommended pressure rating.
Many cars have different air pressure rat>>I have a 1996 SW1, 150K. At 121K, I had 4 new tires installed, not the
Please, oh please, unless you are racing and now what dimension your camber is set at, just leave the tire pressure set at what it says on the placard.
They generate those numbers universally, regardless of change in size or manufacturer. If it says inflate to 30 psi, please just inflate it to 30 psi. I see severly overinflated tires at work everyday, so close to overfull they should have exploded..... but that is another story.....
Thanks for the advice. Yeah, I surfed the articles on tirerack.com, as recommended by Jonnie. They have a lot of useful info on tires. I like how they specifically say that the "max" psi stamped on the sidewall is max the tire can be operated with, and not the proper pressure.
Tire info has been elusive and contradictory to me over the years. As a govt. employee, I drive a lot of different vehicles. Typical scenario has been as follows: Another employee turns a vehicle over to me. Tires are visibly uneven in pressure, meaning that something is quite wrong. I look up "tire pressure" in the owner's manual. The chapter tells me, "Always inflate to proper pressure," but doesn't tell what that pressure is. Finally, after much jumping back and forth through the manual, I read that I'm supposed to check the placard on the door to determine the proper pressure. I check the door, and the placard is gone! Then I go to a coworker and say, "Well, dude, whaddya think the proper pressure should be?" And he or she responds, "What do you mean?! The proper tire pressure is stamped right on the side of the tire!"--like I'm an idiot. I tell you, the vast majority of drivers believe that tires should be inflated to the "max" pressure--if they ever think about their tires at all, that is. I've had so many people tell me this I almost started believing it.
The tirerack.com article says that starting with 2003, owner's manauls are required to provide more info about tires. Maybe now we're not out of luck when the placard comes off. Incidentally, it is also mentioned that the manuals must now state the combined maximum weight of cargo and occupants the vehicle can handle. Jeez, it's about time. All the manuals I've seen just mention the combined weight of car, occupants, and cargo. Like you nothing better to do than look up your car's weight, then do some addition.
Oh--and one other thing I forgot to throw into the equasion--what if you have two different tire gages and each gives a reading 6 psi different then the other? :) I guess there's a limit to how perfect we can be when it comes to such things as tire pressure.
Do you want comfortable ride or maximum mileage? The door placard usually is the manufacturer's recommendation that provides a compromise with the OEM tires.
Me, I usually inflate tires that have maximum 44PSI cold pressure stamped into them to 35PSI for the given temperature (add air in cold winter months, take some out in hot summer months). On my tires that state 35PSI max cold pressure, similarly I inflate to 32PSI. This gives much better mileage and seems to increase tire wear as well. The tradeoff is a bit harsher ride and more wear on front suspension components.
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