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We bought a 1997 Chevy Suburban and recently put new tires on at Walmart. The associate there told us that we had the wrong size tires. Rather than worrying about different rim sizes or something I just had them put the same size tires on that were already on there, since I knew that size had already been on there.

However, I also somewhat recently got a flat tire and discovered that my spare tire is 245/75R16, which is also the number found on the placard inside the drivers' side door. (It also suggests a proper PSI of 45, and all the tires I've bought have a max PSI of 44).

Is there a huge difference between the tires that are on there and the tires that are supposed to be on there? Will there be a problem if I get another flat and say, have to drive 300 miles to the nearest tire repair place?

(These are my specific circumstances, but if there's a general formula for comparing tire size and advice for driving on a different sized tire/wheel (aside from "don't", which I assume is the correct answer), that would be great!

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What you've got there is what we call a plus zero tire size. The tire is wider than stock but fits on the original wheel without changing the outer circumference very much.

Is there a huge difference between the tires that are on there and the tires that are supposed to be on there? Will there be a problem if I get another flat and say, have to drive 300 miles to the nearest tire repair place?

The tire code tells you most of what you need to know: there are differences but they are very slight. If you look at one of the many tire size comparison tools online, you'll see that the wider tires are two centimeters wider and have a 0.45% outer circumference difference. I'm pretty sure that on that vehicle the only difference you'd be able to measure is a very slight difference in your speedometer reading. Cosmetically, the wider tires will bulge out slightly more from the rim. If that doesn't bother you, you're okay.

With respect to the spare, you're almost certainly fine. It's unlikely that the differentials would be stressed by such a slight difference when you're in the mode of "drive carefully so we don't get another flat!"

I do have to wonder why someone bothered with a plus zero size tire on a Suburban. I doubt they were going for better handling on the autocross course.

  • The more I'm learning about the difference in size the more curiousity I have about it, too. We're in Arkansas, so it's not like they could have reasonably been going for better traction on the snow or something. Would it have much effect on traction while towing? – Wayne Werner Sep 7 '16 at 14:06
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    Maybe? I wouldn't want to commit to "this makes a real difference" without doing an actual experiment, though. I suspect it's in the realm of don't care unless you're really working this vehicle hard, though. – Bob Cross Sep 7 '16 at 14:47
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There is not a significant difference in circumference and that's what you need to worry about with your spare. I believe the size you have is for the original, full-sized spare. If you look at the numbers, the 245 denotes the width in mm. The 75 denotes the aspect ratio, or the size of the side wall as compared to the width of the tire. Mathematically, that puts the sidewall at about 183.75mm high. With the second tire's attributes being 265/70, the sidewall is about 185.5mm high. That's less than 4mm difference in tire height (considering you have to add it twice to cover both sides of the tire - top/bottom), which when considering circumference, would not be anything to worry about. Just be aware, it is a spare. Get the regular one fixed as soon as possible and put the ugly rim back where it belongs ... under the truck :o)

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    Sorry for the edit ... thought I'd throw some math in there to prove my point. – Pᴀᴜʟsᴛᴇʀ2 Sep 6 '16 at 23:25
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    Math is good – its even better when it proves your point :-) – dlu Sep 7 '16 at 2:09
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In regards to your tire pressure, I would not suggest exceeding the recommended maximum tire pressure for your specific tire. That being said, the tire won't explode the moment it is inflated over 44 PSI, but it could cause unnecessary and possibly dangerous wear to the tire over time. Your car is heavy, so having your tire pressure as close to the recommended figures is important, but neither you nor your car will notice a 1 PSI difference.

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The 1997 Suburban takes a load D or E rated tire. I'd bet you got the same size tires, but with a lighter load rating (WEAKER TIRES) then the suburban requires, hence the lower max tire pressure.

For a load E 10 ply usually the maximum pressure is 80 psi, and for a load D my guess would be 60-65. They put the wrong load tires on your car, so you should return your tires and make sure to get a load E or at a minimum a load D rated tire. I have the same suburban and get load E rated tires. Almost positive that's what it requires.

  • At Walmart they sell "passenger" or "light truck" tires. The truck tires have a much higher max psi. I forget exactly but I think they're at least 80 psi rated – Wayne Werner Aug 23 '18 at 12:59
  • Welcome to Motor Vehicle Maintenance & Repair! – Cullub Aug 23 '18 at 18:36
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    As Cullub stated, welcome. There's an issue with your answer. What you are talking about would imply an LT (Light Truck) tire. The Suburban comes with "P"assenger tires stock, which is what the OP has on the Suburban. Secondly, what you have written doesn't answer the question. They are worried about the size of the spare vs the tires on the truck normally. We do welcome input on the site, no doubt, but accurate information based on the question is what we are looking for here. – Pᴀᴜʟsᴛᴇʀ2 Aug 23 '18 at 21:29

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