I've just purchased a 2000 Suburban 2500 LS with 125,000 miles. It has Cooper Discoverer A/T3 M+S in LT285/70 R17 size. I think these are too big. Tirerack says that I should have 225/75 R17 (or 265/70 R17 as an alternate). So what I have is about 8% larger (diameter and circumference) than OEM. Will this be a problem? There's plenty of tread left on them.

The spare is 245/75 R16 on a steel rim and looks like its never been used (although the steel wheel is pretty rusty).

If I need to get new tires in the correct size, should I get a 5th on a new 17" wheel for the spare?

Thanks

 

Maybe I should just get a new spare wheel with matching tire (285/70 R17)?

 

Look at the sticker on your door; that will tell you the OEM size. I'm willing to wager that Tire Rack is wrong. 3/4-ton Burbs come with 245/75-16 tires. Here's mine:

 

If you will only use the spare briefly if at all don't worry about it and leave it as is. The only problem with changing tire size is that your speedometer and odometer will be inaccurate by a little bit unless it has been reset.

 

As long as the tires aren't rubbing and all 4 tires have the same circumference, your fine. If the speedo is off due to the larger tire size; have a shop reset the tire size in the ebcm. this will corrrect the speedo and odometer.

 

Yes, you are correct about the 16" OEM. I was mistaken that Tirerack listed the 17" as OEM. They did provide that sizing for 17" inches, though.

Thanks.

 

There's no rubbing as the truck sits pretty high. I will check with a tech on Monday about speedometer and odometer settings.

Thanks.

 

I checked the speedometer readings with the speedo app on my phone and they were pretty close. So it may all ready be calibrated for the larger tire size.

 

then your ok. the only issue is when you use your mismatched spare...don't drive to far or to fast with it or your differential won't like it.

 

Though I am a proponent of using the OEM sizes, there are many who increase their Tire size with no major problems. So other than the correctable Speedometer error, one will feel a decrease in power, breaking and an increased center of gravity, with a larger tire.


One thing that is often disregarded, is, that the width of the Tread, and the Width of the rim, should be the same.


From a performance point of view, keeping the sidewalls of the Tire vertical by having these two measurements the same will considerably enhance controllability, breaking stability, traction on ice or wet roads an mileage.


So, before you arbitrarily select a tire size, check the width of your rims, and allow that measurement to guide you.


Additionally, I recommend using Tire Pressure within 2 lbs of the MCIP.
The MCIP (Maximum Cold Inflation Pressure) for all Tires sold in the USA, is stamped on the sidewall of each tire.