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Please advise is there any adverse imapct if I change tires of my Tahoe 2015 from orinal 265/65R18 to 265/70R18? Any imapct on vehicle warranty from Chevrolet? Thanks MZ-Qatar

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Changing tire size will impact the vehicle.

As you can see below, it tire will be taller and have fewer revolutions per mile.

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This will cause a speedometer error as stated in the last picture.

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Mechanically, this should not have an impact on the performance or safety of the vehicle. You will have to live with the speedometer error.

What we cannot answer is how this would affect your GM warranty. That you will have to ask GM. My guess is they would use the improper tire size as an excuse to not honor warranty claims.

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The largest impact is on how large the tire is diameter wise, which impacts how many revolutions per mile (or RPM) the tire goes. Not knowing which tire you have on the vehicle right now makes it a little tougher to figure out the exact difference, so I chose two tires from the same manufacturer (for some reason, not all manufacturer's specs are exactly the same, go figure!).

The approximate specs for each tire are:

  • 265/65R18 = 659 RPM
  • 265/70R18 = 636 RPM

That's a difference of ~3.5%. Over time, this adds up. Two big things it will affect, which are the speedometer reading as you're going down the road and the odometer reading as it won't be posting as many miles as it should be.

While changing the tire size won't void your warranty outright, the fact you wouldn't be clocking as many miles on the odometer may. If a sharp service technician sees you've changed out the tires to the "wrong size", they may make hay about it and say they won't honor your warranty accordingly.

The easiest way around this is to get your speedometer recalibrated. This is pretty easily done anywhere, even in Qatar. You just have to find a shop which can retune your specific vehicle and ask them to do a recalibration for it.

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