• Welcome to Mazdas247, the 24/7 Mazda Community and Resource. Learn about the benefits of becoming a Member here.
  • We're an Amazon Associate and eBay Partner. We earn from qualifying purchases.

Tire Size Change?

I live in Calgary AB and I'm looking at buying a 2009 CX-9 GS AWD. The first order of business will be changing the tires as we spend a lot of time in the mountains, and we have to deal with ice/snow at least 6 months out of the year.

For the last few vehicles I've run Nokian WR tires year round with great success. Excellent traction in the winter, good performance in the summer and I typically get 60-70k km out of a set.

Unfortunately, the Nokians don't come in a 245/60/R18. The closest I can find is a 255/60/R18 which is 1.6% bigger. There is also a 255/55/R18 which is 1.8% smaller. I'm sure that the fit won't be a problem, but I'm wondering about the odometer and speedometer?

Is it possible to reprogram the CX-9 for a larger/smaller tire size? Is that the kind of the thing that the dealer can do?
2006 Mazdaspeed 6 GT
Get the CX-9 with navigation and base your speed readings off the GPS calculated speed. It's more accurate anyway.
Get the CX-9 with navigation and base your speed readings off the GPS calculated speed. It's more accurate anyway.
Your NAV unit shows speed?? Even when I'm using the routing option, it only shows the time of arrival and distance in a small little box.
2008 MS3 GT
It shows your speed in Diagnostic mode with the Nav. The trick is to go to the Map Version screen and tap on the screen "up up down down" to trigger diagnostic mode.
2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
I wouldn't worry about the difference of 1.6% as long as all four are of the same diameter for the sake of AWD.
If you check tirerack.com on all tires that are 245/60R18, you will see that their diameters range from 29.4" to 29.7". Yes, 1% differnce among all brands already. I cannot find the Nokian WR on tirerack.com. Our OE Dueller has diameter of 29.7" (highest among all).

Do you think Mazda calibrate the odometer between Touring and Grand Touring (the former has 18", the latter is 20")? I doubt it.
On Yako-Spectra-X, the diameter difference is quite significant also (29.5" vs 29.8" - 1%).
Last edited:
the difference between the 18 and 20 inch tire diameter on the CX9s is a couple of mm of height. That allows the same speedo calibration across the board. I would stay within 1-4mm in height difference and not anymore.
2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
In case of the Yoko-Spectra-X, the diameter difference is 0.3" (1" = 2.54cm = 25.4mm) = 7.6mm = 3/4cm
I can't find data on the OE Dueller for the 18". I had to use Spectra-X for example.

I am just showing that tires of the same size rating are of different diameters within 1% variance. No need to worry about the odometer error in such cases.
As an owner of them, I'd suggest just getting the Yokohama Parada Spec-X in the original size. Fantastic tire for this car.

Improved acceleration (reduced torque steer), cornering, braking, and wet traction. I got them because we get ice here (more than snow), and I didn't want to buy snow tires.

They also have the rim guard, like the Nokians. A nice feature.

Too bad Nokian doesn't make the 245/60R18. It is a nice tire for all around. You could just get the 255/60R18, though, and be close.



Last edited:
2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
Compared the reviews of Spectra-X vs Dueller on tirerack.com, it is like day and right.
Bridgestone must have given automakers outrageous deals for them to make Bridgestone as OE tires. A lot of owners who know very little about cars would always get the same tires. I know many people like that despite all my effort to convince them otherwise....

Most H-rated and above tires have rim protectors nowadays. Even our OE tires have it.
2017 Mazda CX-5 GT, 2016 Mazda6 iGT, 2014 Mazda3 sGT hatchback
The calculator is a good tool for giving you a "mean value" of diameter of tires of various brands.

Each brand's tire varies within a tolerable limit. Check the spec of each tire to be accurate. Such spec can be found on online tire store such as tirerack or discounttire.
As I pointed out, the difference can range from 29.4" to 29.7" for for 245/60R18, which comes out to be 29.6" based on the calculator. The calculator also gives 245/50R20 the same exact diameter as that of 245/60R18, when in fact there is a 245/50R20 tire that has a diameter of 30.1".
So is it even possible to calibrate the Speedometer if the wheels are not 18 or 20"?
If 22" wheels will fit, can the speedometer be calibrated to match the larger wheels?
Mazda CX-9 Grand Touring 2016
The Parada Spectra-X is an all season tire, not an all weather tire with the winter severe service rating, the snowflake on the mountain, like the WR is. The all weather tires will be better in snow than the all season tires. Real winter tires will be better on ice than either all weather or all season.

Bridgestone makes 16 different Dueler models. You've got to be more specific when you praise, or pan, a tire. Dueler is the line for light trucks, suvs, crossover vehicles.

Regarding the speedometer, the outside diameter of the tire matters, not the wheel diameter. Generally a 2% difference from original in outside diameter is not a major factor.
So what if I want to increase or put different size on the front and back that are more than 2%?
Can the Speedo be calibrated to compensate for more than 2% difference in diameter?

It's not my style but some owners might want to go to super low profile tires that differ by more than 2%. They will need to recalibrate the speedometer as well.

I have a 2001 BMW X5 that I upgraded the wheels and tires and the speedometer is off by 4 MPH so my GPS is the only true way to know my actual speed. BMW does not allow for recalibration of the speedometer .