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Discussion Starter #1 (Edited)
For those who wish to change their tire or wheel sizes for whatever reason, the following listed sizes will provide 1% or less variation in the tire diameter and speedometer reading ensuring minimal change in overall gear ratio and speedometer accuracy, based on the OEM tire/wheel size of 215/45-18.

The following data is taken from:

Percentage Change
215/45-18 -
205/60-16 = .26%
205/55-17 = 1.01%
235/40-18 = .85%
235/35-19 = .55%

For every tire size their is an appropriate range of rim sizes on which the tire should be mounted. The following list is taken from the European Tire and Rim Technical Organization (ETRTO) standards which are also used in the USA:

Tire/Wheel Combo____ Range_________Measuring Rim Width
215/45-18___________ 7" to 8"__________________7"
205/60-16___________ 5.5" to 7"________________6"
205/55-17___________ 5.5" to 7.5"_______________6.5"
235/40-18___________ 8" to 9.5"________________8.5"
235/35-19___________ 8" to 9.5"________________8.5"

Trouble-free aftermarket fitment can only be assured if the new wheel is the same as, or not to far from, the OEM spec of +45 mm offset (ET45). If the new wheel deviates appreciably from this then such problems as interference or excess wheel bearing wear may arise. However, this is beyond the scope of the material presented here.
 

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For those who wish to change their tire or wheel sizes for whatever reason, the following listed sizes will provide 1% or less variation in the tire diameter and speedometer reading ensuring minimal change in overall gear ratio and speedometer accuracy, based on the OEM tire/wheel size of 215/45-18.

The following data is taken from:

Percentage Change
215/45-18 -
205/60-16 = .26%
205/55-17 = 1.01%
235/40-18 = .85%
235/35-19 = .55%

For every tire size their is an appropriate range of rim sizes on which the tire should be mounted. The following list is taken from the European Tire and Rim Technical Organization (ETRTO) standards which are also used in the USA:

Tire/Wheel Combo____ Range_________Measuring Rim Width
215/45-18___________ 7" to 8"__________________7"
205/60-16___________ 5.5" to 7"________________6"
205/55-17___________ 5.5" to 7.5"_______________6.5"
235/40-18___________ 8" to 9.5"________________8.5"
235/35-19___________ 8" to 9.5"________________8.5"

Trouble-free aftermarket fitment can only be assured if the new wheel is the same as, or not to far from, the OEM spec of +45 mm offset (ET45). If the new wheel deviates appreciably from this then such problems as interference or excess wheel bearing wear may arise. However, this is beyond the scope of the material presented here.
Thanks for the information I have 245/50 16 tires on my 2016 Mazda3 i touring stock wheels they fit fine and ride even better than the original tires I stuck with the same wheel to not affect speedometer readings. When I get newer chrome wheels I intend to go to 17" or 18" wheels and tires.
 

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Discussion Starter #3
Thanks for the information I have 245/50 16 tires on my 2016 Mazda3 i touring stock wheels they fit fine and ride even better than the original tires I stuck with the same wheel to not affect speedometer readings. When I get newer chrome wheels I intend to go to 17" or 18" wheels and tires.
Interesting. What was your OEM tire size before you switched?
 

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OEM tire size should be 205/60-16.
245s will make the car drive like a 1970s Buick.....Way too wide for a 6.5" rim. The rolling resistance will cut into your mpg too.
 

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Discussion Starter #5
Thanks for the information I have 245/50 16 tires on my 2016 Mazda3 i touring stock wheels they fit fine and ride even better than the original tires I stuck with the same wheel to not affect speedometer readings. When I get newer chrome wheels I intend to go to 17" or 18" wheels and tires.
While it's true that your speedometer reading and overall gear ratio will hardly be affected (only a .15% variation), as arathol points out your handling will be noticeably compromised.
 

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I use 225/45/18 and I've not noticed any reduction of cornering capability. I have noticed increased gas mileage, better ride, and quieter, and best of all has been the huge decrease in pothole tire losses now down to 0 losses thus far. I actually had to replace my spare because it got used so much.
 

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I use 225/45/18 and I've not noticed any reduction of cornering capability. I have noticed increased gas mileage, better ride, and quieter, and best of all has been the huge decrease in pothole tire losses now down to 0 losses thus far. I actually had to replace my spare because it got used so much.
Is this in keep your standard rim
is 225x45x18 to wide for 7" rims or just the maximum
Notice on New CX5 have 19x7 rims with 225X55X19
so is it correct with no issues

cheers
 

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Discussion Starter #8 (Edited)
Is this in keep your standard rim
is 225x45x18 to wide for 7" rims or just the maximum
Notice on New CX5 have 19x7 rims with 225X55X19
so is it correct with no issues

cheers
Reading the ETRTO chart, minimum rim width for 225/45-18 tire should be a minimum of 7.5", preferably 8" minimum for best fitment.
I don't have information on the CX-5 model so can't help you out there.

However, in regard to alternative tire/wheel sizes I only included fitments that would result in 1% or less variation from OEM in tire diameter and speedometer readings for the Mazda 3.
 
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