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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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235/40/18 on 18x9 wheel.
Et 42 Front
Et 40 Rear
Lowered on HR Springs
Next set of tires will be 245/40/18 as that will be closer to rolling diameter stock tire. View attachment 275297
@Cra97 Looks really sleek! Don't think I heard anyone mentioned about the ride quality with the spring. Does it affect the ride much in terms or comfort and how do you feel about the performance with the spring?
 

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@Cra97 Looks really sleek! Don't think I heard anyone mentioned about the ride quality with the spring. Does it affect the ride much in terms or comfort and how do you feel about the performance with the spring?
Makes the ride stiffer over bumps but definitely removes a lot of body roll on the turns. On a smooth road/Hwy can’t tell the difference.
 

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OMG So , with a reasonably priced 17X7.5 custom wheel ( https://www.tirerack.com/wheels/results.jsp?&autoMake=Mazda&autoModel=Mazda3+Hatchback+FWD&autoYear=2019&autoModClar=)
you would cut wheel weight by 1/3, give a gentler, quieter ride and save on replacement tire cost while better filling the wheel wells.
With the big decrease in unsprung weight and bigger contact patch, I would not be surprised by a handling advantage as well. Gives just under +1% change in circumference.
Like you said Big increase in handling when you reduce unsprung weight. Adding contact patch also give a better performance. My wheels weight 17.5 lbs plus I added 20+mm of contact patch.
 

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Like you said Big increase in handling when you reduce unsprung weight. Adding contact patch also give a better performance. My wheels weight 17.5 lbs plus I added 20+mm of contact patch.
I was at first not a fan of black wheels, but after experimenting with some light silver ones on my polymetal hatch, I have to say they did not look right.

!7.5 lbs is impressively light for a 18x9. Heck, that is light for a 17x7. What is the brand that I might check it out to see if they have an 18x8 in that model. Should be a lb or 2 lighter still, if there is such a thing.
 

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I was at first not a fan of black wheels, but after experimenting with some light silver ones on my polymetal hatch, I have to say they did not look right.

!7.5 lbs is impressively light for a 18x9. Heck, that is light for a 17x7. What is the brand that I might check it out to see if they have an 18x8 in that model. Should be a lb or 2 lighter still, if there is such a thing.
It’s a 2pc forged wheel.
He can make whatever wheel you want in the specs you want, they’re custom made to your specs.
 

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235/40/18 on 18x9 wheel.
Et 42 Front
Et 40 Rear
Lowered on HR Springs
Next set of tires will be 245/40/18 as that will be closer to rolling diameter stock tire.
Actually, 235/40x18 is nearly identical rolling diameter to stock. According to Tire Rack specs, a Michelin PS4S tire in this exact size has a 25.4"diameter & 819 revs/mile, compared to the stock Dunlop 215/45x18 tires at 25.6"diameter & 816 revs/mile.
I'm awaiting delivery of a set of four of these MPS4S tires on BBS 18x8 ET50 wheels. I don't know how you managed to use ET40 wheels in the rear without the tires rubbing. Did you have to roll/pull the fenders?

Sent from my XT1650 using Tapatalk
 
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