2004 to 2016 Mazda 3 Forum and Mazdaspeed 3 Forums banner

1 - 20 of 42 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter #1
Hey all,

I currently have the OEM iTouring size wheels/tires on my car (16"). In the near future I am planning on upgrading to 18" Enkei wheels and Tirerack has warned me that I would need to reprogram the TPMS to account for a different wheel size.

My question is, will resetting it like you would for a low tire also act as a "reprogram" for a new size wheel, or will I need to take it in and have the system programmed?
 

·
Registered
Joined
·
560 Posts
Xmsteel...would suggest you do a bit more research as to whether you will trigger the TPMS by changing tire/wheel size and not necessarily trust the responses here. Many people here have changed their tire/wheel sizes.

Firstly, the Mazda system is an indirect system vs. a direct system. The indirect system is based on tire revolution where the direct system is based on an actual sensor inside the tire/wheel which measures pressure and temp. Secondly, each car is designed with a specific tire/wheel size as it relates to the speedo....makes sense so far? Some have 16" and others have 18" wheels. Changing the tire/wheel size from original specs will be affected. Therefore, the TPMS system is also designed around the tire/wheel size.

All I'm saying is maybe switching rims/tires won't affect anything based specifically on the Mazda 3 system, but there is enough literature out there which supports what the tire dealer is suggesting. You would need to get further confirmation on people who have made the exact same switch you have in mind...exact same wheel and tire size.
 

·
Super Moderator
Joined
·
5,182 Posts
Its important to inflate all the tires to the same PSI and properly reset the system using the button on the dash to tell the system what is considered "normal". Once that is established, the system looks for individual wheel speed differences that deviate from that "normal" baseline by a preset percentage. The system cannot discern which tire is low however, and it will not trigger an event if all 4 tires are low.
Just FYI, the indirect TPMS system in your 2014 model does not care what size the wheels are. It works by sensing wheel speed using the ABS sensors. A soft tire has a slightly smaller diameter, so it turns at a different speed. When wheel speed difference drops below the preset system tolerance level, the light comes on. So, it does not matter if the wheel is 16", 18" or any other size what so ever.
 

·
Registered
Joined
·
90 Posts
Xmsteel...would suggest you do a bit more research as to whether you will trigger the TPMS by changing tire/wheel size and not necessarily trust the responses here. Many people here have changed their tire/wheel sizes.

Firstly, the Mazda system is an indirect system vs. a direct system. The indirect system is based on tire revolution where the direct system is based on an actual sensor inside the tire/wheel which measures pressure and temp. Secondly, each car is designed with a specific tire/wheel size as it relates to the speedo....makes sense so far? Some have 16" and others have 18" wheels. Changing the tire/wheel size from original specs will be affected. Therefore, the TPMS system is also designed around the tire/wheel size.

All I'm saying is maybe switching rims/tires won't affect anything based specifically on the Mazda 3 system, but there is enough literature out there which supports what the tire dealer is suggesting. You would need to get further confirmation on people who have made the exact same switch you have in mind...exact same wheel and tire size.
With correctly matched combinations a 16 inch wheel and tyre is approximately the same diameter as an 18 inch wheel and tyre!
Therefore approximately the same circumference.
More hub less tyre.
 

·
Registered
Joined
·
560 Posts
All I'm pointing out is the author of the thread did not say either way what tire size they planned...only wheel size. That was key piece of information not included which the tire dealer maybe referencing...or not?
 

·
Super Moderator
Joined
·
5,182 Posts
All I'm pointing out is the author of the thread did not say either way what tire size they planned...only wheel size. That was key piece of information not included which the tire dealer maybe referencing...or not?
Non sequitur....Since the system relies on relative wheel speed rather than overall wheel diameter to function, tire size only counts if the tire sizes are mismatched. Even then as long as the system is properly reset after installation it won't make a difference....:dunno:
 

·
Rubber side down
Joined
·
243 Posts
Non sequitur....Since the system relies on relative wheel speed rather than overall wheel diameter to function, tire size only counts if the tire sizes are mismatched. Even then as long as the system is properly reset after installation it won't make a difference....:dunno:
I have run 19" 225/45/19, 18" 215/45/18 (factory), and 17" 225/45/17. Never had a problem wish the TPMS malfunctioning. Tire/wheel size does not matter as long as they are all the same. TPMS worked fine with all these setups. As arathol stated, the TPMS functions by reading different rotation speeds between the 4 corners. I can tell you this, the TPMS still does its job regardless of wheel/tire size. Crack in one of my 19" wheels caused a slow leak. TPMS picked up on this when the pressure difference was about 10psi. Screw in the tire of my factory 18" wheels, TPMS picked up on this as well, usually around a 10psi difference. 10psi seems to create a drastic enough change in overall rotation diameter that the ABS sensor reads it as a problem.

Moral of the story: feel free to rock them 13" Baby Ds. Just keep all the tires equally inflated and you're good.
 

·
Super Moderator
Joined
·
5,182 Posts
Crack in one of my 19" wheels caused a slow leak. TPMS picked up on this when the pressure difference was about 10psi. Screw in the tire of my factory 18" wheels, TPMS picked up on this as well, usually around a 10psi difference. 10psi seems to create a drastic enough change in overall rotation diameter that the ABS sensor reads it as a problem.
I believe the standard is 26% deviation. For 36 psi that would be about 9 psi, so that 10 psi observed is just about right.
 

·
Registered
Joined
·
560 Posts
Non sequitur....Since the system relies on relative wheel speed rather than overall wheel diameter to function, tire size only counts if the tire sizes are mismatched. Even then as long as the system is properly reset after installation it won't make a difference....:dunno:
Everything you say up to the point where you stop is true. However, in an indirect system the TPMS is connected to the ABS which is connected to the ECU. The car's computer is calculating based on what tire/wheel size is printed on the driver's side door (stock equipment). Granted it maybe marginal, but the ABS in an indirect TPMS system can set off the TPMS with different diameters. Most tire manufacture websites and larger wheel shops indicate changing tire size can affect the TPMS in an indirect system. I suspect that is why the author's tire dealer told him as much. In a direct system the TPMS and ABS are not connected to one another, even though changing tire size may set off the ABS in both direct and indirect systems. There are shops which do the programming.

Digressing even further...most people who indicate a change in tire size may casually only say it affects the speedo, but usually forget it can affect shift points...yes maybe marginal in this specific case...but it may not be beyond Mazda or any other car manufacture to void a warranty should someone bring their car in for service and notice a different tire size?
 

·
Super Moderator
Joined
·
5,182 Posts
Everything you say up to the point where you stop is true. However, in an indirect system the TPMS is connected to the ABS which is connected to the ECU. The car's computer is calculating based on what tire/wheel size is printed on the driver's side door (stock equipment). Granted it maybe marginal, but the ABS in an indirect TPMS system can set off the TPMS with different diameters. Most tire manufacture websites and larger wheel shops indicate changing tire size can affect the TPMS in an indirect system. I suspect that is why the author's tire dealer told him as much. In a direct system the TPMS and ABS are not connected to one another, even though changing tire size may set off the ABS in both direct and indirect systems. There are shops which do the programming.

Digressing even further...most people who indicate a change in tire size may casually only say it affects the speedo, but usually forget it can affect shift points...yes maybe marginal in this specific case...but it may not be beyond Mazda or any other car manufacture to void a warranty should someone bring their car in for service and notice a different tire size?
As said before, tire size differences will only apply if the TPMS is not reset properly. The sensors read the difference in wheel speed at each wheel, nothing more. As long as all four wheels are turning at the same speed, or each wheel is turning at the speed that is clocked in by resetting the system, and the difference in wheel speed does not exceed 26% of the values entered by resetting the system, the system won't register a problem. If one wheel exceeds the preset 26% difference the light comes on. Tire size does not matter. I have used 16" rims with 205-60 snow tires (25.7" OD) and 17" rims with 205-50 summer tires (25.1" OD) with zero issues, didn't even need to reset the system.

As to the other stuff, usually shift points are tied to rpm, not wheel speed. The shift points may register differently only because the speedometer is inaccurate. The shift points are still at the same rpm. And no, nobody is going to "void your warranty" if you put different tires on your car unless the tires are not sized properly for the application, for example if you have two different diameter tires on the drive axle and this causes damage to the driveline.
 

·
Registered
Joined
·
101 Posts
If 17maz3's description is correct, there would be no need for the reset button. With known tire size from the factory (on the door), simple calcs would reveal revs expected and be burned in.

The reset capability seemingly tells us the system is likely entirely independent of fixed size.

Is there any indication in docs to the contrary?

Sent from my SM-N950U using Tapatalk
 

·
Registered
Joined
·
90 Posts
If 17maz3's description is correct, there would be no need for the reset button. With known tire size from the factory (on the door), simple calcs would reveal revs expected and be burned in.

The reset capability seemingly tells us the system is likely entirely independent of fixed size.

Is there any indication in docs to the contrary?

Sent from my SM-N950U using Tapatalk
I agree if you live in a city with a one way system and turn right on leaving home, drive around the block and return from the left, your outside wheels wile have traveled further than the inside ones. So you can't have a fixed calculation, you need a fudge factor. Lets say you always run your car with the tyre pressures at the maximum and you live where there is little temperature variation whereas I run mine softer or live in a climate that has large fluctuations day to night. Perhaps you park with the drivers side in hot sunlight so your tires are warmer than the passengers when you start the journey, so the pressures are up. the diameter larger, less rotations for the first mile or two.
What I am saying is that each ABS sensor passes the wheel rotation info to the computer that says "why is that single wheel going faster that the other three"? and "is it a little over a long time"?
Resetting simple clears the memory so the count starts from zero and removes any flag from the system.
 

·
Registered
Joined
·
44 Posts
Discussion Starter #17
So from what I'm reading it really shouldn't matter as long as all four are matching and properly inflated?

Next question and one I didn't even think of, difference in speedometer accuracy. What would the impact be going from a 16x7.5 wheel on a 205/60R16 tire to a 18x7.5 wheel on a 215/45R18 tire?
 

·
Registered
Joined
·
90 Posts
So from what I'm reading it really shouldn't matter as long as all four are matching and properly inflated?

Next question and one I didn't even think of, difference in speedometer accuracy. What would the impact be going from a 16x7.5 wheel on a 205/60R16 tire to a 18x7.5 wheel on a 215/45R18 tire?
Try Tire and rim calculator - Find correct tires to your car or https://alloywheels.com/tyreCalculator
I think, it looks like the new combination would be 0.3cm less in circumference (0.2%) your speedo would overread by so little it won't show.
If this is correct the difference is less than a worn tyre verses a new one.
 

·
Registered
Joined
·
182 Posts
I have run 19" 225/45/19, 18" 215/45/18 (factory), and 17" 225/45/17. Never had a problem wish the TPMS malfunctioning. Tire/wheel size does not matter as long as they are all the same. TPMS worked fine with all these setups. As arathol stated, the TPMS functions by reading different rotation speeds between the 4 corners. I can tell you this, the TPMS still does its job regardless of wheel/tire size. Crack in one of my 19" wheels caused a slow leak. TPMS picked up on this when the pressure difference was about 10psi. Screw in the tire of my factory 18" wheels, TPMS picked up on this as well, usually around a 10psi difference. 10psi seems to create a drastic enough change in overall rotation diameter that the ABS sensor reads it as a problem.

Moral of the story: feel free to rock them 13" Baby Ds. Just keep all the tires equally inflated and you're good.
I believe the standard is 26% deviation. For 36 psi that would be about 9 psi, so that 10 psi observed is just about right.
Curious to know what you mean "ABS sensor reads it as a problem"? My friend has a 2018 and on several occasions the TPMS light comes on at 32-31 psi. Never had an ABS or traction light. My 2015 I only had the light when I changed wheels and didn't reset it. I check my tires once per month though.
 

·
Super Moderator
Joined
·
5,182 Posts
Curious to know what you mean "ABS sensor reads it as a problem"? My friend has a 2018 and on several occasions the TPMS light comes on at 32-31 psi. Never had an ABS or traction light. My 2015 I only had the light when I changed wheels and didn't reset it. I check my tires once per month though.
I think you will find that 2018 models have gone back to the direct system with a sensor module in the wheel.
 
1 - 20 of 42 Posts
Top