AWD system, tyre profile difference over the axles?

mazdadude said:
I don't recall seeing anyone say that the DSC would be turned OFF?

Yes you can use any size tire you want that is true. 4 different brands, 4 different tread types, what ever.

However the cars computer is not capable nor is it designed to factor in the size of each tire to work properly, it assumes all are equal.

Just as you can use Dishwashing soap in the shower, it may work, but it is not going to give you the optimum performance your body needs.

The question is not whether it would work, it is simply advised against because it does not help the vehicle, and can in fact introduce strange effects or added stress into the cars systems, DSC, Traction, steering, AWD, etc... making it perform NOT AS DESIGNED.

I fail to see the logic in scrimping or using inferior tires, unmatched treads, unmatched sizes on the most important part of your car.
Click to expand...

Agreed. Dishwasher soap will possibly cause skin irritation although I couldn't prove that.

MD, the question as I see it is whether the OP could buy the wheels and tires described in his original post and fit them in to his vehicle. The general jist of the reply was no but I am saying that as long as he matches the tread depth across the axle then he most definitely could. Now you are stating that mixing brands and tread depths (I assume you don't really mean sizes as that was never mooted) will cause the various systems to not perform as designed and that is just the kind of sweeping statement that I have trouble with because you don't know that for sure. Would I do it? No, but I happen to know from people that design these things that they have a built in degree of tolerance.
 
Anchorman said:
The OP asked if it was OK to fit tires with varying tread depths in matched pairs across an axle. You told him to buy 4 new tires as tread depth variation would be guaranteed to cause a DSC malfunction. That is what needs to be proven because I am absolutely certain that it won't.
Click to expand...

Please don't mischaracterize what I said. I didn't say mismatched tires would cause DSC "malfunction", I said DSC would not function properly. And that is exactly what Mazda says in the service info! See my previous post for proof. Why are you twisting my very clear words and making a simple subject complex? This is not a difficult concept





I never said anywhere that the DSC would be switched off. What I said was that unless the light comes on then as far as the system control is concerned, it is functioning properly.
Click to expand...

That is completely false (at least if you believe Mazda's own technical papers). Mazda says DSC and ABS will NOT operate normally with tires of different sizes. Do you not believe them? The DSC light illuminates when the diagnostic system determines an internal fault in the DSC system, not a mismatch of tire sizes. If the diagnostic system doesn't detect an internal fault it does not imply the system is functioning properly. In fact, Mazda says it won't function properly.

Why are you being so stubborn on these very clear points?
 
Last edited:
I just thought about something; a great great grand mother of mine came from Ireland. I wonder if my ancestry is UK or Republic...Mike have you ever driven/ridden in western Europe by the way?
 
Anchorman said:
Agreed. Dishwasher soap will possibly cause skin irritation although I couldn't prove that.

MD, the question as I see it is whether the OP could buy the wheels and tires described in his original post and fit them in to his vehicle. The general jist of the reply was no but I am saying that as long as he matches the tread depth across the axle then he most definitely could. Now you are stating that mixing brands and tread depths (I assume you don't really mean sizes as that was never mooted) will cause the various systems to not perform as designed and that is just the kind of sweeping statement that I have trouble with because you don't know that for sure. Would I do it? No, but I happen to know from people that design these things that they have a built in degree of tolerance.
Click to expand...

Although I have yet to see anything firm from Mazda, It appears that the general auto manufacturer consensus MAX is .25 inch or within 30% or 4/32 difference, or 6.35mm

If I recall the original posters difference was only 3mm or so, which should be within the allowable range.

Here are the differences between the temp tire and OE size.

155/90-18 vs 225/65-17 = Difference

Diameter inches (mm)
28.98 (736.2) 28.52 (724.3) -0.47 (-11.9) -1.6%

Width inches (mm)
6.1 (155) 8.86 (225) 2.76 (70) 45.2%

Circum. inches (mm)
91.06 (2312.84) 89.58 (2275.46) -1.47 (-37.38) -1.6%

Sidewall Height inches (mm)
5.49 (139.5) 5.76 (146.25) 0.27 (6.75) 4.8%

Revolutions per mile (km)
695.83 (432.37) 707.26 (439.47) 11.43 (7.1) 1.6%
 
Last edited:
FSM doesn't list the allowable range... just this DTC

Screen%20Shot%202016-03-08%20at%201.07.01%20PM.png
 
This is interesting quote from FSM.

"If a tire of a different diameter from the standard tire is installed, the TCM determines that the driving mode is the AAS mode, and may change to a different shift timing from the normal timing."
 
mazdadude said:
Although I have yet to see anything firm from Mazda, It appears that the general auto manufacturer consensus MAX is .25 inch or within 30% or 4/32 difference, or 6.35mm

If I recall the original posters difference was only 3mm or so, which should be within the allowable range.

Here are the differences between the temp tire and OE size.

155/90-18 vs 225/65-17 = Difference

Diameter inches (mm)
28.98 (736.2) 28.52 (724.3) -0.47 (-11.9) -1.6%

Width inches (mm)
6.1 (155) 8.86 (225) 2.76 (70) 45.2%

Circum. inches (mm)
91.06 (2312.84) 89.58 (2275.46) -1.47 (-37.38) -1.6%

Sidewall Height inches (mm)
5.49 (139.5) 5.76 (146.25) 0.27 (6.75) 4.8%

Revolutions per mile (km)
695.83 (432.37) 707.26 (439.47) 11.43 (7.1) 1.6%
Click to expand...



Thats an interesting comparison but if you zoom into my photo you’ll see my spacesaver is 16” and my summer wheel is 18”.
 
Kedis82ZE8 said:
This is interesting quote from FSM.

"If a tire of a different diameter from the standard tire is installed, the TCM determines that the driving mode is the AAS mode, and may change to a different shift timing from the normal timing."
Click to expand...

Thank you. The AWD light WOULD come on if the tire sizes were out of range ;-)
 
MikeM. said:
Please don't mischaracterize what I said. I didn't say mismatched tires would cause DSC "malfunction", I said DSC would not function properly. And that is exactly what Mazda says in the service info! See my previous post for proof. Why are you twisting my very clear words and making a simple subject complex? This is not a difficult concept







That is completely false (at least if you believe Mazda's own technical papers). Mazda says DSC and ABS will NOT operate normally with tires of different sizes. Do you not believe them? The DSC light illuminates when the diagnostic system determines an internal fault in the DSC system, not a mismatch of tire sizes. If the diagnostic system doesn't detect an internal fault it does not imply the system is functioning properly. In fact, Mazda says it won't function properly.

Why are you being so stubborn on these very clear points?
Click to expand...

Not agreeing with your opinion doesn’t make me stubborn Mike, it makes me right.

Something may be lost in translation between English and American English but I think you’ll find that if the DSC doesn’t function properly it is malfunctioning;

malfunction
malˈfʌŋ(k)ʃ(ə)n/Submit
verb
1.
(of a piece of equipment or machinery) fail to function normally.
"the unit is clearly malfunctioning"
synonyms: crash, develop a fault, go wrong, break down, break, act up, be defective, be faulty, fail, cease to function/work, stop working

I believe what it says in Mazda’s own technical papers, you should read post No 25 but you might not like it in your current frame of mind. But anyway, while we are debating the subject (would be better with cold beers) where did you hear that the clutch backs off to 2% engaged?
 
Kedis82ZE8 said:
This is interesting quote from FSM.

"If a tire of a different diameter from the standard tire is installed, the TCM determines that the driving mode is the AAS mode, and may change to a different shift timing from the normal timing."
Click to expand...

I had to look up AAS mode. Just a quick Google search...

"Active Adaptive Shift (AAS) automatically controls the transmission shift points to best suit the road conditions and driver input. This improves driving feel. The transmission may switch to AAS mode when driving up and down slopes, cornering, driving at high elevations, or depressing the accelerator pedal quickly while the selector lever is in the D position. Depending on the road and driving conditions/vehicle operations, gear shifting could be delayed or not occur, however, this does not indicate a problem because the AAS mode will maintain the optimum gear position."
 
Kedis82ZE8 said:
I had to look up AAS mode. Just a quick Google search...

"Active Adaptive Shift (AAS) automatically controls the transmission shift points to best suit the road conditions and driver input. This improves driving feel. The transmission may switch to AAS mode when driving up and down slopes, cornering, driving at high elevations, or depressing the accelerator pedal quickly while the selector lever is in the D position. Depending on the road and driving conditions/vehicle operations, gear shifting could be delayed or not occur, however, this does not indicate a problem because the AAS mode will maintain the optimum gear position."
Click to expand...
All good stuff. Have you got access to the FSM?
 
Anchorman said:
Thats an interesting comparison but if you zoom into my photo you’ll see my spacesaver is 16” and my summer wheel is 18”.
Click to expand...

SO SORRY! That is the size here in the US.

Please HELP me out, because I zoomed in and could not read the size in your pic, can you make it easier to compare and provide the numbers between your two tire sizes?

What is the size of the UK temp spare and the Uk 18 tires?
 
Anchorman said:
Not agreeing with your opinion doesnt make me stubborn Mike, it makes me right.

Something may be lost in translation between English and American English but I think youll find that if the DSC doesnt function properly it is malfunctioning;

malfunction
malˈfʌŋ(k)ʃ(ə)n/Submit
verb
1.
(of a piece of equipment or machinery) fail to function normally.
"the unit is clearly malfunctioning"
synonyms: crash, develop a fault, go wrong, break down, break, act up, be defective, be faulty, fail, cease to function/work, stop working

I believe what it says in Mazdas own technical papers, you should read post No 25 but you might not like it in your current frame of mind. But anyway, while we are debating the subject (would be better with cold beers) where did you hear that the clutch backs off to 2% engaged?
Click to expand...

Don't blame it on differences between British and American English, in this case they mean the same thing. And drop the semantical games. Yes, malfunction means fail to operate normally. I was drawing the distinction between the DSC malfunction warning light illuminating and the DSC not functioning normally.

Because Mazda says the DSC will not function normally with tires worn differently (relative to each other). And yet you have confirmed that this doesn't cause the DSC warning light to illuminate. But that does not mean DSC is functioning normally or optimally as Mazda states below:

The DSC and ABS will not operate normally under the following conditions:

-With tires that are not of the specified size, manufacturer or tread pattern or not inflated according to specification.

-With tires that have significant comparative wear variation.

-With tire chains

-With an emergency spare tire.


As far as post #25 goes, that doesn't address DSC, it addresses an AWD fail-safe mode. This prevents the AWD clutch from over-heating and clearly has a larger tolerance than the type of tire wear mismatch that Mazda warns will cause DSC to not function normally.

Why do you claim that different comparative wear variations are not a problem when all the Mazda literature states otherwise?
 
MikeM. said:
Don't blame it on differences between British and American English, in this case they mean the same thing. And drop the semantical games. Yes, malfunction means fail to operate normally. I was drawing the distinction between the DSC malfunction warning light illuminating and the DSC not functioning normally.

Because Mazda says the DSC will not function normally with tires worn differently (relative to each other). And yet you have confirmed that this doesn't cause the DSC warning light to illuminate. But that does not mean DSC is functioning normally or optimally as Mazda states below:

The DSC and ABS will not operate normally under the following conditions:

-With tires that are not of the specified size, manufacturer or tread pattern or not inflated according to specification.

-With tires that have significant comparative wear variation.

-With tire chains

-With an emergency spare tire.


As far as post #25 goes, that doesn't address DSC, it addresses an AWD fail-safe mode. This prevents the AWD clutch from over-heating and clearly has a larger tolerance than the type of tire wear mismatch that Mazda warns will cause DSC to not function normally.

Why do you claim that different comparative wear variations are not a problem when all the Mazda literature states otherwise?
Click to expand...

If you've got your serious head on Mike, I'll tell you why, because in a real life situation, like I've been trying to explain, if an owner bought a new CX-5 and didn't rotate the tires, he would end up with tread wear identical to that described by the OP. in other words, the front would wear more than the rear to the extent of 5.5mm front and 8mm rear. I've worn the tires much more out of balance than that and it made no difference albeit on a RAV - it has the SAME systems. Even on a CX-5 it would not cause malfunction of the DSC, ABS or AWD. if the OP bought and fitted them in pairs as I'm absolutely sure he would, the vehicle would perform faultlessly, even if he continued on and wore the front pair to the legal limit. It's not ideal but it would even though it would be better with the thicker tread on the front to run them off.

Instead of sticking to the original question, the thread has morphed into another over complicated demonstration of your wooley knowledge about the CX-5 driveline and systems. It isn't about the effects of putting different tread depths at random across axles, it isn't about how it compares to other brands, it's about the poor bloke wanting to buy 4 second hand wheels with 2 pairs of evenly worn tyres that are 2.5mm different from the other. Now he's got the impression that the safety systems will reject these tires because the boss of the forum says he's got have evenly worn tires.

Sorry to have crossed you Mike. I tried to keep my opinion light hearted but that seems to irritate you too.
 
mazdadude said:
SO SORRY! That is the size here in the US.

Please HELP me out, because I zoomed in and could not read the size in your pic, can you make it easier to compare and provide the numbers between your two tire sizes?

What is the size of the UK temp spare and the Uk 18 tires?
Click to expand...
I’ll look asap but I think that tire you compared with is a better match than the one I have. I’ll look into it - thanks.
 
Anchorman said:
If you've got your serious head on Mike, I'll tell you why, because in a real life situation, like I've been trying to explain, if an owner bought a new CX-5 and didn't rotate the tires, he would end up with tread wear identical to that described by the OP. in other words, the front would wear more than the rear to the extent of 5.5mm front and 8mm rear. I've worn the tires much more out of balance than that and it made no difference albeit on a RAV - it has the SAME systems. Even on a CX-5 it would not cause malfunction of the DSC, ABS or AWD.
Click to expand...

Mazda says the DSC will not operate normally if tire wear is mismatched. If you don't want to call "not operating normally" a "malfunction" that's ok but it's still not operating as designed. That's one reason of many the Owner's Manual instructs you to rotate the tires every 7500 miles (or sooner if you notice uneven tire wear).

Instead of sticking to the original question, the thread has morphed into another over complicated demonstration of your wooley knowledge about the CX-5 driveline and systems. It isn't about the effects of putting different tread depths at random across axles, it isn't about how it compares to other brands, it's about the poor bloke wanting to buy 4 second hand wheels with 2 pairs of evenly worn tyres that are 2.5mm different from the other. Now he's got the impression that the safety systems will reject these tires because the boss of the forum says he's got have evenly worn tires.
Click to expand...

Hopefully he didn't get a false impression. The safety systems might not "reject" those tires but they will not function properly with tires with uneven wear. I don't recall anyone claiming otherwise so I'm not sure how you ended up believing that. I know I didn't say the safety systems would reject tires with uneven wear, they will cause the DSC to function abnormally. Mazda has no incentive to lie or exaggerate on this point.


Sorry to have crossed you Mike. I tried to keep my opinion light hearted but that seems to irritate you too.
Click to expand...

I'm not irritated. I'm amused at your perspective. Mazda repetitively warns about uneven tire wear and even specifically names the trouble it can cause and yet you think everything will function the same. I can't help it if I find such a disconnect amusing.
 
Last edited:
OK, well answer me this then. If a new car didn’t have the tires rotated until the recommended interval of 7500 miles (or whatever it should be) and by that time the fronts had worn to 5.5mm and the rears to 8mm, would you expect the safety systems to have stopped working properly?

Just curious about your opinion.
 
Anchorman said:
Not agreeing with your opinion doesn’t make me stubborn Mike, it makes me right.
Click to expand...

It's not my opinion, it's Mazda's.

Let's look at your opinion. I'm guessing you don't see anything wrong with this vehicle I came across at the local Ski Area. After all, it obviously made it there so everything must be functioning normally, right?

attachment.php


attachment.php


attachment.php


attachment.php


You might notice something missing in the third photo. Now this won't cause any of the safety systems to "reject" that wheel so everything must be normal, huh? (rofl2)
 
Last edited:
Please log in or register to reply here.

Similar threads

C
    • Like
CX-90 Turbo S vs. Turbo Differences and drivetrain notes
2
Replies
29
Views
9K
roundle1979
R
G
Mazda AWD vs Subaru, a new owner's simple observations
Replies
3
Views
4K
Chris_Top_Her
Chris_Top_Her
F
UK Trip to Burghley Horse Trials with my new CX5
Replies
3
Views
1K
French Snowie
F

Latest posts

Back