AWD system, tyre profile difference over the axles?

K

kapiteinlangzaa

Member
:
Mazda CX-5 GT-M AWD
Might be a daft question, but with the permanent AWD system, is there a max. permissible difference between the front and rear axle tread depth.

I know some older systems were super sensitive, but cant seem to find much info for the Mazda.

Im looking at a set of 4 wheels, 2x 5.5mm profile, and 2x 8mm profile. Would that be OK, or would it screw the gears up?

Thanks!
 
kapiteinlangzaa said:
Might be a daft question, but with the permanent AWD system, is there a max. permissible difference between the front and rear axle tread depth.

I know some older systems were super sensitive, but cant seem to find much info for the Mazda.

Im looking at a set of 4 wheels, 2x 5.5mm profile, and 2x 8mm profile. Would that be OK, or would it screw the gears up?
Click to expand...

Buy 4 identical tires (I believe you meant 'tires', not 'wheels')

Why would the tires have different tread depths if they are identical? Are they used?
 
MikeM. said:
Buy 4 identical tires (I believe you meant 'tires', not 'wheels')

Why would the tires have different tread depths if they are identical? Are they used?
Click to expand...

Yes a used wheel and tyre package from a 2WD CX-5.

Identical wheel and tyre brand, but 2 tyres with 5.5mm profile, and two with 8mm.

Im not interested in buying new tyres, hence the question.
 
I don't know the answer, but surely a Mazda dealer would, or you can e-mail Mazda.

I suspect is is not a critical since the CX-5 system normally applies little torque to the rear wheels until the fronts slip.
 
ColtX-5 said:
I don't know the answer, but surely a Mazda dealer would, or you can e-mail Mazda.

I suspect is is not a critical since the CX-5 system normally applies little torque to the rear wheels until the fronts slip.
Click to expand...

It's quite critical for all tires to have the same diameter because so many systems depend upon the wheel speed sensors.

Also, the Mazda AWD does apply considerable torque to the rear wheels when necessary because it is a predictive AWD system. But even in steady state cruising on clean dry pavement it sends about 2% torque to the rear. This is quite efficient from a MPG perspective until the wheel diameters vary. The more they vary, the bigger the parasitic drag losses are and the sooner your AWD coupling clutch will wear out. So, ideally they are the same diameter, that's why it's important to get regular tire rotations, especially with AWD and especially if your fuel is expensive.
 
erhayes said:
Subaru & Audi stated the tire circumference difference must not exceed 1/4 inch. Ed
Click to expand...

The circumference difference of the tires in question would be 15.5 mm or a bit over 1/2 inch. I wouldn't do it without having the deeper tread shaved to match the shallower tread. More trouble than it's worth, IMO.

Good tires are good insurance against many things, from mechanical wear/failure, accident/injury, fuel economy, inconvenience of tire failure, hydroplaning and this is all before we consider that good tires return more driving pleasure.
 
Tccox said:
So, every 5000 miles ok?
Click to expand...

Most manufacturers call for 5,000-7,500 mile rotations. Sport compound tires wear faster and might require more frequent rotations. I do mine each spring and fall when I switch between my summer/winter rubber.

AWD CX-5 2.0L wears very evenly so I could get by only doing it every 7,500-9,000 miles if necessary. The heavier engine and higher output of the 2.5L probably wears the fronts a bit faster so best to stay with factory recommendations.
 
So far mine have been wearing evenly all around. I rotate at around 7-8K mile intervals.

@8K miles they were 8/32

@around 18.5K miles I notice they had worn to 7/32 all around

Next rotation in a month or two.

EDIT: Snow tires in the mix will decrease this further once we get into the late fall.
 
Sorry to contradict here but can anybody PROVE that the tire circumference be kept the same? My last vehicle was a RAV4 with exactly the same coupling and exactly the same links to the ABS and VSC systems. Here in the UK, tire rotation is not so popular and I certainly wore a set of fronts down to the legal limit while the rears were virtually unworn (maybe 6 or 7 mm/1/4 inch). Nothing happened, nothing at all. The car ran perfectly. Furthermore, I had a fully worn (just legal) spare tire that I fitted and ran for a couple of days on two occasions on one side with absolutely no negative effect.

Now if we apply that to the CX-5, take a look at my supplied spacesaver wheel for my CX-3 which is identical in every way to the CX-5. It isn’t millimetres different, it is inches different. What I do predict by using this is that the TPMS light will light up. I personally would ignore it but it could be reset if needed. Now why would Mazda supply this if it was going to cause a meltdown in safety and mechanical systems? No doubt somebody will quote from the book that tires should be fitted in pairs etc but the Ford Fiesta book will say the same as it is standard practice but once cars get to second, third and fourth ownership, not only do they not have equally worn but a mix of budget brands are the norm over here. I’m not asking for opinion and I’m not asking for experience of other cars like Subaru that don’t share the same AWD system, I’m asking who has some proof of the same system as the CX-5. I reckon this spacesaver is a good 6 inches different in circumference;

image_zpsrisagqdu.jpeg
 
Last edited:
Anchorman said:
Sorry to contradict here but can anybody PROOVE that the tire circumference be kept the same?
Click to expand...

What are you asking us to prove? That the car will not function optimally with different tire circumferences? Because no one said it would instantly explode. Yes, the spare is a different size and the OM says to "only use the spare for VERY short periods." (emphasis on "VERY" from the OM). It also instructs to limit speed to 50 mph. It also instructs to only use it on the rear and to replace it with a matching tire as soon as possible.

For regular tires it instructs to replace all 4 tires at the same time. It warns against using tires with different wear patterns on the same vehicle. It also instructs to rotate the tires at 7500 mile intervals or sooner if there is uneven wear. This is all in your Owners Manual.

What more do you want?

I guarantee that DSC will not function properly with tires of significantly different circumference. That alone is a good reason not to put mismatched tires on. But it's your car and you're in the UK where I guess tire rotation is out of fashion so you're free to do it however you think is best. Those UK roads are probably specially designed to reduce or eliminate the need to rotate tires. Must be nice.
 
The UK CX-5 maintainance screen has a tyre rotation alarm set I believe to 6250 miles which is what I shall be following. The only possible benefit of not rotating your tyres as per manufacturers recommendations is that you'd only have to buy 2 tyres & not 4 in one go. If you're lucky then I guess the hidden costs of premature mechanical wear may pass on to the next (unlucky) owner.
 
Anchorman said:
Sorry to contradict here but can anybody PROOVE that the tire circumference be kept the same? My last vehicle was a RAV4 with exactly the same coupling and exactly the same links to the ABS and VSC systems. Here in the UK, tire rotation is not so popular and I certainly wore a set of fronts down to the legal limit while the rears were virtually unworn (maybe 6 or 7 mm/1/4 inch). Nothing happened, nothing at all. The car ran perfectly. Furthermore, I had a fully worn (just legal) spare tire that I fitted and ran for a couple of days on two occasions on one side with absolutely no negative effect.

Now if we apply that to the CX-5, take a look at my supplied spacesaver wheel for my CX-3 which is identical in every way to the CX-5. It isnt millimetres different, it is inches different. What I do predict by using this is that the TPMS light will light up. I personally would ignore it but it could be reset if needed. Now why would Mazda supply this if it was going to cause a meltdown in safety and mechanical systems? No doubt somebody will quote from the book that tires should be fitted in pairs etc but the Ford Fiesta book will say the same as it is standard practice but once cars get to second, third and fourth ownership, not only do they not have equally worn but a mix of budget brands are the norm over here. Im not asking for opinion and Im not asking for experience of other cars like Subaru that dont share the same AWD system, Im asking who has some proof of the same system as the CX-5. I reckon this spacesaver is a good 6 inches different in circumference;

image_zpsrisagqdu.jpeg
Click to expand...
Page 386 of the CX5 Manual section 7-6

Flat Tire
WARNING
Do not install the temporary spare tire
on the front wheels (driving wheels):
Driving with the temporary spare tire
on one of the front driving wheels is
dangerous. Handling will be affected.
You could lose control of the vehicle,
especially on ice or snow bound
roads, and have an accident. Move a
regular tire to the front wheel and
install the temporary spare tire to the rear.

Or here is a great article from Tire Rack, that also cites some of the Automakers tire difference specs

Here is an excerpt from that article:

"Here are recommendations from some of the manufactures that Tire Rack currently serves for matching the tires used on their four-wheel drive and all-wheel drive vehicles. Additional recommendations from other Original Equipment Vehicle Manufacturers is pending.



Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
Nissan GT-R when replacing less than four (4) tires, each tire continuing in service must have at least 6/32 inch (5 mm) of remaining tread depth.
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth. "

http://www.tirerack.com/winter/tech/techpage.jsp?techid=18
 
Last edited:
You might be able to find a shop that will shave the tires for you. Basically they shave off the excess tread of the tires that are bigger so that all tires match in tread depth. I know places that will do this for new tires if you need to replace just one on an AWD system, I don't know if places will be willing to do it for used tires.
 
MikeM. said:
What are you asking us to prove? That the car will not function optimally with different tire circumferences? Because no one said it would instantly explode. Yes, the spare is a different size and the OM says to "only use the spare for VERY short periods." (emphasis on "VERY" from the OM). It also instructs to limit speed to 50 mph. It also instructs to only use it on the rear and to replace it with a matching tire as soon as possible.

For regular tires it instructs to replace all 4 tires at the same time. It warns against using tires with different wear patterns on the same vehicle. It also instructs to rotate the tires at 7500 mile intervals or sooner if there is uneven wear. This is all in your Owners Manual.

What more do you want?

I guarantee that DSC will not function properly with tires of significantly different circumference. That alone is a good reason not to put mismatched tires on. But it's your car and you're in the UK where I guess tire rotation is out of fashion so you're free to do it however you think is best. Those UK roads are probably specially designed to reduce or eliminate the need to rotate tires. Must be nice.
Click to expand...

Mike, I have a great deal of respect for you and your knowledge (you can spell prove better than me for one thing!) but here’s the thing. Nobody said that it would explode, nor quoted the timescale involved, that’s nonsense and I get that all the tires should in theory be matched by brand and tread depth but in reality, when a car gets older it gets bought by owners on a lower and lower budget. If you look in the parking lot at some of these older cars, they have a complete mix of tires and buying one is often all they can afford and the brand is not important to them. Same goes for shocks and brakes discs - all the things that we buying new cars wouldn’t dream of doing.

Furthermore, you cannot guarantee that the DSC won’t work because i’ve tried it and it does work or at least the system warning light stayed off and that suggests it was as operable as it is any other time.

mazdadude said:
Page 386 of the CX5 Manual section 7-6

Flat Tire
WARNING
Do not install the temporary spare tire
on the front wheels (driving wheels):
Driving with the temporary spare tire
on one of the front driving wheels is
dangerous. Handling will be affected.
You could lose control of the vehicle,
especially on ice or snow bound
roads, and have an accident. Move a
regular tire to the front wheel and
install the temporary spare tire to the rear.

Yes, I get this too but going off the discussion earlier in this thread then a tire that is 1/4 inch difference in rolling radius let alone 2 inches is going to cause big problems even if it is on the rear and of course you could expect safety systems to get confused with such anomalies but the suggestion is that a car with an odd tire cannot be used and this is what I dispute.

Or here is a great article from Tire Rack, that also cites some of the Automakers tire difference specs

Tire Rack are a tire vendor. They will never suggest that you should mix tires depths or brands and what is more, you’ve done exactly what I said not to do and quote the pointless comparisons to vehicles with a different AWD system. I don’t know what your point is from either.

Here is an excerpt from that article:

"Here are recommendations from some of the manufactures that Tire Rack currently serves for matching the tires used on their four-wheel drive and all-wheel drive vehicles. Additional recommendations from other Original Equipment Vehicle Manufacturers is pending.



Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
Nissan GT-R when replacing less than four (4) tires, each tire continuing in service must have at least 6/32 inch (5 mm) of remaining tread depth.
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth. "

http://www.tirerack.com/winter/tech/techpage.jsp?techid=18
Click to expand...

See bold above
 
Anchorman said:
Mike, I have a great deal of respect for you and your knowledge (you can spell prove better than me for one thing!) but here’s the thing. Nobody said that it would explode, nor quoted the timescale involved, that’s nonsense and I get that all the tires should in theory be matched by brand and tread depth but in reality, when a car gets older it gets bought by owners on a lower and lower budget. If you look in the parking lot at some of these older cars, they have a complete mix of tires and buying one is often all they can afford and the brand is not important to them. Same goes for shocks and brakes discs - all the things that we buying new cars wouldn’t dream of doing.

Furthermore, you cannot guarantee that the DSC won’t work because i’ve tried it and it does work or at least the system warning light stayed off and that suggests it was as operable as it is any other time.



See bold above
Click to expand...
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.
 
Last edited:
Anchorman said:
Mike, I have a great deal of respect for you and your knowledge (you can spell prove better than me for one thing!) but here’s the thing. Nobody said that it would explode, nor quoted the timescale involved, that’s nonsense and I get that all the tires should in theory be matched by brand and tread depth but in reality, when a car gets older it gets bought by owners on a lower and lower budget. If you look in the parking lot at some of these older cars, they have a complete mix of tires and buying one is often all they can afford and the brand is not important to them. Same goes for shocks and brakes discs - all the things that we buying new cars wouldn’t dream of doing.
Click to expand...

You didn't answer my primary question which was simply asking you to clarify what your question is. What (specifically) are you asking us to "prove"?

We all agree CX-5 internals are robust enough that they won't instantly and catastrophically fail due to tire circumference differences.
We all agree optimal function comes from matched tire sets.

Furthermore, you cannot guarantee that the DSC won’t work because i’ve tried it and it does work or at least the system warning light stayed off and that suggests it was as operable as it is any other time.
Click to expand...

I'm sorry but that's incorrect. I didn't claim any variation in tire circumference would disable DSC, I said it wouldn't function properly. You suggest it will have the same operation whether the tire circumference are matched or mismatched. It won't but you don't have to take my word for it, just check your owner's manual:

The DSC may not operate correctly unless the following are observed:

> Use tires of the specified size on all four wheels of your Mazda.
>Use tires of the same manufacturer, brand and tread pattern on all four wheels.
> Do not mix worn tires.
> The DSC may not operate correctly when tire chains are used or a temporary spare is installed because the tire diameter changes.
Click to expand...

The factory service information for the CX-5 states the same thing even more definitively:

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.
Click to expand...

Note that it doesn't say tire size variation will disable DSC and ABS, it says they won't operate normally.

Do you want computers that have ultimate control of your throttle and brakes as you hurl down the highway at 70 mph to function abnormally? I guess if you live in the UK this is not considered a big deal?
 
MikeM. said:
You didn't answer my primary question which was simply asking you to clarify what your question is. What (specifically) are you asking us to "prove"?

We all agree CX-5 internals are robust enough that they won't instantly and catastrophically fail due to tire circumference differences.
We all agree optimal function comes from matched tire sets.



I'm sorry but that's incorrect. I didn't claim any variation in tire circumference would disable DSC, I said it wouldn't function properly. You suggest it will have the same operation whether the tire circumference are matched or mismatched. It won't but you don't have to take my word for it, just check your owner's manual:



The factory service information for the CX-5 states the same thing even more definitively:



Note that it doesn't say tire size variation will disable DSC and ABS, it says they won't operate normally.

Do you want computers that have ultimate control of your throttle and brakes as you hurl down the highway at 70 mph to function abnormally? I guess if you live in the UK this is not considered a big deal?
Click to expand...
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. 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.

It's funny but Toyota always insist that shock absorbers be fitted in pairs but if they find one leaking that is all that they replace. Of course the best practice is to have reasonably matched tires but in real life, that won't always happen despite all the warnings you have quoted.

To summarise, I know what is best but I know what happens in real life.

Your old ancestors on the island might not have the money to send a shuttle into space but we tend to have at least some regard for road safety.
 
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