Worried that I'm damaging my AWD Infinti

[OhioMazda]

Hi, All-

I own a 2008 Infiniti M35X AWD sedan with about 125k miles that is driven by my wife. In 2016, I had a set of Kumho Solus TA71 tires in the standard size of 245/45R18 from Tire Rack installed.

Last May, the two rear tires had non-repairable punctures, and my wife took the car to a local retailer, who replaced the two rear tires with Firestone Firehawks in the same size. It rubbed me the wrong way at the time not to have matching tires, but the shop did not have matching Kumhos in stock.

I just came across this video, which advises against mismatched tires on the front and rear axles of an AWD car.

John Cadogan on YouTube

The car drives fine, with no mechanical failures yet. Should I just go with the hand I've been dealt, or buy a new set of four identical tires?

 

[skyactiv]

Here's the deal, many a Subaru owner messed up their center diff by having mismatched tires and didn't know it until their car had lousy traction in the snow because the vehicle was now front or rear wheel drive, depending on the mood.

 

[tnt31]

The only AWD vehicle I had (Saturn Relay) the owners manual said to always change all four tires due to the AWD. It had a matched set on it then I put a new set all the way around (Kumho TA11s) but then got rid of that piece of junk about a year later. Wish I had not put the new tires on it.

 

[maxdustington]

I'm not sure if shaving them would be an option because they are different tires. I'm shocked that shop missed the opportunity to replace two good tires with a full set on an AWD car, electing to just replace the two.

 

[OVERKILL]

As long as the tires are the same diameter, you'll be fine. Did you look up both tires to compare how close they are new?

 

[krzyss]

What does the manual say?

KrzyÅ›

 

[Andrew1972]

Be more objective on it.

Measure the circumference(distance around the entire tire) or rolling distance of each wheel and compare. Subaru does not recommend more then 1/4" difference between front/back I think Audi is more 1/2". My Subaru expert says 1" breaks the internals of Subie AWD.

 

[SwampSurvivor]

It also depends on how the AWD system works. If it is just FWD and kicks in the rear as needed, you'll be fine.

 

[Eddie]

The 1/4 inch (0.250), is the normal maximum circumference recommended. I'd measure the tires and decide on which way to go. Put a highly viable mark on the tire next to the ground and mark the ground. Roll the car so the tire rotates one full turn and measure the distance. Do the same for from and rear to determine the delta D. Ed

 

[Virtus_Probi]

Originally Posted by Miller88
It also depends on how the AWD system works. If it is just FWD and kicks in the rear as needed, you'll be fine.

I would tend to agree with this, my old RAV6 seemed to just send power to the rear when the front tires slipped...which made for some interesting moments turning on ice. WHOOSH here comes the back end!
It did have an electronic "4WD" that only worked under 25mph when I hit a special button, maybe that could have had issues with different tires sizes?? At least it was only low speed.

 

[Astro14]

If the AWD system uses a viscous coupling - then that diameter difference will be important, because you'll be turning the viscous coupling constantly and potentially wear it out.

But, I think your Infiniti is going to be OK.

From what I've found, you've got an electronic system that only engages with slip.

I would still like to know what the owner's manual says, but this is your system:

https://en.wikipedia.org/wiki/ATTESA

And the ATTESA E-TS is what they say is in your car...

 

[MoneyJohn]

I don't know how your AWD system works but if you are worried, you can get these new tires shaved. I replaced one tire of my Forester and got it shaved.

 

[GZRider]

You should be fine with ATESSA, as long as they are matched side to side. Check out the G37 owners forum website to be sure. They have a lot of very good info on tires and wheels (along with other things Infinti) stickied there and a tire and rim size calculator for staggered setups. Good luck.

 

[DzoG20]

Originally Posted by madRiver
Be more objective on it.

Measure the circumference(distance around the entire tire) or rolling distance of each wheel and compare. Subaru does not recommend more then 1/4" difference between front/back I think Audi is more 1/2". My Subaru expert says 1" breaks the internals of Subie AWD.


1'' difference in the circumference to brake the AWD internals looks scary - that is 5/32 difference in the tire tread.
It could be also sensitive how closely one monitors the tire's pressure

 

[benjy]

there are MANY variations of AWD systems + most only activate the rear as needed + run in FWD mode for meeting EPA mileage standards. 4 real snow tires-winter tires will do as good or better than most AWD cars using all season but winter tires IMO. i regularly passed struggling AWD + 4 WD vehicles in my 2001 Jetta with snow tires in some rough Pa winters, guys on the job with their gas guzzling 4 wheel tanks-trucks could not believe how well my little car went.

 

[Cujet]

Even the viscous systems will tolerate a typical tire mismatch. The spare tires on many AWD vehicles with viscous couplings is often not the same diameter. The amount of "slip" the coupling has to endure is very minor.

 

[PeterPolyol]

Seems like a fully clutch-based torque delivery system anyway, so that clutch is always slipping at any command lower than 50%, regardless. In this case if the TCS is happy with the wheel speeds then it's probably fine

 

[krzyss]

Originally Posted by Cujet
Even the viscous systems will tolerate a typical tire mismatch. The spare tires on many AWD vehicles with viscous couplings is often not the same diameter. The amount of "slip" the coupling has to endure is very minor.


They are called temporary spares for a reason. I think the limit is 100 miles.
So you can drive mismatched tires for 100 miles and then cool the system ;-)

KrzyÅ›

 

[UG_Passat]

Originally Posted by benjy
there are MANY variations of AWD systems + most only activate the rear as needed + run in FWD mode for meeting EPA mileage standards. 4 real snow tires-winter tires will do as good or better than most AWD cars using all season but winter tires IMO. i regularly passed struggling AWD + 4 WD vehicles in my 2001 Jetta with snow tires in some rough Pa winters, guys on the job with their gas guzzling 4 wheel tanks-trucks could not believe how well my little car went.


This topic is about Infiniti, before their AWD systems got infected by Mercedes-Benz, which is RWD until the front wheels are needed.

 

[sxg6]

Originally Posted by skyactiv
Here's the deal, many a Subaru owner messed up their center diff by having mismatched tires and didn't know it until their car had lousy traction in the snow because the vehicle was now front or rear wheel drive, depending on the mood.


I'm surprised that they didn't know it, the steering will bind when turning with tires that are mismatched enough to make the diff unhappy.

I've always been careful about running tires within 2/32" of each other on my Subaru, but my center different still went bad at around 200k. When my transmission was warm, I'd get a loud clicking noise when turning at lower speeds. Wasn't the cv axles either, was very much temperature dependent, new center diff fixed the problem.