You experts have explained here that in AWD systems the tire sizes need to be closely matched (i.e., might have to shave the new tire when replacing a single) to avoid damage to drive train mechanism.
I have never heard about this for 2WD – front or rear – and I’m wondering if it applies.
(Yes, I had to get some new tires for the Camry today. But this question was not part of the issue. I’m just curious.)
No, it doesn’t normally apply to anything aside from all-wheel drive. Everything in an AWD system needs to be rotating at the same speed, but 2WD/4WD systems don’t really have that problem. The only stipulation is that you don’t want to operate 4WD on dry pavement regardless of tire sizes, because that will eventually wear out components.
If it’s on the drive axle, they should be the same size, though unless it’s a car with a limited-slip differential you don’t need to be too worried about the tread wear difference. If you’re talking about the two non-driven tires, they’re just along for the ride so they don’t really need to match at all, although it might lead to unpredictable handling if they’re too far off.
Drag racers use oversized tires on the rear for better traction on the drive wheels. They save weight by using smaller ones on the front.
Tire dealers will sometimes have three matching tires and will put two (let’s say) 175’s on opposite corners like left front and right rear. To keep equal weight on all four, they will put a 185 on the right front and a 165 on the left rear. They can only do it on 2WD vehicles if there isn’t a limited slip or posi differential. They can’t do it on AWD and shouldn’t do it on 4WD. It shouldn’t be done at all but they can get away with it on many cars.
It is not the same for 2WD. On a 2WD you would want the two tyres on the drive wheels close for the same reason, but it is not as big an issue as 4WD or AWD. However there is also an issue with front to back matching. Having tyres that don’t match reasonable close (like those who use oversize and over wide tyres on the back (I guess that would be on the front for most of today’s cars) is also not a good idea as it can effect handling and could cause you to loose control in a emergency situation.
No, No, No, No, No!!!
The load carrying capacity of a 165 is different than a 185 and the tire is going to react differently depending on how much of the load carrying capacity is being used. Any reliable tire dealer will put 4 of the same size on the car (same design, too!) Any tire dealer that does something different than that should be avoided at all costs.
It’s best to have 4 of the same tire on the vehicle - that’s the way the vehicle engineers designed the vehicle. If you put different sizes on, the vehicle may not behave predictably, and you might not know this until you do an emergency manuever - just when you need the vehicle to be the most predictable it can be.
So while there aren’t any broken trannies when using different tire sizes on a 2WD, it’s still a good idea for handling reasons. (Exception: If the vehicle came from the factory with a “staggered” fitment - or you are specially modifying the vehicle and intend to test that arrangment.)
Thanks, all, for the info. I had negelcted to mention that I was talking about same size for the two driven wheels, concerned about strain on the differential or whatever it is that lets them turn a different speeds.
If you have a limited slip differential installing a new tire on the same axle can damage the differential. This was the more likely case of that Subaru posted about before as nearly all Outbacks and upper model Subaru’s have a limited slip rear differential. Basically different size means slippage and constant slippage means you are constantly shearing the fluid and heating it up eventually burning it up. This is true of ANY vehicle with limited slip.
The poster who complained about the differential did not realize that 50 miles is not emergency nor temporary. A spare is intended to get you to the next service station NOT clear across a smaller state.
So do some stock performance cars.
While it won’t damage the car, it will affect handling. On a Camry you’re better to stick with one size all thw way around.
The true answer can be found in your owner’s manual. Some 2WD cars warn you that if you have the small spare mounted as a drive tire, you should not exceed 45 MPH. If I was mounting a donut spare on a front wheel drive vehicle like yours, and I was planing on driving anywhere except a tire store or repair shop, I would probably move tires around so the donut spare is on the rear axle.
No doubt. Very true.