4WD with mismatched tyres
Discussion
Just starting to ponder changing the car to something with permanent 4wd like a Subaru Outback which seems to tick a lot of my boxes.
Looking at autotrader, I’m seeing such cars with mis matched tyres when I’ve always believed that different tyres on the same axle of a 4WD was a big no no and preferably all the tyres should be same and rotated now and then to maximise their life.
Is this still correct as I’m seeing main dealer cars with odd tyres and whilst I can easily change them, would any damage be done by running for some time on odd tyres?
Or am I being a bit paranoid?
Looking at autotrader, I’m seeing such cars with mis matched tyres when I’ve always believed that different tyres on the same axle of a 4WD was a big no no and preferably all the tyres should be same and rotated now and then to maximise their life.
Is this still correct as I’m seeing main dealer cars with odd tyres and whilst I can easily change them, would any damage be done by running for some time on odd tyres?
Or am I being a bit paranoid?
I was always led to believe that Subarus, which all have permanent mechanical AWD, can be particularly sensitive to tyre wear.
So in my experience, and I’ve had 6, I always changed all 4 tyres at the same time, kept all four to the same brand/size, and rotated front-to-back at every service. In 15 years of ownership I never had a problem with transmission/drivetrain, or with tyre wear. Anecdotal I know, but it’s why we’re on this forum!
If I was looking at a Subaru with mismatched tyres, or tyres with different wear rates across the same axle, it would put some doubt in my mind, depending on age and condition of the car.
So in my experience, and I’ve had 6, I always changed all 4 tyres at the same time, kept all four to the same brand/size, and rotated front-to-back at every service. In 15 years of ownership I never had a problem with transmission/drivetrain, or with tyre wear. Anecdotal I know, but it’s why we’re on this forum!
If I was looking at a Subaru with mismatched tyres, or tyres with different wear rates across the same axle, it would put some doubt in my mind, depending on age and condition of the car.
On a true 4x4 the issue with mismatched tyre sizes is that the centre differential bevel gears are constantly moving due to the difference in rolling radiuses. In extreme cases this can cause them to wear/seize. Same reason a 4x4 shouldn't be put on the brake rollers during MOT.
On a Haldex AWD vehicle mismatched tyres aren't an issue as the drivetrain only becomes 'locked' when the system detects slippage.
On a Haldex AWD vehicle mismatched tyres aren't an issue as the drivetrain only becomes 'locked' when the system detects slippage.
As above, have run Subarus for some 10 years and Toyota 4x4's for many more years, i rotate periodically and always replace in full sets (if i got a wrecked tyre would try and find a suitable part worn) and have never bought one with anything other than a full set of identical tyres, seeing mix n match all sorts on a potential buy would put me off buying, always try and zoom in on pics to view wheel/tyres/brakes before bothering to travel.
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