Worn GR Yaris tyres.

[RSstuff]

I looked a nice 2022 car with 8.5k miles yesterday and it had almost new Michelins on the front, and what were probably original Michelins on the rear, and the rear tyres were down to 3-4mm. I remember Audi used to say on their cars with torsen quattro, running new tyres with old tyres could damage awd system, due to differing diameters. So I wondered if Toyota say the same, particularly when the Yaris is in 50-50 mode.

[Roono]

Hi.
You might find the tyres were recently changed, they tend to wear out the inner edges, so the old fronts also probably had 3-4mm but the inner edge wore too much.
The torsen diffs are for left to right torque distribution so the tires should not make a difference there.
Front to back axles are not mechanically locked together, there is a clutch pack which is constantly slipping (amount depends on torque setting).
So although the handbook might say it's not recommended running old and new tyres it's probably not as bad as if front to back axles were mechanically connected/locked and different rolling diameters of tyres would cause differentials to fight against each other.

[RSstuff]

Thanks for the reply. A dealer is selling the car and I probably would have bought it, if we could have come to an arrangement over the tyres. If it mentions tyres in the Toyota Handbook, I'd go with their recommendation, incase there was a warranty claim in the future.

[Roono]

In the handbook there is the following Warning:

When inspecting or replacing
tires
Observe the following precautions to
prevent accidents.
Failure to do so may cause damage
to parts of the drive train as well as
dangerous handling characteristics,
which may lead to an accident resulting in death or serious injury.
●Do not mix tires of different makes,
models or tread patterns.
Also, do not mix tires of remarkably
different treadwear.

[RSstuff]

Just what I was looking for. Thank you.