Question about replacing tyres
 

I just replaced the two front tyres with new ones.
The fronts had worn down way more than the rears.

I left the rears because they still have some tread and I wasn't planning any major off road trips until late Jan 2019.
There was also some money/cost considerations with getting all the tyres replaced.
I was hoping the rears could last until the new year, when I intend to replace them before my trip.

I was talking to a friend who is a mechanic, and he said that tyres on AWD drive cars should ALL be replaced at the same time.

He said that having new fronts & worn rears means that the wheels are rotating at different speeds all the time.
This puts more stress on the transmission and can result in premature wearing of diffs etc.

Anyone here got any opinion, or experience, with this?

I have known people who have switched out one or two tires and have driven with "no problems" - however I would think it really can't be good for your drivetrain. It may not grenade out your TC but it will cause some stress as everything fluctuates due to different wheel spin rates. Also not sure but couldn't an AWD notice two wheels were spinning faster and go into 4W lock?

Personally I would replace all of them. I know tires are expensive but it is just one of those things that may never affect you - or it may bite you hard. January isn't far off, so you *should* be fine.

In the future it may be worth rotating your tires more often to get the wear to be consistent. Front ones will sometimes wear faster with AWD.

The "damage from uneven tyre wear" business is in the same category as using Nitrogen to inflate tyres - nice idea and theory but in reality is basically nonsense.

The whole point of "differentials" is to enable different wheels on the vehicle to rotate at different speeds - and there will be MUCH more variation being caused by any curves in the road (prolly even wandering within the lane!), the road surface itself - and even small differences between the pressures in all 4 tyres - than any effect from tyre wear.

You should definitely not use different types of tyres on the same vehicle unless its unavoidable and only for a short while, but differing wear isn't an issue in real life terms.

If you're anything like most people you have lots of things in your life that cause you stress - this shouldn't be one of them - it's not a problem so relax :-)