Change tyres in pairs or not?

[Orionaut]

Tyres are an unusual class of wear item.

Most wear items will perform well right up to the point that reach end of life (Or shortly before)

Tyre performance begins to decline from the moment they start being used.
.
The replacement point has therefore to be a compromise between declining performance and getting good use from the product.

A 3mm limit will significantly increase the "Turnaround" for tyres. Not only does this risk massively increasing the number of scrap tyres that will need to be disposed of each year (Already a major problem)

But it also risks the "Unintended consequence" of driving people towards cheaper. poorer quality (Or harder wearing, which even with good tread, will still take longer to stop) tyres in order to mitigate the greater costs associated with reduced tyre life.

The downsides of this could very easily indeed massively out weight the limited safety benefits from having deeper tread in wet conditions.

 

[Pulsedriver]

Don't forget that being a RWD BMW, you most likely have wider tyres on the rear so you won't be able to swap back to front like you would a normal car.

This... I just realised that after posting, the rears are a different size damn it!

 

[Vanquish-Storm]

I'm actually amazed if that's representative across other tyre brands that the legal limit hasn't been bumped up to 3mm. I guess the one major factor comes down to speed, i suspect (having not watched the video), that these tests were at high speed. At lower speeds say 30mph, the difference will probably be much less.

However, seeing as we'd have no way of stopping people driving on 60/70mph roads without checking they have at least 3mm of tyre tread, i wouldn't mind that limit being raised to 3mm.

It's not:

http://www.consumerreports.org/cro/...at-doesn-t-give-up-grip-as-it-wears/index.htm

 

[theone8181]

It's not:

http://www.consumerreports.org/cro/...at-doesn-t-give-up-grip-as-it-wears/index.htm

That link shows that with less tread depth the stopping distance in larger in the wet (as you would expect) which is my main reason for changing at 3mm or so. That test was performed with about 4mm of tread.

Edit sorry i missread it, typically a tyre takes longer to stop as it cant clear the water away. Seems suspicious that this tyre performs differently to pretty much every other tyre.

 

[Psycho Sonny]

I think a lot of people overthink this.

I was told you must not use runflats with normal tyres, etc. Then others suggested so long as it's not on the same axle your fine. I bought a car with runflats on the front and normal on the back and it's been fine for a year now.

I would get alignment done first and foremost. That is what will cause uneven wear. Try and get it done from a specialist using the diamond tracking stuff.

Then just replace tyres as necessary. If your feeling flush then sure change the same axle at the same time. If you need to ask however then I wouldn't say it's 100% necessary.

Drive safely and you shouldn't have any issues.