Tyre thread diff between axle in xdrive

[AdamsX5]

Merry Xmas to all.
Quick question I know it’s been answered before but search doesn’t get me results.
What is the tolerance between axles front to rear on a square setup on the E70.
I’ve just bought 2 new winter tyres and have 4 used ones.
Is it 2mm or 3mm across axles.
One same axle I will have zero diff.

[StuBeeDoo]

I read somewhere (more than likely on here) that it's a maximum of 1% of the rolling circumference of the tyres - which is why *marked tyres are important.

When I worked-out the figure for the (17") wheels on my F25 it came out as 3mm front-rear. I can post my workings-out, if it helps anyone.

[AdamsX5]

Yes I assumed it was 3mm.
My fronts will be 5mm and rears 8mm new.
Hope that will be ok as they are not staggered but square all round. They are not all star rated though as I assumed that was important in staggered setup.

[X5Sport]

3mm is the maximum permitted but you need to know the actual diameter of the tyre when inflated. It isn’t unknown for non-‘*’ marked tyres to increase their diameter when in motion and that could damage your transmission. It depends upon the manufacturer and tyre. Tread difference is important regardless of staggered or square as that affects the actual rolling diameter.

3mm is above the legal limit but your aquaplaning/wet performance will deteriorate. It’s one of the reasons that insurers ‘prefer’ tyres to have more meat on them. They can’t stop you using them of course. When I worked for the Police, all of our fleet had tyres replaced at 3mm for this reason.

[AdamsX5]

I’m currently on 6.5-7mm summers all round and plan to change winters in April again. However for winters I’ve got 4 used ones at 5mm and plan to put new ones at rear for better traction.

[Leslie]

If you have 4 with 5mm fit all 4 if you are still struggling the rest of the country will have ground to a halt in those conditions !

You can only go as far as the que in front ,if they block the road you are boxed in too .

I'd run them all year after the winter as below 4mm winters are far less effective due to the way they grip by the tread blocks flexing .

[X5Sport]

I’m currently on 6.5-7mm summers all round and plan to change winters in April again. However for winters I’ve got 4 used ones at 5mm and plan to put new ones at rear for better traction.

Your car is variable AWD so it will just shift the torque to the other axle in any event. Use all four wheels.