BMW 840 tyres

[thebullettrain]

The car is a 840d.

Two MOT advisories being a bulge in a rear tyre and a front tyre with a low thread.

Does this mean that I need to replace all four (having to replace both axels with it being a 4 x 4)?

I’ve currently Bridgestone Potenza runflats, any suggestions on whether to stick or switch?

I may update this if any questions come in.

[texaxile]

As a rule I've always swapped 4 out at a time on a 4WD or AWD car, as having different tread depths can cause issues with the system.

If the 2 "good" tyres are of similar tread depth then you may get away with moving them to the same axle and putting 2 new ones on the other axle, but on a great car like an 840 I'd be tempted to swap all 4 to new and then prevent any longer term issues potentially caused by having the different depths across the platform.

I'm sure there will be someone with more knowledge than myself to answer. Again, regarding the Potenza, they're a damn good tyre and I'd see no reason to move away from manufacturers spec, but maybe a post in the BMW sub forum might yield a better response.

[Bobupndown]

In an ideal scenario yes, but how much tread remains on the two tyres which aren't in need of replacement?
If they are nearly new then I'd not be concerned but if they are well worn the difference in tread might potentially cause issues.

[Regbuser]

thebullettrain said:

The car is a 840d.

I’ve currently Bridgestone Potenza runflats, any suggestions on whether to stick or switch?

840i owner here, the car sits on the potenza, but non-runflat; much softer ride.