I put four new Wranglers on 17" wheels just over 20k miles ago. They are now down around 4mm at the rear and 4.5 at the front and all of a sudden, on some road surfaces, I am starting to hear noises from the rear like wheel bearings going. I will probably move the car on in less than a year so don't really want to spend £450+ for someone else's benefit. 3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE

My tyres are now nearing 4mm and I am sure that they are starting to get noisier on the rougher grained road surfaces. I noticed it today on some middling to minor roads. Background vibration is apparent on some surfaces.
It is road noise as it dies away on the smoother surfaces.
The wear pattern of the treads appear normal, so if it continues to get worse, I will wait until autumn before thinking of changing the 4 tyres. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 76k+ miles) (MY2015)