Yes didn't explain it properly I guess. I lose the grip on corners, steering feels light but not really understeer and that's not cornering hard either just normal driving speeds it feels a bit like driving on black ice, it's only on wet roads, grip is there in the dry.
First time I noticed was a couple of weeks ago on a gentle left hand bend doing about 40mph where in the past I could probably have taken it easily at 60+ but I wasn't in a hurry it was raining just enough for intermittent wipers so I put it down to the road surface being oily after a dry spell and I drove with care, roads were dry on the journey home and car handled normally so I thought no more about it.
Happened again, same roads the following week, ( I drive 25 miles to go trout fishing
) and I've been aware of it since but not had much rain until last week when we had some torrential downpours so Friday morning roads were quite wet so a lot of water near home where you would normally expext some aquaplaning but much better further on with roads just wet no running water and there was no grip.
When I got home I went straight back out in the wifes mini which has FWD and her front tyres are just under 5mm and it handled as it always does like a go cart. The BMW loaner we had was a top spec 320d RWD and it handled beautifully.
The reason I moved away from BMW to Audi was the former car handling in the wet and ice, my Audi quatros never felt short of grip and to date niether has my GLC in fact after the knuckle fix I posted that I didn't notice any difference in handling but I hadn't had a problem with skipping before that just wanted the fix done to future proof the car for when I change. I've been driving for a very
long time, had company cars changed every 2 years and covered hundreds of thousands of miles so not inexperienced.
I'm going to drive to the dealer on Monday or tuesday and ask them to check it out and in the meantime had emailed Vredestein UK to ask for an opinion.
Just as an aside to that the Mini was in for a service last week at 13400 miles, which is why I know what her tread depth is and they wanted me to buy 2 new front tyres
I gave them a firm no though will put some on before winter.