I suppose I could seal them in with silicon ![Lips sealed :-X](https://clubjazz.org/forum/Smileys/SoLoSMiLeYS1/lipsrsealed.gif)
When I eventually fitted my wifes Nokian winter tyres a couple of weeks ago I use some good quality silicon 'engineering' sealant (gasket grade - which I already had) to hold in the 47mm front wheel grease caps and they hold in just fine, surprisingly the rear hubs already had ' knock in' grease caps fitted - so best to check both ends of the car.
Checked out the level of grip with Nokians on a frosty road yesterday and braked hard, ABS only cut in a couple of times and car came to a halt in record time - wheels didn't spin when pulling away either. I tried the same in my Civic with Michelin ES summers on and it was a different story altogether.