I used PS4 and PS4S. Both 18 and 19 respectively since 2-3 years ago.

But now no more. Changing to a more practical one.

For me, PS4 or PS4S only required if you really doing track or tougue. If not, its pretty useless, and the tire itself not that realible due to chopping issue.

Now just using MaxContact 18". Lesser grip just a little bit during raining, but more than satisfactory.