X04 means hard, they go up to X14 which is super soft for use as a wet, 4's and 6's are best for track/£. You can get maxisports which are better than a road tyre, just, and last forever!X14's on the strip wouldn't last, but would stick mega, Demon Tweeks also sell a tyre softening brush on liquid, but I've never used it so can't say if it works or not?