I’ve been using the Rocket Rons that came on my Spark and they seem ok.
Don’t seem to roll that fast but fairly grippy. They are useless in the mud though when they seem to clog up really easily. If I was going to keep them I would go for a Racing Ralph on the back, but I’m after a pair of X-kings after my friend reccomended them.
Did buy a pair of Bonty Mud-X 1.8’s and really liked them. Used them when it was soft a month ago and they seem to grip really well and roll quite quick. Not sure how well they would cope on really rocky stuff and I managed to snake bite the rear on a kerb running it at 35psi. Want to get a set of new wheels and run them tubeless on them for winter.