Tier 4 tires are mostly unknown. Probably most of them should be put in Tier 5, but these need more research. The best you can say about them is that they don't have the reputation of being among the worst - because no one has ever heard of them. Some of these are underrated and deserve being rated higher. So I would avoid them unless you have heard something good about them.
Advance, Advanta, Airloc, Alliance, American Farmer, American Road Star, Americus, AMP, Apollo, Ardent, Arisun, Ascenso, ATF Tires, Atlas
BKT, Blackhawk
Cambridge, Castle Rock, Celimo, Centennial, Cosmo, Crop Max, Crossmax, Crosswind
Deestone, Delinte, Delta, Doral, Double Coin, Duramas, Duro, Durun, Dynatrac
Eurogrip, Evoluxx
Federal, Forceland, Forceum, Freedom Hauler, Freestar, Fullrun, Fullway, Fury, Fuzion
Galaxy, GBC, Giovanna, Gladiator, Goodtrip, Grand Spirit, Green Max, Greenball,Gremax, Grit Master, Groundspeed
Haida, Harvest King, Heritage, Hi-Run, HiFly
Iris, Ironhead, Ironman, ITP
JK Tyre
K9, Kanati, Kontio
Lancaster, Landgolden, Landsail, Landspider, Leao, Lexani, Lionhart
Master, Mastercraft, Matrax, Maxxis, Mesa, Mickey Thompson, Momo, Montreal, Mud Claw, Multi-Mile
NAMA, Nanco, National, NeoTerra, Nika
Ohtsu, Otani, OTR
Pantera, Paragon, Patriot, Performer, Petlas, Power King, Predator, PrimeX, Prometer
RBP, Road One, Roadmaster, RoadX, Rovelo, RubberMaster
Samson, Sceptor, Solar, Sotera, Starfire, Starmaxx, Sumitomo, Summit, Supercargo, Supermax, Suretrac
TBB, Tesche, Titan, Tornel, Tourador, Towstar,Trac Gard, Trail Guide, Trailer King, Trailer Master, TransEagle, Transmax, Transporter
Vantage, Vee Rubber, Velozza, Venezia, Venom Power, Vercelli, Versatyre, Vitour, Vizzoni
WDT, Wild Spirit, Wild Trail
Zeemax, Zeetex, Zenna, Zeta