MT21 front TKC 80 Rear works for me everytime
had this combo on Xt660R X2, Xt660Z X2, 800GS,s X3 the TKC is good but allows the rear to be used to steer the bike ie sliding the bike out when you want to and the MT21 grips like ****e to a blanket offroad

dry tarmac both very good
Wet Tarmac and the front can feel a little un nerving good compromise if your not going mud plucking and want goot wet road grip go with the TKC 80s its a trade off

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My 5th XT660R Mods so far, K+N, Kev Mod, Yamaha Hand guards, Engine bars, Yam Sump guard, Yam Rack, Heated Grips, MT21s, Raised rear XTX dogbones, Front Raised with spacers, Extended Side Stand, Yam Touring Screen, Carbon fibre heel guards, CNC Short Levers, Snorkle Removed, 100W headlight bulbs, Rear pannier rack as rear crash bar CCC oval Cans, Zumo 660 +++