Towing a ~6500lb trailer (with new good quality trailer brakes) from Ouray Colorado to Durango Colorado really changed my mind on the Grenadier's brakes (at least with the petrol engine and its poor engine braking). Despite me going much slower than the speed limit, not riding the brakes, keeping engine braking at ~5,000 rpm, and making sure the trailer brakes were carrying their share of the load, the brake fade was so bad that I had to take multiple breaks to let the brakes cool. The last time I pulled into a stop it took me about 200 meters to stop from 35 mph and most of that braking came from the trailer.
I have the Agile Big Brake Kit installed now but haven't actually towed with them yet. Around town though, they just feel so much more responsive. Better braking with faster response and better pedal feel.
The two piston front brakes and one piston rear are just not adequate for the towing loads the Grenadier is rated at. Sadly, it is only a matter of time until someone learns this the hard way.
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EDIT - All that being said, I wish someone would create a brake kit for the rear axle that maintains use of the handbrake.