Just set up a friends 2015 SRW 1 ton... with the Kelderman 2-Stage Rear Air Suspension. (NOT the 4 link).
The 2-Stage does not add additional capacity... but it did transform night/day the ride of the truck when empty... rides better than most SUV's out there.
He ordered it bare steel and had the local shop clean-up welds and powdercoat to a really high standard... I have the same unit on my 2500HD... and the pow coat from Kelderman went bad in one year.
We both went with the upgraded compressor and added a tank so we have onboard air.
The Kelderman 4-link systems are the best riding/loading setups I've seen...they DO add capacity and also have amazing ride quality... but have a premium price over the 2-stage rear setups. The auto level system works very nicely.
http://kelderman.com/chevy_gm_gmc_silverado_2_stage_rear_air_suspension
https://kelderman.com/silverado_sierra_heavy_duty_4_link_rear_air_suspension_towing
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