Rear suspension on a motorcycle is a subjective experience. That is, the "best" shocks for a 300-pound buddy aren't likely to meet the demands of your 105-pound girlfriend. Or what about the difference in feel between riding solo around town and packed to the hilt for a weeklong trip? Other than swapping out your shocks to meet your changing riding demands, another way to go is with an adjustable air-ride suspension system that allows the air pressure to be varied to suit specific riding conditions.
To satisfy each of the various editors here at HOT BIKE, we contacted Big Dog Motorcycles (BDM) about suspension possibilities for the '06 Mastiff that'll reside in our stable for the next year. BDM's kit (part No. 133-000020-00) includes shocks, compressor, air-pressure gauge, air line, bracket, and all mounting hardware. Big Dog did its homework on this system by having the wires and controls for the air ride already engineered into the stock wiring harness.
We took the Mastiff down to V-Twin City in Santa Ana, CA, and had Dave Donato take us through the install.
Opening up the box from BDM we found (clockwise from top) the compressor bracket, air compressor, standard hydraulic shock, air shock, nylon tubing, and air-pressure gauge. | 
After the seat was taken off, the motorcycle was tied down to the bike lift and the battery removed. | 
The wires we would need to power up and operate the air pump were already in place in the wiring harness-cleanly zip-tied together, ready to be used. |
The compressor bracket with the air compressor attached bolts up to the right side of the battery box. This configuration places the air compressor neatly between the top of the starter and the bottom of the battery box. | 
Before going any further, Dave reattached the battery to ensure that the air pump was operating. BDM built a nifty mechanism into its factory-equipped electronics that uses the existing handlebar buttons to engage and disengage the air pump. | 
To activate the pump, the key switch was turned on. Then the air-ride system was activated by pressing the start button. Once activated, the Hi/Lo switch on the left-hand control either pressurizes or depressurizes the system. |