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...  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,...  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...  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 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,...  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...  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. |
 Once the pump and electronics...  Once the pump and electronics checked out, the next step was to remove the shock plate... |  ...and the two horizontally...  ...and the two horizontally mounted Softail-style shocks from beneath the bike. |  Once the OEM shocks were removed,...  Once the OEM shocks were removed, the air shock was installed into the left side of the bike. |
 Then the hydraulic shock was...  Then the hydraulic shock was bolted up to the right side. An added safety feature of this system is that if for some reason the air pump loses power or an air line gets cut from road debris, the hydraulic shock will keep the bike raised enough so the fender can't rub on the tire. At the very least, it will get you home while saving your paintwork. |  At this point it was time...  At this point it was time to hook up the air line from the compressor to the air shock and the line for the pressure gauge. |  The oil-filled pressure gauge...  The oil-filled pressure gauge was fitted to the right rear rocker-box cover with the provided longer bolt and adjusted for optimum visibility. BDM suggests typical running pressures of 90-120 psi without the rider aboard. Total ride-height adjustment of the air system was 1-1/2 inches with a nice plush ride. |