How do I set the air pressure in my shocks?

My owners manual has a chart showing a general guideline for air pressure in my rear shocks but I can't make heads or tales of what it means, what pressure (if any) should I use?

This is another of those very subjective settings that is mostly dependent on the kind of riding you do, where you do it and the load the bike is carrying. The stock Nomad (1500) and 1500 Classic FI shock not only has an air pressure adjustment but also numbers that can be set by turning the upper shock cover. Those numbers set the 'rebound' of the shock, the speed the suspension is allowed to extend.; The 'pressure' setting (being discussed here) controls the 'compression' of the shock or speed of upward movement. The idea is to balance the two so the back tire is always on the ground no matter what conditions you're riding in. If the tire is in the air you have no traction and that is a bad thing.

So, about the pressure.

The most important thing is what you fill the shock with. Never, Never, Never use a gas station air hose. There is potentially far too much pressure for the shocks to handle. The air cylinders in these shocks are very small and only require a few pumps from a bicycle pump designed for air shocks (not tires) or something like the specially made pump sold by Progressive Suspension. The bike shock pumps are available at most bicycle stores, the Progressive pumps online or at almost all Harley Davidson stores if you can't get one from your dealer. Try to find a pump with a 0-60 psi readout on the gauge. Higher scales (some go to 300 pounds) mean much finer markings making it a lot harder to set both shocks at exactly the same pressure.

These pumps come with a "zero loss" fitting so no pressure is released from the shocks once you've gotten them to the desired pressure. In addition if you use anything but a zero loss type fitting on the shock you will probably release some or all of the air you just added. The slightest "pfft" and the 25 pounds you thought you had added are gone. Zero loss pumps also feature a gauge for getting the exact pressure you want. Both shocks should have exactly the same pressure. Adding the Progressive air shock balance kit to your Nomad or Classic will help. Details are on this Gadget page. Your dealer will probably have one of these pumps. If you're on good terms maybe they'll let you borrow it for a couple of hours.

And what pressure? The good news is you need to go for a ride (take the pump with you). Ride the roads you normally enjoy traveling on. Are they billiard board smooth? You'll need little or maybe zero pressure. Got dips? You'll need a bit more. Got potholes? A lot more. Speed bumps are the worst. If any of these things cause your bike to bottom out at speeds you'd normally hit them at, put in some air. If you generally ride two up be sure and do this test with your passenger. When the bike doesn't bottom out any more under the most severe test you expect to give it you've found your pressure. Remember if you're on a trip carrying more than the normal amount of gear you might need to add a couple of pounds. Never exceed the manufacturers suggested 43 pound maximum.