Galvanized rims on a trailer are an excellent and common choice due to their heavy-duty nature and ability to stand up to the elements. Since trailers can be subjected to anything, from mud when hauling equipment to a worksite to water when lowering a boat down a ramp, galvanized wheels will be sure to stand the test of time. The downside is that cleaning them can be more difficult than normal wheels, and considering the amount of grime your trailer rims are sure to pick up, you'll need a good cleaning regimen to keep them looking sharp.
Using a pressure washer or standard hose with water on full power, thoroughly spray down the rims. A pressure washer is ideal because chances are it will wash off a good deal of loose grime on its own; but if you don't already own one, there's no sense in spending extra money. A powerful garden hose will work just fine.
With the wheels thoroughly soaked, apply a liberal amount of brake cleaner to a shop rag and work it into the rims all over. Think of the pressure you use when applying wax to a car and mimic that in cleaning the wheel. You want to work the cleaner deep into the grime in a circular buffing motion and have the entire wheel deeply scrubbed with the cleaner before proceeding.
Holding the hose close to the wheel and working with a clean rag in your free hand, spray the wheel down completely. You want to wash away all the cleaner and dirt that it loosened up, but stop every once in a while and use the rag to wipe it away as well. The water itself won't wash off some of the stubborn dirt that the cleaner loosened, but using the rag in combination with the water will easily wipe most of it off.
Apply some dish soap to a rag and clean the wheel just as you did with the brake cleaner. This will remove any last bits of dirt as well as any leftover brake cleaner that could damage the galvanized material over time.
Before rinsing one last time, use a soft brush to dig deep into hard-to-reach areas such as around lug nuts or between spokes in the rim. This will loosen up any last bits of dirt that the brake cleaner couldn't reach.
Finish with a final rinse of water to remove the soap and any remaining dirt, and you should be left with a set of galvanized wheels that look as good as new and ready to take on the elements once again.
