Your boat trailer likely came with a safety feature you hope never gets used: a spare tire.
Like those on your car or truck, your trailer’s tires are at the mercy of whatever road hazard might be present, such as nails, screws, scrap metal and the like. While most of us only subject our trailers to a fraction of the miles we do our vehicles, the spare tire on your trailer is just as important as the one on your car or truck.
In fact, many would argue that trailer tires are more prone to a flat than the typical vehicle tire for several reasons. Number one, at highway speeds your tow vehicle’s rear tires can kick up debris that can be launched at and imbedded into your trailer tires. Secondly, tires that sit in one spot, supporting a weight, are much more prone to dry rot, cracking and sun damage than tires that get used more often. The list goes on, but no matter the reason for a flat, if it happens, you’re not going anywhere without a good spare and the means to change it.
To be prepared for the possibility of a flat, you’ll need to check the air pressure on your spare every time you check your in-use tires – at least several times a season and before any longer-than-average trip. Once a year you should do a little more maintenance as described in this Mercury Quick Tip Video. This task requires only a few items that should already be in your mobile toolbox and perhaps 20 to 30 minutes of your time. If handled at the beginning of boating season, this minimal investment of time and effort could save you a major headache on a roadside someday.
To do the job, get out an appropriately sized lug wrench or ratchet wrench with socket, a tire pressure gauge and wire brush, as well as spray cans of lubricant/rust inhibitor and tire cleaner.
Then follow these steps, as demonstrated in the video:
- Remove your spare tire cover. If you don’t have one, get one. They’re inexpensive, and they’ll extend the life of your spare and help keep the lug nuts from seizing.
- Using the lug wrench or ratchet and socket, remove the lug nuts and set the tire on the ground.
- Use the wire brush to clean the threads of your lug bolts and the bolts on the spare tire bracket, as well as the mating surface where the bracket meets the spare tire rim.
- Loose bracket nuts should be tightened.
- Spray the lug bolt threads and bracket bolt threads liberally with lubricant/rust inhibitor, and put a light coat on the mating surface where the bracket meets the rim. While you’re at it, spray a little inside the lug nuts as well.
- Clean the inside of the rim – where it meets the hub or spare tire bracket – with a quick pass of the wire brush and a little lubricant/rust inhibitor.
- Check the tire pressure and add air if needed. The correct operating pressure is usually listed on a tire-and-load sticker somewhere on the trailer. It’s also available in the owner’s manual. Don’t forget to replace the valve stem cap when finished. If the pressure is very low it could mean you have a slow leak, and you should take it to a tire shop to be fixed.
- Clean the tire using a commercial cleaner made especially for tires. This will not only make the tire look better, but it will help keep your spare from drying out and cracking.
- While cleaning, inspect your tire thoroughly for potential problems such as cracks, wear and unusual bulges. A tire that shows such signs of decay should be replaced immediately.
- Reinstall the spare on its bracket and snug up the lug nuts. They don’t need to be torqued down as tight as on a running tire, but good and firm so the lug nuts can’t vibrate loose. Pro tip: If your spare tire bracket has only two or three lug bolts, as most do, rotate which holes in the rim you use. Doing so will help keep corrosion from forming in any one spot on the rim.
- Replace the tire cover.
NOTE: For safe operation, always follow the trailer manufacturer’s recommended tire pressure and tire size guidelines.
It should go without saying that you should never tow a trailer without a serviceable spare and appropriate jack and lug wrench on board. If your boat trailer doesn’t have a spare and a mounting bracket, you can buy these items, as well as a lug wrench and trailer-specific jack, quite reasonably at any Mercury Marine Authorized Dealer or most other marine retailers.