Automobile owners who are diligent with maintenance on their cars schedule annual checks at tire specialty stores to check the alignment of their tires. Doing so extends the life of their tires, makes the cars handle better and improves fuel economy. The same thing can be said for the tires on a boat trailer, though the trained professionals at most tire specialty stores don’t know any more about aligning the tires on a trailer than you do. So do it yourself.
1. Leave the boat on the trailer and park the trailer on a straight and level paved area.
2. Check for “tow-in/tow-out” to make sure the tires are exactly parallel. On the inside front of one of the tires, mark a spot at the outer edge of the wheel rim halfway up the rim (bottom to top). Measure the distance of that mark to the surface of the pavement. Use that measurement to make another mark on the rim at the back of that tire and on the front and rear of the rim of the tire on the other side.
3. Measure the distance between the front of the rims on each side of trailer at the marks you’ve made. Measure the distance between the marks on the rims at the rear.
4. Compare the measurements. Identical measurements are preferred; for most applications, measurements within 1/8 inch are acceptable.
1. Consider removing the boat from the trailer at this time. Making adjustments will be easier if the boat isn’t in the way. There are no built-in adjustments on boat trailer axles. The axle will need to be bent to align the tires.
2. Determine which way the axle will need to bend to bring the wheels into alignment.
3. Think of an archery bow, where the axle is the bow and the chain is the bow string. Securely fasten a 5/16-inch or larger chain to each end of the axle, loose enough to allow a jack to be inserted between the chain and axle. Insert the jack parallel with the ground, either ahead of or behind the axle (depending on which way the axle needs to be bent). Position a stout block of wood between bottom of the jack and the axle to spread the force over a larger part of the axle.
4. Lever the jack until the chain comes tight, then continue jacking until the axle begins to flex.
5. Measure the front and back of the tire rims to determine when the wheels are parallel. Chances are, the axle will spring back slightly when the pressure of the jack is relieved. To compensate, you will have to over-tighten slightly and then let the axle flex back. Continue the process until the measurements between the front and back of the wheel rims are identical.
Items you will need
- Tape measure
- Hydraulic jack
- Wood blocks
- A helper to hold the end of the tape measure and assist in inserting the jack will make the job go much easier.
- Alignment is only one factor which could affect tire wear. A broken spring, improper tire inflation, incorrect tongue weight on trailer, bent rim, unbalanced tires or mismatched tires can also wear tires unevenly.
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