Bald Tire Pattern
Boatcraft Q&A
by David G. Brown
July 1, 2007
Q: We trailer our boat quite a bit. While getting ready for this summer, I noticed one of
my trailer tires is badly worn on the outside edges, but the center of the tread is fine. I have a
tandem-axle trailer with four tires. Why has this happened to just one tire?
- Jim Simpson, Maquoketa, IA
A: Tread wear on the edges of a tire is a good indication of under-inflation. Most likely,
this tire has been running slightly soft, causing that wear pattern. If the tread had been worn
down the center but not on the edges, over-inflation would have been the first thing to suspect.
The wear on the edge indicates a slow leak that has allowed this tire to run "soft" for some time.
It probably didn't catch your attention because the other tire on that side of the trailer picked
up the load.
Have a tire shop pull the wheel off, and check the wheel and tire for a slow air leak. There
doesn't have to be a nail in the tire to cause problems. Edge bead leaks around the rim of
the tire aren't uncommon. Also, the valve and valve stem are often to blame.
Having a professional check your tire will yield another benefit. Under-inflation can damage
or destroy a tire through heat buildup as the wheel rolls down the highway. Running a tire at just
20 percent under its rated pressure can begin to break down the internal construction. A tire with
signs of damage such as a bulge in the sidewall should be replaced.
Remember, tire
pressure should be checked "cold." This means in the morning, before you start rolling down the
road. Even a properly inflated tire gets warm in use, and that heat causes the pressure inside to
rise slightly. The rule of thumb is that tire pressure rises 1 pound for every 10-degree increase
in ambient temperature. Checking pressure and filling any low tires before every trip is a good
practice. All tires leak a little air over time, usually a pound or two per month.
The amount of pressure in the tire is determined by the tire and the total load (boat plus
the trailer) that it carries. Look on the tongue of your trailer for a plate that lists the
manufacturer's tirepressure recommendations. The tire will also be stamped with its maximum safe
pressure.
Trailer axles do get out of alignment. It can happen if the wheel strikes the side of a deep
pothole or if the wheel is dragged across a high curb. "Feathering," or other unusual tread wear,
is a typical sign of an alignment problem. As with under-inflation, misalignment causes tires to
run hot.
Don't be fooled by tires that have nearly new tread. Although trailer tires are designed for
long periods without moving (like winter storage of your boat), they deteriorate over time, even
when they aren't rolling. Manufacturers say that tires more than five years old should be replaced,
especially if the side walls are showing signs of cracking.
Q: What's the deal with bulbs for boat lights? The cabin light burned out in my boat, and I
couldn't find a replacement anywhere, except at a boat store, where it was twice the cost of other
bulbs. Why would it cost so much? The bulbs in my car face winter salt and lots of vibration, so it
can't be the "marine environment."
- Phil Ridgman, Hoffman Estates, IL
A: The truth is that marine lights are manufactured in factories all over the world. Often,
the manufacturer chooses a bulb that's commonly available in that country but isn't common in North
America. So, you have to pay a premium for the importation of replacement bulbs in the relatively
small numbers used aboard boats. It's a simple matter of economics.
Even though they're more expensive than common domestic automotive bulbs, the cost of those
in marine lights is still reasonable in the overall scheme of things. You may replace one or two
over the entire period of time you own the boat.
Because foreign-made bulbs can be hard to find, you can prevent a lot of frustration by
purchasing spares and keeping them handy. You don't want to be stuck without a running light while
an expensive special order of one bulb comes via airfreight.
Q: My boat trailer has chrome wheels with stainless-steel lug nuts. I've tried to get the
nuts off to remove the tires so I could inspect the bearings and brakes, but I couldn't budge those
nuts. I had to take the trailer to a shop, and even there, they broke a stud getting the nuts
off. What's the deal?
- Tom Boyer, Jacksonville, FL
A: Believe it or not, stainless steel isn't perfect. It can "gall" or corrode when in contact
with dissimilar metals like the common steel of your wheel lugs. Backing your trailer into either
brackish or salt water doesn't help the situation. Over time, corrosion almost welds the nuts to
the studs.
The easiest
way to avoid this problem is to loosen and retighten each lug nut once a month. This breaks the
corrosion so that it never builds to the point where you can't get the nuts off. Rinsing the
trailer after every saltwater use with fresh water and a salt-dissolving solution will also help.
A lot of trailer owners apply a coat of anti-seize compound to the studs before installing
the lug nuts. This definitely works to prevent corrosion, but beware of two things:
First, some anti-seize compounds are slippery enough that lug nuts may work loose while you're
rolling along. The other problem with using anti-seize compounds is that they allow overtightening
of the lug nuts. Even using a torque wrench won't yield the correct tightness because of the
lubrication of the compound in the threads. Overtightening can lead to broken studs.
Q:My center console fishing boat has the batteries mounted in the stern. I'd like to move
them forward into the console to improve the weight balance. This will require running longer
battery cables, about 10 feet long. I have a lot of heavy welding cable, but everyone says not to
use them. Why not?
- Tor Jensen, Milwaukee, WI
A: Honestly, I don't know the precise technical reason why welding cables don't work in
boats. What I do know is that welding cables eventually build up enough internal resistance that
the starter won't crank. This happens even in fresh water like Lake Michigan. Last winter, I had to
replace welding cables used on a classic wooden runabout that isn't even kept in the water between
boat shows. Whatever the reason, welding cable doesn't work and shouldn't be used as battery cable
in boats. The only way you'll be satisfied with moving your batteries is to spend the money for
true marine battery cable wiring.
Remember that the length of the starting circuit is twice the distance between the batteries
and the engine. Your batteries will be only 10 feet from the outboard motor, but the circuit is 20
feet long. This means the size of the wire must be increased because electrical resistance
increases with the length of the circuit. Using larger cables helps overcome this current loss.
The size of the cable needed can be surprising. For a 3-percent drop over a 20-foot
circuit with a 100-amp draw, you'll need at least AWG #2 wire, which is 15/32 inches in diameter.
That's the diameter of your little finger. With cable ends, expect to put $150 into just the two
wires from the newly located batteries to the engine. Double that for AWG #1 wire.
You probably won't be able to run the heavier battery cables into the outboard motor cowl.
The entrance hole through the shroud probably won't accommodate such large wire. Instead, you'll
have to install a junction at the transom. Blue Seas brand PowerBar (#2104) will work. Or, use a
single terminal connector (#2003). An optional protective cover is available for the buss bar,
while the single-terminal connector comes with a protective rubber boot. You'll need two connectors
or buss bars, one for each of the positive and negative leads, with the protective covers.
Don't skimp unless you want to be good friends with your local towboat operator. A battery
that has enough cranking amps to start the motor on a short cable may not get enough "juice"
through highresistance wire to turn the starter.
Send your Boatcraft Q&A questions to Dave Brown c/o Boating World,
2100 Powers Ferry Road, Atlanta, GA 30339. You can also e-mail your questions to
editor@boatingworld.com. Due to the volume of inquiries Dave Brown receives, he will be unable to
answer every question.