It is where the manufacturer places a mark (dot) on the side of the tire near the bead to line up with the Valve Stem. My guess, they (the manufacturer) have taken into consideration as to the balance point of the tire and the opposite side of the tire is where the "bands" start and stop to the weight of the valve stem.

It is generally a small (1/4") round dot, usually in red or orange, but I have seen them in green.

I was told about this a number of years ago, and if you do it correctly, it should balance out once mounted. I did try it a few times with a bubble balancer to see if it was true, low and behold, each time it was right on. I have since stopped balancing my TRAILER tires. But as stated, It is still a better choice to balance overall.

On my truck tires we always use the balance beads in addition to lining up the little dot. I have gotten approx 10% better return on our tires since we started balancing that way.

Most spin balancers (Hunter, Coats, etc) give the tech an option on static (1 plane) vs. dynamic (2 planes). The factory steel wheels on mom's grocery getter almost always balance on both planes, provided they haven't been bounced off a curb or three. Now if you have crappy low budget cast rims, monster tires (TSL comes to mind), or a mildly bent steel rim, (or if you specify weights inside only), you're getting static balance only, in many cases. Centrifugal force is a mother, and the vibration/shimmy may only occur under braking or high speeds. The point here is, know what you're paying for with the service, because it suc&$ going back to a shop repeatedly, only to have the pimply faced teenager performing the service tell you the tires are balanced and the vibration "has to be" caused by something else.....
FWIW, I was that pimply faced teenager many moons ago, and I apologize if my manager sold you a brake job to "take care of" the vibration ( Mr. obsessive compulsive 10-year-old-Jaguar owner.)

Oh yeah, almost forgot..... Generally, the narrower the rim, the less important dynamic balancing becomes. Skipping the salty veteran motorcycle mechanic that still uses a bubble balancer in favor of last week's MMI grad with the spin balancer isn't going to do much, if any good.

Thank you, I honestly thought dynamic was spin balancing in general. I'm pissed now because I have two tires out of balance on my truck. I honestly thought about buying my own balancer because these ****s at the tire shop can't seem to get I rite.

Go to a Ford Dealer Quick Lane. They have TOP of the line equipment due to all of the nice wheels/tires that are on factory cars now.
I have been very impressed with them; and I visit so often they only charge me a few bucks each visit. A pizza, case of beer, and/or Girl Scout cookies goes a long way too.

I agree with Sydwayz, but I just pulled up the operators manual for a Hunter GSP9700 road force balancer, and it still has a static option on page 38-39.....

Better make that beer German or the King of Beers, no PBR!

balance balance balance

That was cool to learn about the dots. To answer the original question, my new trailer tires were not balanced. The shop said it wasn't needed for trailer tires. The tires came from tirerack. The affiliated shop said the mounting job was so easy that he wasn't charging me anything, even for new valve stems. Gotta go see if the dots are still there.

I just checked and my dots are within a few inches of the valve stems.

I had the wheels Index Balanced on my custom lowrider Tahoe a few years ago if you guys want to get all crazy on balancing.
You teach the machine where the spokes are, and the stick on weights are then split up accordingly so that they are only applied/hidden behind the spokes. When you look in the wheel, the barrels appear perfectly smooth/clean/open.

years ago I owned a 18' dual axle landscape trailer and I will never forget the day I had four new wheels and tires put on. I instantly felt a vibration starting around 55-60 mph. I went back and he argued with me that its a waste to balance trailer tires. After several minutes of listening to his stupid mouth I went down the street and had a diferent place balance them for free to prove them wrong and get my buisness. Weirdest thing, no vibration whatsoever! It's a non perfect round object going in circles, makes no sense not to. Just my 2 cents.

The dots indicate the radial and lateral runout points of the tire. Usually only the red and yellow dots mean any thing; however, it is different between manufactures. The red dot takes precedence over the yellow dot if it has both. The yellow dot is actually the light point of the tire and the valve stem location is the heavy spot on the wheel so in theory the two are helping balance each other out. It even gets more complicated between steel and aluminum wheels. Aluminum the valve stem is always the heavy spot of the wheel. On steel wheels many times there is a dimple that is not at the valve location indicating the heavy spot, this is were the yellow dot needs to be placed, if there is no red dot then the yellow dot gets placed by the valve stem. Now the bad news, most of your 13",14",15",16" steel trailer wheels will not have this dimple. It is primarily only found on 19.5" and larger wheels. The red dot is the radial runout point of the (or high spot, high spot does not always mean the heavy spot), this gets placed by the valve stem on aluminum wheels and the dimple on steel wheels. Again the different weights of the tire and wheel help balance each other out.

With that said doing this does not by any means balance the wheel and tire combinations, it only helps. As Sydwayz says, road force balancing is the best thing out there right now; however, most of the time a simple spin balancer will do just fine.