Trailer Wheel Measurements

Measurments of Trailer Wheels

In this video we are going to describe how to measure a trailer steel wheel. I have two examples here one is a 14 X 5-1/2, 5 on 4-1/2 bolt pattern steel wheel. This other one is a 16 X 6, 6 lug on 5 steel wheel, and the way to measure to know what size it is, on the diameter of the wheel, in other words what size tire will fit on this wheel is you want to measure from the inside to the inside where the bead seats and protrudes 60 inches. In other words thats the bead seat to the bead seat. You do not want to measure over all length from edge to edge, okay and to measure the width of the wheel. Again you will not want to measure, do not measure overall because it will show 7 inches incorrect.

You will measure bead seat to bead seat again, which is 6 inches. And then on the bolt pattern, there are 6 lugs, so when there is an even amount of lugs, you will measure from the center of one lug directly across to the center of the other lug. In this case if we put a ruler on it, it would measure 5-1/2 inches, so its 6 lugs on 5-1/2 inches. The next measurement you would want to do is the pilot diameter, which is where the hub from the trailer would stick through. In this case it would measure 4-1/8 inches, and the reason that is critical is because on some trailers they would have a hub with lug holes that a lug bolt would screw into.

You would need to have a hub centric wheel, in other words this pilot diameter would have to be the same size as the hub on the trailer so when you slide it on there you can turn it, line the holes up, and put the lug bolts in. On most other trailers they would use a lug centric wheel, which means it will have wheel studs coming out of the hub, you set the wheel up on there, screw it down with the lug nut as long as this pilot diameter is bigger than the hub that is on there it is centering off the lugs so its no problem. Next measurement I want to do is the backspacing; now the backspacing we measure from the back of the wheel to the mounting surface that goes onto the hub. The easiest way to do that is if you lay a straight edge across the wheel, and then just measure down to the top of that mounting surface. In this case it is about 3-3/4 inches, so that is the backspacing.

I want to also show you how to measure the wheel that would be an odd amount of lugs, like in this case, 5 lugs. The way you would measure it is you would measure from the center of this one wheel all the way to the edge of the wheel or the hole across from it. So in this case if you measure from the center all the way across to the edge of the wheel it is 4-1/2 inches, so this bolt pattern would be 5 on 4-1/2. Another thing that is critical on trailer wheels, most trailer wheels will have a zero offset, offset means where this mounting surface is with relation to the wheel. A trailer will be 0 which means 0 is right at the center of the wheel, and the reason they do that is the weight of the trailer, they want it to be evenly distributed onto the wheel, same amount in front, same amount in back.

In a lot of car wheels this offset would change if they move it this way to the outside of the vehicle thats a positive offset. If that mounting surface back here would move to the inside of the vehicle makes the wheel tire come out, that would be a negative offset. Its very hard to measure the offset, because they, when they do that at the factory they use precise measurement tools that would be able to do that. You cant really do that on your own, but that will give you an idea, most trailer wheels are a 0 offset, and each wheel will also have a load carrying capacity. Most of the time, sometimes it might be stamped on the back of the wheel, on a lot of the steel wheels theres a tag on here and it would say, it gives you the size of the wheel 16 X 6 and then that number says 3,050 pounds. That means this wheel is tested at 3,050 pounds at 90 PSI. So you just want to make sure whatever tire you put on there does not go over that capacity. On this 14 inch wheel if we look at the tag it would say 14 X 5-1/2, 1,870 pounds and that was at 50 PSI. So same way you dont want to put a tire on a wheel that would be over those capacities, and that will do it for measuring a trailer wheel. .