Weight Capacity

[pete.wilson]

hey

I have an older trailer that I had bought which is 4.5 X 8 ft long, 16 in high sides, very stout, heavy duty frame, very stable at highway speeds. The axle required 2 1/4 bearing buddies (not 1.98in ones) and the tires used to be 5.30 X 12 but I now have the ST175 X 13 which are rated at 1100 lbs capacity. Is the trailer weight carrying capacity rated then for the 1100 lbs. or is there another formula taking into account two tires? I believe this is less than the original weight capacity on the frames data plate which I belive was around 1200-1300lbs. Also can the axle be flipped over to gain more clearance (spring over)? Thanks all.

 

[ntsqd]

Capacity is based on what the frame was designed for, what the springs are designed for, and what the tires (combined) can carry. The lowest number rules.

A lot of leaf trailer axles have Camber bent into them so that when loaded the axle is sprung such that the tires are flat on the ground. Such axles will show the tires to be tilted slightly out at the top when unloaded.
I would expect this to be less so with lighter capacity axles, but only an inspection will determine this. If axle does have this feature then I would say no, you can not flip it.

In any case it's not a great idea. Better would be to go to a straight axle if this one has drop in it (as it sounds like it does), or to move the axle under the springs, or to move the spring attachment points further away from the bottom of the frame, or all of the above. Note that if you move the mount points that they need to be far stronger than the current mounts are.

 

[pete.wilson]

Hey

I found the data plate which states max. load capacity is 1700lbs but then below that is a chart (weight and load not to exceed)with different tires (the 5.30 X 12 states = 4ply...1960lbs, 6ply...2165lbs). The tires I mounted are: ST175/80 D13 (B78-13) 4ply Load Range B 1100lbs.
Would this then make the actual capcity then 2200lbs max. or 1700lbs max?

Forget the axle flip thing, it has a straight axle, it just the center of the axle shaft is at the top of the square axle housing..if that makes sense. The trailer is series 17 built by shore station/marine division, midwest industries inc. Ida Grove, IOWA in 1971. It's been a very good trailer which tows well and will become my camping gear hauler. I just don't want to overload it.

 

[Martyn]

Hey

I found the data plate which states max. load capacity is 1700lbs but then below that is a chart (weight and load not to exceed)with different tires (the 5.30 X 12 states = 4ply...1960lbs, 6ply...2165lbs). The tires I mounted are: ST175/80 D13 (B78-13) 4ply Load Range B 1100lbs.
Would this then make the actual capcity then 2200lbs max. or 1700lbs max?

Forget the axle flip thing, it has a straight axle, it just the center of the axle shaft is at the top of the square axle housing..if that makes sense. The trailer is series 17 built by shore station/marine division, midwest industries inc. Ida Grove, IOWA in 1971. It's been a very good trailer which tows well and will become my camping gear hauler. I just don't want to overload it.

Assuming that everything is good as new and not rusted, fractured, or broken the trailer has a load capacity of 1700 lbs. That is the amount of weight the trailer can carry. To that you have to add the weight of the trailer itself. This is the weight that the tires (I'm assuming there are two) have to share between them.

If the trailer weighs 1000 lbs and your maximum load is 1700 lbs the tires have to safely carry a load of 2700 lbs. As it's shared between them the minimum rating should be 1350lbs. The tires should also be rated for use on a trailer.

As NTSQD pointed out the axle, bearings and spring are all rated separately. With older trailers it's best to check the bearings and re-pack them. See http://www.atreport.com/resourcelibrary.html#bearings while your there get the numbers off the bearings and see what their weight rating is.

Check the springs, U bolts and brackets for wear and damage. Some older units have grease able shackles.

If you have more questions it would help if you could post a picture of the VIN label and any other weight and safety labels on the trailer, as right now it's all just guess work.