How to Determine the Axle Weight Rating of a 1989-1990 Trailer

Published 11/22/2017

Question:

We have a 2-axle equipment trailer made in 1989-1990. Its had moderate use. The manufacturer went out of business in 1994. Our records for the trailer got lost. The trailer’s GVW is 10,000 lbs. It originally came with LT9.50x16.5 load range E tires. After the wheels cracked, the wheels and tires were replaced with LT245/75R16 E steel sidewall commercial tires because there is tight space in the wheel wells. LT or ST 235/80R16 E are too big in diameter and will interfere with each other. I think it came with Hayes axles, but I don’t know how to identify the axle weight capacity. This matters for tire fitment. Using DOT’s FMVSS tire down-rating for LT tires, the maximum capacity for the original tires is 5809 pounds per axle. If those requirements were in effect in 1989, would the mfr would have used 5,000 lb or 5,500 lb axles and not 6,000 lb axles? The tire down-rating also will permit LT 245/75R16E tires if the axles are 5500 lb or 5000 lb. The axles are a little rusty, but not bad. The original brake drums had 1/2 inch lugs. The complete brake drum-to-plate assemblies were replaced with Dexter self-adjusting assemblies with 9/16 inch lugs, and 7000 lb per axle capacity. We have the trailer serial number but no weight plate or sticker. I count seven spring leaves. Does that help? The wheel well is close to the tires and is why tires have to be no more than 30.5 inches in dia. Bottom line: How can I tell what the capacity of the axles is? I am stumped.

asked by: Matt

Expert Reply:

The good news is that since you know that the GVWR of your trailer is 10,000 lbs it wouldn't be a huge deal to replace the axles if it came down to it; you would just need to get axles that have a slightly higher weight rating.

Trailer axles should actually have the weight capacity stamped into them somewhere. This is typically found towards the middle of the axle somewhere. If I had to guess I would say that it probably has 5,200 lb axles, but on a 30 year old trailer there is no telling what was used.

The closest tire size we have to the 30.5 diameter size that you referenced is an ST235/80R16 size tire, like the Provider # TTWTRTM2358016E, but it has a diameter of 30.8 inches.

expert reply by: Jon G