Determining Correct Axle To Upgrade Single 3500lb Axle Boat Trailer To 5200lb Axle

Question:

I have a single axel trailer rated for 3500 lbs and the tires are rated at 1750 lbs each. The boat and trailer weigh 4400 lbs. Is this a safe and or do I need to make changes to be legal and safe I am in Illinois but travel to other states

asked by: Tom W

Expert Reply:

Since you have a single axle that is rated to 3500lbs, and the combined tire rating is also 3500lbs, I do not recommend using the trailer as it is with the weight of the trailer and boat being 4400lbs. Before making any changes I recommend verifying the maximum weight capacity of the trailer with the manufacturer, as just changing the axles and suspension may still not give you the weight capacity you need.

If your trailer does have a high enough weight capacity for the weight you mentioned, I recommend going with a 5200lb axle but to determine what length axle you will need you will need to take a few measurements from your current axle. Using the included diagram you will need to measure from hub face to hub face, and spring center to spring center on your current axle and the look for those measurements for a replacement. The hub face measurement is the most important as spring seats can be moved if needed.

For example the Dexter Trailer Axle Beam with E-Z Lube Spindles # 8327820 has a hub face to hub face measurement of 89" and a spring center to spring center measurement of 74". So if your current axle has these same measurements this axle will work great. If you find your current axle has different measurements just let me know.

Since your boat trailer will be in water you will also need hydraulic brakes and hubs, and will need to upgrade your leaf springs and wheels/tires, but the correct parts will be dependent on the axle you choose. If you can let me know what axle you decide on I would be happy to recommend the correct parts.

expert reply by: Samuel C