Will Changing Trailer Axle Increase Trailer Weight Rating

Updated 04/03/2017 | Published 04/01/2017

Products Featured in This Question

Dexter Trailer Axle w/ Idler Hubs - EZ-Lube - 5 on 4-1/2 Bolt Pattern - 89" Long - 3,500 lbs

(411)

$414.27

Timbren Axle-Less Trailer Suspension w Electric Brakes - Standard Duty - No Drop - 5 on 4-1/2 - 3.5K

(26)

$1478.57

Trailer Axle w/ Electric Brakes - Easy Grease - 5 on 4-1/2 Bolt Pattern - 89" Long - 3,500 lbs

(246)

$522.32

Question:

I want to change my single axle boat trailer to a tandem axle. Do you have a kit foot for this? It is a 3500 lb axle and the axle that is currently on it is a square tube and 81-inch backing plate to backing plate. Thank you in advance.

asked by: Craig

Helpful Expert Reply:

It sounds like your single-axle boat trailer currently has a square torsion axle rather than a leaf spring suspension. You can swap this out for a tandem beam axle setup using 2 axles, 4 leaf springs plus hangers and equalizers but note that doing so will not necessarily give your trailer any additional capacity.

A trailer's weight capacity is a function of its overall design and construction, but most directly it is a function of the lowest-rated part of the trailer. This COULD be the frame, or it could be the leaf spring suspension or the axle itself. Doubling your axle capacity does not mean you have doubled your trailer's capacity. You could replace the single 3500-lb torsion axle with a pair of 2000-lb-rated beam axles and you might prefer the ride quality of such a setup, but again, unless the trailer manufacturer can tell you that this will result in a higher overall weight rating for the trailer do not assume this is the case just because you added axle capacity. Same goes for changing tires to a higher load range; it does not necessarily increase carrying capacity.

To select an axle of the correct length it is best to use the hub-face-to-hub-face dimension. If you measured your 81-inches between the brake backing plates then you may need an 89-inch axle such as # 35545I-EZ-89 (idler hubs - no brakes) or # e43SR (with electric brakes and hubs/drums). You can refer to the linked article on trailer suspension for more background.

We also offer Timbren's axle-less trailer suspension kits that can bolt on to the trailer frame. Kits like 3500-lb-rated # A35RS545E are often preferred for axle retro-fits since they dispense with the complexity of leaf spring set-ups and can give you better ground clearance since there will be no axle beam under the trailer.

expert reply by: Adam R