Converting a Single-axle Trailer to Two-Axle

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Converting a Single-axle Trailer to Two-Axle

Postby Newportme » Tue Mar 28, 2017 3:56 pm

If I wished to add an axle to a trailer, should I just find the center of the existing axle, then using appropriate spacing move one axle forward half that distance and the other rearward the other half of the distance?

Or are there other things that I am not thinking of?

The trailer currently is towing nicely and the tongue weight is appropriate. I would be using torsion axles. I don't want one to carry more weight than the other. Am I over thinking this?


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Phil T
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Re: Converting a Single-axle Trailer to Two-Axle

Postby Phil T » Wed Mar 29, 2017 7:55 am

Hi Bruce -

Your logic reads accurate. Need to allow for the gap between wheels. Maybe use your Outrage 22 trailer as a guide.
Do you know the rating of the existing axle?
Is there sufficient frame space to add the new axle?
Have you considered replacing the existing axle with one that has a higher weight rating?

Regards to the fam!
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

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Re: Converting a Single-axle Trailer to Two-Axle

Postby Newportme » Wed Mar 29, 2017 9:09 am


Thanks for the reply, give your family my best as well. I believe the axle manufacturer will provide minimum axle spacing for dual applications. The trailer does not "need" dual axles, but I haul it on the golden road, and telos road, so I want the redundancy of dual axles. The trailer may end up with more capacity than I need but I will keep the spring rates as close to existing as I can.


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Re: Converting a Single-axle Trailer to Two-Axle

Postby Jefecinco » Wed Mar 29, 2017 10:13 am


I assume you trailer over some poorly surfaced roads and want to avoid stranding due to tire or axle failure.

I towed a tandem axle rig for several years. Both of our boat trailers are now single axle types, one with conventional leaf springs and one with a torsion axle. There are several advantages to a single axle boat trailer with a torsion axle. Far less maintenance is a big advantage and, depending upon the terrain conditions where you do most of your backing, single axle rigs are more maneuverable and thus easier to back. A single torsion axle trailer is lighter and thus does not require as much towing capacity, as much fuel (negligible) to tow or as much braking capacity to stop (unless a tandem axle trailer has four wheel brakes).

Before converting your trailer you could consider replacing your current axle with a new highly rated and regarded torsion axle with EZ Lube hubs and E rated or higher tires. Two spare tires installed on hubs could be all the backup needed.

If your tow vehicle jack is insufficient for changing your loaded trailer tires carry a hydraulic bottle jack and a piece of 2X10" plank for a stable surface for the jack.

I believe that a single torsion axle trailer with the appropriate rating is easier to use and requires far less money to buy and maintain than does a tandem axle trailer. One of our trailers is due for tires this year and I'm glad we only have to buy two.