I Bought a $500 Trailer for my Mobile Sauna but had to Completely Rebuild it

Since my last post I decided to throw in the towel on trying to build an under-2,000-pound mobile sauna an SUV can pull.

I’m building a full-sized 8×12 mobile sauna with a changing room. Being over 4,000 pounds I’ll need a pickup truck to pull it. I’ll rent a pickup truck a few times first to see how it feels. If I love the mobile sauna life I’ll trade in my trusty, beat-up Nissan Altima for a pickup.

As I studied how to approach and build a mobile sauna, my friend and sauna sensai Matt told me to just start with a trailer. I looked at buying a brand new trailer but given the $4,000 budget my wife and I agreed on I thought maybe I could save some money with a used trailer.

After scouring craigslist and Facebook marketplace daily for a few weeks, a 6×10 trailer popped up about 25 minutes from me for $500. My dad and I made the trek to have a look, in separate vehicles and wearing masks with covid still roaring. We were happy to discover all of the bolts were stainless and the entire body was aluminum which saves 400-500 pounds vs. a steel trailer. The tires were in obvious disrepair but everything else looked solid. There was no rot on the axles or anything overly concerning. I signed the P&L for the fair asking price of $500.

We jacked the trailer up and removed the two rear wheels, figuring we can make it home on 2/4 new tires. I ordered two trailer tires and had them mounted locally for about $200. The next day we rented a pickup truck and to our surprise when we plugged in the trailer lights and they actually worked!

Al Cook, the oldest living Cook, circa 1953

Luckily the ride home was smooth and uneventful yet in the following weeks I realized something: Pretty much the entire trailer had to be rebuilt.

Homemade trailers can be Frankenstein. This trailer seems like it’s made from repurposed highway guardrails (all aluminum, which is a huge plus), two different sets of wheels from two different 1970s Volkswagon Rabbits, and the axles had no markings.

Trailer axle capacity can be estimated by removing a wheel and the underlying hub and taking a measurement with a depth caliper. My axles measured at just under 1″.

After reaching out to 5 different axle manufacturers I learned 1″ axles vary widely: 480 – 2,000 pounds depending on who makes them. The most common is 1,000 pounds with 2,000 pounds being a rare bird featuring markings my axles lacked. Some good news, though: On getting the trailer home we realized it’s 6×12 not 6×10 as the previous owner thought — big enough for a full sized 8×12 sauna!

Being a civil engineer, safety is my wife’s thing. The last thing I want to do is roll down the highway and have a catastrophic failure with her as culpable passenger. I ordered:

  • 2 new axles rated 3,500 pounds each (total 7,000 pound capacity)
  • 4 new leaf springs rated 1,750 pounds each (total 7,000 pound capacity)
  • 4 new wheels rated 1,666 pounds each (total 6,664 pound capacity)
  • 4 new tires rated 1,360 pounds each (total 5,440 pound capacity)

The trailer capacity is 5,440 pounds with the tires as the weakest link. After ordering these parts for $1,323 I found out the guy who made the trailer used an obscure, custom spacing between the old leaf springs. I brought my brand new axles to a local welding shop who moved the plates on the axles in by 4″ for $200.

Growing up my dad ran a landscape contracting business and still owns his skid steer. He offered to flip the trailer over to make it easier to install all the new parts.

My dad and I in his Bobcat skid steer circa late 1980s

Over a couple afternoons, I put on my Trailer Rebuild Guy hat and got to work. I removed all the old hardware, installed the new axles and leaf springs, packed bearings with grease by hand, and installed the 4 new wheels.

The trailer flipped over and partially rebuilt; My brother Adam is a free agent junkyard model
Completely rebuilt.
Ready to haul materials!

I’m not surprised I’m in this trailer for $2,223 which is far more than the too-good-to-be-true $500 I paid. I haven’t started building anything and I’ve already blown just over half of the $4,000 budget my wife and I set. But I got an education on how trailers are made, I’m more confident the wheels won’t fall off while rolling down the highway, and if they do I’ll know how to put them back on! Now I just have to figure out how to build an 8×12 sauna for under $1,800 with lumber prices at record highs.

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