Spare Tire Mount for Tongue

Wanting to carry two bicycles on the rear of our RP-175, I fabricated a spare tire mount for the tongue.

 

 

Trailer Spare Tire Carrier from Cabela’s (Item # IK-015644)   $27.99

2.5” x 1” x 25” steel tube (1/8” thick walls)   $25.50

2.5” x 1” x 3” steel tube (1/8” thick walls)     $ 3.18

17.25” x 2” x 0.25” steel bar                         $13.11

(All steel purchased from OnlineMetals.com)

(2) 4” x 3/8” bolts with 2 flat washers and 1 lock washer

(1) 4.5” x 3/8” bolts with 2 flat washers and 1 lock washer

(1) 2” x 3/8” bolt with 2 flat washers and 1 lock washer

(2) 4-inch long backing plates fabricated from 1” x 0.25” steel bar stock from Home Depot

1 can Rustoleum primer paint

1 can Rustoleum black paint

I mounted the assembly on the inside of the tongue’s frame to minimize the distance between the tire and the trailer’s center line so that there would be little or no impact on the turning radius and to facilitate access to the WDH’s tensioning mechanism which is just below the tire. Since it was going to be a tight fit for the tire between the front of the R-POD and the single propane tank, I modeled the assembly out of plywood first. I ended up with about 2 inches of clearance on the front and back of the tire. That is more than enough because the mount is rock solid, meaning I don’t have to worry about the mounting post flexing and allowing the tire to move around.

I attached the tire carrier to the mounting post with the hardware that came with the carrier. I turned the mounting brackets 90-degrees to the normal orientation and cutoff the excess bracket length. This allowed me to mount the tire carrier to a basically vertical post instead of the horizontal tongue frame that it was designed for.

I attached the mounting post to the tongue frame with two 4” x 3/8” bolts inserted thru 13/32” holes drilled all the way thru the frame and mounting post. A 4.5” x 3/8” bolt attaches the ¼” thick steel bracing bar and 3” long steel tube to the frame. (The 3” tube is used as a spacer between the frame and the steel bar.) The 2” x 3/8” bolt attaches the ¼” steel bracing bar to the mounting post.

 

 

After my initial installation (which is pictured above), I noticed that the bolts thru the frame had deflected the center of the frame side inward about 1/16^th inch even though they were only torqued to 16 ft-lbs – the recommended torque for the 3/8” bolts (SAE2).  To prevent damage to the outer side wall of the frame, I added backing plates (pictured separately below) made of ¼” thick by 1” wide steel. (If I were to do this again, I would probably go with a 5/16^” or 3/8” thick backing plate, or 2 bolts, for attaching the brace bar to the frame since even with the 1/4” thick plate, the side wall as well as the plate deflected inward slightly.) (On the other hand, I did not observe any deflection where the 2 bolts attach the mounting post to the frame.)