When we purchased the RV the very first thing we did was remove the tire mount off of the bumper so it’ll fit on our RV pads. We’re able to park the RV at home on the side of the house (and save a bunch of money doing it) but we’re limited by the amount of space between the side-yard gate and the city sidewalk. We can fit it in the backyard, but we actually need a new driveway first so the top of our rig doesn’t lean in and grind against the house… again.
Ever since we puled it off the bumper we’ve been storing the spare tire in the garage laying flat on the floor so it doesn’t move around. But if there’s a way to keep that area neat and tidy and reclaim some floor space, we’re all for it. So we purchased an underslung tire mount and I installed the spare under the RV.
I was surprised at the condition it arrived in, actually. It doesn’t come in a box, just the ends wrapped in very thin foam sheets, plastic wrap, and shipping labels pasted to the actual metal. This method could not handle the rigors of standard shipping as there were tears and scuffed paint as a result.
The kit does not come with any mounting hardware, only the bolts to secure a wheel to the frame. I thought about the installation process and decided that instead of securing it with a bolts and nuts, I would drill and tap the frame and just use 5/16-24 bolts, lock washers and Loctite. Here’s the only included hardware and directions.
I wanted to have the unit telescope out towards the passenger side because if we blow a tire on the highway, I’m not pulling the spare out into traffic. In CA, that’s a deathwish. The next thing to consider is where to place it under the frame. I wanted it as close to the axles as possible to keep ground impacts to an absolute minimum. Having it in front of the axles is best since we back onto the sidewalk curb and the spare tire mount would likely hit first. The space shown below is almost perfect except those pesky gas lines.
I test fit the unit using C-clamps to look for clearance issues. It looks like I need to get it as close to the gas lines as possible. The tire fits under the chassis just fine, but it collides with the axle’s front tire when sliding in/out. Since the unit pivots a little left and right while sliding in or out, I didn’t mind moving it around the front tire.
Mounted up, it’s fine with plenty of clearance, but you can see where the spare tire will hit the front axle’s tire. Again, I’m able to pivot the unit around the front tire while sliding it out, so no worries. I also checked the tire position under the chassis to be sure it’ll fit. There’s about 2″ of clearance between the underbelly and the tire. I could make it snug, but I may get wider tires in the future.
I used the mounting bracket’s holes as a template and center-punched where I needed to drill. In order to tap for 5/16-24 I should use an indexed letter “I” bit. Since mine is broken, I opted to drill using a 17/64 bit which is .265″ thousandths. This will actually give me deeper threads and the shank of the bolt will be nice and tight. Since the thickness of the frame isn’t that much, I chose a 24 pitch which gives me plenty of threads.
Using the 5/16-24 tap went great. It’s always important to take small bites and then reverse to break the chips. You’ll never break a tap if the right sized hole for the tap was used, good lubrication, as well as this method.
Since the thickness wasn’t as much as I hoped, I wanted to make sure I used lock-washers and lots of loctite.
Here the driver side all drilled, tapped, and bolted up.
And now to secure the bolts that will go through the carrier and the wheel. I used fender washers underneath the plate, and lock washers on top of the plate and secured it with the included nuts. Unfortunately the pitch isn’t the same as a standard wheel nut, so you can’t use the nice tapered wheel nuts. Lame. Once I mounted the wheel, I noticed that it was too easy to make it too tight, which would result in bending the plate that’s welded to the frame rails.
Here’s the final pics after the install. It took about 2hrs with time to document the procedure and frequent beverage breaks. 🙂 If you look closely, you can seen the frame imprinting on the tire, It’s quite snug.
Check out our other upgrades! Have any questions about this project? Please chat below and I’ll try to respond in a reasonable time. Remember, we have full-time careers and this blog is just a hobby. ☺️
Best regards – RVTherapy