I am not real sure of the application, but if it is the vehicle that you have pictured in your avatar, I'd like to suggest another option.
Originally Posted by Jerry
A little background... I did have a swing away spare tire carrier on my last truck , Thunder II. I worked great and was a fantastic place to mount a sprayer for hand washing as well as a place to hang the Trasharoo. I opted not to mount gas cans to it for a few reasons.
#1- Out of sight, out of mind. No matter how securely you mount them, they are still in view of those who might want to take the fuel. As the price approaches $5 that becomes a big chunk of change hanging on the back. Plastic cans are vulnerable to something as silly as vandalism. A good sharp knife could create a hazardous situation. Many carry rock hammers , punch a hole and catch it in another can.
#2- Heat of the day. Exposed to the sun and dirt on the back of a vehicle. In the high desert changes in temperature can be extreme. Freezing at night and baking in the day. The best can in the world will crunch and swell to the point of leakage eventually. Stopping to relieve pressure at mid day gets old. Cleaning off a layer of silt and then having it all over yourself when you fill the rig is tiresome too.
#3- Safe fill. To safely fill a portable gas container (one that is not properly grounded as a part of the vehicle) It MUST be placed on the ground to fill. The filling nozzle must remain in contact with the container during the filling process. Plastic cans can be more prone to static discharge, but metal can do it too. IT CAN AND DOES HAPPEN. I have personally put out three such fires. The pumps , vehicle and in one case the person were seriously damaged. Be prepared to remove those containers from the rack each time you fill them. Those who do not are tempting fate.
#4- COG. While rack mounts are lower than a roof mount it is still above the level of other tanks on the vehicle. Anything you can do to lower the center of gravity is an advantage.
#5- Travel abroad. I have been told that portable fuel containers must be empty for border crossings. Built in tanks are not usually questioned. I want to have plenty of fuel to get far away from the border before dark. border towns can be troublesome , or so I am told.
I'd mention that they are exposed on the back to a vehicle accident, but they are high enough and the newer containers are extremely durable. I don't see them as a hazard.
OK, now that I have given you some words of discouragement, you do need to increase your range by carrying extra fuel. A fuel tank underneath where the spare tire hangs is a great option, IMO. Here are several links to look through, three of which I have done:
Expeditions West: Toyota Tacoma Auxiliary Fuel Tank System
Auxilary Fuel Tank
Avalanche - BLT Offroad (scroll down toward the end of the page)
A very "factory like" transfer tank install can be done inexpensively.
The convenience is refreshing. At a glance I know how much fuel that I have remaining. I can keep the main tank topped off at all times and keep a couple gallons in reserve.
In a pinch I have a fuel pump that can be adapted to get me going should the main pump fail.
550-600 miles range is the sweet spot. This offers range far enough to not have to buy fuel in those price gouging out of the way stops. I have done many trips with auxiliary tanks and others with fuel cans. 15-20 gallons of additional fuel is the best choice for the traveling in my experience. Packing four five gallon cans takes up quite a bit of space and is kind of a pain.
At one point I had a range over 800 with three fuel tanks. Carrying that extra 20 gallons was just not needed and I removed the third tank.
I have seen expedition vehicles with fuel cans stacked all over the vehicle. I still have a dozen old "jerry cans" and half a dozen mounts for them. I should probably sell them as I find the auxiliary fuel tank much less trouble to store.
Now to address the swinging spare tire carrier:
I had one for many years. It was handy and added a "cool" factor. More often than not it was in the way to open the back. Swung out when not properly latched, or in the way when I needed to haul something with the gate open. On the latest vehicle I have made a conscious decision to avoid the swinging spare tire carrier on the back. Yea, yeah, I know all the cool expo rigs have them.
You could easily get $1000 invested in a swing away rear mount. That is a pretty big investment. It would be less than half that for a fuel tank under the back and a basket for the roof rack. The tank under my Avalanche came in under $150 installed.
I still have issues to resolve now that I no longer have a rear rack. Carrying the spare underneath may not be a viable option. Putting it in the roof basket may be my best option even though the COG will be affected.
A basket to carry the spare on top can easily be done for most vehicles.
A place to mount the sprayer/hand washer and Trasharoo are still items to figure out. If my trailer is behind us this is less of an issue.
Kind of a long post. Sorry. I did wish to relay my experiences and give you some food for thought.
"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond