Rubicon tires are expensive. If I were you, looking for an extra spare, id buy a take off steelie, then buy a 265/75/16 tire used on Craigslist(it's as close to stock circumference as you will get with a 16) then I'd just plop it in the trunk standing up and ratchet strap it to the roll cage. I'm not sure If an extra tire is necessary but this would probably be less than $100. No point wasting $400 on a matching tire and rim for a 6th tire
if your traveling in unpopulated areas' i wouldn't skimp on a spare. i wouldn't worry about what wheel i ran it on but i would spend the money on a matching tire. as well as a dependable air compressor and flat repair kit.
Remember, weight is going to be a big consideration for your Overland trip. The 6th spare is too much weight for such a "what-if" scenario. You would be better served with a good air compressor with a tank (in case you need to re-seat a bead) and a good quality plug kit like ARB's tire repair kit, with plenty of tire plugs. Unless you cut a long gash on the side of your tire, you should be able to repair it with plugs. If you have a compressor with a tank, you can even remove the tire and repair long cuts with patches and plugs by removing the tire from the wheel and repairing it. You should be able to re-seat it by using a ratchet strap along the circumference of the tire (use it to tighten down the tire on to the wheel and create a small seal) and a good compressor with a tank that can output a steady volume of air.
Of course, the good compressor and plug kit are going to cost more than a spare tire, so if you are not intending to do more overland trips in the future, then you may be better served sourcing a spare tire. But, for a 6th tire, it doesn't even have to match the others as noted by other posters.
You may also want to consider a rack, that would be a great place for a 6th wheel. The JK, as spacious as it is, can get crowded when packing up for Overland trips.
* 2012 JKU Rubicon Deep Cherry Red - 4.10 Gears - AEV 4.5" DualSport RS Suspension - 35x12.5 BFG KM2's on Pro Comp 8069 Wheels - ACE Rock Sliders - Gobi Stealth Rack - Tom Wood's shafts - M.O.R.E Dual Battery Tray with 2 Optima Yellow Tops, Smart Isolated.
* Military M416 Trailer in Olive Drab - Custom Aluminum Lid - Mombasa RTT on lid - ARB Awning w/privacy room on custom low sitting extension arms - Custom Rear Swing-out Tire Carrier - Custom Fuel Carrier on Tongue...
yeah if you really want the extra spare, find a cheapy on c-list. I'd say a good air compressor and then buy one of those nice tire repair kits, i carry one and their professional grade and have the same tools and supplies that your local shop would use to repair a tire, also they'll come with enough stuff to do 30 repairs or so, so as long as you can find the hole you'll be set. good luck on your trip!
You can go with a Viar onboard air system, which works great, but is expensive. You can also get by with a portable system such as the MV-50 which you can find on Amazon. Do not get the kind that plugs into the cigarette lighter.
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