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Discussion Starter #1
Hi all, I have a question. I'm looking at a full size spare for when I go out on the sand dunes. I have a 2014 JGC Limited. 18" wheel. The rim size shows 8Jx18 ET 56.4. I found a Wrangler rim that is 18x7.5J ET44.45. Will this work?
 

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When I did some research, I found that 17" and larger Wrangler wheels will work. I elected to purchase a wheel from Discount Tire that matched and it was less than $200. I had been watching Craigslist for months for someone selling them to no avail.
 

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Discussion Starter #3
When I did some research, I found that 17" and larger Wrangler wheels will work. I elected to purchase a wheel from Discount Tire that matched and it was less than $200. I had been watching Craigslist for months for someone selling them to no avail.
My concern is that will it cause a problem with driving if i was just going to use as a spare. Can I get from point A to point B without doing damage to the jeep? How far can I drive on it?
 

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If you have a 4WD you need a spare that is the same overall diameter as the service wheel/tires. Or at least very close, and if it's not exactly the same diameter drive slowly and not very far before repairing and getting the flat tire repaired and back on.

4WD has a differential or clutch pack between the axles, if the axles do not turn at the same speed, then the differential/clutch pack will spin/slip. Sure it's designed to do this in turns, but not steady state for long periods of time, so if put a different overall diameter tire on one wheel, you will different axle speeds constantly and exceed what the center differential/clutch pack is capable of, it will overheat or suffer excessive wear.

If you off road, you need a full sized spare. If you get a flat off road, the compact spare likely will not survive getting off the trail and back on road, or at least not give you the traction needed to get back to the road.

The OEM Tire size will not fit in the spare tire compartment and allow you to close the lid the whole way. The OEM Full Sized Spare is slightly narrower than the OEM tire, I think 245mm, not sure if its a higher profile or the same to be slightly smaller in diameter. So if you have the OEM full sized spare, you might not want to drive far or very fast on it, if you need to use.
 

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The ET or offset as that's referring to won't have an effect on anything but how the wheel sits in relation to the hub. If you use a JK wheel with less offset and mount it on the WK2 it will stick out slightly further than the stock wheels. For spare use that isn't going to hurt. Where it may cause an issue is if you are trying to put the OE jack kit inside the wheel. It may hit off lid.

Keep the tire diameter close and with open diffs you won't have an issue.
 
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Discussion Starter #6 (Edited)
If you have a 4WD you need a spare that is the same overall diameter as the service wheel/tires.
So Mongo with that being said if I get the wrangler tire which is an 18" same as my rims know it would work as a spare? I'm taking the Jeep through sand dunes and need a full size spare.

Thanks, Scott
 

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A compatible 18" wheel with a tire that's the same diameter as the regular tires on the four corners is all you need to worry about. If you are running OEM size tires, that's ~30.6" in diameter. If you're running up-sized tires, you need to match that diameter with your "full size" spare. Please be aware that the OEM full size spare is the same diameter, but narrower than the regular tires so it fits under the lid in the spare compartment.
 
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So Mongo with that being said if I get the wrangler tire which is an 18" same as my rims know it would work as a spare? I'm taking the Jeep through sand dunes and need a full size spare.

Thanks, Scott
Rim size doesn't matter as long as it is larger than 17" to clear the brake calipers. Tire size is what matters.
 

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Discussion Starter #9 (Edited)
A compatible 18" wheel with a tire that's the same diameter as the regular tires on the four corners is all you need to worry about. If you are running OEM size tires, that's ~30.6" in diameter. If you're running up-sized tires, you need to match that diameter with your "full size" spare. Please be aware that the OEM full size spare is the same diameter, but narrower than the regular tires so it fits under the lid in the spare compartment.
Ok Jim/IAmTodd so my other Jeep is a 2015. It has 265/50/20 on her. So if I'm doing the math right. 265*.50=132.5mm. 132mm+132.5mm+(20*25.4)=773mm.

733mm/25.4=30.4"

2014 Jeep 265/60/18 (Taking in the sand dunes)
265*.60=159mm. 159+159+(18*25.4)=775.2mm

775.2mm/25.4=30.5"

I could use my 2015 tire and rim as a spare for emergency for my 2014? And drive on it?

Close enough right?

At this point I'm just trying to avoid the extra cost for a full size spare.

Thanks in advanced.
 

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Yes. That 265 tire is going to be too wide for the spare tire well but for temporary homing you'll be set. Be careful how far you air down the 20 as well as it won't have as much sidewall flex as the 18 and you'll risk unseating the bead in the sand.

If you do a lot of highway travel a fullsize spare isn't a bad thing to invest in as you won't be limited on speed. Just something to keep in mind.
 

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Yes, the OEM tires are the same diameter regardless of whether they are on 18" or 20" wheels.
 

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Tire sizes are Nominal, meaning they are NOT exact, you need to look up the detailed spec.

Detail spec for the OEM tires might be 30.6" overall diameter, while if you calculate it by the size specs it comes out 30.4". The best spec is "Revolutions per mile", if the tires have the same revs per mile, they are the exact same diameter.

Like mentioned, SD brakes can fit within 17" wheels, HD brakes will need 18" or larger wheels. The size of the rims make no difference in overall diameter of the tire, the wheels have to fit the tire and the car. Offset does make a difference, it doesn't have to be dead on, but wheels vary so much in offset, if you don't check it is possible to get a wheel with offset so far off it will never work or won't drive right at all.

The OEM Full Sized Spare is 245mm wide on an 18", I don't know the aspect ratio/profile for it. Its 245mm so the lid to the spare tire compartment can close fully. It might be a taller profile to match the diameter of the OEM 265mm tires, or it might be the same profile and thus slightly smaller in diameter than the OEM 265mm. Again, it should serve fine a spare tire, but just like the compact spare that says on it "Don't exceed 50mph", if its not the exact same diameter as the other tires, you'd want to drive slowly and not to far on it.

Someone said something about Open Diffs and not to worry, I don't think he was implying you don't have to worry about tire diameter if you have open diffs, but in case you took it that way, it's not true. A former Jeep engineer used to post at Allpar.com and he said he proved just the difference between tires worn to the tread bar on one axle and brand new on the other would create excessive wear on the center differential. The differential is designed to allow you to turn, and spend most of its time driving straight, and even when turning the speed the diff turns is relatively small, you have different sized tires the diff will spin constantly at a higher speed, it will overheat.
 

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Yes. That 265 tire is going to be too wide for the spare tire well
Not sure about that.

You can fit a 265-65-18 (~1" taller/wider than OEM) on an OEM alloy into the spare tire well - you do have to jettison the cubby boxes but no great loss really.

I've done it and so have a couple of others here. Stock tire on stock rim should fit too.
 

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FWIW, I put a 265/65 R18 Hankook Dynapro HT tire on my stock steel spare to match the size of the 265/65 Conti ATs I have, and in the '15 Overland we had before, at 30 psi, it fit in the spare tire well and the cover would latch, with the storage boxes in there as well.

IDK what changed, but in the '18 TH we have now, the cover will not latch and sits up about the thickness of the cover. I haven't had tim to dig around to see if they added sound deadening material in there or extra padding, but something must have changed. Main point being, this size spare may actually fit with no majore changes, or may not as we found out between the '15 and '18 MYs.
 

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Discussion Starter #15
Yes, I just purchased a full size steel spare rim for $60 and put one of my old Goodyear Wrangler tires on it (265/60/18) and it fit in the spare tire compartment on my 2014. I had to take the foam out of the bottom, but I don't think that's a big deal. So now I have a full size spare. :thumbsup:

Scott
 

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Yes, I've done it too. I switched over to 265 65 R18s and I have a full size same tire as a spare. I removed the bottom foam ring and took out the side cubby holders. I aired down the spare to 30 psi and it fits in the spare wheel well and the lid closes. I carry a portable air compressor to fill spare back up to 36 psi if I need to use it. So a 265 65 18 spare on a full size 18" spare steel rim will fit 8n the well with a little air taken out using a Falken wildpeak AT3w tire. I still have the jack kit in the foam holder stored in the middle with no problem.
 

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I'll try removing the foam bottom, maybe that will do the trick. Thx.
The only function of the foam ring on the bottom is to keep the temporary spare in place because it's so thin and you don't want it to rattle around but with a full size spare you can still screw down the coupler that comes with it and it doesn't move around at all. If your using stock tire size it will fit no problem. May have to air it down a little to close lid but if you carry a portable compressor then it's no problem. I would rather have a full size spare anyway over that crappy little temp spare any day especially if your going on a road trip or off roading.
 

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The only function of the foam ring on the bottom is to keep the temporary spare in place because it's so thin and you don't want it to rattle around but with a full size spare you can still screw down the coupler that comes with it and it doesn't move around at all. If your using stock tire size it will fit no problem. May have to air it down a little to close lid but if you carry a portable compressor then it's no problem. I would rather have a full size spare anyway over that crappy little temp spare any day especially if your going on a road trip or off roading.
Ya, the weird thing for me is that on my 2015 Overland, the 265/65/18 on steel rim fit and the lid closed with a little pushing. Fast forward to this 2018 Trailhawk, and now it's not even close. I just can't figure out what changed, but I also haven't dug around down in there yet either.
 

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I am having the same problem on my 2017 WK2 Trailhawk. I am researching options to place the OEM drive tire/rim under the load floor of the cargo hatch so I can include a true full size spare tire matching the vehicle tire and close the lid. I am curious if you have discovered the difference between the two models. I have seen some persons referencing a thread to modify the cargo space to fit a true full size spare but have been trying to find it with no luck. If anyone would be so kind as to post a link I would appreciate it.
 
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