4 WD and spare size requirements, I noticed my Gladiator has a 245/70/18 spare but the running tires are 255/70/18? Is this safe in 4WD?

[jbn40301]

4 WD and spare tire size requirements, I noticed my new Gladiator Overland has a 245/70/18 spare but the running tires are 255/70/18.
Is this safe in 4WD? (If I run the spare)

Sponsored

 

[Hootbro]

You should have a equivalent/full size spare. I would make a warranty claim for a replacement at the dealership.

That is a 0.6" diameter difference between the two. Might get you by for a few miles until an exit but I would be worried about axle wrap for any long distance using that much of a mismatch

 

[ddom]

You should have a equivalent/full size spare. I would make a warranty claim for a replacement at the dealership.

That is a 0.6" diameter difference between the two. Might get you by for a few miles until an exit but I would be worried about axle wrap for any long distance using that much of a mismatch

FWIW, My Overland came with 245/75R17 spare. Running tires are same 255/70R18

 

[jbn40301]

FWIW, My Overland came with 245/75R17 spare. Running tires are same 255/70R18

I was always told to never run smaller size tires on any 4X4, because it would destroy the gears.....!

 

[Hootbro]

I am just wondering, does your tire label inside the drivers door jam list the spare as the off size compared to the main tire size? If the tire label lists the off size spare, dealership probably will not even entertain a warranty claim to get a same size spare tire.

I have a Rubicon and it has the same size spare as the main tires. Looked at a few Overland build sheets and it just says "Full Size Spare Tire" but does not list the size. Makes me wonder if Jeep short changes the overland models with these short size spares on purpose?

 

[jbn40301]

I am just wondering, does your tire label inside the drivers door jam list the spare as the off size compared to the main tire size? If the tire label lists the off size spare, dealership probably will not even entertain a warranty claim to get a same size spare tire.

I have a Rubicon and it has the same size spare as the main tires. Looked at a few Overland build sheets and it just says "Full Size Spare Tire" but does not list the size. Makes me wonder if Jeep short changes the overland models with these short size spares on purpose?

I just looked and it showed a smaller tire size, I guess the Overland buyers all get the shaft.......

 

[Hootbro]

Considering the Sport and Rubicons run a 17" tire/rim combo, I suspect FCA did not want to spend the coin on having a 18" steel wheel made for spare tire purposes and punted on this for the Overland folks.

 

[Darel]

OK, here's the deal.

The issue is that if you have a different size spare, that wheel will turn at a different speed as the rest.

Do you need to worry about it? Follow this handy chart.

Rule #1 you NEVER have to run a same-size spare on a STOCK Gladiator! Read on.

1. If you have OPEN differentials you NEVER need to worry about it. Open diffs are DESIGNED to let wheels travel at different speeds so they're just operating like normal.

2. Do you have a limited slip (Trac-Lok) differential? You KINDA have to worry about it. Only in so much as you don't want the mismatched spare on the axle with the limited slip. Now, why do I say KINDA? Because Gladiators with a Trak-Lok rear have an OPEN front differential. So, it's a little bit more work on your part, but you can swap a front wheel to the rear and put the smaller spare on the front, if you got a flat in the rear. (Disclaimer: I'm not 100% positive Gladis don't currently come from the factory with front and rear LSDs, I'm pretty sure they don't but someone feel free to correct me if I'm wrong).

3. Do you have a Rubicon or Mojave with electric lockers? Again, you don't need to worry about it! Why? Because the only time you would engage the lockers and not allow those wheels to turn at different speeds is off-road. When you are not on a paved surface the wheels can slip a little on the dirt or mud, and this slippage takes care of the mismatch in sizes. The only time this would be an issue is if you were using the lockers on a paved road, which you should NEVER do anyway, and regardless of tire size this will seriously mess your stuff up.

4. So when DOES running a same-size spare matter? If you have AFTERMARKET limited slips or automatic lockers in BOTH axles. Now, let's be realistic. No one buys an aftermarket LSD. So let's forget about those. So the only time you need a matching fullsize spare is if you have aftermarket, AUTOMATIC lockers in both the front and rear diffs. Note that I specify AUTOMATIC lockers, ones you can't manually disengage. ARBs don't count because you can just deselect them and drive on open diffs. I am talking about Detroit lockers, or Lock-Rites or some other lunchbox locker. Now, the other caveat to all this is, if you are installing aftermarket lockers in the front and rear, YOU ALREADY KNOW THIS STUFF so this entire guide I just spent half an hour typing is totally superfluous.

So, to sum up:

If you have to ask, you do not need a matching fullsize spare tire!!!!!

 

[Mr._Bill]

4 WD and spare tire size requirements, I noticed my new Gladiator Overland has a 245/70/18 spare but the running tires are 255/70/18.
Is this safe in 4WD? (If I run the spare)

It's a spare tire, it's for emergency use. If you are in 4WD, then you should be on a surface where it's not really an issue. The spare is only meant to be on long enough to get the tire repaired and back on the vehicle. Unless you're doing five tire rotations, a matching spare is unnecessary. I drove my last truck almost 14 years. The spare never came out from under the truck.

Sponsored