Larger tire with stock spare tire?

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Intense-Dakota

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I have a 2017 Rebel (5.7L 4wd) and I am going to replace the stock tires. I have almost 90K on the stock Toyo Open country and they still have tread, but they are looking a little dry. I am thinking of going with the 305/70R17 over the stock 285/70R17, but don't really want to replace the spare tire if not needed. My question though, is with the difference in tire size will it cause an issue if/when I need to use the spare? I do have limited slip in the rear. Would the difference in size (+20 revs per mile) be an issue? I really don't want to have to spend an extra $350 if not needed, but also don't want to trash the truck in the event of needing to use the spare.
 

Richard Kim

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I have the same issue on my 2016 2500. I am running Toyo OC2 in 295/65R20 (35.1"X11.8") vs my OEM 275/70R18 (33"). If I get a flat in the rear, I would have to put the spare in the front and take the good front tire and put it in the back. The 2" difference would mess up the diff (correct me if I am wrong). I plan on getting a used 35" tire for my spare.

In your case it would be a difference of 1.1"; from what I read anything over .25" difference would be not be good to your limited slip clutch pack. Hope this helps.
 

csuder99

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That's not enough of a size difference to cause issues in the short term. If you know you're going to drive on the spare for a while swap a good wheel from the front to the back and use the spare upfront.
 
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Intense-Dakota

Intense-Dakota

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I thought about swapping front to rear in the event of a rear flat, but didn't think about getting a used larger. Thanks.
 

Socalramfan

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When I went to 35’s I considered getting a spare the same size, problem is…… it won’t fit under the bed where the spare typically goes. not enough room in the space provided, unless you toss it in the bed.

As it is now, I’ve got the original spare in place to at least get me to civilization or the next tire shop.
 

Brian2081

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Hi Socal, I have a 35 12.5 18 Falken MT on a factory aluminum rim in my spare location under the truck at 50 psi. Snug fit but fits.
 

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KoboldTaco

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Maybe it’s just me, but tires need to match. Don’t count on the ‘oh, I’ll be quick‘ on the spare. You never know the situation which requires you to use the spare tire and, it’s your spare! What if you are off the grid a bit. But, I get it….tires are not cheap.

Consider an alternate brand for your spare - it can be the same size but with different tread etc. Its going to get you out of trouble someday in the future - don’t let it be the reason your tow bill goes up.
 

Socalramfan

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Hi Socal, I have a 35 12.5 18 Falken MT on a factory aluminum rim in my spare location under the truck at 50 psi. Snug fit but fits.

Just curious, do you have a tow hitch installed?
 

Elvira

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I have a 2017 Rebel (5.7L 4wd) and I am going to replace the stock tires. I have almost 90K on the stock Toyo Open country and they still have tread, but they are looking a little dry. I am thinking of going with the 305/70R17 over the stock 285/70R17, but don't really want to replace the spare tire if not needed. My question though, is with the difference in tire size will it cause an issue if/when I need to use the spare? I do have limited slip in the rear. Would the difference in size (+20 revs per mile) be an issue? I really don't want to have to spend an extra $350 if not needed, but also don't want to trash the truck in the event of needing to use the spare.
Unless you are willing to switch the flat to a front non driven wheel, get a spare equivalent to the same diameter as the tires you are using. Any difference in diameter can cause stress that could amount to damage to diff or transfer case etc.
 

BlackGold6.4

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I have a 285/75R17 (34")spare for my mudders and when I put on my Toyo's RT's which are 34.8" I put a mudder (34.5) as a spare. Like said above as long you go short distance and get the flat fixed you won't have any issues. 35's (34.5) are very hard to put under the box and my Toyo's will not fit in the spare tire slot at all.
 

Dean2

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Most front diffs are open, so whether it is in 4x4 or not, the tires size difference doesn't matter but if I was running in 4x4 I would turn off the traction control just to be safe. On the rear, at lower speeds and for a short period, no big deal. If I was going to be doing 60 mph+ for any distance I would put the smaller tire on the front.
 

bcbouy

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my wifes mazda cx5 is awd and the oem spare is quite a bit smaller than the rest.it's temporary use only so i assume it would be safe for a short time on a ram.i had to deflate my spare 35 grabber before i could get it seated in the spare tire space under the bed and filled it up once it was up there.i have no idea if i will be able to drop it if i need it.good thing i carry a viair pump when i travel.
 

BlackGold6.4

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my wifes mazda cx5 is awd and the oem spare is quite a bit smaller than the rest.it's temporary use only so i assume it would be safe for a short time on a ram.i had to deflate my spare 35 grabber before i could get it seated in the spare tire space under the bed and filled it up once it was up there.i have no idea if i will be able to drop it if i need it.good thing i carry a viair pump when i travel.
Ha ha .. it should come out ok .. but what a pain it is to get it in there though.
 

bcbouy

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Ha ha .. it should come out ok .. but what a pain it is to get it in there though.
truth.the tire shop didn't even try,they just threw it in the bed.funny side note,whden i got my ridge grapplers installed there were 3 other hd rams that came back because they all had the balance weights torn off from being installed too close to the brakes.mine included.
 

BlackGold6.4

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truth.the tire shop didn't even try,they just threw it in the bed.funny side note,whden i got my ridge grapplers installed there were 3 other hd rams that came back because they all had the balance weights torn off from being installed too close to the brakes.mine included.
I use balance beads in my off-road tires.. no weights on the rim at all. But my highway tires have both weights and beads but on stock rims. never had any issues with loosing weights though that's a new one to me.
 

corneileous

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my wifes mazda cx5 is awd and the oem spare is quite a bit smaller than the rest.it's temporary use only so i assume it would be safe for a short time on a ram.i had to deflate my spare 35 grabber before i could get it seated in the spare tire space under the bed and filled it up once it was up there.i have no idea if i will be able to drop it if i need it.good thing i carry a viair pump when i travel.
Does that Mazda have Positrac, or limited slip anywhere in either one of those two differentials? I would think that in the case of that car, it would be OK to run a smaller tire but not on a pickup.
 

corneileous

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I have a 2017 Rebel (5.7L 4wd) and I am going to replace the stock tires. I have almost 90K on the stock Toyo Open country and they still have tread, but they are looking a little dry. I am thinking of going with the 305/70R17 over the stock 285/70R17, but don't really want to replace the spare tire if not needed. My question though, is with the difference in tire size will it cause an issue if/when I need to use the spare? I do have limited slip in the rear. Would the difference in size (+20 revs per mile) be an issue? I really don't want to have to spend an extra $350 if not needed, but also don't want to trash the truck in the event of needing to use the spare.
Being that we’re only talking an inch difference between your stock 285s and the 305s you’re thinking about but instead of buying five new tires, if you do go with those then why not ask around at all your local tire shops to see if they may have a used tire in that size that won’t cost you near as much?

Far as I’m concerned, if I have a four-wheel-drive vehicle I want all four of my tires to be the same size. Matter of fact, I’ve actually had to do that twice so far. I bought a 98 ram 1500 years and years ago that had 33” 285/75/16’s on it and the previous owner never bothered to upgrade the spare as it still had the same 245/75/16 that originally came on the truck and later on when I decided to downgrade the size on that truck from the 285s to a 265, I had to do the same thing again so that all four tires were still the same size.
 

Socalramfan

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Mine as well. Was wondering if that might have been a reason.

Im running Yokohama Geo‘s 35’s. Still have lots of miles left, but figured when it’s time to change them out, that I’d try to see if one would fit then seeing as how the diameter would be smaller by that point.
 

Elkman

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With the spare tire a different diameter the safest approach is to stay in 2WD and if the limited slip or locking rear differential can be turned off this would also be a good idea if the spare is on a rear wheel.

Smartest move is to replace the spare tire with one that is the same size as the other four tires. You can include the tire in the rotation so you get 25% more life out of a set of tires. It can be a cheaper and even a narrower tire so long as it is the same diameter as your other tires.
 
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