Biggest Spare Tire that Fits?

DavidNJ

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There is another one where someone fit a 34" and it was concerned about the distance to the muffler. In another forum I recall some shaving some bolt heads to increase the space, but I think that was for a 4th gen. In any case, all real full size spares (the same size as on the truck) are going to be among the lowest points on the truck. A 12.5" wide tire (305mm r 12.5) would probably be the lowest point.

How do you like the 275/65-20s? I'm beginning to think they are the best size, at least for a truck with 20" wheels. Actually just over 34" at 34.1", very high load rating so 35psi is an ok pressure (maybe 40 or 45 for towing heavy) and articles/videos I've seen are indicating narrower is better except in sand/mud where floatation could be an helpful...except that a 6000+ lb truck isn't likely to see much difference between 11.2" (275 on 9" rim) and 12.5.
 

ColoradoCub

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Looking at those pics it sure seems like a 34 would be stuffed in there pretty tight. I have the 18” spare, might have to just pick up a 275/70/18 to mount on it and play with air pressure to offset the 3/4 inch if I ever need to mount it.

I like the 275/65/20’s, ride is smooth , fuel mileage doesn’t appear to have taken much of a hit and its even lowered my highway rpms a little with the 3.92’s. Fills the wheel wells better than the 33’s did. I’m running 38 psi in the fronts snd 36 in the rear, seems about right.
 

DavidNJ

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Looking at those pics it sure seems like a 34 would be stuffed in there pretty tight. I have the 18” spare, might have to just pick up a 275/70/18 to mount on it and play with air pressure to offset the 3/4 inch if I ever need to mount it.

I like the 275/65/20’s, ride is smooth , fuel mileage doesn’t appear to have taken much of a hit and its even lowered my highway rpms a little with the 3.92’s. Fills the wheel wells better than the 33’s did. I’m running 38 psi in the fronts and 36 in the rear, seems about right.
Which tires do you have? With the higher GAWR in the rear, I would have thought that would have the higher pressure.

This the thread where the bolt was shaved on a 4th gen to fit: https://www.ramforumz.com/threads/oversized-spare-tire-what-sizes-fit.249477/post-2170349

With ORG a 34" has the same distance between the fender and tire as a 32" without ORG/Rebel. With your 2" level, a 35" would have 1/2" more. But the larger diameter brings inner fender interference issues closer, although it appears with the 285/65 they don't yet occur. But I guess those owners haven't had a flat yet.
 

ColoradoCub

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Which tires do you have? With the higher GAWR in the rear, I would have thought that would have the higher pressure.

This the thread where the bolt was shaved on a 4th gen to fit: https://www.ramforumz.com/threads/oversized-spare-tire-what-sizes-fit.249477/post-2170349

With ORG a 34" has the same distance between the fender and tire as a 32" without ORG/Rebel. With your 2" level, a 35" would have 1/2" more. But the larger diameter brings inner fender interference issues closer, although it appears with the 285/65 they don't yet occur. But I guess those owners haven't had a flat yet.
Running around empty the rear end is pretty light hence why I run a couple psi less than the front where the motor,front diff and tranny is.
 

DavidNJ

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Running around empty the rear end is pretty light hence why I run a couple psi less than the front where the motor,front diff and tranny is.
Makes sense. Have you tried even lower pressures? If you're empty, with those tires, you probably could drop to 30psi or even less. At 35psi, the lost on the LT load table, they still are about the same place as the OE tires at load capacity.

BTW: Have you the ORG and have you considered adding balancing beads?
 

ColoradoCub

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Makes sense. Have you tried even lower pressures? If you're empty, with those tires, you probably could drop to 30psi or even less. At 35psi, the lost on the LT load table, they still are about the same place as the OE tires at load capacity.

BTW: Have you the ORG and have you considered adding balancing beads?
I could drop down some more, not every tire openly lists an inflation table, but using Toyos chart even at 35 psi each tire is rated at over 2000 lbs and we both know the rear axel of an empty ram 1500 is not carrying 4000 lbs. That’s why it blows my mind to see guys inflating their rear tires to 45-50 psi which is so much more air than these tires need to be at. I ran my 2500’s at 45-50 in the rear when empty.

Never have considered balancing beads
 

carpram1500

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Just fit a LT285/75R-17 COOPERDISCOVERER AT3 XLT into the spare tire location without any fabrication work. The nearest points are the exhaust on both sides with it being about 3/4 inch of space. Hoping it is far enough away for the heat not to negatively impact the spare tire. I got a 1500 Classic.
 

rzims

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I just ordered a 285 70 18 to put on the spare rim. Ordered a Suretrac AT off walmart.com so we'll see how it works. I have 295 60 20s on the truck so that size seemed to be the closest I could get with the spare
 

rzims

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yeah, I saw those, but for my spare I figured I would try to pinch some pennies....hopefully the cost/value tradeoff doesn't bite me in the butt at some point
 
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