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Old 02-14-2014, 01:09 PM   #11
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I still say an aspect ratio of 65-70 will give you the best stability. With a decent tire you probably wont notice much difference in the 18 or 20 rim with the same overall dimension tire, but there will be some. Especially if you are looking at a 1500, hopefully you rarely/never have enough weight to play that much difference.

If you are looking at 10 ply tires (which I recommend) you shouldn't notice much difference.

Something else to consider is that there are more tires that will fit an 18" wheel than there will be a 20" wheel with the same overall stock height. You will still be able to find them with the 20's but will be a little more limited...


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Old 02-14-2014, 01:22 PM   #12
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I would pick the 18" over the 20" but prefer 17"my myself. For towing I want LT tires with a beefy load range.
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Old 02-14-2014, 01:42 PM   #13
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Also with a 20" rim and a decent towing tire like a lt275/65/20 you need a decent ammount of wheel well clearance!!. Thats almost 35" tall of tire and wheel!...many stock pickups just won't clear that kinda rubber unless lifted. Your better off with a 17 or 18 to get enough meat on the side wall

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Old 02-14-2014, 03:51 PM   #14
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Our Ram 1500 came with 20" on it. I like them, but in our neck of the woods to get a heavier sidewall tire in 20" the selection is limited. I'm having to go with Nitto Dura Grappler E rated (10ply) 275/60R20 and they are expensive.

Defintely a lot more LT tire selection for 17" wheels and I imagine 18" as well.
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Old 02-14-2014, 05:43 PM   #15
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I looked on the Michelin website and neither tire is available as an LT type tire, they are all P metric. Both tires are only rated at about 2200 pounds of load. I would look for a package that will allow the use of LT rated tires. they will wear, perform, feel much better. P rated tires are for all purposes passenger tires. LT is a truck tire and will do much better for trailer towing. My son in law has an ecoboost truck that came equipped with P series tires that were able to be swapped for identical size LT rated tires No comparison when pulling the trailer and none in the wear of the tire.
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Old 02-14-2014, 08:12 PM   #16
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Three things to consider.
The Load capacity of the two different tires.
Higher Aspect ratio tires will be less prone to pot-hole damage
Check the cost for a set of tires. I expect you will probably need at least one complete set. What is the total cost difference?
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Old 02-14-2014, 08:28 PM   #17
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P rated tires are definitely not good for towing regardless of the size.
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Old 02-14-2014, 10:52 PM   #18
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Originally Posted by tipakajohn View Post
Sorry. The tire size would be 265/65/18 or 275/55/20. My question is there an advantage to one size over the other? Either would be factory installed options.
So I just ran your numbers on my tire size calculator. And heres my findings
------265/65/18 =
- 31.5" tall
- 10.4" wide
- sidewall 6.8"
- typical weight 45 lbs

- 31.9" tall
- 10.8" wide
- 5.9" sidewall
- typical weight 44 lbs

Of course the 20s may be slightly stiffer due to the fact there is almost an inch less of sidewall.
-typically the 18" tires have a higher load rating than 20s- thats why you cant get 20s stock on Gm 3500hd srw trucks.
Also these are almost exactly the same size as a 265/75/16 tire they are all within about 1/4" to 3/8" of each other.

Ps. My 295/70/18 - 35" class (actually about 34.3") have a 10 ply rating and 4080 lb load rating (nitto trail grapplers)
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Old 02-15-2014, 12:06 PM   #19
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Another note the 20s seem to cost a little more than the 18"tires. But I think the 20s look a little better- money aside. I only got 18s cause of the cost factor though. But if its on a new truck, id get the 20s for sure!!

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