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  #13  
Old 02-10-2016, 07:07 AM
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Re: ORA II advice for purchase

But maybe the OP is not looking to replacing his OEM tires (crappy as they are for off-road duties) right away. The 20" may work for you E7T because you run oversized tires whereas a regularly sized 20 inch tire cannot be aired down to be of any use on the trail.

The other - often neglected - aspect is that of handling, fuel economy and acceleration. Running oversized tires will kill acceleration. But let's dwell on handling and acceleration for a second.

A virtual shopping spree on TireRack.com for wheels and tires for a Grand Cherokee Overland, shows that the 18" rims are generally lighter than the 20" (in O.E. width of 8" or 8.5", respectively). I did not check for every wheel out there, only for those wheels styles that were offered in both sizes, e.g.:
American Racing AR890 - 4 lbs
Enkey Performance SVX - 5 lbs
Platinum Allure - 5 lbs

then i looked up my favorite tires: Continental and a few others and looked up their weights. as a side note, there were no On-/Off-Road All Terrain Tires for the 20" rims. It turns out that a 265/50/R20 may be one or two pounds lighter than P265/60R18, but it also varies among manufacturers.

Bridgestone Dueler H/P92A - 5 lbs (20" is heavier)
Firestone Destination LE 2 - 3 lbs (18" is heavier)
General Grabber HTS - 2 lbs (18" is heavier)
GoodYear Wrangler SRA - 1 lbs (20" is heavier)
Michelin Defender LTX M/S - 0 lbs

All in all, the 20" wheel and tire combo is more likely to produce more unsprung weight - a rotating mass 2-3 lbs per corner higher than the same 18" wheel-tire combo. And if you get a tire that is actually lighter in 18" size, that difference will favor even more the 18". So while looking good in the hood, you probably also think you get better handling and driving dynamics from a package....that is actually heavier and negatively affects the handling and the fuel efficiency of the car (not only is the 20" wheel tire combo heavier, it also has a larger contact area with the road).

Me ? - I would just crank up the PSI in the 18 inch tires to stiffen the sidewall a bit more for asphalt duties rather than spin around a heavier mass.

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  #14  
Old 02-10-2016, 12:00 PM
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Re: ORA II advice for purchase

Quote:
Originally Posted by f1anatic View Post
But maybe the OP is not looking to replacing his OEM tires (crappy as they are for off-road duties) right away. The 20" may work for you E7T because you run oversized tires whereas a regularly sized 20 inch tire cannot be aired down to be of any use on the trail.

The other - often neglected - aspect is that of handling, fuel economy and acceleration. Running oversized tires will kill acceleration. But let's dwell on handling and acceleration for a second.

A virtual shopping spree on TireRack.com for wheels and tires for a Grand Cherokee Overland, shows that the 18" rims are generally lighter than the 20" (in O.E. width of 8" or 8.5", respectively). I did not check for every wheel out there, only for those wheels styles that were offered in both sizes, e.g.:
American Racing AR890 - 4 lbs
Enkey Performance SVX - 5 lbs
Platinum Allure - 5 lbs

then i looked up my favorite tires: Continental and a few others and looked up their weights. as a side note, there were no On-/Off-Road All Terrain Tires for the 20" rims. It turns out that a 265/50/R20 may be one or two pounds lighter than P265/60R18, but it also varies among manufacturers.

Bridgestone Dueler H/P92A - 5 lbs (20" is heavier)
Firestone Destination LE 2 - 3 lbs (18" is heavier)
General Grabber HTS - 2 lbs (18" is heavier)
GoodYear Wrangler SRA - 1 lbs (20" is heavier)
Michelin Defender LTX M/S - 0 lbs

All in all, the 20" wheel and tire combo is more likely to produce more unsprung weight - a rotating mass 2-3 lbs per corner higher than the same 18" wheel-tire combo. And if you get a tire that is actually lighter in 18" size, that difference will favor even more the 18". So while looking good in the hood, you probably also think you get better handling and driving dynamics from a package....that is actually heavier and negatively affects the handling and the fuel efficiency of the car (not only is the 20" wheel tire combo heavier, it also has a larger contact area with the road).

Me ? - I would just crank up the PSI in the 18 inch tires to stiffen the sidewall a bit more for asphalt duties rather than spin around a heavier mass.
You raise many good points, f1anatic. I agree with much of what you say. Regarding two things, I will add:

Quote:
Originally Posted by f1anatic View Post
The 20" may work for you E7T because you run oversized tires whereas a regularly sized 20 inch tire cannot be aired down to be of any use on the trail.
I have taken my rig with the stock tires on the trail a few times. The stock rubber on a stock JGC suspension is nicely capable off road. Some of my experience is in these threads, for the OP or anyone else looking to see what stock WK2s can do off road.

Mainly this one: Hollister Hills, Esprit de Four Safety Clinic? (2014 off road clinic)

But also these: HDC (Hill Descent Control) is great!

Fun on the sand dunes at Pismo Beach, & front skid plate thrashed

Hollister Hills, Esprit de Four Safety Clinic? (2015 off road clinic)

Airing down with low-profile tires, to go wheeling

f1anatic, you've done some wheeling too. Here's one of your threads, with some good pics. The 2014 Grand Cherokee is quite capable off-road

Our rigs are not garage queens. They are capable off road while also giving a luxurious ride. I love this rig.

And then with this:
Quote:
Originally Posted by f1anatic View Post
as a side note, there were no On-/Off-Road All Terrain Tires for the 20" rims
Several of us here on JG have 275/55-20 all-terrain rubber. There are several good options. I started with the Duratracs after the stock Forteras wore out, and after one month am happy so far.
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  #15  
Old 02-10-2016, 12:47 PM
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Re: ORA II advice for purchase

I'm waiting for pricing back on a '16 Limited or the 75th anniversary edition, both with ORA-II. I have a '14 Limited with ORA-I currently and though I don't take it off road too often, there's been times I've been thankful for the plates simply when something on the road bangs into the bottom of the car. I've heard a nice ring a few times. Other reason I want ORA is I don't particularly like the 20" tire choices, and I don't want to change the size. I run the Goodyear AT Adventures, and want to stick with them. Also want the Quadralift this time around, so we'll see.
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  #16  
Old 02-10-2016, 01:19 PM
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Re: ORA II advice for purchase

Quote:
Originally Posted by Weeds View Post
I went with the 18s and have thought about switching to 17s. There is a better tire selection for the smaller wheel size and I almost always air down when leaving the pavement.

Around here the dirt and gravel roads are rough.
I don't think 17's will fit around the brakes on your diesel--it and the hemi require 18s unless you want to get into adapters, etc.

I'd go with the OR-II for the OP... better selection of tires, a tad better ability to deal with rougher trails, and more likely the skid plates will be installed properly.
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  #17  
Old 02-10-2016, 09:46 PM
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Re: ORA II advice for purchase

Quote:
Originally Posted by f1anatic View Post
But maybe the OP is not looking to replacing his OEM tires (crappy as they are for off-road duties) right away. The 20" may work for you E7T because you run oversized tires whereas a regularly sized 20 inch tire cannot be aired down to be of any use on the trail.

The other - often neglected - aspect is that of handling, fuel economy and acceleration. Running oversized tires will kill acceleration. But let's dwell on handling and acceleration for a second.

A virtual shopping spree on TireRack.com for wheels and tires for a Grand Cherokee Overland, shows that the 18" rims are generally lighter than the 20" (in O.E. width of 8" or 8.5", respectively). I did not check for every wheel out there, only for those wheels styles that were offered in both sizes, e.g.:
American Racing AR890 - 4 lbs
Enkey Performance SVX - 5 lbs
Platinum Allure - 5 lbs

then i looked up my favorite tires: Continental and a few others and looked up their weights. as a side note, there were no On-/Off-Road All Terrain Tires for the 20" rims. It turns out that a 265/50/R20 may be one or two pounds lighter than P265/60R18, but it also varies among manufacturers.

Bridgestone Dueler H/P92A - 5 lbs (20" is heavier)
Firestone Destination LE 2 - 3 lbs (18" is heavier)
General Grabber HTS - 2 lbs (18" is heavier)
GoodYear Wrangler SRA - 1 lbs (20" is heavier)
Michelin Defender LTX M/S - 0 lbs

All in all, the 20" wheel and tire combo is more likely to produce more unsprung weight - a rotating mass 2-3 lbs per corner higher than the same 18" wheel-tire combo. And if you get a tire that is actually lighter in 18" size, that difference will favor even more the 18". So while looking good in the hood, you probably also think you get better handling and driving dynamics from a package....that is actually heavier and negatively affects the handling and the fuel efficiency of the car (not only is the 20" wheel tire combo heavier, it also has a larger contact area with the road).

Me ? - I would just crank up the PSI in the 18 inch tires to stiffen the sidewall a bit more for asphalt duties rather than spin around a heavier mass.
Thanks for the detailed discussion-you make a convincing argument for 18 inch wheels when offroad driving.
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