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Discussion Starter #1 (Edited)
There have been many different people asking what will and won't fit, how big is this tire, etc.

Tire Stuff
This is how to read the sizes and calculate the size in inches.

The stock 18" size is 265-70-18.
The first number is the width of the tread.
The second number is width of the sidewall expressed as a percentage of the tread width.
The third number is the rim diameter.

Converting, 25mm = about 1".
Using this, the tread width is 265 / 25 = 10.6" wide.
The sidewalls are (265 x 0.7) / 25 = 7.4" tall
The overall diameter is 18" (Rim) + 14.8 (Two sidewalls) = 32.8"

The stock 17" size is 285-70-17
This becomes 285 / 25 = 11.4"
(285 x 0.7) / 25 = 8" sidewall
17" + 8" + 8" = 33" overall diameter.

Using this, here are some common replacements that people like.
Yokohama Geolander H/T-S GO51 in 275-65-18
275 / 25 = 11"
(275 x 0.65) / 25 = 7.15" Sidewall.
18" + 7.15 + 7.15 = 32.3" Smaller diameter than stock by 1/2".

BF Goodrich All Terrain T/A KO in 285-65-18
285 / 25 = 11.4"
(285 x 0.65) / 25 = 7.4"
18" + 7.4 + 7.4 = 32.8"

The largest ones you can fit without lifting are 305-55-20.
This works out to
305 / 25 = 12.2"
(305 x 0.55) / 25 = 6.7"
20" + 6.7 + 6.7 = 33.4"

Larger tires in width or height will start rubbing like crazy. These actually rubbed a little on mine and I needed to melt the tire wells with a heat gun to make them fit. See here about doing this. http://www.clubarmada.com/forums/showthread.php?t=1310

You can use this system to read any tire size and convert to see if they will fit. Smaller than 17" rims and you will have problems with the brake calipers fitting. Lower than 6" in sidewall and you will start having problems with off-road driving. Over 7" is preferred for off road. Under 5" and you will have problems on groomed dirt roads and potholes. You will also loose some ride quality and tow rating. Under 4" and you better start riding on freshly paved stretches.

The stock tires are All season Highway tires. All-season highway tires are good in most conditions but not optimal in snow or off road. The stock tires are poor examples of HWY A/S tires and really just stink in most conditions. Changing to a good quality tire will increase most tire properties. A/T tires increase poor weather traction and off road traction but add weight, may add noise, and may ride a little rougher than Highway tires. Makers can often design the tires to eliminate excess noise and rough ride.

Rim Stuff:

Larger rims give you better handling (To a point) and a firmer ride. They also allow for larger brakes. You give up progressively tow rating, mileage, acceleration, smoothness of ride or ride quality, rim strength, and gain weight and cost. Forged rims are more dense and less prone to cracking than cast. This allows for either stronger rims or more delicate rim designs while retaining strength. They weigh more per amount of material used as the metal is more dense. They are usually twice or more as expensive as cast rims.

Rim width is also critical. A rim that is too narrow will pucker the tire. This may lead to the tire breaking its bead and immediately deflating, causing a crash and destroying the tire, etc. A rim that is too wide will have the rim stick out as far as the tire sidewall. This makes rims prone to scraping curbs and breaking beads as well. Check with the maker to see what width tire you should get, usually 2"-4" or so wider than the rim width.

Rims come in painted, Aluminum, and Chrome finishes. Painted is the most resistent to weather, salt, etc. Aluminum is usually brushed or polished. These require a lot of maintainence to keep looking good. Expect to do a lot of polishing. Aluminum can often be clear coated to keep most of the shine of a polished rim but give them more resistence to salt, tarnishing, etc. If this is available, I"d go this route if you choose aluminum. Chrome is the least resistent to salt but very resistent to tarnishing. You will polish, but not as much as with aluminum. Keep a good coat of wax on them and clean the brake dust off weekly and you will be fine. For salt, wash and scrub them the day you get salt on them or they may start tarnishing and pitting.

Hope this helps. ;)
 

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so even .2 or .4 of an inch difference.. won't that change the odometer, the gear ratio, and the gas mileage??

I am no mechanice by any means.. just wondering if that small of a difference will cause any problems....
 

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Discussion Starter #3 (Edited)
Heat03 said:
so even .2 or .4 of an inch difference.. won't that change the odometer, the gear ratio, and the gas mileage??

I am no mechanice by any means.. just wondering if that small of a difference will cause any problems....
.2" to .4" is within the tread wear. Shouldn't make it too inaccurate.

To calculate the change in diameter to find the amount the odometer is off, to this:

Diameter x 3.14 (pie) gives you the circumference.
Stock is 32.8 x 3.14 = 103 inches.
My tires are 33.4 x 3.14 = 104.9 inches.

104.9 / 103 = 1.018. Multiply this by the speed you read and you get your actual speed. 65mph x 1.018 = 66.19mph actual. Not much to worry about. ;)

However, if you make a tire larger or smaller than the rest, say put big tires on the back, this will throw off the VDC and ABS. There is a 2-3% buffer built in for replacing a worn blown tire with a fresh new tire but put on dramatically different sizes, say a 35" with 33" tires, and you will have problems. Don't forget you need to change your spare also if you change your tires by a lot. :D
 

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Ok .. time to ask (inquire) what may have already been answered (elsewhere, but I couldn't find it) .. that will reflect my relative newbieness w/respect the the Armada ..

It is my understanding that the OEM wheels come w/low pressure sensors?

Q .. for those that have gone BIG .. say only to 20" .. are there wheels available (aftermarket) w/the low pressure sensors .. or by changing to aftermarket wheels do you give up that feature?

Q .. by giving up the low pressure warning .. what else do you give up? I'm wondering if there are any other things tied into the low tire pressure warning system?
 

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Discussion Starter #6
inqui-Z-tor said:
Ok .. time to ask (inquire) what may have already been answered (elsewhere, but I couldn't find it) .. that will reflect my relative newbieness w/respect the the Armada ..

It is my understanding that the OEM wheels come w/low pressure sensors?

Q .. for those that have gone BIG .. say only to 20" .. are there wheels available (aftermarket) w/the low pressure sensors .. or by changing to aftermarket wheels do you give up that feature?

Q .. by giving up the low pressure warning .. what else do you give up? I'm wondering if there are any other things tied into the low tire pressure warning system?
A. The pressure sensor is on the valve stem of the stock tires. If you want them, you need to dismount the stock tries, remove the sensors, and add them to the new tires. You probably will want to remount the old tires. Up to you.
A. Nothing. The loss of the sensors will make a small gauge light go on from time to time. I've seen it twice in 5K miles and it goes away when you restart the engine. ;)
 

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I had my sensors reinstalled in my aftermarket rims and tires and tested each one after wards by lowering the tire pressure to the level it is supposed to alert you at. Each tire was successfully tested and reinflated to the proper amount and have not had it alert me since.
 

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OK .. thank you ... OK .. learned something today .. fantastic.

The sensor is located on/in the valve stems.

??? Are these sensors then available to purchase for use w/aftermarket wheels/tires??

There a few wheels I've been looking at .. 20" (20x9.5) Giovanna Gello

http://69.93.164.27/giovanna/trucks.php?wid=GELLO&wtype=truck&wbrand=giovanna

I'd have the cap (currently shown black in the photo) painted red brawn to match the Armada ...
 
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