Wheel and tire ...FAQ

Discussion in 'Exterior' started by ramhunter9, Jun 30, 2010.

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  1. ramhunter9

    ramhunter9 Supporting Member

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    There are a lot of questions posted about which size to use, and how wide of a wheel to use. So, here is an easy guide to refer to when looking for replacement tires. First, let's breakdown what the size numbers/letters mean:

    P245/50R17 93V

    P = Passenger Tire (does not appear always) // LT = Light Truck
    245 = Section width (in millimeters)
    50 = Section height or aspect ratio (ie. sidewall is 50% of section width)
    R = Radial construction
    17 = Rim diameter (in inches)
    93 = Load Index
    V = Speed symbol

    All of the components of your tire size are important, but when choosing a replacement or plus size, many of those numbers will change. You may have a wider tire with lower aspect ratio and a larger wheel. However, the last two characters are the most important.

    Standard Tire Sizing:

    1500 4WD
    Stock height: 265/75R16 (this is the stock tire size).
    Probably OK: 285/75R16, 235/85R16, 255/85R16, 32/11.50-16.5
    With a 2-3" lift: 33/12.5-16.5, 315/75R16
    With a 4" Lift: 35/12.5-16.5

    2500 4WD

    6.5x16" steel wheels - 1994-2000 ST/SLT, 2001 ST

    LT255/85R16D fits the stock rim, 33+" tall, spare fits in frame, 3000 Pound capacity (many reports)
    33-11.50-16 thornbirds on stock rim
    8x16" Forged Aluminum heels - 2001 SLT

    LT295/75R16 on stock rim 33.5" tall - no rub
    315/75R16 on stock rim and it only rub lightly at full lock.
    Aftermarket Wheels and/or lifts:

    LT285/75R16D fits with aftermarket rim, 33" tall. no lift needed (many reports)
    33/12.50-16.5 - no problems
    35/12.50-16.5 - Tires rub plastic inner fender when the steering is locked.
    305/70R16 - Light rubbing at full lock of the wheel.
    305/85R16 - ( 36" tall, 10.5" wide) with just a front leveling kit.

    3500 2WD, 4WD

    LT235/85R16E is generally agreed to bew the maximum size without spacers between the wheel rims, but brands vary in width - max section width is 9.4".


    Bolt Pattern
    The bolt pattern or bolt circle is the diameter of an imaginary circle formed by the centers of the wheel lugs. Bolt patterns can be 4, 5, 6, or 8 lug holes. A bolt circle of 4x100 would indicate a 4 lug pattern on a circle with a diameter of 100mm.

    The bolt pattern for the Dodge Ram is 5 x 5.5” (inch)





    Offset

    What is an offset and how does it play into my wheel choice? First let's answer what an offset is. The offset is the distance from it's hub mounting surface to the centerline of the wheel. You have a positive, zero, or negative offset.

    A simple picture...


    Zero: The hub mounting is even with the centerline of the wheel. I rarely see a zero offset...

    Positive: The hub mounting surface is toward the front or wheel side of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.

    Negative: The hub mounting surface is toward the back or brake side of the wheels centerline. "Deep dish" wheels are typically a negative offset. Mostly found in alot of RWD cars.

    As a side note...

    If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won't work correctly.

    Offset also becomes important if you are thinking about lowering your ride. If the offset is to not correct, you will have rubbing against the fenders. To get rid of this you will have to perfrom what has been popularly called "Fender-rolling", rolling the fenders out/in to give clearance for the new wheel/tire combination.

    Backspacing

    The distance from the hub to the back of the rim. This determines with how far the tire reaches into the wheelwell. If you get wide wheels and keep stock offset, the wheel will increase backspace toward the inside. If you want to keep stock backspacing, then you need a lot of offset (NOT desirable).
    A wide wheel, with less backspacing puts extra stress on the bearings and seals, etc, etc because the center of the tire is farther away from the hub. A wide wheel with less backspacing can also cause more rubbing on the control arms and a reduced turning radius.

    Ram Rim Dimensions

    1994-1999 1500 2WD/4WD Aluminum Wheels
    • Lug Pattern - 5 on 5.5", 1/2" bolt
    • Rim Size - 16x7.0"
    • Offset - +13.97mm
    • Backspace - 5"
    • Max Tire Size -
    • 15x8.0 rims with 3.5" backspace will fit, but they stick out of the wheel wells.

    2000-2001 1500 2WD/4WD 16" Aluminum Wheels• not posted yet

    2000-2003 1500 2WD/4WD 17" Steel Wheels (Chrome or painted) • Lug Pattern: 5 on 5 1/2
    • Rim Size: 17x7"
    • Fits 94 and up 1500 trucks

    2000-2003 1500 2WD/4WD 17" Aluminum Wheels:
    • Lug Pattern: 5 on 5 1/2
    • Weight: 23.5 pounds
    • Rim Size: 17x8"
    • Actual width edge to edge: 9 1/16"
    • Backspacing: 5 9/16".
    • The space from the outside edge to the mounting surface (against the rotor) is 3 1/2".
    • offset calculate: 1 1/32"
    • Fits 94 and up 1500 trucks

    1994-2002 2500 2WD/4WD Steel Wheels:
    • Lug Pattern - 8 on 6.5", 9/16" bolt
    • Rim Size - 16x6.5"
    • Offset - 4.75"
    • Max Tire Size - 245/75R16, 255/85R16

    2000-2002 2500 2WD/4WD Forged Aluminum Wheels:
    • Lug Pattern - 8 on 6.5", 9/16" bolt
    • Rim Size - 16x8"
    • Offset - 6.25"
    • Max Tire Size - ??
    o Rear: Have a machine shop turn the widest part of the brake drum down by about 1/8.
    o Front: If clearance is a problem, grind the steering components just enough to clear the wheel rim. The tie rod ends may need to be lightly touched with a peanut grinder. Make sure the front wheels are pushed all the way back to the rotor, or you could cinch up the lugs and bind the wheel in a bind/angle= wobbly wheel. It is a very close tolerance at the center circle in the wheel in front, but the wheels will fit.

    Lug Nut Torque Specs:

    • 80-110 ft lbs (108-150 Nm) on 5 stud wheels
    • 120-150 ft lbs (163-203 NM) on 8 stud single wheels
    • 130-160 ft lbs (176-217 NM) on 8 stud dual wheels
     
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  2. ramhunter9

    ramhunter9 Supporting Member

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  3. KGBIGCOUNTRY

    KGBIGCOUNTRY Senior Member

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    Great infro from Ryan aka Truckin151

     
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  4. MADDOG

    MADDOG Super Moderator Staff Member

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    Speedometer Error Calculations

    When you change tire sizes, you will experience some speedometer error. Indicated speed may not be your actual speed.

    So, if you are curious about how big of a change you will experience, go here:

    Tire Change: Speedometer Error Calculator

    Then, plug in your stock tire size (or your current tire size if you have adjusted your PCM for this using a programmer) and the new tire size to see what the change will be.
     
    Last edited: Jul 22, 2012
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