Before mounting larger tires to your Rubicon, be aware of the following:
- Installing larger tires will decrease gas mileage and performance due to a decrease in the effective gearing and higher unsprung weight.
- Larger tires will increase braking distance due to increased inertia.
- Larger tires will increase the stress on driveline and suspension components, particularly axles and u-joints.
Wheel Considerations
Before deciding what tires to buy, determine what wheels you want to use. For an explanation of wheel terminology, see the following link on elff's website: http://www.4ezt.com/Vroom/wheel.html
16 Inch Wheels
The stock Moab 16x8 inch wheels will accommodate up to 35 inch tires. A disadvantage to running these wheels is that 16 inch tires are more expensive than the equivalent 15 inch tire. Aftermarket 16 inch wheels are available, although the selection is considerable smaller than 15 inch wheels.
15 Inch Wheels
15 inch 4.5x5 bolt pattern wheels will fit a Rubicon without problems. There are no issues with clearance on the brake rotors or any steering components due to the wheel diameter. There is a huge variety of 15 inch Jeep wheels available from aftermarket suppliers.
Backspacing
Stock Rubicon wheels have 5 inch backspacing. This backspacing creates clearance issues at full steering lock on the front lower control arms when installing larger tires. The interference be corrected by placing a few washers under the steering stops on the front steering knuckle or by installing wheel spacers. Installing washers under the steering stops will result in a loss of turning radius, but the cost is virtually nothing. When aired up, the rears will clear completely in the back. When aired down, even with the washers you will rub the front control arms because the tires will bulge out. In the rear, due to the same reason, you will slightly rub the spring perch. This problem will be compunded if your rear axle is not centered.
If wheel spacers are used, be sure you DO NOT install cast wheel spacers. Only use machined aluminum wheel spacers made by a reputable supplier such as Spidertrax or Mountain Off Road Engineering.
If you are changing wheels, many members have reported wheels with backspacing between 3.5 and 4 inches eliminate interference and provide additional track width without excessive exposure past the edge of the stock flares.
Wheel Materials
For a given wheel size:
- Steel wheels are the least expensive, but are the heaviest.
- Cast aluminum wheels are more expensive than steel, but are lighter. Stock Moab wheels are cast. All cast wheels are easily scratched and gouged on rocks.
- Forged aluminum wheels are the most expensive, but offer the best combination of weight, strength, and scratch resistance.
Choosing Tires (Finally)
33 Inch
Representative Sizes:
285/75R16 and 305/70R16
33x10.50-15 and 33x12.50-15
- Require a minimum of a 2.5 to 3 inch lift to avoid rubbing the fender with the tire fully stuffed. This can be accomplished with a 3 inch suspension lift or combination of smaller lift and body lift. Bumpstops may have to be lengthened.
- Wider flares may be required for tire widths larger than 11.50.
- Your stock speedometer will now read correctly.
35 Inch
Representative Sizes
315/75R16
35x12.50-15
- Require a total of 4 to 4.5 inches of lift to avoid fender rubbing at full stuff. Bumpstop mods are required.
- Wider fender flares probably required.
- A CV driveshaft and adjustable control arms will be required to maintain pinion angles within specs and to avoid driveline vibrations.
- Serious consideration should be given to upgrading axles and u-joints at this level to avoid potential breakage.
- With stock gearing your speedometer will read lower than your actual speed.
- A number of members have changed gears from the stock 4.10 to 4.56 or 4.88 at this point to regain lost performance. Regearing will require the installation of an interface module to correct the speedometer reading.
37 Inch
Representative Sizes
37x12.50-15
- Not for the fainthearted. For the vast majority of owners, this is not a practical choice for a street Jeep.
- Requires a minimum 6 inch lift
- Significant upgrades are required in the driveline and steering to maintain any degree of reliability and drivability.
