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Jeep Tech: Tires

Tires

Upgrades
Factory Options
Essentials


Subjects

Tires
Wheels
Suspension
Steering
Axles
Drive Shafts
Transfer Cases
Transmissions
Engines
Electrical
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Upgrades

Big Tire, Little Lift: The best set up for your Jeep is to use the least amount of lift possible to fit your target tire size. Here's how to optimize.
What fits and what hits: The lift needed to fit the tires you want.
Tire size tradeoffs
Tread patterns: The Good, The Bad, and the Knobby

Reviews

As with anything in life there are tradeoffs when it comes to selecting tires for your vehicle. Whether the tires are bridgestone, goodyear, or Michelin tires, different sizes and treads can offer different benefits as well as downsides.

 


What Fits and What Hits*

Wrangler (YJ)* (TJ's May use up to 1" larger tire on street)

Tire Size (Diameter)

Suspension Modifications

Body Lifts

Fender Trimming

30" No lift required - however small lifts will increase articulation greatly No lift required - however a 1" or 2" body lift could be used to increase articulation No trimming required and none recommended
31" No lift required for street use but there may be some slight plastic fender rubbing. 2" to 3" lifts are recommended for trail use to increase articulation No lift is required but a 1" or 2" body lift can be used in place of a suspension lift to gain clearance and eliminate rubbing No trimming is required and none is recommended
32" A 2" to 3" lift would be recommended, a 4" lift would provide greatly increased articulation without rubbing A 2" body lift combined with 1" lift extended shackles could be used to clear this size on an extreme budget. With extended shackles or small suspension lifts there may be some rubbing at the corners of the plastic fenders under extreme conditions.
33" A 4" suspension lift or spring over conversion is recommended. A 1" or 2" body lift is recommended to increase clearance Some rubbing may occur Some trimming of the bottom trailing edge of the rear fender may be useful.
35" A 4" suspension lift or spring over conversion is necessary. Axle & brake upgrades are highly recommended as well. A 2" body lift is recommended, a 3" lift can increase clearance. With a 2" body lift trimming some fender edges as much as 1" or 2" may be needed.

CJ*

Tire Size (Diameter)

Suspension Modifications

Body Lifts

Fender Trimming

30" No lift required - however small lifts will increase articulation greatly No lift required - however a 1" or 2" body lift could be used to increase articulation No trimming required and none recommended
31" No lift required for street use as this is close to stock size. 2" to 3" lifts are recommended for trail use to increase articulation No lift is required but a 1" or 2" body lift can be used to gain clearance and articulation No trimming is required and none is recommended
32" A 2" to 3" lift would be recommended, a 4" lift would provide greatly increased articulation without rubbing A 2" body lift combined could be used to clear this size. No trimming is required unless rubbing is actually observed in use.
33" A 3" to 4" suspension lift or spring over conversion is recommended. A 1" or 2" body lift may be used to increase clearance Some rubbing may occur Some trimming of the bottom trailing edge of the rear fender may be useful.
35" A 4" suspension lift or spring over conversion is necessary. Axle & brake upgrades are highly recommended as well. A 2" body lift is recommended, a 3" lift can increase clearance. Some trimming of fender edges may be needed to eliminate rubbing problems


Cherokee (XJ & ZJ)*

Tire Size (Diameter)

Suspension Modifications

Body Lifts are not available.

Fender Trimming

30" No lift required - however small lifts may increase clearances & articulation N/ASome minor fender trimming may be required if rubbing is a problem with wider tires
31" 3" lifts are possible, 4" lifts would be better for trail use. N/ATrimming may be required with wider than stock tires
32" - 33" A 5" or larger lift is required. N/ASome trimming is required
33"-35" A 6" or larger suspension lift is required N/ASerious trimming may be required

* IMPORTANT NOTE:
The above tables are only guidelines reflecting popular trends or upgrade combinations. Other combinations are possible, for example: I know of a YJ owner who uses a 3" body lift and a set of 1.5" lift Con-Ferr extended shackles to clear 33" tires. This is not what I would run or recommend - but it works for him. Your mileage may vary and we do not claim that the above is the definitive word of god on the subject of tire clearance. Some other combinations may work fine or on some vehicles the guidelines shown above may not apply.


Tradeoffs - Tire Size (diameter)

As with anything in life there are tradeoffs when it comes to selecting tires for your vehicle. Increasing tires size can greatly increase the off-road capabilities of your vehicle. Larger tires provide increases in total ground clearance, an increased traction footprint & flotation, make climbing obstacles easier, can be easier on the environment and just plain look better on your Jeep. However all of these benefits have a price.

Larger tires are more expensive in general and may require expensive suspension upgrades for proper clearance, especially on the trail.

Tires more than an inch or two larger than stock may require you to change the ring & pinion gears in the differentials of both the front and rear axle in order to keep your engine running in the optimum power range - especially when off-road, going uphill or driving on the freeway.

Increased tire diameter increases the torque loads on the axles, u-joints & drive shafts. For significantly larger tires it is usually necessary to upgrade these components, especially where traction aiding devices such as lockers or limited slip is used, or you may risk breaking one of these components on the trail.

Bigger tires are heavier tires. This increased rotating mass and the increased leverage provided by the larger tire often call for increases in braking power: changing brake pad materials, rear disc brake conversions, beefing up the master cylinder or even switching to larger disk and calipers are all options. Driving a tall, heavy, modified short wheelbase Jeep with 35" tires and stock brakes in poor condition at highway speeds can be a recipe for disaster!

Increases weight caused by the larger tire and any axle or brake upgrades also increases unsprung weight. This does not matter much on the trail, but can make the ride a higher speeds much more harsh. When mounting the tire you will find that it is often much more difficult to balance the tire correctly. This is due to the extra weight of the tire, the increased rotating inertia of the tire and manufacturers tolerances on larger tires. It can take quite a bit of weight to balance a large tire and many shops that do not routinely handle tires of this size may not do a good job.

So - bigger tires have a price, the bigger the size change the more modifications are needed to properly set up your Jeep; still, on the trail, there are times when putting more rubber on the ground, or more space between the vehicle and the ground, is exactly what you need.

On my 1990 Jeep YJ I decided to switch from 31" tires to 35" tires while not wanting to risk breakage on the trial. The total price of those 4 35" tires was probably close to $7,000 dollars!. This included a 4" suspension lift, a 2" body lift, fender trimming, changing to heavy duty, custom modified, 1 ton truck axles, changing to 4.10 gears in both differentials (+ lockers and carrier changes), and adding rear disk brakes. In addition the lift and axles necessitated transfer case modifications and custom drive shafts in both ends. It was not a simple, cheap or fast project - but on the trail it sure is sweet!

Trade-Offs Tire Size (width)

Tire diameter is not the only issue - tire width is important to. Wider tires increase footprint which can be important for traction or increased flotation. The tradeoff include that wider tires can also require extended fender coverage in many states and may require changes in wheel width & offset to work properly. On stock offset wheels the tires may be mostly covered by the stock fender flares but rub on suspension components when turning thus reducing effective turning radius. The incredibly tight turning radius of a jeep is one of it's important advantages on the trail. Wider wheels or wheels with increased offset move the tires outboard and can greatly reduce the rubbing when turning but make the vehicle wider. This increased width may be an advantage for stability if you drive a lifted vehicle or a disadvantage of you are squeezing down a trail better suited for a Samurai or a quad. Lastly narrower tires can sometimes be an advantage where the best traction is located just a few inches below the surface (such a shallow snow or mud) and the decreased footprint and increased pressure aids the tires in getting down to where it can get a bite.


Tread Patterns

The choice of tread pattern is important in your new tire decision making process. Tread pattern should be chosen based on the intended use of the Jeep. The most popular tread pattern for all around off-road use is a mud terrain pattern.

The mud terrain or mud tire pattern is characterized by large lugs on the tire with large voids between these lugs. The large lugs provide plenty of bite in low traction conditions while the large voids allow the tire to clean itself by throwing off mud or other material when spinning thus providing a good bite on every rotation of the tire. These tires are also very popular for rock crawling as the large lugs can provide a way of gripping and pulling the tires up and over irregular rocky edges where a smoother pattern would just spin. The biggest disadvantage of these patterns is that they run rough and loud on the highway. To reduce this problem choose a tire with irregular or asymmetric spacing of the lugs and voids to reduce harmonic vibration at highway speeds. There are also situations such cold powder snow or sand where an all-terrain pattern would be better.

The general purpose all terrain tire generally has an interlocked tread pattern with siping (small cuts) on the tread blocks. The voids in these tires are also generally much smaller than those on tires designed for use in the mud. The denser pattern of blocks and smaller voids make these tires quieter on the street. It also increases the surface area of the tread which gives the tire improved flotation on surfaces such as light powdery snow or sand. The increased siping can be important in snow were it is the number of edges, even quite small edges, biting into the snow that provides the "bite". The downside is that the smaller voids cannot clean themselves as easily of packed mud or slush as the larger voids on mud tires do. If these voids fill up with mud the tire loses much of it's "bite" and traction is lost.

While the all terrain pattern's improved flotation and additional siping may be an advantage in absolutely dry powder or packed snow, the mud terrain may be the wiser choice if the snow or underlying terrain is, or can turn, slushy or muddy. In these cases the all terrain pattern can become packed with mud and stuck where a mud terrain pattern would self clean and plow on through.

In sand the improved flotation provided by the dense tread pattern of the all-terrain tires can be a distinct advantage.


A variety of manufacturers also offer a family of tires sometimes called trail tires or something near that. These are most often tires designed for use on light trucks or sport utility vehicles which see most of their use on the street. They will generally be quieter, get better gas mileage and last longer than either of the other off-road patterns. The tread patterns are designed to provide significantly improved comfort or performance on the street which can sometimes compromise serious off-road capability. I personally would not recommend them for anything other than light off-road use in dirt, on unpaved roads or trails where you are unlikely to encounter mud, significant rocks or other unpleasant conditions. Fortunately this is the limit to which most of their intended market are likely to take them.

Factory Options

Essentials

Metric Tire Sizes Explained: A complete explanation of metric tire sizes including an applet to convert metric tire sizes to inches
Tire Industry Safety Council: A page dedicated to tire safety and care.

Last modified Wednesday, 01-Dec-2010 09:20:20 MST


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