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Contents: Gear Ratio Guide | Ratings
Larger tires give your more clearance for obstacles, but usually require a suspension lift and/or fender trimming (See Lift at Jeep Config) for proper clearance. Mud-terrain tires with larger lugs and bigger gaps between them are the preferred tread pattern for off-road but all-terrain tires which are better on the road are used by many.
Wider tires may require wheels with less backspacing (See wheels at the jeep configuration page) to get enough clearance from control arms up front and spring cups in the rear.
Stock Tires are 28-31" (Sport has 29", Sahara & Unlimited has 30" and Rubicon 31". Optional 30" tires avail. on Sport). Each inch in diameter gives you 1/2 in. lift. E.g. 33" tires give 2" of extra clearance on the differential over a 29".
Del Albright says "To many folks, 33 inch tires are barely adequate. That's what I run and I drag a lot."
Note: The higher the center of gravity the more likely you are to roll in emergency maneuvers on the road. Wranglers have a wider track than CJs, so are safer. Wider tires and wheels with greater offset will compensate to some extent.
Fuel economy will drop by 2-4 mpg with the popular 33x12.5s and by 4-5 mpg with 35s.
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. Wider tires may also put more wear and tear on wheel bearings and steering components. 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.
In "4-Wheel Freedom: The art of off-Road Driving" they say:
On firm slippery surfaces like packed snow, trails covered with a layer of silty dirt, or wet roc, the footprint of wider tires tends to be more rounded.
The footprints of narrower tires act somewhat like skis, pointing the rig along the track. However, the footprint of a wider tire is more like a saucer, letting the rig slide off ther road with a sideways slope.
According to a Jan. 2004 ConsumerReports article, a 245/40ZR18 tire (with 9% more contact area) will be 25% more likley to hydroplane and have 20% less traction in snow than a 225/55ZR16 tire, but will have a 4% advantage in wet/dry cornering and a 5% advantage in ice braking.
In Tire Selection for Expedition Travel: The impact of tire width on traction", Scott Brady of Expedition's West makes the case that tall narrow (10.5) tires are better with the exception of soft sand, snow and soft mud that's depth exceeds 110% of the vehicles minimum ground clearance.
Glenn Bontly says: "When replacing your tires, you have a choice between All Terrains (ATs) and Mud Terrains (MTs). All Terrains are far superior on wet or icy roads, and they also do well on many types of off-road terrain (except for mud, where the narrow channels quickly get clogged). On the other hand, MT's are great in all types of off-road terrain, from plowing through mud to climbing over rocks. They are also better in soft snow. The great majority of trail riders that I know use Mud Terrains.
In "Back Country Adventures" they say:
| ||Off-Road |
| ||Off-Road |
|All-Season tires have the deeper water channels than standard auto tires, but often have harder rubber compound for greater tire life in warm weather. ||All-terrain tires have a more agressive tread patterns. Wider spacing to evacuate mud from the tread. A stiffer sidewall for greater resistance against puncture when traveling off-road. ||Off-Road
Mud-terrain tires have the most agressive (large, chunky) tread patterns designed to bite into muddy surfaces and provide grip. They can be noisy at highway speeds, and due to the open tread design, they have less of a contact area with the road, limiting traction. The large lugs on mud tires tend to tear and chip on roads, because they are made from hard rubber compounds that do not bend easily.
|All-season and all-terain tires have siping (small cuts on the tread which open up on packed snow or ice and increase traction). The siping usually goes down only half the tread depth so some dealers will add additional, deeper siping. ||They usually do not have siping to avoid small bits of gravel getting stuck and generating noise and wear. Tire stores can add siping.
"Light Truck ("LT" before the number) tires are more rugged than passenger ("P") tires. ...
Although mud tires have an advantage in muddy conditions and soft snow, all-terrain tires perform better on slickrock, in sand and particularly on ice and paved roads."
The the Feb. 2002 4 Wheel Drive & sport utility magazine
they tested Mud-terrain vs. All-terrain tires and found:
On steep rocks many enthusiasts used all-terrain tires for the greater tread area and contact patch, however they found the Mud tires clawed up in a slower, more stable manner than the all-terrain tires. The tread's large lugs seemed to conform to the rock ledges and outcroppings, pulling the Jeep along without tire spin.
On the street the all-terrain tires were marginally better in cornering and braking even when the street was wet or icy. They should also provide 7-10,000 more miles of tread life and are quieter.
In the mud the mud-terrains were much better, but if kept spinning the all-terrains were acceptable.
In the sand they thought mud-terrains, known for digging into deep sand, would not be as good, but they actually performed better going up steep sand dunes. Their guess was the large, open voids delivered more contact with the sand.
* Jeep: X - X; S - Sahara; u - Unlimited; R - Rubicon
|Size ||Type ||Diam ||Diam |
|P215/75R15 ||AT ||27.5 || ||8.5 || ||755 ||X, S(-2002)
|P225/75R15 ||AT ||28.5 || ||8.9 ||6.5-6.75 ||733 ||S, X(O)
|LT235/75R15 ||AT ||29 ||29/29.1 ||9.25 ||7.5 || ||
|30x9.5xR15 LT ||AT ||29.5 ||29.7/29.8 ||9.5 ||7.38 ||719 ||S(O), U
|LT245/75R16 ||on/off ||30.5 ||30.7/30.7 ||9.6 ||7.25-7.38||677 ||R, U(O)
|LT325/60R15 ||on/off ||30.5 || ||12.8 || || ||
|P265/75R15 ||AT ||30.5 || ||10.4 ||8.75 || ||
|31x10.5xR15 LT ||AT ||30.5 ||30.7/30.8 ||10.5 ||8.38 || ||
|31x11.5xR15 LT ||AT ||30.5 ||30.7/30.8 ||11.5 ||9 || ||
|LT265/75R16 ||on/off ||31.5 || ||10.4 || || ||
|P255/70R15 ||on/off ||29.1 || ||10.0 || || ||
|32x11.5xR15 LT ||AT ||31.5 ||31.5/31.8 ||11.5 || || ||
|LT285/75R16 ||on/off ||33 ||33/33.1 ||11.2 || || ||
|33x12.5xR15 LT ||AT ||32.5 ||32.7/32.8 ||12.5 ||10 || ||
|35x12.5xR16 LT ||AT ||32.5 ||34.7/34.8 ||12.5 || || ||
1. Section width will be about 0.4" wider on an 8" wide rim than on a 7" rim.
Optional 30" tire and wheel package
2. Because many tires have rounded sholders, tread width measurement is not standardized and is usually not specified. I got these by going to tire shops and measuring them myself.
Diameter table at: buicks.net, BFGoodrich (BFG), Goodyear
Wheels at the jeep configuration page.
4-Wheel Drive / Offroading / Tires at about.com
Matching Tread Types with Terrain and Conditions at FourWheeler.com
Differental Gear Ratio:
When ever you change tire size from the original size to another there will
be a direct effect on power and drivability. We have developed this chart to
help you select the optimum gear ratio to put your performance back where you
Using the chart below, first determine your original gear ratio and tire size
and follow to the intersection that should be your approximate RPM at 65 MPH.
Next find your new tire size and follow that across to the closest RPM to your original
and that will be first choice.
If you are interested in a change that will give more power or better fuel mileage
use the color coding as a guide.
||Highway Driving, Good Fuel Economy 2600-2800 RPM
||Daily Driver, Best Overall Performance 2800-3100 RPM
||Most Power and Towing, Reduced Fuel Economy 3200-3600 RPM
This chart is based on 65 MPH and a gear ratio of 1:1, on a manual
transmission in 4th gear. Please NOTE: If you have an automatic transmission
your RPM will higher due to slippage (10-15%) in the transmission and the torque
converter. With an overdrive transmission your RPM in overdrive will be 15% (4 cyl) to
21% (6 cyl) less than indicated.
Based on table at: Gear Ratio & Tire Size Chart at 4lo.com, but modified to use an effective diameter based on actual revs/mile of a tire under load rather than the actual rated (nominal) tire size (e.g. 33").
1. Standard on most stock jeeps is 3.07
Optional 30" tire and wheel package and 4 speed automatic have a 3.73 ratio.
Dana-44 option includes 3.55
Rubicon has 4.11 ratio and 31" tires.
A 33" tire is actually 32.5 to 32.8" in diameter with no load and less when compressed by the vehicle weight (radius is decreased by about 1" standing at normal pressure, but less when moving because of centripetal force). Revs/Mile are not reduced in proportion to the reduced radius since the whole circumference of the tire must move across road even if there is a flat spot at the bottom.
All the other tables like this I could find on the Internet don't take this into consideration, but the effect is only about 3-4%. (It was 7% when I calculated it on my TJ after calibrating my spedometer. I don't know why?)
See: Gear Reduction at off-road.com and Revs/Mile at BFGoodrichTires.com
Gear Ratio & Tire Size Chart
All-Terrain | Mud-Terrain
See consumer reports ratings on tires in the products area.
Tire Survey Results for Off-Road All-Terrain tires at tirerack.com
Tire Reviews and Ratings at 1010tires.com
Combined Ratings: TR-Tire Rack (1-5), 1010-1010tires (1-10)
Tire Survey Results for Off-Road Maximum Traction at tirerack.com
Tire Reviews and Ratings at 1010tires.com
Recommendations by jeep contacts: Maxxis M-8090 Creepy Crawler, Goodyear Wrangler MT/R (MT = Maximum Traction), BFGoodrich Mud-Terrain T/A KM
Combined Ratings: TR-Tire Rack (1-5), 1010-1010tires (1-10)
Tire Performance Guide, March 2005 jp Magazine
|Tire ||Street ||Mud ||Sand ||Heavy
|BFGOODRICH KRAWLER T/A KX ||*** ||*** ||**** ||**** ||
|GOODYEAR MT/R ||*** ||*** ||*** ||**** ||
|DICK CEPEK F-C KEVLAR ||*** ||** ||**** ||**** ||
|BFGOODRICH BAJA T/A ||** ||*** ||*** ||**** ||
|MICKEY THOMPSON BAJA CLAW ||** ||*** ||*** ||**** ||
|SUPER SWAMPER IROK ||** ||**** ||*** ||*** ||
|SUPER SWAMPER TSL ||* ||**** ||*** ||**** ||
|SUPER SWAMPER SX ||* ||**** ||*** ||**** ||
|SUPER SWAMPER BOGGER ||* ||**** ||*** ||*** ||
|PRO COMP XTERRAIN ||*** ||*** ||*** ||*** ||
|YOKOHAMA M/T ||*** ||*** ||*** ||*** ||
|BFGOODRICH MT KM ||*** ||*** ||*** ||** ||
|BFGOODRICH AT KO ||**** ||* ||*** ||** ||
|The BFG AT KO tends to clog in heavy mud and, like the MT KM, has a sidewall that can be cut in sharp rocks. However, its mild tread pattern works well in sand without digging to China and excels at giving a quiet, smooth street ride. The tiny sipes on the tread blocks help on pavement in rain, snow, and ice, and help make the AT KO an acceptable tire in some rocky conditions.|
|GOODYEAR AT/S ||**** ||* ||** ||* ||
|We've found the traction to be good on light rocks, but the paper-thin sidewalls wouldnÕt hold up to sharp rocks or branches. In the sand, traction is middle-of-the-road, which surprised us. Where these tires excel off-road is in high-speed dirt sections where the two circumferential grooves keep the vehicle on the course you set it on. Street driving is superquiet and smooth, and wet-weather traction is excellent.|
Cooper Discoverer ST - They have a sweet AT tread pattern, excellent in the snow, rain and never left me stuck in a muddy field while hunting. The tread wear was excellent and the pricing is much lower then a BFG. (2 recommendations)
Larger tires require less pressure.
"Y-hike" posted the following tip on kcjeepclub.org/forum:
One simple method for finding the right pressure for your Jeep is to draw a chalk line across the tread, then drive a bit and check the line. Even wear is good, while the line fading in the center indicates over-inflation. Worst is when the chalk mark wears off at the outer edges (shoulders) first, meaning that the pressure is too low.
Tire Dealer Profile
Les Schwab Tire Centers
Tires under Products.
Tires in the Jeep Configuration Page
Tire Terminology at offroaders.com
Off-road tires at Wolfgang's Mercedes-Benz M-class page
Other Links above.
Wheels at jeep.us41.org
Tires at jeeptech
Jeep Wheels (and tires) at jeep.us41.org
last updated 5 Jan 2007