• Barbara Toy, an Early Land Rover Heroine
    Just like the Land Rover broke down barriers, Barbara Toy did too, taking some of the first extremely long-range expeditions with the new Series I Land Rover in the early 1950s. A woman traveling solo, she took her truck, Pollyanna, around the world, focusing often on the deserts of North Africa and the Middle East. […]
  • The Armored Range Rover Sentinel Brings Style to Security
    Perhaps you're an oil baron, railroad magnate, or high-level mobster, susceptible at any time of day or night to ambush or attack. You need a safe vehicle, but you also want a bit more style than a pedestrian armored Suburban. Enter the Range Rover Sentinel, the 10,000-pound armored behemoth for those who legitimately need to […]
  • Land Rover Execs Drop Hints on New Defender
    The new Defender will be very different from the old one. This has been common knowledge for years. Land Rover has stated it over and over, to try and deaden the blow to old school Land Rover enthusiasts. Several Land Rover executives have now detailed a few ways that the new truck will be the […]
  • A History of Discovery, Part 2: 2005-2019
    To celebrate the 30th anniversary of the Discovery, and its 25th anniversary in North America, we continue our History of Discovery, picking up in the early 2000s with the launch of the Discovery 3/LR3 and continuing through Discovery 4/LR4 and the current Discovery 5.  

Tire Sizes

The first question is, what size tire can I put on my vehicle? First we must look at what size will fit and how sizes are determined. In this article I will use a 225/75/16 tire. The average size was computed averaging the sizes posted on the different manufactures web sites for a M/T tire. The rim size came out of the owners manual.

Here are a few terms that need to be explained. This is based on tires with the correct inflation specified for the tire and load of the vehicle.

Aspect Ratio:
The “75”is known as the Aspect Ratio. It is calculated by dividing the section height by the section width and multiplying by 100. (In this example, the sidewall will be 75% of 225)

Overall Diameter: diameter of the tire from tread surface to tread surface while inflated but unloaded This is the number off roaders are most interested in. As in a 33inch tire.

Static Loaded Radius:
distance from the center of the axle to the ground under the specified load with recommended tire inflation.

Rim Diameter: diameter of the rim from bead seat to bead seat.

Overall Section Width:
distance between the outer sidewalls of an inflated tire.

Rim Width: distance between the inside of the rim flanges. The rim width is important to consider when looking for larger tires.

Section Height: distance from the bead seat to the outer tread surface of the inflated tire Section height effects the way your vehicle responds to input from the steering wheel. The taller the section height, the less responsive a tire generally is. This decreases as you “air down” for trails.

Section Width: distance between the outer sidewalls of an inflated tire, less any ornamentation, side lugs or curb ribs. The “225” is the width of a tire and is measured in millimeters when mounted on the correct rim and inflated to the recommended tire pressure. Section width increases as you “air down” for the trail. Be mind full of springs and steering gear that could rub with the inside of the tire.

Tread Width: the width of the tread surface, designed for contact with the road. Often referred to as footprint. Foot print also includes the length of the tread area on the ground and increases as you “air down” In theory the larger the foot print, the more traction.

Now all this said, here is the formula to figure out over all diameter of a tire. I will use 225/75/16 tire as an example. The width is 225, aspect ratio is 75 and the wheel size is 16.

1.Convert the width in millimeters to inches. This is done by dividing 225 by 25.4

225/25.4=8.86

2. Determine the section height by multiplying the aspect ratio. In this case 75

8.86X.75=6.645

3. Now all you have to do is add the two section heights to the rim size.

6.645+6.645+16=29.29

Your tire is 29.29 inches tall when inflated to the recommended pressure and your vehicle is not loaded (dry weight).

Now the answer to the question. How much ground clearance do I gain? Take the one section height for the current tire/wheel combination and subtract it from the new tire/wheel combination. Remember. You only gain one tire section height plus the difference in the rims diameter from the axle to the rims edge. Going from 15 inch to 16 inch in reality is ½ inch. The other half is above the axle and will not effect ground clearance. It does effect fender clearance.

Chart

Disclaimer:
These are not recommendations or suggestions, but only the information as it has been harvested from various sources including other web sites. They are presented for the informational use of the reader in making their own decisions. There are too many variables in tire use and applications to recommend a size for a particular use. Also there are too many brands, and they are like all opinions, very personal.

Leave a Reply

Comment spam protected by SpamBam