Tires, they seem pretty basic, they’re round (usually), rubber, knobby, and the bigger the better. But what seems like a pretty simple thing is actually one of the most complicated, expensive, and important decisions you can make in your Jeep build. Important aspects of tire selection include architecture, tread pattern, rubber composition, and size.
There are three questions you need to ask yourself when shopping for tires: What do I really need out of these tires, what do I intend to use them for, and what am I willing to sacrifice to get what I want. Picking tires is almost always a compromise of some type. In general, the better a tire works off-road the poorer they function on the highway, the better the traction the faster they wear out, and the bigger the tire is the more stress it puts on internal parts.
Bias ply Vs Radial
For half a century the bias belted tire was really the only choice; the belts of the tire wrap from bead to bead and provide excellent puncture resistance (especially if steel belts are used). Bias tires are still used in industrial applications (tractor tires) and include some of the most aggressive off-road tires. They are rarely a good choice unless you have a dedicated trail rig where highway manners and ability to balance well are unimportant. The radial tire uses belts that go diagonally from bead to bead and generally are more street friendly, and actually have more flexible sidewalls, providing better floatation when aired down. Outside of purpose built buggies, mud trucks, and rock bouncers, the radial is generally the better choice.
MT vs AT
Most people assume that the more aggressive the tread pattern is, the better off-road tire it is in all situations, but that is not true. MT (mud terrain) tires are designed with a high void to tread ratio that allows mud to clear out of the tire when spun to give clean traction for biting into the mud continuously. MT tires have a smaller contact patch on rocks (due to the high void ratio) and are troublesome in sand (they like to dig) and ice and snow. The other downside of the MT is they are loud on the road and wear out very quickly. AT (all terrain) tires are a much more street friendly tire and will often perform better in rocks, sand, and dirt than their more aggressive counterparts. They wear much longer but tend to “goop up” in sticky mud and lose their effectiveness.
Mileage vs Traction
Two main factors affect the mileage you get out of a set of tires: Tread pattern and rubber compound. The more aggressive the tread pattern the less actual rubber you have on the road surface and the more quickly it will wear. The softer the rubber compound, the shorter its lifespan. Conversely, soft tires stick much better on the rocks, and an aggressive tread pattern is far better for the mud, so there really is a direct correlation between off-road performance and tread wear. Becoming more popular are the hybrid or dual purpose tread designs that incorporate multiple patterns into one tire. Goodyear seems to be on the cutting edge of this technology with their MTR Kevlar and Duratrack, which actually use 3 and 2 different tread patterns on each tire respectively.
Tire Size, Big vs Small
Everyone knows that bigger is better, right? If 31s are good 35s must be great, but don’t forget about 37s or even 40s!! It’s true that there is only one way to get a solid axle up off the ground and that’s larger tires. Larger tires also make rocks smaller, dig deeper into mud and float better across sand. So what is the downside? Larger tires suck horsepower and torque by effectively raising your final drive ratio, and the larger tire you have the more stress it puts on internal parts like axle shafts, differentials, and drive shafts. This makes breakage more likely. It is a delicate balance, then, to get the largest tire that will fit on your vehicle without over-sizing your gears, and having the proper driveline upgrades to handle the increased stress.
The conclusion then? There is no perfect tire, only a set of tradeoffs and compromises. By considering how you intend to use your vehicle the majority of the time, what’s important to you, and what you are willing to give up, you can narrow down your choice of tire to a shorter list.
P.S. Reading reviews from other wheelers is also a helpful tool in choosing the right tires for your needs, but if you want to start an instant argument among Jeepers, just ask on a public forum “what is the best off-road tire”. 😉