Another View point. Excellent post ( not mine)on off road tires.
Scott Brady said...
"Well, we are having an interesting discussion on tires* , aren’t forums great!
So here is one man’s opinion on tires, with a little bit of science thrown in for fun:
Stability:
For a vehicle to handle similar to stock you would need to increase the tire width for every inch of lift and for every inch of tire height from the hub centerline to the ground (or half of the total tire height).* Of course even with the correct amount of width added, your truck will respond slower, and have greater roll-in due to the*deflection of the taller sidewall (that is why sport cars run large wheels and low aspect ratios).*
Uwe’s truck started with a 28.3" tall / 8.8" wide tire. So if the truck is lifted +3 inches and a 33" tall tire (+2.35") is added, the replacement tire would have to be 14.15" wide!* Ouch.* I have found that suspension design and bushing/roll bar strength are better compliments to a reasonably wide tire.*.* Flotation tires were developed for the US market about 20 years ago to address our larger vehicles (more flotation required) and higher road speeds (better handling).* Common metric (European) sizes are always narrower than the equivalent flotation (inch) tire.* For example, a common flotation 33" (32.6" typical)*tire*has a*12.5 section width; whereas the 285/75 R16 (32.8") is only 11" wide at the section width.*A 33 or 35x12.5 is a good choice for a full size (heavy) vehicle. Anything wider than a 12" tire on a light vehicle is actually a detriment to traction on hard surfaces (see below)
Traction:
Tread design- The tread you select needs to be appropriate to the terrain you are driving on. A mud tire will perform poorly on the sand compared to an all terrain, etc.
Contact Pressure- This is an often overlooked factor when selecting a tires width.* The weight (Lbs. per square inch) of the vehicle is spread out across the contact patch of the tire.* If you have a wide tire on a light vehicle you will have poorer traction on rock, but great traction on sand.* Of course there is a limit to this (point of diminishing return), and is very situation specific. If you look at the tires used in competitive rock crawlers they are rarely over 13.5" wide, even on 40" diameter tires. Tires in the 10 to 12" range on a light vehicle are perfect for most terrain. A narrower (within reason) tire will always provide better traction than a wider tire unless flotation is required due to the contact pressure.*
Durometer Rating- The durometer rating of the rubber compound also contributes to improved traction.* A softer tire (lower durometer) like a Goodyear MTR or BFG Moab edition will perform better than other tires, as the tread "lugs" can deform under pressure to conform to the terrain, similar to lowering the air pressure.* The down size is greater propensity to cuts and torn lugs, and a higher wear rate. It does seem that Goodtimes has had good luck with wear on the MTR's, but I think the lighter Jeep help a lot. The tires on my Jeep's always seem to wear well. Here are some internet comments on the MTR.* Most love the tire, but many note high wear http://www.epinions.com/Goodyear_Wra...splay_~reviews
Siping-Tire siping and grooving also improves tires traction on most surfaces.* The benefits are most apparent on ice and wet surfaces.
Given the same height, tread design and sidewall thickness; here is a review of the benefits of different widths:
Wider Tire (12-14"):
Benefits:
Greater flotation on soft surfaces (less contact pressure per square inch)
They do look cool
Increased stability
Disadvantages:
Greater rotating mass- It takes more power to turn, and a greater likelihood of broken parts
Fuel Economy- Greater resistance to the road and air
Less traction on hard surfaces (less contact pressure)
Less traction in snow, ice and mud where flotation is not required
Narrower Tire (10-12"):
Benefits (other than the disadvantages of the wider tire):
Less unsprung weight
Easier to fit on factory wheels, and less lift is required (usually)
You can fit in tighter areas (every little bit helps)
Less engine power is required to gain wheel speed, or push through shallow mud and snow
Disadvantages:
Less Flotation on soft surface (this can be a major factor in sand)
Less stability
Potential for increased damage to terrain on muddy tracks
Practical Application: If you look at any major expedition effort, the tires of choice are almost always narrower. For example, the Turtle Expedition who has literally traveled around the world used a 255/85 R16 (33.1 x 10) for many thousands of miles on their full size Ford. Land Rover uses narrow 7.0 R16 XCL*tires in all of their Camel Trophy events. Rain Forest Challenge and The Trophy challenge have all been won by the aggressive Simex Trekker tire (35x11.00).*Even Tom Sheppard the "god" of expedition travel uses the 7-7.5 R16 Michelin XZL and XCL*for most of his expeditions. Most of this information can be found in the Land Rover Driving Instructor Curriculum.
The choice of tires and width has always been a point of serious discussion (camp fire talk), and the opinions are as varied as the types of tires available.* Everyone needs to pick what works for them, and the terrain they most frequently drive.* I certainly respect the ideas of others on this subject, especially those of Goodtimes and Baja, as*their comments come from direct experience***.* After many vehicles (16+) and tires (30+ sets) *I have settled on a 10-11" width and 32-33" height as what works best for me, and the type of terrain I drive.
Goodtimes: The Yokohama Geolander A/T you are refering to is likely the older tread design.* The new A/T+II has only been on the market for about a year.* They make less noise than the BFG A/T's that I replaced (I have a Db meter).*I have not experienced the sidewall damage you refer to on the BFG tires (I have had about 10 sets), the MTR and BFG both have 3-ply sidewalls.* I may seem that they*fail at a higher rate because BFG is a more common tire on the trail*
Sorry for the long post, but I do love this stuff! "
Neither ordinary or extraordinary, just indefatigable.
2000 VX Green Dragon- Chick Demagnitizer-Supercharger-Injen Intake- Cold air box-K&N- Power Vault SS Exhaust-265-75-16 BFG MT kms-On Board CO2- Custom Boulder Bars- Custom Skid plates- PIAA 520 Fog Lites-3inch lift with OME 912 Springs-LINE X Bedliner on Cladding & Hood Insert-ARB Front Lockers & Custom Bull Bar. Vintage Offenhauser Hood scoop Thule Rack. XM Radio-Custom Storage Box-First VX to surmount the RUBICON.Thanks Sierra Stompers