Q I have been working on my Jeep XJ for while now. I'm 14 years old. Some of the things I have done to the rig are a 41/2-inch lift, 33-inch Mickey Thompson Baja Claws, and cutout fender flares for some flexing room. I have a question about the stock axles, a Dana 35 rear and 30 front. I know these aren't the best for wheeling, but are they good enough to hold up as trail-worthy daily driver when I'm 16? If not, is there anyway to beef them up, or should I look for a 44? And where could I get one for cheap since my budget is almost nonexistent? The rig is going to be used for mostly mud with a little rockcrawling.
A Your axles will be fine for daily driving and four-wheeling. These axles are not the strongest, but they don't just explode at the first sign of dirt either. There are chromoly upgrade axle kits available along with locking differentials, but I would leave them alone for now. Save your money and just go have fun. I'd invest in a winch before I would spend money on a Dana 35 or 30. Realize that Trent Mcgee, who goes on our Ultimate Adventure each year in a Jeep-based buggy, is still running a Dana 30 front axle, but his ride is lightweight and he doesn't abuse the axles.
Nuts, I'm Confused
Q Will you please give me and the rest of us nonmetric guys a formula for figuring out the sizes of these metric tires without having to call the tire store every time and then being made to feel stupid by some youngster?
Santa Rosa, NM
A No kidding, Wes!
Inch measurements make sense. A 35x12.50R15 tire is a 35-inch-tall tire with a 2.5-inch tread width, and it fits on a 15-inch wheel.
A metric tire measurement, however, is nothing but confusing. Say we have an LT285/75R16. We know the R16 means it is a radial tire on a 16-inch rim, just like our inch-sized tire. (It's weird that they measure the rim in inches but the rest of the tire in millimeters!) But what is all this LT285/75 stuff?
LT means the tire is for a light truck, while P in that position would mean a passenger vehicle. The larger number, 285, is the section width in millimeters. So to determine the width in inches, simply divide by 25.4, the conversion of any millimeter measurement into inches. This still leaves us with overall height to figure out, and usually that's the number we want.
The 75 is called the aspect ratio. It is the height of the tire expressed as a percentage of the width. We know the width is 285 mm, so if the height is 75 percent of that, the height is 213.75 mm (285 x 0.75). But that is just for the height from the tread to the rim, so we need to double that, and we get 427.5 mm. Then we divide that by 25.4 and it changes to inches: 16.83. Then we add the diameter of the wheel (16) and get 32.83, or roughly 33 inches.
Thoroughly confused? Just remember "SA2 by 25.4 plus rim." That means section width (S) times aspect ratio (A) times 2 divided by 25.4 plus rim diameter. The result is tire diameter.
Thanks for the great question. Your letter was picked as this month's Nuts, I'm confused letter. We'll be sending you a $100 gift certificate for 4Wheel Parts (www.4wheelparts.com), where you can choose from any number of metric and standard-size tires.
Confused? Email your questions about trucks, 4x4s, and off-roading tech using "Nuts, I'm confused" as the subject and include a picture (if it's applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I'll be checking the forums on our website (www.4wheeloffroad.com), and if I see a question that I think more of you might want to have answered, I'll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245 fax to: 310.531.9368 Email to: email@example.com