TW - tires arrive.jpg (79977 bytes)

A Jeep owner's favorite person - the UPS man!


In my goal to achieve more ground clearance, a better ride, and a more trail-worthy Jeep, I had finally settled on a three-phased plan.  Phase 3 of my plan, the final step, was to add the taller tires and new wheels.  Before just throwing the taller tires on the Jeep, I first needed to update the suspension (Phase 1) by adding the Rubicon Express Extreme Duty 4.5" lift kit.  Then to allow the Jeep to pull the load of the bigger wheels, I needed to change the gearing to a lower 4.56 ratio - which was a good time to throw in the one-piece axles and the ARB air lockers (see the lockers project).  Now, the package is complete!

Not Just A Fashion Statement!

Phase 3 - shinny.jpg (110204 bytes)  Bigger tires and wheels are for more than just good looks.  A taller tire will provide additional ground clearance for the axles - something a lift kit won't do anything to help.  However, there is a point of diminishing returns.  With the stock Dana 30 front axle and the AMC 20 rear axle (even with the one-piece axle shafts), I felt the 33" tire is about the most you can expect before the size of the wheels overwhelms the ability of the axles.   Additionally, the 35" tire necessitates the need to make modifications to the body to accommodate the wheels into the fender wells when the suspension is compressed - something else I wasn't ready to do to my CJ just yet.

TW - tight-fit spare.jpg (71328 bytes)  However, when it comes to looks, I wanted an aggressive tire for the mud and snow in winter, durable in the rocks in the summer, AND have decent road manners on the pavement.  A pretty tall order!   I have always been a fan of the steel wheels over the aluminum wheels - mostly due to their costs!  I also have been working toward eliminating most of the chrome on my CJ (just my personal preference).  So with all this in mind, I settled on the Super Swamper SSR new-version radial tires mounted on the all black Rock Crawler steel wheels.

A typical view of a dirty steering gear box brace.  If you're going to move to a bigger tire (read: heavier) you should also be thinking about beefing up the steering gear box.  This doesn't mean replacing the unit altogether (though some do), it just means adding a simple steering box brace.  The steering box brace essentially ties the steering box to a separate point elsewhere on the frame (often to the opposite frame rail or cross member) and in addition to the original mounting point on the frame.  This one is from Tomken Machine.  I chose this particular design because I liked the fact that it sort of doubles as a guard for the steering box.

Need to change your speedometer gears?  Remember, taller tires, or any tire size height change for that matter, may result in the need to recalibrate your speedometer.  Click on this photo to see the Speedometer Gear Change project!

Rim Widths and Back Spacing

I prefer running my tires on slightly narrower rims.  This helps keep the tire seated on the rim when they're aired down.  Airing down the tires helps improve their traction off road, and also serves to soften the ride.  (For information on airing down your tire's pressure, follow this link.)  When running a tire on a narrower rim, the tire's sidewalls will also help protect the rim from rock and root abuse.

The size of a rim is measured from where the tire actually seats in the rim.   Therefore, an 8" wide wheel will actually be slightly wider (about another inch) than eight inches from edge to edge.  Similarly, the height of a wheel is measured the same way.  In the first photo below, the front of the tape measure is just at the lip of the wheel (where the tire seats), notice where the 8" mark is on the tape (where the other side of the tire seats).  In the second photo below, the overall width of the wheel is 16" but this is a 15" rim and tire.  This shows the difference.

TW - 8 inch.jpg (51349 bytes)   TW - 15 inch.jpg (72268 bytes)

Backspacing is often misunderstood.  The importance of proper backspacing is to insure the tire and wheel will not place undue stress on the wheel bearings or interfere with the turning of the front wheels.  Backspacing is the amount of depth of the rim - considered from the back side.  The actual "depth" is the measurement from the inside wheel mounting surface (where the base of the lugs go through the wheel) to the edge of the inside wheel mounting surface (about the "8" mark on the first photo just above).  In the photo below, the picture is a little deceptive due to the camera angle, the backspacing is less than 4 inches (and not 6 inches).

TW - backspace.jpg (67503 bytes)

Thoughts on Mail-ordering Tires and Wheels...

Mail-ordering can sometimes be a real challenge.  As a consumer, you are always looking for the best deal.  Mail-order retail businesses offer great prices typically because they usually are coming directly from a distributor or larger retailer who has the ability to buy in bulk and obtain the original merchandise at a low price.  The lower prices can be great enough to still be low when the merchandise finally comes to your door even with the extra costs for shipping.

Problems, however, with buying through mail-order businesses is knowing exactly what it is you are really buying.  This can be really tough if all you are looking at is a tiny picture in a magazine add!  The internet has helped this tremendously, but you still need to be really cautious when you are ordering.  Returning merchandise back to a mail-order business quickly diminishes any savings.

When buying tires and wheels through mail-order (or on-line), I recommend you use their 800 number and actually talk to someone in person.  Make sure you have all your questions written down in front of you before you make the call.  Make sure you also understand the answers.  Finally, get the name of the person you spoke to in case you need it for future reference.

Thoughts and Deals on Tires and Wheels:

bullet Shop for package deals!  If you are looking for the best deal, it may not be worth saving $5 per wheel if you're buying them from a different company than the company whom you're getting your tires.  You'll essentially be paying high shipping charges twice.
bullet I always recommend having matching spare tires and doing a five-tire rotation.   You'll get 20% longer tire wear, too!  Many times, companies will give you a better deal if you buy five tires than if you only buy four.  (Something to ask about.)
bullet Get the tires and wheels mounted and balanced!  Most places already do this, but make sure.  Otherwise, factor the additional costs of having your new tires mounted in town.  That being said, many times the pre-mounted tires and wheels may not be well balanced - but this is only a slight risk.
bullet Does the package include new lug nuts or center caps?  Many offer these as part of the deal, take advantage of this if you can.
bullet Is the company out of state?  If so, often you can save sales tax - which can make up for more than the shipping costs.
bullet Contrary to the comment above, shipping charges are significant!  Try to find a business that is relatively close.  Especially if you think there's a chance you may be sending them back!