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4x Forum - Editorial

Posted in Features on October 1, 2007
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Send questions, comments, and suggestions to: 4 Wheel Drive & Sport Utility Magazine, Attn: Christian Lee, 2400 E. Katella Ave., Ste. 700, Anaheim, CA 92806, or

Onboard Air Plumbing
Q: I've seen and read about various ways to plumb an onboard air system. Basically, you have a pump and various valves and safety switches that fill a tank. However, if you want to direct the air for more than just filling up tires or running air tools, how do you "switch" the air to other sources? For example, let's say you have shocks that you can change the damping on, air lift bags for towing, ARB Air Lockers, and air for the tank. It seems silly to install multiple dedicated air pumps for each item, but what type of "air switch" exists to direct the air to an accessory?
Bob Moritz
via e-mail

A: Bob, depending on the size of the air compressor and air tank, you can run all of the accessories you mentioned and more from a single unit. A smaller compressor and air tank will do the trick for most air-driven accessories; however, it will be significantly slower in completing jobs that require constant flow for an extended period of time, such as airing four tires from 10 psi to 35 psi. According to Kilby Enterprises, a manufacturer of engine-driven onboard air systems, your accessories should be built around the compressor, not the other way around. This means that you should first establish a well-functioning onboard air system and then add the extras. Part of the "various valves and safety switches" involved in the plumbing of an onboard air system are air manifolds, which are available with varying amounts of ports to meet the needs of any air system. Typically, a manifold will host the air inlet from the compressor and the outlet to a tank, a pressure safety switch, a pressure gauge, a check valve, and an adjustable relief valve. Air manifolds can also be purchased with multiple outlets to accommodate accessories (if you plan to install more air-driven accessories, you can install a manifold with multiple outlets and unused outlets can be plugged until needed).

Most accessories, such as air lockers and air horns can be connected to the air manifold or directly to an outlet on the air tank. Air suspension or adjustable-ride shocks should typically pull air straight from the air tank. If an air tank has only one outlet, a T-connector can be used to create additional ports. Each accessory will require separate on/off switches for individual operation, and the compressor must also be switched on so it will continue filling the tank as its content is exhausted. Provided the other accessories are not switched on at the same time, only the desired accessory will function, though the others will still be ready to receive air at the flick of a switch.

For more information about onboard air system plumbing, contact Kilby Enterprises [(818) 565-5945,]. Power Tank [(800) 574-3701,] can also offer a variety of onboard air plumbing ideas.

Morse Code Not Required
Comment: First, the individuals who assemble 4 Wheel Drive & Sport Utility do a great job. I enjoy every issue. Second, it is good to see articles such as "Remote Contact" (June '07). I'm a ham radio operator and have at least one ham radio in each vehicle. There has been a change in policy regarding licensing that you may not be aware of. Morse code is no longer required for any license level. This change went into effect in February 2007 (I realize you have a publishing schedule that forces you to assemble the magazine well in advance of the actual issue date). Ham radio is a great way to communicate across the trail or across the globe. I appreciated your article.
James Reeves

A: James, I'm glad you enjoyed the "Remote Contact" article. I'm still playing with the Icom IC-208H VHF/UHF FM transceiver a good bit trying to familiarize myself with all of its functions, but it has already come in handy at a couple off-road races and trail runs. Thank you for the heads-up about Morse code no longer being required for any of the ham radio operator licenses. This may open the door to new users who may have been apprehensive about owning and using a ham radio as a licensed operator. Thanks for writing. Ham on.

Will Wheels Swap?
Q: Perhaps you can advise me or offer some suggestions. I currently have a '99 Jeep Wrangler Sahara that I bought new in the fall of 1998. It has 23,000 miles, and everything on it is original. I really like the wheels and tires on the current Rubicon (16-inch versus 15-inch current wheel). My plan was to buy some refurbished wheels and new tires similar to the factory Rubicon. If I do this, I suspect I will need some minor suspension modifications. Best I can tell, the Rubicon tires stand 2 to 2-1/2 inches taller than my stock tires. As you know, there are a gazillion lift kits available for Wranglers. Due to the age of the vehicle, I was thinking of a lift kit that includes shocks and probably springs. My guess is that I should be looking at a kit that lifts the vehicle 2-1/2 to 3 inches. Any suggestions pro, con, or otherwise?
Scott Goth
via e-mail

A: Scott, provided you are interested in Rubicon wheels and tires from a pre-'07 Wrangler, you should not have any trouble with fitment. The '07-model Wrangler uses a 5-on-5 bolt pattern and will not fit earlier models with the 5-on-4-1/2 pattern. As far as suspension improvements to fit the 31-inch tire, the easiest and most inexpensive route would be to install a coil-spring spacer kit along with new shocks. This will give you the needed space (usually about 2 inches) to fit the slightly taller-than-stock tires under the fenders and still have some space for suspension articulation (you'll also gain use of longer-than-stock shocks). If you feel that the stock coil springs have seen better days, you can also opt to install slightly taller new coil springs in the 2- to 3-inch lift range. Either method will create ample space for 31-inch tires on 16-inch wheels. Thanks for reading.

Grand Suggestions?
Q: I have an '03 Jeep Grand Cherokee WJ with a 2-inch budget boost. I have found myself down trails without enough ground clearance and am looking to go higher. My question is: bolt-on or weld-on? From what I can tell, there are just a few lifts. A couple are bolted to the unibody, and some are welded. I hear welding can crack or tear the unibody if not done right and that bolting just isn't as good. I would like to run 32s (possibly 33s) and from what I can tell I would need about 6 inches of lift, and I would like a long-arm system (at least up front). I am also concerned about death wobble and have read that shorter springs are better to combat that and that some people run 4-inch springs and the 2-inch BB spacers. Did I mention I was on a budget?
Bryan Barry
via e-mail

A: Bryan, bolt or weld, bolt or weld? Both are solid methods of attaching lift-component brackets on a WJ, but welding is decidedly more permanent. If it were my vehicle, I'd stick with a bolt-on kit until I was absolutely positive that it's the lift system I want for my 4x4. After that, I'd prefer a mix of both methods, retaining use of bolts and adding welds to areas that show signs of weakness. However, if you are on a budget, you might steer away from the weld-on kits since they may require additional labor costs, whereas most bolt-on kits can be installed in your driveway using basic handtools (pneumatic tools make it even easier) and a jack and jackstands. Either way you do it, there is a chance that the unibody will crack, but that's also true if left in stock form and subjected to heavy trail use.

Regarding lift size, you should be able to fit your desired tire size using a 4- to 6-inch lift, depending on the manufacturer. When you lift a vehicle, you will run into issues that must be addressed, and bumpsteer and death wobble are some of these issues. Most lift manufacturers have already invested a good deal of time to ensure that these negative driving effects are eliminated through the design of their systems, but you should still talk to the company to find out what changes in driving characteristics you can expect from installation of its lift system.

For more information about Jeep Grand Cherokee WJ lift kits, check out Kevin's Off-Road in Phoenix, Arizona ( Kevin's offers a 4-inch Ultimate kit to fit 33x12.50 tires and can also provide its Anti-Death Wobble dual steering-stabilizer kit. Wheel on.

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