Frequently Asked Questions
1) What do I do about Death Wobble?
2) How much lift do I have? The easiest and best way to figure lift height is with a hub to fender measurement. Using a tape measure, measure from the center of the hub (or wheel) in a straight vertical line to the bottom of the fender (assuming stock, uncut fenders and the vehicle is parked on a level surface). The measurements below are stock hub to fender measurements. The difference between your measurement and the number below is your lift height.
3) Do I need an adjustable track bar? We recommend adjustable track bars when you may change your lift height in the future, either up or down, with taller springs or spacers, or heavy gear/bumpers/other armor. If that is not you, then stick with the fixed length bar.
4) Do I need adjustable long arms? We generally recommend adjustable arms when you are looking for over 6.5" lift and/or want to run larger tires (bigger than 33's). All of our rear long arm systems come completely adjustable, with no upgrade necessary.
5) What shocks do I need? This one is sometimes hard to answer, since "ride quality" is very subjective depending on the person. We will describe the shock options we have listed on our site for you to be able to make a good decision you can be happy about.
6) Do I need shock boots? No, shock boots are a nice upgrade, but not a requirement. Some people like them, some people hate them. You get to decide!
7) What size tire can I run? This question is another one that is hard to answer. There are many variables that you have to consider.
9) Do I need long arms? You might need long arms to have your vehicle perform the best both on and off road. Here are some signs that you might need long arms:
9) Do I need a Slip Yoke Eliminator? If you are experiencing vibrations from your rear driveshaft after installing a lift, we recommend using a slip yoke eliminator in combination with the correct axle pinion angle setting to minimize or eliminate the vibrations. Here are some things to consider about slip yoke eliminators:
10) Are IRO coil springs made for the 6 Cyl or V8 engines? Simply put, both! Some would lead you to believe that there is an extreme weight difference between them, but really they are quite close. For the applications our springs are used, the weight differences will not effect the advertised lift height.
2) How much lift do I have? The easiest and best way to figure lift height is with a hub to fender measurement. Using a tape measure, measure from the center of the hub (or wheel) in a straight vertical line to the bottom of the fender (assuming stock, uncut fenders and the vehicle is parked on a level surface). The measurements below are stock hub to fender measurements. The difference between your measurement and the number below is your lift height.
- TJ front: 18", TJ rear: 19"
- WJ front: 18", WJ rear: 18.25"
- XJ front: 17.5", XJ rear: 17.5"
- ZJ front: 18.25", ZJ rear: 18.5"
3) Do I need an adjustable track bar? We recommend adjustable track bars when you may change your lift height in the future, either up or down, with taller springs or spacers, or heavy gear/bumpers/other armor. If that is not you, then stick with the fixed length bar.
4) Do I need adjustable long arms? We generally recommend adjustable arms when you are looking for over 6.5" lift and/or want to run larger tires (bigger than 33's). All of our rear long arm systems come completely adjustable, with no upgrade necessary.
5) What shocks do I need? This one is sometimes hard to answer, since "ride quality" is very subjective depending on the person. We will describe the shock options we have listed on our site for you to be able to make a good decision you can be happy about.
- IRO Hydros: These are a excellent quality Gabriel manufactured heavy duty hydraulic shocks. They will provide a firm but controlled feeling ride. You will feel more of the road with the use of these shocks. They come in many lengths to properly fit your application.
- Doetsch Tech 8000 Prerunner: These are an excellent quality Doetsch branded heavy duty hydraulic shock. They will provide a firm but controlled feeling ride. You will feel more of the road with the use of these shocks. Head to head with the IRO shocks, they are slightly softer in valving. The DT8000's are a natural fit with those running long arm systems, becasue they offer very good control, and they come in the longest lengths available for a bolt in shock! They also feature a built in bumpstop and a massive 11/16" chrome shaft. They come in many lengths to properly fit your application.
- Bilstein 5125: These are top of the line quality, Bilstein branded, monotube shocks. The Bilstein shocks come with a brushed aluminum finish that is both attractive and durable. They offer the best in terms of simulating factory ride quality. This means they are the softest shock in our lineup. With the soft valving also comes more body roll while cornering. These shocks are offered in many lengths to work with your application, however they typically have significantly shorter travel ranges than the IRO's or Doetsch shocks. They also come with black shock boots AND shock adapters for no extra charge!
6) Do I need shock boots? No, shock boots are a nice upgrade, but not a requirement. Some people like them, some people hate them. You get to decide!
7) What size tire can I run? This question is another one that is hard to answer. There are many variables that you have to consider.
- Wheel backspacing or wheel spacers - Typically less backspacing means you will need a smaller tire.
- Lift height - Typically the taller you go, the bigger you can go.
- Axle position - If you have moved the axle much forward or back of its original position, you may have to run smaller, or have the ability to go bigger.
- Trimming - No trimming will require the smallest tires. Generally the more you trim the bigger you can go.
- Bump stops - With factory bumpstops, your suspension will be able to go as high as the factory intended with stock size tires. Increasing the size/length of your bump stops will allow a larger tire to fit by stopping the upward travel of your axle sooner.
- Will you disconnect sway bars? - If you do, your axle will travel further. The more travel, the smaller the tire will fit, without other mods, like trimming and longer bumpstops.
- Tire brand - Tires vary in actual size depending on what brand you get. Most listed tire sizes are larger than the actual tire. For example a 33x12.5x15 tire may only turn out to be 31.5" tall in real life. Research the tires you want before you buy. Most manufacturers will tell you actual diameter.
9) Do I need long arms? You might need long arms to have your vehicle perform the best both on and off road. Here are some signs that you might need long arms:
- Your ride quality is poor and you wish the ride was softer.
- Your vehicle hops somewhat violently over bumps.
- You have Death Wobble.
- You can't crawl easily over uneven terrain.
- You're embarrassed to have your family or friends ride with you.
- You are constantly lifting a tire in the air, and losing traction off road.
- All your buddies already have long arms.
- You want the biggest ride quality improvement you can get in a bolt on package.
9) Do I need a Slip Yoke Eliminator? If you are experiencing vibrations from your rear driveshaft after installing a lift, we recommend using a slip yoke eliminator in combination with the correct axle pinion angle setting to minimize or eliminate the vibrations. Here are some things to consider about slip yoke eliminators:
- A slip yoke eliminator does 2 major things to help with vibrations:
- Requires a longer driveshaft than stock which improves the angle of the driveshaft as it sits in the vehicle and
- It requires the use of a double cardan style CV driveshaft, which further decreases the working angle of the universal joints, resulting in a smoother turning driveshaft and less opportunity for vibration.
- Slip yoke eliminators require different pinion angle adjustments than regular slip yokes. See drawings courtesy of Tom Wood's Custom Driveshafts for visual explanation:
- For leaf sprung rear suspensions, it will likely be necessary to use leaf spring shims to set your pinion angle up as shown in the illustration above.
- For coil sprung with control arm suspensions, you can adjust your pinion angle up or down with the use of adjustable control arms.
- Iron Rock Off Road does not know the length of driveshaft your vehicle will need with an SYE. The reason for this is because there are many different factors that effect the length required such as: lift height, axle position forward or back from stock, different engine/transmission
/transfer case combinations, different stock axles with varying pinion length, swapped in axles form different vehicles, different manufacturer's have different suspension
designs. Can't I just reuse my stock driveshaft? Sorry, you can't use your stock driveshaft here. You wouldn't want to even if it was the right length! Getting rid of the two joint shaft
and replacing it with a double cardan CV is one of the keys to successfully running vibration free. How do I get the right driveshaft?
- Plan ahead. Because a SYE typically needs a custom driveshaft, think about another mode of transportation while your custom shaft is being built and shipped to you.
- Install your suspension lift first.
- Install your slip yoke eliminator next.
- Make pinion angle adjustments until you are close to proper geometry for CV driveshaft.
- Measure from center of u-joint at the transfer case yoke to center of u-joint at the pinion yoke. The following illustration shows the arrows
pointing to the flat mounting surface on each yoke from where it's easiest to measure:
- Call IRO (or your preferred driveshaft supplier) with the length you measured accurate to within 1/8" inch.
- Double cardan driveshafts can be purchased at many different retailers. Iron Rock Off Road does fulfill custom driveshaft orders all the time and the typical turn-around time is 3 business days.
10) Are IRO coil springs made for the 6 Cyl or V8 engines? Simply put, both! Some would lead you to believe that there is an extreme weight difference between them, but really they are quite close. For the applications our springs are used, the weight differences will not effect the advertised lift height.
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Approximate "dressed" Jeep engine weights:
- Inline 6 cyl, 4.0L, 515 lbs.
- V8, 5.2L, 525 lbs.
- V8, 5.9L, 550 lbs.
- V8, 4.7L, 440 lbs.