So do the front or the rear seperately. Keep in mind you need a floor jack that can travel at least 10-12" (that was a big issue for me for a while) you can crib the rest with wood blocks. you'll also need four 6-ton jackstands, and two 2/3-ton'ers would help, but not required.
Typically you want the bumpstop needed for SHOCKS ONLY to determine your TIRE requirement. Then you basically get the longest travel use out of your shocks. Generally speaking, its better to get more shock travel, aka more uptravel and downtravel, and run smaller tires than it is to run those same shocks and lots of bumpstop in order to run larger tires. With the latter idea, you're limiting your uptravel
I give you a general idea of what you're looking for with 33" tires and 3" lift.
for the front:
This is a budget boost for the rear, but the bumpstop extension shows where the spring compresses:
Bumpstop extensions for the front should always go on the axle pad, extensions for the rear should always go on top.
Another cool fact worth taking note of is that 1" of body lift means you need 1" less bumpstop to fit the same tire size that would require 2". So there is definitely an advantage to a small body lift!
And for reference:
1. Remove the shocks - fully compress them and measure the length from eye to eye, or base of the stud to eye.
2. pull the springs from both sides.
3. Now set the shocks back in, connecting them at the top, disconnected at the bottom.
4. You should have unhooked the axle side of the track bar to pull the springs, but here you can leave it unhooked. We'll be playing the interference game (with your stock bar you won't have any problems)
5. Pull the jounce bumper out (rubber bumpstop thing inside the cup)
6. Now jack the axle up (or lower the frame) SLOWLY.
7. You should get something that looks like this:
2. pull the springs from both sides.
3. Now set the shocks back in, connecting them at the top, disconnected at the bottom.
4. You should have unhooked the axle side of the track bar to pull the springs, but here you can leave it unhooked. We'll be playing the interference game (with your stock bar you won't have any problems)
5. Pull the jounce bumper out (rubber bumpstop thing inside the cup)
6. Now jack the axle up (or lower the frame) SLOWLY.
7. You should get something that looks like this:
8. Watch for the shocks bottoming out...in other words the Jeep starts lifting, or you start compressing the bushing at the top of the shocks. You should measure your shocks fully compressed length before hand so you know what you're dealing with. 13.5" shocks will fit inside the stock compression location, 14.5" will require 1" bumpstop extension, 15.5" will require 2", and so forth.
8. Now once you get the bumpstop cup setting on the axle pad, slide a tire on if you can. Make sure you've supported the axle with jack stands for safety here. You can hold the tire on by hand, or use two lug nuts hand threaded on. You'll notice very soon if you'll clear or not. This is where removing the flares is helpful.
9. If you couldn't get the bumpstop cup down all the way because the shocks were too long, then you need to measure the distance from the bumpstop cup to the spring pad, as you just back off the shocks about 1/4". Thats how much bumpstop extension you need FOR SHOCKS ONLY.
10. If you don't clear the tire fit test, measure from the hub center to the sheet metal in a vertical fashion (you'll need to eye ball this a bit because the axle is a bit wider than the tub).
11. Now, move the axle down until you can fit the tire size you want. When you can just barely slide the tire on, and clear the steel fender lip, measure the distance to the bumpstop cup and the spring pad. Thats the minimum bumpstop extension you need FOR TIRES.
12. Now while you're doing all this you need to keep checking for track bar interferences. Will the track bar hit the diff cover? Will the track bar hit the tie-rod? Since its disconnected, its an easy check by lifting it up and position it in the mounting location. You can slide a bolt in if you like, or just hold it there by hand and check, or even zip tie or duct tape it. While you're moving the axle, the distance between the mounting points is changing, so don't freak out if you can't get the bolt in.
8. Now once you get the bumpstop cup setting on the axle pad, slide a tire on if you can. Make sure you've supported the axle with jack stands for safety here. You can hold the tire on by hand, or use two lug nuts hand threaded on. You'll notice very soon if you'll clear or not. This is where removing the flares is helpful.
9. If you couldn't get the bumpstop cup down all the way because the shocks were too long, then you need to measure the distance from the bumpstop cup to the spring pad, as you just back off the shocks about 1/4". Thats how much bumpstop extension you need FOR SHOCKS ONLY.
10. If you don't clear the tire fit test, measure from the hub center to the sheet metal in a vertical fashion (you'll need to eye ball this a bit because the axle is a bit wider than the tub).
11. Now, move the axle down until you can fit the tire size you want. When you can just barely slide the tire on, and clear the steel fender lip, measure the distance to the bumpstop cup and the spring pad. Thats the minimum bumpstop extension you need FOR TIRES.
12. Now while you're doing all this you need to keep checking for track bar interferences. Will the track bar hit the diff cover? Will the track bar hit the tie-rod? Since its disconnected, its an easy check by lifting it up and position it in the mounting location. You can slide a bolt in if you like, or just hold it there by hand and check, or even zip tie or duct tape it. While you're moving the axle, the distance between the mounting points is changing, so don't freak out if you can't get the bolt in.
Typically you want the bumpstop needed for SHOCKS ONLY to determine your TIRE requirement. Then you basically get the longest travel use out of your shocks. Generally speaking, its better to get more shock travel, aka more uptravel and downtravel, and run smaller tires than it is to run those same shocks and lots of bumpstop in order to run larger tires. With the latter idea, you're limiting your uptravel
I give you a general idea of what you're looking for with 33" tires and 3" lift.
- Based on TIRE SIZE ONLY - the require bumpstop will be about 2-2.5" without a BL. With a BL, that will be 1-1.5".
- Based on SHOCK LENGTH ONLY - a collapsed length of 15.5" will require 2" bumpstop, 14.5" will be 1", and 13.5" will be no addition bumpstop extension.
- Everything i've said has been for the front. for the rear, the general rule of thumb is to add 1" to the bumpstop extension you determined in the front. thats a good starting point as a guide.
- When testing the rear axle, make sure to mount the tire up at full compression - look for clearance issues in the BACK of the fenderwell. 35s will rub on stock length control arms, 33's may too, or they may be stupid close.
- Don't throw the giant 2.5" bumpstops you have away. Find out how much you need based on what i've listed, then cut it down if you need less. Slap it in a vice and use a wood saw/band saw to cut it down. Save the scrap piece and use it later if you need additional bumpstop. Or use it as a bumpstop extensionfor the rear if its thick enough.
for the front:
This is a budget boost for the rear, but the bumpstop extension shows where the spring compresses:
Bumpstop extensions for the front should always go on the axle pad, extensions for the rear should always go on top.
Another cool fact worth taking note of is that 1" of body lift means you need 1" less bumpstop to fit the same tire size that would require 2". So there is definitely an advantage to a small body lift!
And for reference:
