I like to know what I'm doing when I do a suspension.

I like to get under there, and get dirty, and take things apart, and see how it works...and, what will probably break, etc...and, what that will MEAN if it does, etc.

So far....it seems that the JK has typical live axle related issues...and, all I need to really get going are some dimensions.

My wife has been having strokes and brain seizures, and the weather has been horrible most of the time, and I just got the JK last weekend...so, my typical approach is being stymied by logistical limitations related to hospital and dr visits, extra work to make up for time at Drs and hospitals, etc.

:(

I like articulation...and, to maximize it...I need to:

1) Compress the suspension all the way, and measure the resultant eye to eye shock distances...take a bit of fudge factor for suspension crash events, and that will tell me the shortest that the shocks need to get.

2) Disconnect the shocks lower mounts, and start drooping the suspension all the way down, as far as it goes until interference, binding, too short a line for brake or breather, a short linkage, shaft or cross member contact, etc...and axle shift, etc...

3) I take off/extend each interference as I go, and mark each as to where it becomes a problem...what it needs to allow continued droop.

4) When I hit a practical stopping point, I look at what I would need to correct the interferences, and my own point of diminishing return on doing the work, etc.

5) Whatever the practical droop limit ends up at, I look at where the lower shock mount ended up, and what the shocks needs to do to reach the extra distance/if anything would now have swung into the way, etc.....if its a clear shot, I mark the new extended length I'd need...add a fudge factor for forced droop extension, and that tells me the longest that the shocks need to be.



That's pretty much my traditional starting point...what shock extended/compressed range to get. I then just calculate appropriate compression/rebound rates for the expected rig mods, etc....and start seeing what might work, say over at Bilstein, etc.

As they will work at stock height, or with any lift I might do, I can get them anytime, w/o waiting as far as fit goes.



My problem is I just have no time to DO the measurements. :(

Does anyone ELSE go through this? Anyone WANT to?



Does anyone WANT TO KNOW the outome if I ever get around to it?

 

I feel bad because I did all this a few months back. But I threw out the pages of notes when I abandoned the lift for a year (financial disaster). If you don't get what you need in a week I can go back out in the garage and document. I won't have time until then.

Just the summary on the front as the real numbers are gone:
The stock shock was about 15 inches compressed with slam factor. After the shock the sway bar was the problem even disconnected. Then the brake and ABS lines/wires were next. With those fixed (moved) the DS gets close to the skid. This was in the 27 inch neighborhood for a shock limiting travel. A 15 inch to 27 inch shock is almost possible. With top out hardware inside the shock (every major brand) you'd need a few inches of additional bump stop to get full droop.

Please don't rely on the summary numbers, they have been stored in my scrambled head for a time.

If you don't get any takers I can do it on the weekend of Jan 20th. I may as well take a few pictures when I do it. Many people here could use them to check their own rigs. Mine is a JK unlimited Rubi. I have 3/4 inch spacers in the front, but they will be gone during the tests. Will numbers from my rig help?

I hope your wife's condition improves.

 

That would be great!



She can talk a bit now and move her left side...most of the damage is to her right side.



Any way - the disco'd sway bar still limits travel? You have the electric version, I'll probably use an adjustable JKS, etc....that might help.

Making the brake, etc lines have some slack is easy enough...

The DS getting down to the skid sounds like a harder fix......

So, up front at least...it looks like the DS clearance means the shock droop will be drivetrain limited anyway.....and / or the need for a 15" compressed length will limit the available shocks with 27" extension?

I think the stock Front shocks are 14.5" - 22"?

I still have no rear shock measurements.



I am REALLY looking forward to your info!

 

I can do it next weekend. I'm sorry to make you wait but I can't get to it sooner.
In the front I first removed shock's lower bolt , obviously that allowed more droop.
The next think to stop the axle from dropping was the swaybar. Even with it disconnected the length of the link was such that it make a straight line from the axle mount to the frame mount where the pivot bushings were. This is the culprit of the "folded over" links we hear about here because the link can fold over itself and cause all sorts of trouble. A picture here will be worth a 1000 words.
I agree that a replacement ASB system or links would alleviate the problem. The longer links like the ones in the fancier suspension packages look like they would do the trick too.

 

I took some measurments on my JK today. First off I have a 2007 JK Unlimited Rubicon. It is mostly stock, but it has 3/4 inch spring spacers in the front to help offset the factory rake that got worse when I added my winch. My JK does have the dual top group, the Rubicon model included sway bar disconnect. I’ll try to note if I think that my modifications and hardware have an impact on my readings.

I wanted to take these measurements for a few reasons. I wanted to know what I was getting into when I lift and modify my JK. I wanted to share my info because a forum member asked me for some numbers. I also wanted to encourage others to repeat some of these steps so they know that their modified rigs aren’t dangerous. I see far too many people bolt stuff on and then find out about brake line, abs wires, and other limiting factors that show up on the road or on the trail. I did find a few interesting things during my investigation that everyone should consider and address when modifying their JK.

Just a quick disclaimer. I do not claim to be the guru of steering and suspension. I am not reinventing the wheel, this ground has been covered by others before and I learned from others. I believe that if you modify your junk, you should be capable of checking it so you don’t kill someone, damage your expensive rig, or waste your recreation time. But, I am not teaching you to do this, I am only explaining what I did.

I took a few measurements with the Jeep as it sits on the tires. Then I jacked up my Jeep as high as my huge jack stands would allow. I started in the front. I got both front tires many inches off the ground with the suspension fully drooped. Then I took some more measurements. The shock was limiting more droop, so I removed the lower bolt. Then the sway bar was limiting droop. I took some measurements and then I removed the lower bolt and drooped some more. Then the ABS wires and brake lines limited droop, so I temporarily made a bit more room there until I got more droop. With the passenger side drooped, I finally stopped when the upper control arm contacted the frame bracket from the sideways droop. On the driver’s side the front drive shaft contacts the skid, so I stopped there. Then I pulled out a shock and took compressed readings.

 

Then I reassembled the rear and performed the procedure in the rear. The rear procedure was similar to the front with a few changes. The rear e-brake cable limits travel at one point during the tests. I disconnected it and moved on. Also there is no anti-sway bar (ASB) disconnect, so the rear ASB limits travel before it is actually pulled straight. I still pulled the bolt because I could droop more (obviously) without it. To get max droop numbers without removing the driveshaft and control arms I stood on the rotor to weigh it down.

All shock numbers are bottom of the Jeep metal mounting surface to center of the bolt. This gives specs at “like points” as compared to my KYB shock dimensions guide. Numbers with a * are influenced by my 3/4 spacers. My Rubi sagged some after the winch install, but before the spacers so my springs may be about stock anyway.

Front in inches
Floor to bottom of flare lip RH* 34 3/4
Floor to bottom of flare lip LH* 34 3/4
Bump stop plate to stop tip ride height* 1 7/8
Front shock compressed length 15
Front shock extended length 22 1/2
New shock length that factory coil unseats 24
New shock length with ASB with barely detectable angle 23 3/4
New shock length with new ASB links, stock lines, abs wires 26 1/2
New shock length when arms and drive shaft is an issue 27

Rear in inches
Floor to bottom of flare lip RH 35 7/8
Floor to bottom of flare lip LH 35 3/8
Bump stop plate to stop tip ride height 2
Rear shock compressed length 15
Rear shock extended length 23 1/4
New shock length that ASB limited travel (no trail forces) 24 1/4
New shock length that factory coil unseats 24 1/2
New shock length where e-brake cable, abs wires, and ASB limit 24 1/4
New shock length with new ASB links, stock lines, abs wires 27

 

There were a few surprises.

I calculated the minimum shock length with the bump stop plate touching the bump stop plus a fudge factor of 1 1/4 inches bump stop compression. The shock min length is almost exactly 15 inches front and rear. If you use a shock with a compressed length of over 15 inches you need longer bump stops or damage on a big hit will occur.

With factory ASB links, you can only go to a 23 3/4 extended length shock in the front without possibly folding over the stock ASB links. When folded over the ASB links rudely hit the crossover steering. Danger, danger.

In the rear I really don’t know what limits travel after 27 inches. I could identify the next part to remove to get more droop. I do know that you can articulate with a jack and stand and bounce on the rotor and not get over 27 1/4, so it is a solid stop. I suspect the driveshaft.

My factory 32s on factory wheels rub my factory anti-sway bar. I have pictures.

At 27 inches of droop in the front (max with factory arms), I can shift the axle enough with jack articulation and hand force to almost touch the driveshaft boot against the transmission pan lip.

 

I took about 30 pictures of the process. I'll try to get them in an available place soon.

 

Considering I have zero response, even from the person that requested the data I am not going to bother with the pictures.

 

Sorry - My wife was in the hospital - I was tied up with Dr's and stuff - you are doing GREAT STUFF!

I wish I'd been back in time to see this earlier...but, I WILL be looking at your points made....very good observations.