JK Lift Install & Suspension Lessons Learned
I am doing this write up to help inform JK owners what to look out for and how to set start the process of setting up their JK's during and after a lift. This write up is not intended to be a "How to" as lifting a JK is the same as lifting a TJ in most regards other than steering, and I have not upgraded any steering components as of yet. I will also begin a build thread of my jeep and update it with more info specific to my Jeep.
The victim: 2010 JK Rubicon Unlimited with 54,000 miles.
The first thing we decided to do was take some before measurements.
Front Uptravel = 3.5 (bumpstop pad to bumpstop cup)
Rear Uptravel =5 (bumpstop pad to bumpstop cup)
Clearance to frame = 13.625
Clearance to gas tank skid = 10.5
Front hub center to fender flare lip = 20.5
Rear hub center to fender flare lip = 21.25
To get an idea just how good Jeep engineers are, we wanted to cycle the axles and get a baseline for a completely stock setup.
We positioned two floor jacks (with wood cribbing on top) under the axle in order to push the axle to full bump. We checked these with a totally stock suspension setup; stock tires and 35s (315/70/17).
The first thing that we noticed was the stock front track bar flag caused interference at the frame. This flag must be positioned horizontally inside the bracket. If yours is sticking out of the top of the bracket like this, then you need to change it so it clears.
You can see the track bar has a severe bend to clear the stock diff cover. You can also see the drag-link, tie-rod, track bar and control arms tuck nicely. The upper control arms actually tuck into the engine compartment in front of the engine. Notice the frame side front track bar mount will tuck well below the tie-rod, and even below the axle tube. Notice the track bar also has a bend to clear the pitman arm.
In the rear, you can see the axle tucks nicely as well, and the track bar has a bend to clear the diff. Notice the frame side rear track bar bracket will pass by the bumpstop pad - beware of this for bolt clearance. Notice the exhaust has a specifically placed dent to clear the track bar on the driver's side.
FULL FLEX & TIRE CLEARANCE: We installed a tire on each axle, and used the floor jacks to push the axle to full flex on the side where the track bar mounts to the frame, in order to check fender clearances. As expected, no clearance issues are observed with stock tires.
Looking good up front.
However, upon installing the new 35 (315/70 R 17) tires, we find major clearance issues do arise.
We find the front needs 2.5 bumpstop extension to prevent major tire vs fender flare damage. Also note the tire rubs the front bumper extension, therefore we did not check lock-to-lock tire clearances in order to check/adjust steering stops.
After taking the Jeep for a shakedown run the rubbing on the front bumper extensions was the largest problem with this lift. For this reason I am recommending anyone with 35's and 2.5-3 inch lift to get a mid width or stubby bumper. Personally I am going to go with the endcaps that go over the stock bumper. Below is a picture of the rubbing that occurred on the trail.
We find the rear needs 3 bumpstop extension to prevent major tire vs fender flare damage.
Bottom line: the stock flares & bumper ends need to go, so bumpstop extension can be reduced to regain uptravel.
BRAKE LINE LENGTH
At full droop the track bar pulls the axle to the driver's side, extending the driver's side brake line tight. We find the front brake lines to be too short, and used a length of string to measure for new lines. We find the new lines need to be about 27.5 from end to end (approx 3 longer than stock).
During full droop check, we find the front brake lines to be too short to allow the axle to rear full droop with the new shock length. It was necessary to loosen the brake lines from the frame, and allow them to hang loosely so we could complete all the necessary testing. Using a length of string to measure for new lines, we find the new lines need to be about 25 from end to end (approx 3 longer than stock).
We also find breather hoses, locker wiring, and e-brake line length will could be adjusted slightly to accommodate the increased travel.
AFTERMARKET TRACK BARS
Before reaching full bump, we find the front track bar has major clearance issues with stock length control arms. We measure 2.5 bumpstop extension requirement to prevent the track bar from hitting the diff. This is a disappointment since this is not mentioned on their website, and this track bar is advertised to fit 1+ of lift. Clearly this is not the case, and you would need 2.5 of lift just to maintain stock uptravel with this track bar. Due to these issues, the stock track bar was reused after the lift install. We may sleeve the track bar to extend its length, but the axle was only off center about ½ after completion.
Front track bar vs diff cover issues are well known in the TJ series, with a multi-year, 100+ page thread still active today.
We find the rear track bar clears nicely from stock height full bump to full droop with the lift. This was a pleasant surprise based on the issues seen in front, and the issues previously seen in the TJ series. The rear track bar was not a limiting factor of uptravel or downtravel, when using the stock mounting points. A raised bracket has high likelyhood of pushing the bar into the exhaust or other components, and would require adding bumpstop extension. Also, if you using adjustable control arm arms, lengthening the arms to push the axle back in the wheelwell may also lead to issues with the bumpstop pad, exhaust clearance, track bar clearances, etc.
We measured the stock shock length to be:
Front = 14 compressed, 22.75 extended (8.75 travel)
Rear = 14.75 compressed, 23 extended (8.25 travel)
At full bump, we measured the distance between the front shock mounts to be 15
The new Bilstein shock lengths are:
Front (PN:24-146708) = 15 compressed, 24.65 extended (9.65 travel)
Rear (PN:24-146715) = 15.4 compressed, 26.4 extended (11 travel)
This indicates the new front shocks could potentially fit with no bumpstop extension and the rear shocks need 0.75 bumpstop extension.
Upon installing stock Rubicon rock rails, we notice clearance issues. The rock rails were cut using an angle grinder + sawzall, and endcaps were reinstalled.
Final Product. You can see the pinch seam is also trimmed. We ended cutting off about 2" from the end of the rock rail.
SWAY BAR LINKS:
Front = attempted to use JKS links, found them to be too long, even if cut, so we used rear sway bar links and found them to be the perfect length to keep the swaybar nice and level.
Rear = attempted to use JKS links, found major tire clearance issues. Even if axle was centered perfectly, there was very little space between the tire and the sway bar link to allow for flex. We left the rear sway bar disconnected, and zip tied out of the way, until lower profile heim ends can be found to make custom links.
To ensure that the rear links would not be near the tire heim joints were purchased from McMaster Carr. I used 1.5" 14-20 grade 8 bolts as well to finish the simple mod to increase the clearance.
CONTROL ARMS & AXLE POSITION
Eventually all arms will be replaced as funds allow. Due to long wheelbase and long driveshaft length, the rear control arms were left stock, as no immediate pinion angle changes should be necessary. Front uppers remain stock, and Clayton Off-Road front lowers were installed to correct caster.
Eye to Eye measurements were as follows:
Stock front uppers =18-3/4”
Stock front lowers =22-5/8”
Stock rear uppers = 17-1/2”
Stock rear lowers = 19-5/8”
Clayton Off-Road front lowers = 22.75”
We took a guess on front lower control arm length and ended up being spot on for the caster.
As shown above, we also verified axle position at full bump to ensure proper control arm lengths & bumpstop alignment. As lift height goes up, control arm lengths need to be adjusted to ensure the bumpstops are centered at full bump, proper caster is maintained, and pinion alignment is appropriate while at ride height. This can lead to clearance issues, so make sure you check full bump/full droop/full flex when installing a lift or changing lift components.
This section is more for suspension characteristics and is nothing that can be changed unless you start moving the mounting points of the control arms. The spreadsheet that was used here was created by Dan Barcroft of Pirate4x4. http://www.pirate4x4.com/forum/gener...uest-help.html
This stock 4-door JKU had about 96% anti-squat.
Notice the lift changes control arm angles and yields an increase of the anti-squat to 140% . This is because the mounting points have not changed, and this is expected with any lift using stock mounting points.
FINISHING THE LIFT INSTALL
After all the components were checked and installed, we set the Jeep down on its new feet. We grabbed the Jeep by the roll bar and bounced it violently in order to “reset” the factory rubber bushings (remember we loosened all the control arm bolts before starting).
During the bounce exercise, we also disconnected the adjustable rear track bar from the frame side, allowing the axle to center itself. We then adjusted the rear track bar to line up to the holes, and replaced the bolts. This works on the front as well, if using an adjustable front track bar.
All bolts were torqued to spec.
Front: LCA = 125 ft-lbs; UCA = 75 ft-lbs
Rear: LCA = 125 ft-lbs; UCA = 125 ft-lbs
Front track bar = 125 ft-lbs, frame and axle ends.
Rear track bar = 125 ft-lbs, frame and axle ends.
After the completed install:
Caster (factory spec = 3.2-5.2°):
After lift install = Left: 3.9°, Right: 4.6°
The steering wheel was off center slightly, and corrected. In trying to correct the slight change in toe, the tie-rod adjusting sleeve was found to be seized. The tie-rod needed to be replaced. If your Jeep is still under the warranty for steering go and check to see if the sleeve is seized. If it is take it in to the dealership to get it replaced. From the dealer the whole assembly runs just under $300 dollars. After speaking with my local dealership they informed us that this is a common problem on even the 12 and 13’s. The design of the sleeve allows water to get deep inside the sleeve and rusts. If the sleeve is not seized take the tie rod off and apply anti seize to all the threaded surfaces.
Below is what the sleeve of the trackbar looks like, you can see how the sleeve has "mushroomed" out. only way to fix this that I know of is to replace the tierod.
LIFT HEIGHT GAIN:
The lift is still settling, but post-install measurements are....
Front uptravel = 7.5"
Rear uptravel = 8.625"
Clearance to frame = 18.625
Clearance to gas tank skid = 15.5”
Front hub center to fender flare lip = 24”
Rear hub center to fender flare lip = 24.5"
The after uptravel numbers do not include the bumbstops that will be required. These will be added at a later date as we needed to set the system up to find out what bumpstop lengths were needed. Overall I am very happy with the amount of clearance that was gained and how the lift and tires look in general.
I also want to thank Unlimited 04 for his help in creating this writeup and his help with the lift itself. Zetto was also a valuable resource during the lifting process and I thank you as well.
Wow! Very nice write up. Great stance.
Nice writeup. We did not have all the same issues with the wifes JK as you, it's a good idea to check all those things anyhow.
Our wheels don't stick out as far, so the rear tire stuffs inside the fender and the front don't rub the bumper. Our JKS tracbar does not hit the diff cover although it does slightly scrape the RC diff guard. We have the JKS rear tracbar links and they do not rub the tires, but I attribute this to our narrower wheels. So far, the Teraflex rear tracbar mount has not caused any issues, but I will be looking at that again to be sure.
Like I said, very nice. I'm sure there are many people who never think to check things as thoroughly as you or I.
Stock Moab wheels with 1.5" spacers, 35x12.50-17 Toyo AT IIs.
badass documentation and investigation
Well done. That's precisely the way to fit a custom suspension build. Never assume that every kit out there has been as carefully engineered and tested for fit.
Great thread, should be a sticky. :-)
Thumbs up! Impressive and thorough!
|The time now is 01:22 PM.|
Powered by vBulletin Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.