FLEX TEST : Will 37's Clear a JL Rubicon running 2.5" of Lift & Without Rubbing??

wayoflife

Administrator
Staff member
FLEX TEST : Will 37's Clear a JL Rubicon running 2.5" of Lift & Without Rubbing??

There was never any question for Cindy and I that JET Li, our brand new 2018 Jeep JL Wrangler Rubicon Unlimited, would be running a set of 37" tires and much sooner than later. What was in question was, how would we get there? How much lift would it take to clear them and could it be done with wheels that have a bigger amount of back spacing especially now that JL Rubicons come with 68" wide axles? In the end, we decided to run 37x13.50 Cooper STT Pros mounted on KMC XD231 beadlock wheels that have 4.75" of back spacing and try to make it all work with an EVO 2.5" Stage 4 Budget Boost, complete with all 8 adjustable control arms.

Soon after getting everything installed, an initial test drive showed us that this setup worked great or at least, around town anyway. The 2.5" coil spacer lift provided plenty of room to clear the 37" tires and we saw no rubbing at a full lock, in either direction and this in spite of the tires being 13.50 wide and mounted on wheels with 4.75" of back spacing. So, the real question now was, how would this setup do off road? Fortunately, for us, a good flex test was just down the street from us and the following are pics of what we found.

While ramping a Jeep or lifting it from one corner with a forklift can give you an idea of things, the best way to see just how much flex it really has is to get it twisted up. The opposing flex will force the axles to mash into the bump stops and drop the opposite side down to a full droop. Unfortunately for us, we were already hearing a good amount of rubbing well before we could work our way up into our testing obstacle but, here we went anyway. For our first test - driver side front up and turned to the left.
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As you can see here, the front jounce stop or bump stop is fully compressed.
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In spite of how this pic may look, there is no rubbing of the tire on the driver side fender liner, coil perch, frame rail or other wise that we could see on the driver side and with the wheels turned to the left.
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At a full droop, the passenger side coil is still seated properly.
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Brake and ABS lines all seem to be good.
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Turning to the right to check for any rubbing or clearance issues.
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Here you can see that the tires clear the front bumper and grill.
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Amazingly, the 13.50 wide Cooper STT Pros tuck up and under the fender as well but then, a lot of this has to do with the 4.75" of back spacing that the KMC XD231's have.
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View from the back of the driver side front wheel well to show the fully compressed bump stop and shock.
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With the wheels turned, you can get a better look at the passenger side front coil bend.
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Moving to the back of our JL Wrangler to get a better look at things.
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With the driver side rear tire drooped out, we could see where it had be rubbing a bit on the lower fender liner that covers the bumper.
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On the passenger size, we could see that the tire was making full contact with the lower fender liner that covers the bumper.
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The bigger problem we found was that the lip of the main fender liner was catching on the tire lugs and getting pulled up. In fact, you can see that a push tab had already gotten pulled out. This was clearly the source of most of what we were hearing.
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Looking toward the front of the rear wheel well, we saw that things were clearing well. Certainly, no issues with the pinch seam or rock slider like you would have seen on a JK.
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Moving forward through the obstacle so that we can switch our twist.
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Verifying that we have full stuff by making sure that the bump stop is fully mashed.
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It's close but the back of the passenger side front tire just misses the fender liner when turning to the right.
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Turning about half way back to the left, the tread just kisses the fender trim as you can see here. Being that we are at a full stuff, this shouldn't be a problem.
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At a full stuff and lock to the left, everything clears and you can see where the tread just kissed the fender trim.
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Toward the front of the fender, you can see how the tire is just making contact with it here.
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And toward the very front as well.
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Like the driver side, the tire clears the grill just fine.
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Pushing all the way through the obstacle.
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Back on level ground, you can see where the passenger side front tire was brushing up against the fender liner.
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Looking back at the passenger side rear wheel well, you can see how mangled the fender liner got.
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The driver side rear fender liner fared better but I think it'll just be a matter of time before it gets mangled up too.
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And that concludes our first flex test running 37x13.50 Cooper STT Pros mounted on KMC XD231's and all sitting on top of an EVO 2.5" Stage 4 Budget Boost. As you can see, we'll need to head back to the shop and make some modifications. :cool:
 

wayoflife

Administrator
Staff member
FIX for the FENDER LINER
Back at the shop and ready to get our fender rub fixed, I started out by removing the lower liner that covers the bumper. On the driver side rear wheel well, this is where we were seeing most of our rubbing and an 8mm socket and 3 screws removed later, this is what we were looking at.
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Again, using an 8mm socket to remove 3 more screws, this is what the bumper looks like without it's plastic end cap.
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Using a 16mm socket, I then removed the lower liner bracket with the hope that would clean the look of things a bit. Here's a few shots of what the rear end looks like with just the steel bumper installed.
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Moving over to the fender liner itself, I used a heat gun to help me reshape the embossing and concave it out of the way.
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That ought to do it!
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Not super thrilled with how the bumper was looking, Cindy and I decided to reinstall just the plastic end cap.
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As a reminder, this is what the passenger side rear fender liner looked like after our flex test.
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And, with the help of a heat gun and a bit of reshaping, this is what it looks like now.
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More of a profile view to show much I was able to push the embossed feature of the fender liner out of the way.
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With that, we should be good to go. Just gotta take JET Li back out on the same obstacle and see if the fix did the trick. :cool:
 

wayoflife

Administrator
Staff member
FLEX TEST 2 : Did the Fender Liner Fix Work?
The following morning, Cindy and I headed back down the street to see if my fender liner fix did the trick. As you can see here, we worked our way up the same obstacle and if anything, went high enough to hang a tire.
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So far so good. Time to twist up the other way.
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Just because I thought it's worth noting, what you see here is our Cooper STT Pro squashing out and planting its tread firmly on the rock face below with 29 psi as verified by our TPMS.
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So.... how'd the fender liner fix do you might be asking? Well, here's a shot of the driver side rear and as you can see, the fix worked out great. The tire came close but cleared it without any problems.
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Same is true of the passenger side. As you can see here, it got close but the tire totally cleared.
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Not a mark can be seen, felt or found on the fender liner.
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And there you have it, no more rubbing or none that really matter anyway. Clearly, 37x13.50's mounted on wheels with 4.75" of back spacing can be run with just 2.5" of lift so long as it comes with the right amount of bump stop extensions and your rear fender liners are modified. I hope you found the information on this thread to be helpful. Please let me know if you have any questions. :cool:
 

77ironhead

New member
Wow THANKS! THis is great to watch. THank you for taking the time to go through all of this so we can know what to expect when our JL arrives.
 

TrailHunter

Hooked
Great Write up! No Problems....Just Solutions!! Jet Li looks good flexing!! Are you thinking about trimming off the lower black part of the fenders? (Evo’s new Rear Fascia with integrated D-Rings would look sweet... )
 

jeeeep

Hooked
nice how easily the offending pieces unbolt - engineers really thought it out :thumb:

37's on 2.5" with minor adjustments, that's pretty damn cool
 

wayoflife

Administrator
Staff member
You're making me want to sell my JK and buy a JL.

:cheesy: Sorry about that :)

Wow THANKS! THis is great to watch. THank you for taking the time to go through all of this so we can know what to expect when our JL arrives.

Awesome, glad to know posts like this will be of help to you :)

Great Write up! No Problems....Just Solutions!! Jet Li looks good flexing!! Are you thinking about trimming off the lower black part of the fenders? (Evo’s new Rear Fascia with integrated D-Rings would look sweet... )

Oh, removing the rear bumper and running D-rings are high on my list. Not so sure I care for a fascia though. As far as fenders go, there will most likely be a day when we remove/trim the trim but for now, we like how things look and hope to keep it that way for a while. :)

That’s awesome only 2.5 lift to clear 37’s.

Crazy ain't it - we LOVE it :yup:

Great FLEX!!!!

Kinda funny that it's the same amount as stock but it does look bigger with the bigger tires :crazyeyes:
 

Ragnar JK

Member
Great walk thru of this set up - and agree with others, does get me itching for a JL and to start all over again....I must be crazy...
:crazyeyes:
 

wayoflife

Administrator
Staff member
nice how easily the offending pieces unbolt - engineers really thought it out :thumb:

37's on 2.5" with minor adjustments, that's pretty damn cool

LOL!! They really did a great job on the JL :yup:

Great walk thru of this set up - and agree with others, does get me itching for a JL and to start all over again....I must be crazy...
:crazyeyes:

In my opinion, you'd be crazy NOT to start all over again my friend :D
 

ibgpin

New member
Maybe no rubbing with a 3" lift. Even with the 2.5" lift the rubbing is minor and easily remedied. When my JL arrives I am going with the 2.5 or 3" spacer lift and 37" tires, just need to decide on tires and wheels. thanks for the pictures, really helps to see what is really going on with the suspension.
 

NV375

Active Member
I was just explaining to my wife this morning that there were many improvements to the JL compared to the JK. I have been without a Jeep for going on fifteen months now and really getting the itch to get another one. A JL sounds like the ticket now. I have been wondering what it would take to get a JL to ride as good as my JK with the enforcer with EVO spec. Kings.
 

Bald1man

New member
I've been following this build closely. I just ordered mine so I have a bit of a wait. Meanwhile you are really making me drool.
 
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