First post, be gentle.

I have a 2012 Rubicon Unlimited that came from the dealership with a 2.5" coil spacer lift and 33x12.5x17 tires. Rode well, not super smooth but no complaints.

This weekend I put on 20x12 Fuel Hostages with 37" Procomp A/T tires, and aired them down to 30psi. The Jeep rides absolutely terrible now, darts all over the road, randomly pulls, wanders, shakes and vibrates over the smallest bumps, essentially rides like the suspension has been completely removed and sits solely on the bump stops.

I've read numerous threads on various forums speaking about ensuring parallel alignment of trackbar and draglink, playing with tire pressure, steering stabilizers, alignment issues, etc. Provided the Jeep drove perfectly with the 33" tires then immediately disastrous with the 37" bolted on, I'm thinking this is purely a steering geometry issue... but no geometry has changed? How do I fix this? I need to park in a parkade so could at max do a 3.5" lift, is this the best solution? What about the suggestions below:

- track bar and steering stabilizer relocation kit
- adjustable track bar
- adjustable control arms
- drag link flip

 

Some quick snaps underneath. Are my bump stops supposed to be so close to the bump plates? That's not a lot of spring compression before the bump stops connect.

 

First your sway bar should be parallel with the ground not at an angle. Are your tires balanced that could be why your shaking much. Your bump stops look Ok they aren't that close.

 

Tires are pretty wide. That will cause the jeep to follow ruts in the pavement. 20" rims are not helping your ride quality either. Are those shock extenders? Also not contributing to stellar ride quality. I'm guessing it's mostly the tires though. 20s and 37" tires is not a lightweight combo and you will notice the added rolling/unsprung weight.

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If it drove fine with the 33's, but horrible with the 37's and nothing in the suspension has changed. Then we need to look at the tires as they are the likely culprit. Ensure they are balanced, but also check what your toe angle is set at. The larger diameter tires could of exposed poor allignment. You will want 1/8" toe in.

 

Drove ok with 33's. Drives like crap with the new 37's. So your 'fix' is to remove the lift and go taller?

You might consider doing some investigating to find the problem before throwing a ton of money at a new lift. Rotate the tires to see if there is any change. Get them re-balanced. Verify that the retaining clips were removed from the lugs. Post your alignment specs. etc

 

Tire balance and/or psi. I run my 35's at 25 psi. Do a chalk test and I bet you can run lower. The bigger the tire less psi in required. What's the load of the tires C,D,E?

At 2.5 I doubt you need steering correction (Highsteer) for bumpsteer.

A adjustable track bar is always nice to center up the front axle.

Also ... Do you know what the toe is set at ? You will need to run closer to 0. Stock can be as much as 1/4 in I believe.

 

Your 37's on 20's have just about the same amount of sidewall as stock 32" tires and 17's. BUT now you have a much much stiffer sidewall tire on there, of course the ride is going to feel harsh. Not saying it's 100% of your problem, but not helping

 

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Yes you need to extend your swaybar links. I don't think this is your issue if you did not have issues before 37's. Most BB kits supply longer rears and you move the stock rears to the front. You want parallel +/- a few degrees at ride height.

The yellow bump is not your actual stop. That's like a cushion or a shock. The actual bumpstop is the hard plastic/rubber the yellow jounce is pressed into. The bumpstop extension is the block attached to your lower coil perch.

 

Exactly. I'd add that tires also twist sideways. Small sidewalls stiffen the tire and reduce this twist by much. The lower the sidewalls, the stiffer the steering becomes.
For a Jeep -- like others said -- 20" rims with 37" tires is less than ideal.

Yes, 30 psi may be too high. (Also, the small sidewalls allow less room for offroad airing down, vs, say, 17" rims and 37" tires.)

Whatever problem there is, it had been there before but you didn't notice it, and it was increased by the new wheels.

Yes, a lift is much better than spacers.

After you sort out the problem and fix it, softer shocks are the most effective way to soften the ride, but I'd join the suggestion to first solve the problem before changing anything.