I just put E-rated Nitto Ridge Grapplers on my Disco 2 with SLS and I now hate the ride. I believe my front springs are stock.
OME shocks up front and bags in the rear with stock-looking(?) shocks. 192K miles
It's really harsh @ 35 PSI.
Any do this and figure out the "right" air pressure to run?

 

30-35 is a good place to be usually in my experience. Blown out springs and shocks can provide a super harsh ride. E rated tires are also simply firmer than stock sized highway tires, unfortunately there is a penalty with lifting and going bigger tires and ride quality is usually what takes the biggest hit. What you will love is when off pavement and you air those tires down to 12-15psi, it's like riding on clouds lol

 

Yes, I can't wait and I'm tempted to run them at 15psi on the highway!
My suspension was amazing (riding on clouds!) 2 minutes before I put these tires on. I really bummed actually - that ride is why I bought this disco over some others.
That was an expensive lesson. I really wanted 10 ply because of the sidewall strength (I gashed my Goodyear Duratracs on some rocks in my 76 suburban. I put 10 ply on that and it rides great at 45psi).

 

The old axiom is true, whenever you upgrade one piece of a system the other weaker pieces suddenly come to light.

I would guess your springs are the issue at this point. I've been down this road and back several times over the years. New shocks on old springs will just wear out the shocks faster and the worn out springs will win every time.

I finally got the dreamy cloud ride back when I switched from OME Nitrochargers to TF shocks. I rode with stock springs for way to long myself... Originally went to OME MD springs with the nitrochargers and that was a firm ride as my truck is mostly unladen with no heavy duty steel accessories or cargo. Finally after about 50k miles on that setup i switched to the TF shocks and the magic carpet was back!!! I never did have the magic carpet ride with the OME shocks... Even before that I ran two sets of Bilsteins and never had a particularly smooth ride... Those were ok for about 5k miles then not so much. It caught me by surprised because I never thought the cheapest shocks would ride the best!!!

Every truck and every setup is different so your mileage may vary, but I'd look into replacing those springs... and the steering damper if it hasn't been done. You will notice that too.

 

yea 10 ply stuff is just harsh. Duratracs are garbage, I'm definitely not a fan. Nor K02s if you wheel a lot, my set took a beating but ended up with sidewall damage on multiple tires and blow out coming up the mountain to the eisenhower tunnel on 70 (aka the worst place ever for a blow out...). I did buy another set for the green disco as it's my wife's daily and they are a fantastic tire in the snow.

I would replace springs and shocks which luckily it isn't a huge expense (compared to coilovers on newer vehicles...)