gravel road vehicle?

Shocks are the secret to this.  It's worth noting that driving fast down a washboard road beats the heck out of the un-suspended components even if suspension system keeps you from feeling it in the cockpit.  When  I lived on a dirt road I was forever replacing ball joints and wheel bearings in my wife's cars.  She'd hammer whatever she was driving down the road like Colin McRae.  On the plus side I never had they typical Upstate NY rear quarter panel rot issue.  They were sandblasted to bare metal but since they were blasted daily they never rusted.

In reply to Toyman01 + Sized and :

Lots of sidewall and low tire pressure is a crutch for not having a soft enough suspension with enough travel. You're effectively using soft side walls to soak up more and serve as part of the suspension because the actual suspension is inadequate. 

A few years ago, i did a little day trip out of town, which put me on a secondary highway.  The paved surface was very much like the surface of the moon, except between two towns where it had gotten so bad that they had turned it back to gravel.

I ran up to about 150 kph and just cruised.  So much better than bad pavement.

That was in an supercharged 82 Camaro with 245/50 16s on lowering springs and Konis.  No washboard, though.  It doesn't handle that quite as well, although at 150, even that is pretty smooth.

Rebound is really the key regarding shock or strut dynamic. Dampening is fairly easy, but without a remote reservoir effective reserve capacity can run out if the rebound isn't fast enough to get back to the ready position to have full suspension travel available again for the next ungulation. If the rebound is too fast or utilizes too much force, then it will upset the chassis and make it jittery. Keith noted earlier in the thread that you don't want Bilsteins, this is why. 

Low speed versus high speed dampening comes into play as well but rebound is so underlooked with regards to its importance and the role that it plays. 

High speed damping: washboard

Low speed damping: whoops

The remote reservoir also provides more heat capacity so it's less likely your shocks will overheat.

In reply to rslifkin :

Street pressure on the XJ is 35 psi. It is very controlled over washboards at that pressure but you can feel them and they do make things rattle. In the woods, I typically run 20-25 psi. At 20 psi, you can't even feel the washboarding at speed. The tires never transmit the bumps to the suspension. At 20-25 psi, the tires are fine at highway speeds as well but it does handle like a pig.

90% of the E36 M3ty ride in an XJ is caused by the shocks. The OEM and replacement shocks are horrible. It banged over everything. At a guess, too much compression damping and not enough rebound. Airing down helps a lot and covers up the washboard, but it can't fix crappy shocks.

A good set of offroad shocks are kind of an epiphany. If you ever buy a set, you will want them on everything that goes offroad. At this point, the XJ rides much better than any vehicle I own. Railroad tracks at 70 mph. No problem. 8" deep potholes in a gravel road, it sucks them up. Speed bumps in a parking lot, no issues. Even the road repairs I dodge in everything else aren't worth steering around. If Fox made a replacement set for the Ridgeline, I would have bought them. 

In reply to Toyman01 + Sized and :

Oh yeah, good shocks make a huge difference.  I do need to play with the valving a bit, but the ZJ has Bilstein 7100s on it.  And with some work in the spring rate selection department, that suspension works far better than most people would expect a pair of solid axles to do. 

I bought a 2011 Subaru Outback for just this purpose; the wife and I take days trips to numerous ghost towns and historic places that require driving 30 miles of gravel roads and crossing sand washes.

The stock suspension is pretty soft; not good for serious off roading but does well on gravel. I routinely drive 60 mph on gravel roads. 

I bought the car at 29K it now has 114K. To date I've replaced the clutch, done the timing belt at 95K, front brake pads and oil changes. That's all the car has needed in 7 years.