Gas shocks vs Foam cell shocks

[Rahimdad]

From my recent exposure to changing the shocks on my Nissan Pathfinder 2001 model R50 I came to know about the different types of shocks available in the market. Oil based shocks which last a bit longer, Nitro shocks which add a lot of comfort and Foam cell shocks which I know nothing about. The little I have discovered is that the Nitro and Foam Cell shocks are almost similarly constructed but have the foam along with the nitro. Anybody who has used the Foam Cell shocks and Nitro Shocks swears that the Foam Cell technology is much more comfortable. However my application will be more for off-road. The only drawback I have heard about the Foam Cell shocks is that although it does not get so hot so soon, but if overheated it takes time to recover after they fade.

Any takes from anyone who can explain this all to me in lay man terms and give me an educated guess as to which one would suit better for off-roading?

[Barry]

I’ve never heard of foam cell shocks until now, had to do a bit of reading on it. Sounds good for on road every day driving but in an off road situation where the suspension is constantly working, it can’t be a good thing. When your shocks fail, you’re relying solely on the springs for your suspension, and that makes your ride bouncy as heck and you’ll bottom out a lot. 

I’m not an off roader but from what I’ve learned, oil filled seems like the king. Sometimes old school is best. For on road use, I’d always go for gas.

[Rahimdad]

Thanks @Barry, but somehow offroaders here prefer the nitro shocks because they're stiffer. Maybe we can get some shock company to demonstrate the different shocks on road and off road.

[Javier M]

It would really depend the intended use of the shock. There are nitro, oil and foam shocks for on-road and off-road use. 

Gas/Nitrogen shocks are oil shocks with added gas. The purpose of the gas/nitrogen in the shock is to keep the oil under pressure so it is less likely to foam (bubbles). The foam makes the shock to loose some of it's absorbing properties. 

Nitrogen is a really bad heat conductor helping on keeping the shock cooler. This is why the foam shocks will always run hotter than the other two types. Depending on the shock brand it is well known the foam shocks will eventually give up when used off-road because of overheating. There are some brands specialized in foam off-road shocks but I have never used them. 

At the end, they all use oil, the just took different approaches on how the oil interacts with the up and down motion.