Suspension (strut) Experts?

[JasonA]

This isn't a question about the struts on the Cadillac, but for a different vehicle we own, but I don't think the make or model matters as this is really a theoretical question that I'm having a hard time getting answered.

If you lean down on the front of the vehicle, like do to a "bounce test", the front will deflect down and then back up, gracefully. If you do that a few times in a row, using the momentum from the first bounce to help you with the second, you can get it into a nice cycle. Not uncontrolled, but nice and smooth.

However, on the 2nd or 3rd up/down cycle, SLAM, the strut gets real firm and almost feels like it's locked up. You can strong-arm the front of the car all you want, but the movement in the suspension is very restricted. Half the oscillation from that point forward is in the sidewalls of the tires.

I'm experiencing a pretty stiff ride from this vehicle, especially when the weather is cold, and I'm thinking that this change in damping may indicate a malfunction, at least I'm hoping so.

But I'm not all that optimistic. I once had a set of Rancho RS-5000 shocks on a truck that acted the same way. They were supposed to have some type of variable damping mechanism. My father-in-law has Monroe Sensa-Trac shocks on his Toyota Tacoma and they're the same way, on the rear shocks. I do know the struts on this particular vehicle are from the factory, with about 68k miles on them. It's possible that they're some type of variable damping struts, but I wouldn't think so.

Either way, does that sound right, from a performance standpoint? Is that standard for a strut to act that way? The rear SHOCKS on this vehicle don't act that way. They're reasonably tight, and you can push the back of the vehicle down, and it'll come back up, and that's it. The resistance doesn't change, no matter how many times you do that. Out on the road, the resistance feels uneven, front to rear. The front rides pretty stiff, the rear more like our Cadillac in comparison.

Anyone here an expert in strut technology and could shed some light?

Thanks.

[What job]

Jason,

Having worked in R&D with shocks the only thing I can say is this.

Without knowing what type of shock/strut you are dealing with any answer is just a guess. There are many different types of shocks and struts as you know.

All work in different ways. But, if the strut gets firm after it has cycled a few times then returns to a soft state after sitting awhile it is a safe bet that the strut is a self damping model.

[JasonA]

Thanks very much for your reply. I'll be happy to provide some more information in this case.

Specifically, it's a Macpherson type front strut on a 2003 Dodge Grand Caravan. It's not supposed to have any special variable suspension like our Cadillacs -- just standard struts in the front and shocks in the rear.

What is a "self damping" strut? Is that the same thing as you might find in an aftermarket strut like a Monroe Sensa-Trac? Are these "variable damping" struts (like the Monroes) or just a different kind of constant rate strut? Also, if you could, what are the differences between a "self damping" model, and a standard damper, like what's on the REAR of our van?

Lastly, what would be your opinion of a replacement strut that would give me the very best ride (meaning softest, most Cadillac-like)? Most aftermarket companies emphasize "no compromise between ride and handling/control" or something like that. I assume that ANY new strut is going to give me the control I want. I just want something tuned on the softest side possible.

Thanks very much for your response.

Edit: I also sent this as a PM, so we can take the discussion off the board for this mostly non-Cadillac topic.