I searched but didn't feel like looking through hundreds of threads whose titles did not seem to have anything to do with my question. Do coil springs get "tired" after years of heavy use like light off roading, towing and carry big loads?

I've got 200k mi on my 97 now and I am going to replace my Bilsteins with some Tokiko's from Steve because they are getting close to 100k on them and I don't like the "sports car" like feel. I want something a little more forgiving. While I am replacing those, would it be good to put on some newer used springs off a recently lifted truck?

 

Well, newer springs will give you some ride hieght back because yours are probably sagging. your ride may actually get stiffer with new springs though, cause if yours are sagging, then your springs have gotten nice and squishy soft...

 

That makes sense, older == softer. I'm not really concerned about ride height these days although I wouldn't mind more clearance. I'm not ever going to get 33's or anything so I am happy with my current ride height.

 

new shocks may very well give you what you are looking for, so if your going to change those, go ahead, and if you want more, get the springs also...I would do just shocks first though.

 

Shocks contribute almost all of the ride stiffness or softness, not the spring rate.






Fred

 

Thats only partially true. You can't make a Buick handle like a corvette by just changing the shocks. Shocks only control dampening, but some have a much higher resistance to compression and therefore they do stiffen the ride.
That said, I don't think you need new springs. I have a 65 chevy and a 71 Buick with original springs. They both sit about 1" lower than stock and ride nice from the years of weight bearing. Time is more of a factor in spring wear than miles. On the other hand I used to have an 86 volvo 740 turbo with rock hard springs. They were hard when my dad bought it in '88. When I sold it in 2004 they were still rock hard, but they also sagged a little.

 

I suggest that you re-read my post. You're saying the same thing BTW(note the part in your quoted post that I made bold).

We're talking about ride quality, stiffness or softness of the ride, NOT HANDLING !!!
Regarding handline, one doesn't need springs with a high spring rate for "race car" type handling. The current stock car (NASCAR, etc) asphalt tracks, are "soft spring/big bar" setups.


At any rate, shocks contribute a TON to handling also.

Shocks contribute more to the ride quality than springs.

BTW, shocks do more than just "control dampening" (which I'm not sure is a correct description anyway)

Shocks do "dampen" the spring movement (which is why that they are more correctly called dampeners and not shocks), but they also control the rate of weight transfer.

If you can tell me what an easy up shock is and what's it's used for, or what a tie down one is and what it's used for, then you'll have understood a little more about what dampeners (shocks) do.

So, back to my original, shocks have a much greater effect on ride quality (stiffness or softness of the ride) than spring rate (for any spring that one is likely to use on these vehicles anyway).

Find someone running the RS9000 series shocks or the Procomp MX's (both are adjustable).
Set 'em to the softness end and drive the vehicle around a few blocks, then set the shocks to the stiffest end and repeat.
HUGE difference in the ride.




Fred

 

Back to your original question.
If the springs are showing signs of fatigue (rear sitting low) then go on and replace then also.
It won't really change your ride quality that much, the shocks control stiffness or softness of the ride more than the springs do.

Yes, springs can fatigue, most often caused by overcompression.
For some reason 4Runners are prone to that with the rear springs (2nd generation 4Runners). You could adjust the bumpstops down some to prevent the springs from compressing as much and that would probably help.
I suspect that most of the problems with the rear springs comes from overload the vehicle to begin with and over time.




Fred