constant vs variable rate coil springs?

[Blue91Ex]

Hey, im looking at replacing the coil springs on my 91, mine are sagged out quite a bit and only offer about half an inch of up travel before they hit the bumpstops now. My question is, for 95% on road, street driving, lots of bumpy dirt and tar roads but also high speed road curves (55 zones through the mountains), but also able to have some flex off road (logging trails, rutted woods roads, etc), would variable rate heavy duty coil springs in front be better suited for me than stock replacement constant rate springs?

someone i saw briefly discussing the variable rate springs said they make long sweeping corners/curves better because the truck resists sway better, but were softer than stock at small compression for say rocks and washboard on dirt roads etc.

i plan to replace my springs at some point and i am trying to figure out which type is best for me, as im not sure how much the variable rates change from the stock constant rates..

any opinions, past experiences and thoughts would be greatly appreciated!

thanks!

 

[Anime]

There are linear rate springs, dual-rate springs, and variable rate springs.

Linear rate springs are like the stock springs, one constant rate throughout.

Dual-rate springs are what the Moog replacement springs are, one rate when compressed up to a certain rate, then another rate for any compression past that point.

Variable (or progressive-rate) springs get progressively firmer the more they are compressed - they are similar to dual-rate springs, but with more than two rates. They can be wound so they have a different rate for each coil that is compressed.


The Moog dual-rates are about the only stock replacement springs out there, other than some custom spring shops that make replacement coils. The CC868 coils seem to be what you want for a 4WD. They are decent for what they cost, and will restore ride height and add some ride quality. They will compress easier than stock springs for the first inches of travel then get firmer than stock for the last few inches. The only "bad" thing about dual-rate (and variable rate) springs is that they are harder on shocks. Regular shocks are made for linear-rate springs. The softer initial rate and the harder secondary rate gives the shock quite a workout as it's damping a lot to first control a soft spring, then having to work hard to control a firm spring. There aren't a lot of complaints about having to replace shocks more often with the Moog springs, but I'm not so sure people keep track of their shock replacement intervals anyway.

If cost is a consideration, you can always re-use the stock springs and just make your own spring spacers. Use steel washers with a 1-1/4 inch hole and a 3 inch outer diameter, or just make your own from scrap. You will probably need anywhere from a 1/4 inch to 3/4 of an inch thick spacer (or stacked spacers) to raise the front end up back to stock height. The geometry of the TTB front end gives 1.5 times the lift of the spacers, so a 1/2 inch spacer will lift the front end about 3/4 of an inch.

http://www.therangerstation.com/tech_library/WasherCoilSpacers.shtml


I would say the Moog dual rate springs would be for if you wanted a comfy ride and slightly better handling. Otherwise the stock springs are fine. With spacers and the front end ride height restored, the ride will be back to stock and the front end travel will be back too. The spacers also give the extra advantage of being able to fine-tune the alignment (at least the camber) without having to mess with the alignment bushings.

 

[Blue91Ex]

thanks for the reply anime, this is exactly the info i wanted. See my goal wioth the new springs is that they will restore the ride hight and help the ride quality, so that later when i build spacers (2" lift, your info on 1.5xspacer hight is helpful, i didnt know that, it seems backwards of leaf spring shackles) it will put the truck 2" over factory stock, instead of 2" over crappy worn out stock. i did see raybestos constant rate springs on rockauto so you can get them, but im leaning towards the variable/dual rate springs now instead.

 

[Anime]

Keep in mind - new springs will eventually sag too. When those dual-rate springs sag, those "soft" coils that are so close together for the soft ride will then be in constant contact - effectively making the shorter part of the spring a linear-rate with a stiff ride.

The stock springs have already sagged and broken in. The coils are far enough apart that the sag doesn't affect the rate or travel.

I'd say just add short spacers for now to restore stock height and make taller spacers if you want more lift in the future.

As for the Raybestos springs, it's my understanding that ALL of the springs, from Raybestos, AC Delco, Rockwell, etc. etc are all just re-branded Moog springs. They are all dual rate. If you wanted linear rate you'd have to get them custom made or find a spring company like Eaton Spring that has specs to manufacture stock replacements.

 

[Blue91Ex]

Well i did buy the new springs, they wer ethe moog dual rates, though by the looks of the spacing between coils there is 3 rates, a soft then the middle is a bit closer together and then teh top half is closer and stiffer. anyways so far i am very happy with them, the front of the truck rides much softer and the cornering is sliightly better, the amount of sway around corners is noticably less, and the best part, the front of teh truck sits about 3/4" taller, maybe a bit more, i finally installed the custom leaf spring shackles i built as well to even out the ride hight. i am very happy with the setup.

 

[plcrew]

Is there a better shock to match with the duel rate coils and also for the constant rate coil springs?

 

[Blue91Ex]

i would assume any decent shock would work, the ones i have are just budget crap shocks and they have lasted for several years being beat on on dirt roads with ruts and winter frost heaves and still work alright, i doubt these springs will really cause any noticable extra wear.