Dual "rate" coilovers - red flag check

Coil masters, lend me your eyes. I want to replace the 14" 650lb coils on my ADS adjustables with dual springs (can't say dual rate because they're the same rate) to take the harshness out of the road and gain some stability in a straight line.

The 650 is too stiff (I've made other threads about this), and even if I don't follow through with duals, it seems like going to single 550s would be a better option for me, though barely. AFAIK I've never hit the bumps on these... 4800lbs is a lot of force for a corner. The math seems to check out... 1.5" of compression at level on a 14" coil leading to 3.8" of up travel and 1.5" of down. My intuition says this should be close to 50/50 instead for optimal articulation. The typical springs seem biased towards like...jumps.

Does this setup check out? I've kept the same 2" of preload that come with the typical adjustable ride height coilovers, and followed the rule of longer spring's rate >= shorter spring's (although the opposite seems to reveal itself more optimal).

 

You will not be able to fit two springs on an OEM fit coilover. Even 8" travel coilovers found on long travel kits will use a single spring.

Have the shocks been tuned for your truck yet? Majority of the ride quality you experience from coilover's will come from the internal valving.

Depending on your vehicle and sprung weight, 550s would the absolute lightest option for a Tacoma. Those would be for something like a 2wd truck. 600 LB spring is most common.

 

How about a 14" 500lb coil spring and larger diameter front sway bar?

@treyus30 is this for a 1st gen or 2nd/3rd?

 

In what way will they not fit?


In fact the block heights actually suggest there will be more room even after a slider..

 

Possible. Do they make larger sway bars for a 1st gen?

 

https://www.addco.net/product/toyota-tacoma-4wd-1995-5-01-front/

 

You had me curious so I ran out with my calipers - stock is already 1.07"

 

I’m no expert but what benefits are you looking to achieve with a dual rate springs that has the same spring rate that a single spring can’t accomplished? Eibach do make a 6” & 8” spring but as mentioned, most coilovers are custom tuned/valved to run a lighter dual rate: 150/200 or 175/250 ball park, depending on corner weight etc.

Had you consider a 16” 600lbs spring? If you have the length room, this will prevent you from adding excessive preload to achieve the same ride height and provide a smoother ride.

 

Larger sway bar diameter, type of material, and how it is heat treated makes a difference. The thicker it is, the harder it will take to twist when turning, preventing body roll and you’re able to feel the road better. This creates a flatter body when cornering and allowing the vehicle to plane faster.

 

You're saying that getting a 2" longer sppring, thus causing an extra 2" of preload will result in a smoother ride? I can't visualize how that works..

I think those extremely low combinations are more common on UTVs with like 24" shocks and stuff. For a more practical reference, typical sedans run in the 250-350 range and some have dual rate built into a single spring. From my calculator, I can't go lower on the top spring without bottoming it out stationary. If I made the longer one lighter, things change, but that goes against rule of thumb.

Ya my point was the one he quoted is basically same as stock (unless there's some unnamed treatment)

 

I too am not following what you're trying to do...

Two 600lb springs together will be same as a 300lb spring... That is much too light of a spring rate to properly support the weight of a Tacoma.
"Typical sedans" run in the 250-350lb range because generally they also have McPherson strut suspensions that don't have an almost 2:1 leverage ratio working against the coil springs (instead it's essentially a 1:1 ratio... This means the rate at the wheel will be similar whether it's a 650lb coil on a Tacoma or a 325lb coil on a sedan).

A little more studying (specifically on what is called "Motion Ratio" and "Wheel Rate") may be in order here... As has already been said above, the shock valving is more likely your issue (assuming you have reason to be running 650lb coils, carrying a winch & bumper on the front of your truck for example... If not, then you should actually be running 550-600lb coils).

https://www.autospeed.com/cms/a_2904/article

 

I feel like nobody is taking the time to look at my original post

 

Well you need to explain better what the heck you're trying to do then...
I tried to decipher your math, and I can only get your numbers if I leave out the motion ratio factor of the Tacoma suspension.

 

I left that out because it's a comparison to the same truck, they are relative performances. (I don't actually know corner weight either). I'm trying to "float" over road imperfections

 

Motion Ratio is an important part of the equation... You can't leave that out and hope to get any meaningful figures.

If it's harsh and not "floating" well over road imperfections, then again, that is more a shock valving issue (the valving is too stiff, and is why the harshness). The other possibility is you are lifted up too high (too much angle on the control arms causes ride harshness / poor handling as well). How lifted are you? Do you have a winch/bumper hanging off the front of yours?

 

I'm at about the middle tick on the adjustable. I can go softer, but then I get vibrations on the freeway in certain instances. Lift is at nearly a minimum on these, I actually went down to 30" tires so I need a drop too. No bumper (yet - I'd like to make a custom one at some point) or winch but recently finished 4x4 conversion so I've got that weight

 

If no bumper or winch, then dropping to a spring rate ~550lb may be an improvement (assuming this for your '99).
The weight of a bumper & winch however also can greatly smooth out your ride by a lot too (likely more so than just switching to 550 coils). If those items are in the near future, I'd probably say leave things alone for the moment... Otherwise you might find yourself in the opposite predicament afterward if you swap the springs now. Once the bumper is on, you can better evaluate then whether the ride warrants doing anything further with the springs/shocks.

A vibration on the freeway could also be from a tire issue (tire imbalance or maybe too much PSI).