Do I Need New Springs…

I will be adding a steel bumper, winch and lightbar to the front. Below I have listed what I have or will have on the vehicle. I currently have 600LB springs on the front they are kings. I would like to maintain current stiffness and height. Would I need to go to a 650LB spring or 700LB spring? Can anyone chime in, any input would be greatly appreciated. Thank you.



Bumper:108LBS
Winch:68LBS
Lightbar:10LBS
Rci Sliders:98LBS
RCI Ifs, trans and diff skid aluminum:68LBS

Total Weight:352LBS
Total Weight Up Front:195ish LBS.

 

You’ve added over 200lbs up front or 100+ pounds per corner. Given the same dimensions 700lb coils.

 

I’m not sure how spring rates work and how you calculate spring rate need based off weight. could you break it down for me, sorry I just want to educate myself on this.

 

The super short answer is that a 600 pound spring takes 600 to compress 1 inch, 1200 for 2 etc. Adding weight causes the springs to compress more. People offset the changes in ride height from compression either with more preload or swapping springs.

 

thank you for the information.

 

I think you can get away with either spring rate 650/700. Just hard to calculate without corner weights. A lot of people only count what’s up front but forget that the sliders and skids add some as well based on weight distribution.

In the early part of my build I went with 700 and was very happy

 

is the 700 super stiff? I want to maintain what I currently have and I don’t want to do anymore preload to maintain the height I have.

 

I had 650's on my icons but switched to 700's because the 650's settled A LOT. I would make adjustments only to have it settle down to the original ride height a few weeks later.

Noticed a very very slight increase in stiffness when switching to 700's but barely. Drove a 3/4 diesel Silverado before and its butter compared to that thing.

My truck is pretty heavy weighing in at 5900 pounds with just me and fuel in it.

I vote 700's

 

A 600 lb/in spring will compress 1" for every 600 pounds. Because the spring is connected at about the halfway point of the lower control arm, there is a 2-1 "motion ratio" and thus each 1 pound you add to the truck is effectively 2 pounds. Additionally, because of the 2-1 motion ratio, the for every 1" the spring is compressed the wheel moves 2".

Therefore given some added weight, the height will change thusly:

height = weight * 4 / 600

Example:

height = 100 lb * 4 / 600 lb/in = 0.66 in

I suggest attempting to get the 0.66" back by increasing preload. If you max out preload and still cannot get to your desired ride height, then replace your springs with 650 or 700 lb/in ones.

 

yeah play with preload first. Otherwise i'd say go with 650lb.

 

Thank you for the detailed breakdown.

 

Here is some other resources.

https://accutuneoffroad.com/articles/coilover-spring-rates-for-toyota-tacoma-4runner/
https://accutuneoffroad.com/oem-front-coilover-shock-setup/

 

Yup agreed. Preload doesn't hurt ride quality unless you are coil binding or you have no droop. My trucks 5700lbs, and Im still rocking the stock 13'' 600lb springs and they are great. Im only sitting maybe 1.75"-2" over stock, so anymore preload would be coil bind and to get more height if I wanted for some reason I would just go to a 14'' 600. Could see someone going to a 650lb for the height they want, otherwise I see no need for a 700lb spring.

 

^ yup. Im full steel skids, sliders, no bumper or winch but on icon 13" 650lb springs and they're too stiff for weight transfer when articulating. Going to go to a King or Eibach 14" 600lb spring to soften up the front.

 

Yeah that's one thing that's a huge downfall of 650/700lb springs. Under flex, the front end will hardly do anything if the weight transfer is to the rear. For example driving up onto an ecology block, my front still fully compresses. 650 or 700 the front wouldn't see the same compression.

 

Boom. Its nice to see others understand the differences in springs and preload and what they affect. Theres sooooo much misinfo out there about it. Took me awhile to understand what was correct.

Ideally we want to run the softest springs we can until it causes sag issues due to weight.

 

I agree try more preload before going with heavier springs. I have more weight then you have listed OP and am on Dobinsons 580lb springs. I'm also at the max preload for the lift I want. They've been holding the weight, ride great, and articulate easily.

 

Why?

Preload should be used to adjust ride height, not compensate for poor rate selection.

When building custom suspensions you start with the corner weight, not whats the lowest spring rate I can run without binding

 

I’m not following you. Can you elaborate?

 

Just to throw in my .02 since I was in the same boat with much more weight - I was sure I needed 650 or 700lb springs.

Reached out to Accutune to see what they suggested. My rig: fully armored w/ 33" tires, front & rear bumpers, winch, Diamondback, roof rack, etc: additional weight - Front - 375 Rear - 500. This was actually before the RCI full steel skid package & roof rack. Mix of 70% onroad, 30% offroad driving. Mostly high speed desert runs and overlanding, not much technical rock crawling. Crunched the TRD pro front aluminum skid so aggressive at times and encounter many rocks. Hence the decision to go all steel.

Here was the recommendation from Accutune: 05+ Tacoma Mid Travel Suspension Kit, Stage 4A – Fox
2.5 inch lift
14" 600# Spring
RXT Option 3 with additional leaf.
Adventure Tune
DSCs will be set at softest setting and can adjust hi/low speed compression.

They were spot on with their suggestion, but I do have to adjust the DSC dials when encountering whoops and such. Just one more thing to do when airing down. Also have to keep track of different settings for different terrain. Bit of a pain in the ass, but the increased performance is worth it. Then you have to remember to dial it back when you're done playing. I have a buddy that has the Pro suspension on his OR and with C rated tires, doesn't air down. He's always waiting on me whenever we hit trails. Something to be said for simplicity.

This is how she sits



Lastly I say 'high speed desert runs'. Very subjective. My rig is still a heavyweight pig and even with top of the line suspension, you'll still feel it. If you really want a capable high speed desert vehicle, buy a Razr.