5th Gen -What are TRUE FR & RR spring rates?

[STLDAVE]

Ok, I've searched for this and have found info saying the front spring rates are 500, 580, and 590. I've found info saying the rear spring rates are 150 or 180. I've talked to vendors (who I won't name here) and have gotten conflicting information there too.

Can anyone tell me what the actual spring rates are (and provide the source of the info) for the 5th gens? If there is a difference between the trim levels I need the Trail Edition info, but others could possible use the info for theirs too.

 

[harper7]

Ok, I've searched for this and have found info saying the front spring rates are 500, 580, and 590. I've found info saying the rear spring rates are 150 or 180. I've talked to vendors (who I won't name here) and have gotten conflicting information there too.

Can anyone tell me what the actual spring rates are (and provide the source of the info) for the 5th gens? If there is a difference between the trim levels I need the Trail Edition info, but others could possible use the info for theirs too.

First the question of ...why?

I've read 580lbs/in and 180lbs/in as a reference point for the FJ's and 4th Gens on the FJ and 120 forums. But the ONLY way to get TRUE spring rates on your truck is to buy or find a race shop that has a spring rate tester like one of these......Coil Spring Rate Testers - SummitRacing.com
Take your springs off and test them .
I never heard of anybody taking their springs and testing them on a 5th Gen. yet or cared enough to go thru all that work and trouble as most just upgrade to aftermarket springs of known spring rates.

All that being said, spring rates even when new from the big manufacturers like Eibach, Eibach Springs ,have manufacturing tolerances and can vary 10 lbs/in or more . I helped in the pits for a friends M3 track car a few years back and he had several sets of springs that we swapped in and out dialing it in per the track.They were special ordered the same spring rate but were off up to 10-20lbs/in high or low when tested on a spring rate tester.We'd mark them and change them out as needed.

SR5'S and TE's all have the same part number for the springs and Limited's are a different PN and I assume a little higher spring rate as less complaints on nose dive.But that may be due to the XREAS but they are different PN's. Also some are different side to side as told by the colored rings on them as the factory tries to put the ones that tested higher on the drivers side(gas tank) I assume.

 

[1engineer]

http://www.toyota-4runner.org/5th-gen-t4rs/116375-spring-rate-question-engineers.html

Here is an earlier post I think explaining his question. We pm'd back and forth and apparently I was absolutely no help lol.

I explained that if there was no geometry change (ie length, angle) of suspension components then spring rate (and ultimately ride stiffness) would be proportional to increase/decrease of the new springs vs the old springs. I also explained that due to new springs being stiffer, the spring would not compress as much under the exact same conditions as the old spring thereby causing a small geometry change in itself. How much? I do not know but probably not much.

Sorry I can't help you more Dave. Maybe Harper or the Orange Texan can!

 

[harper7]

http://www.toyota-4runner.org/5th-gen-t4rs/116375-spring-rate-question-engineers.html

Here is an earlier post I think explaining his question. We pm'd back and forth and apparently I was absolutely no help lol.

I explained that if there was no geometry change (ie length, angle) of suspension components then spring rate (and ultimately ride stiffness) would be proportional to increase/decrease of the new springs vs the old springs. I also explained that due to new springs being stiffer, the spring would not compress as much under the exact same conditions as the old spring thereby causing a small geometry change in itself. How much? I do not know but probably not much.

Sorry I can't help you more Dave. Maybe Harper or the Orange Texan can!

Thought maybe you would bring in Hooke's law of elasticity.Hooke's law.
The way I understand it is,the more the spring is compressed the greater it's spring rate. So ,if you dial in more height or add extra weight ,like a Shrockworks bumper on the Icon CO's for example the spring rate goes up and takes load off the back so rear spring rate decreases.

 

[STLDAVE]

http://www.toyota-4runner.org/5th-gen-t4rs/116375-spring-rate-question-engineers.html

Here is an earlier post I think explaining his question. We pm'd back and forth and apparently I was absolutely no help lol.

I explained that if there was no geometry change (ie length, angle) of suspension components then spring rate (and ultimately ride stiffness) would be proportional to increase/decrease of the new springs vs the old springs. I also explained that due to new springs being stiffer, the spring would not compress as much under the exact same conditions as the old spring thereby causing a small geometry change in itself. How much? I do not know but probably not much.

Sorry I can't help you more Dave. Maybe Harper or the Orange Texan can!

Actually, I admit it took a bit for your info to sink in, but i got it.
Now on the the next step, and in answer to Harper's question:

I'm looking at coilovers and rear springs for the TE and would like to know the difference in rates between the OEM springs and the after market springs offered. I don't think it would make sense to put a spring with a rate 40% higher than stock on one end of the TE and a spring that's 10% higher on the other end. Or am I missing something?

 

[1engineer]

Thought maybe you would bring in Hooke's law of elasticity.Hooke's law.
The way I understand it is,the more the spring is compressed the greater it's spring rate. So ,if you dial in more height or add extra weight ,like a Shrockworks bumper on the Icon CO's for example the spring rate goes up and takes load off the back so rear spring rate decreases.

Yes you are right. I could not remember the name of he law!

Actually, I admit it took a bit for your info to sink in, but i got it.
Now on the the next step, and in answer to Harper's question:

I'm looking at coilovers and rear springs for the TE and would like to know the difference in rates between the OEM springs and the after market springs offered. I don't think it would make sense to put a spring with a rate 40% higher than stock on one end of the TE and a spring that's 10% higher on the other end. Or am I missing something?

Only if you would want to tow would I increase the rear non-proportionally. It would stiffen it up and not have as much sag.

 

[STLDAVE]

Only if you would want to tow would I increase the rear non-proportionally. It would stiffen it up and not have as much sag.

And there's the problem; Since I won't be towing, I don't want to increase the rear non-proportionally. But how do I know what front spings will give me that proportional increase with the rear springs unless I know what the OEM spring rates are?

That's why I'm asking if anyone knows what the stock front and rear spring rates actually are.

 

[1engineer]

And there's the problem; Since I won't be towing, I don't want to increase the rear non-proportionally. But how do I know what front spings will give me that proportional increase with the rear springs unless I know what the OEM spring rates are?

That's why I'm asking if anyone knows what the stock front a rear spring rates actually are.

Man, I bet your head is hurting about now lol. I think the ONLY way you will know for sure is to take it off and test it and I know you don't want to go to that trouble. So, here is what I would do:

1. Try to locate someone through this forum that has theirs modified that is relatively close and go ride or drive their vehicle so you can feel the change.

2. Contact every known aftermarket spring and lift manufacturer that makes products for the 4Runner. There can't be that many maybe three or four. Find out every combination of spring they have. If at the end of your search they only have product that is 40% stiffer on one end and 10% on the other then that is what you will have to go with unless y0u want to go custom. Going that route opens up a whole new can of worms though.

Even if the rear uses 40% stiffer springs the ultimate ride will not be increased 40%. If you increased BOTH front and rear by 40% then you could expect that. Increasing one by 10% and the other by 40% will average it out to somewhere in the middle, or around 25%. As I said in my pm's, to some people that would be a lot and to some they would not even feel the difference.

Let me put this another way:
Let's say you only went with new shocks and stock springs. You decided on really stiff shocks though. You would have increased the "stiffness" of the ride by "X" amount because shocks "dampen" the effects of the springs so you won't have bounce. Unfortunately "X" cannot be defined as a percentage because it will change depending on the speed and severity of the bump you hit. Think about it: Hitting a pothole on the interstate at 70 mph vs. hitting a speed bump at 5 mph. Standard shocks respond differently at different speeds because of their inherent design using fixed orifices. XREAS and KDSS for example do not act like that though and they have their own advantages and disadvantages.

Again, I do not think a definitive increase in the stiffness of your suspension after modification can be calculated because there are too many unknowns. I think you are either going to have to do it - or not.

 

[BigredTEX]

I'd like to chime into this thread, if nothing else to add to the confusion. I too am an engineer, but not of the caliber of 1Engineer, since I am an Industrial Engineer (otherwise known in the engineering community as an Imaginary Engineer).

Straight wound springs have a constant spring rate, meaning that a 100 lb/in spring increases at the rate of 100 lbs per inch of compression. It takes 100 lbs to compress the first inch, 200 lbs to compress the second inch and 300 lbs to compress the third inch. Most of the aftermarket lifts for the T4R achieve the lift by using higher rate springs and therefore, they do not compress as much under the weight of the vehicle resulting in a higher ride height. They also use higher spring rates since most people installing a lift also add other aftermarket components like bumpers, sliders, winch, etc., which add to the overall weight of the vehicle. You can also use a longer spring of the same rate to achieve a taller ride height, but if you add other aftermarket components, any increase you get in ride height is quickly lost to the additional weight you are carrying.

The reason the spring rates differ so much front to rear is due to the suspension design and the front/rear weight distribution of the vehicle. The rear springs act directly on the rear axle with no mechanical leverage. The fronts, with the wishbone design, have a significant cantilever which increases the effective weight acting on the spring, requiring a higher spring rate. From an aftermarket perspective, it would not be out of the ordinary to see the front spring rates increase by 40% and the rears increase 10% to achieve the same relative "effective" rate increase.

The advantage of adjustable coil overs is you can raise the lower spring mount, which has the same effect as using a longer spring of the same spring rate. That is until you raise the lower mount to the point that the vehicle no longer settles when the wheels are on the ground. At that point you have effectively increased the spring rate by compressing it against the maximum travel of the shock.

 

[proquip]

I struggled with this as well...

when I was looking to lift my TE. Ultimately, I went with Icon coilovers in the front and SAW coils in the rear with Icon monotube shocks. Here was my logic then, and what I would do differently if I did it again.

I knew that I wanted the front to be firmer to eliminate the front end dive during hard braking along with getting a mild lift. Spring rate as a basis of comparison is a little misleading. As pointed out above, the vehicle dynamics will be dependent on the amount of preload/lift on the coilovers. It was easier to think in terms of % difference from stock. Icons were advertised as being about 10% firmer than stock with 650#/in springs, and since I knew I wasn't adding an aftermarket bumper, I really didn't want the ride to be any firmer than necessary. I had also read that Icons were very smooth - a lot of debate in fact about whether Icons use progressive rate springs. While I don't think 4Runner coilovers use progressive rate springs, I believed that Icon as a leader in the market would do their homework to dial in the coilovers - this was confirmed by many who had already installed Icons on their 5th Gen 4Runners and were very happy with their choice. With about 3" of lift in the front, the ride is very controlled and smooth. Yes, you feel the smaller ruts and imperfections of the road a bit more, but that's the tradeoff when trying to get rid of the brake dive and mushiness of the front suspension. Personally, I still feel this was the best possible choice for me, even though they were more expensive than the Toytec/Bilsteins, OMEs, or OW/Radflo. As an aside, since I wasn't sure how much lift I would want, I decided I wanted adjustable coilovers. This would also help compensate for the added weight of an eventual winch, and allow me to fine tune ride height.

Regarding the rear, I went with SAW coils and Icon monotubes. Different from the front, the stock rear suspension seemed plenty firm to me, particularly since I don't load up the 4Runner very often and I don't tow. Even though the SAW coils were the softest springs out there (about 10% increase over stock), the rear is noticeably firmer. I've gotten used to it, but in hindsight, I would consider doing a Daystar 1.5" lift in the rear with the Icon monotube shocks. I would still want to upgrade the rear shocks to match the dampening characteristics of the front coilovers.

I know it might not make sense to spend $1,100 in the front and $300 in the rear if you go with rear spacers/shocks, but when you think about it, the front end is what really needs the upgrade.

Just my 2 cents. Good luck!

 

[Scratch and dent]

Has anyone taken their stock coils to a race shop for spring rates?

Reviving an old thread as I think it is a valid question and have yet to see a solid answer.

I like the stock spring rate on my 5th gen V2, and want to get the front leveled out. Softer springs with adjustable compression shocks would be optimal and spending thousands of dollars for a proprietary coil over set seems overboard for an occasional rally over water bars. I have installed top hat spacers in the front (huge mistake), but it did give me the answer to a difficult question; how much will the suspension firm up from a mild lift.

Looking for stock spring rates of front and rear coils with corresponding year and trim level of 5th gen 4runner.