All UTV's Figuring Dual Rate springs

[Wild Earp]

Anybody want to share some insight into picking dual rate spring setups?

Ive got 8" FOX shocks - at 90deg at full bump - and looking for 50% droop. To get that height (with no Preload) with single springs gets met right at 200lb Front/250lb Rear. 16" springs.

So to figure out dual rates (say for the front), Im aiming for that same 200lb spring rate for the combined rate? With a 250% Step Up Rate, that puts me at a 500lb bottom spring, and a 333lb top spring.

That should put me at the same ride height as the single spring, correct?

Are my numbers adding up? Am I on the right track here?

For the rear (250lb combined), I get 625 bottom, 417 top. So for the back either 400 over 650, or 450 over 600. For the front Im thinking of running 350 over 500.

Anybody care to confirm my findings, or point me in the right direction if Im off? I would greatly appreciate it! (this springs are $$! )

Thanks

(To Clarify: The rhino is primarily a short course car, but will be doing some short desert and grand prix races too, so dont want to go too low. 50% droop puts me at 10-11" of ground clearance at ride height.)

 

[07fj]

if you put those springs on it will ride and handle like crap.

your top spring will prob be around 90-150lbs, you will use them to set the car ride height, adjust transfer collar so it is just above or touching your main spring collar. (at ride height) that is the one you will use mostly during racing. prob 250-275 front and 300-350 rear.

also I recommend a shorter (by 2") upper spring then lengthen the lower by 2"
so say, instead of two 8" ones, use a 6" upper and 10" lower as an example.

 

[Wild Earp]

Thanks Rog. I figured it was more complicated than an hours worth of Googleing.

 

[racemx587]

Interesting.. I'm curious to see where this goes

 

[07fj]

I am going off of something very similar to the best handling car around.

I do not know the specific valving, nor would I say if I did, but this spring combo is close for a starting point.

 

[Wild Earp]

I really appreciate any input you (Rog) and anybody else can give. I know I will never really figure out the Black Art of Spring/Shock tuning, but I really like having some knowledge over how this stuff works. Im not the kind of driver that just can leave "X" on the car completely up to someone else. I like having at least an idea of whats going on mechanically on every part of my car.

And i totally understand not being able to giveaway ALL your secrets!

 

[07fj]

I really appreciate any input you (Rog) and anybody else can give. I know I will never really figure out the Black Art of Spring/Shock tuning, but I really like having some knowledge over how this stuff works. Im not the kind of driver that just can leave "X" on the car completely up to someone else. I like having at least an idea of whats going on mechanically on every part of my car.

And i totally understand not being able to giveaway ALL your secrets!

no problem, however I am not the master, Todd Arthur is. I am sure for not a crazy amount of $$ he could set you up and let you know how to adjust things from that point, depending on what you want to do with your car besides short course.

 

[Wild Earp]

Thanks Rog.

Anybody else have any input/knowledge to share with the forum on this??

 

[LSRGreg]

I can tell you that we use nothing over a 400 lb spring rate for a dual rate set up.. even on our taller desert cars. Your 400 and 600 rates can't be right, unless you have a really high leverage ratio.. (ie.. having 20" plus of wheel travel with an 8" shock.. ) Our XTR-F kit for the Rhino uses a 300 over 300 on the front to give you an idea, and that is with an 8" stroke shock, with about 15" of wheel travel.. My race car is running springs down in the 200lb range to get the ride height so low. One thing i have learned, is that with all the calculations in the world, 99% of the time, you end up running something different than what the math says.. Sway-a-way has a good spring rate calculator on thier website fyi.

Good luck!

 

[Wild Earp]

Thanks Greg. Yeah, I used Sway aways in part to figure my math out, but I dont have corner weights yet, so I was just going off of what I know in a single spring, will give me the right ride height.. I think the 250% Step up rate is whats throwing it all off. That number must just not work with our setups.

Thanks for the input!!

 

[woodysfj40]

F-O-A OFF-ROAD Shock Absorbers ,FOA Springs, Coil Over, Offroad <--that's a link

I run 12" 250# single rate fronts and 12" 275# single rate rears on my RZR...handles excellent, rides excellent. Have plans to change the rear over to dual rates down the road. Ran 300# single rate rears and they never achieved full shock compression, the 275's solved that with no ill effects.

I know RacerTech dual rate rear coils use a 275# primary, perhaps they'll share the rate of the heavier coil

 

[tatum]

This may not help at all because I am running a 10 inch travel shock stood pretty straight up at about a 1.5 to 1. I have 100/150 10 inch springs in frt and200/250 10 inch springs in rear.40% droop in frt and 45% in rear.

 

[Darryl89]

This may not help at all because I am running a 10 inch travel shock stood pretty straight up at about a 1.5 to 1. I have 100/150 10 inch springs in frt and200/250 10 inch springs in rear.40% droop in frt and 45% in rear.

Sounds almost like the setup my new car has. 10" travel shocks at a 1.5 to 1 with almost the same dual rate spring setup. My new shock mounts aren't as upright as yours Hans, but maintain the 90 degree angle at full compression.

 

[Wild Earp]

ALL very helpful info guys! Thanks a lot!

Heres my new setup to give an idea of what Im working with. I just put some 14" springs on to roll it around the shop.

 

[tatum]

I noticed you have your PS in front of the steering quickener.I just got a unisteer for my car and the easiest place for me to mount it would be between the quickener and the rack.Do you know if it matters were its at?

 

[Makin' Trax]

Ben - This is the formula for Primary rate
(tender x main) divided by (tender + main)

or using Rog's numbers (150 x 250) / (150 + 250) = 93.75 Primary Rate. The secondary rate after the step up would be 250 or same as the main.

If I read your post correctly you achieve 50% sag or 4" with a 200# spring with 0 preload, that is 800# load on the spring at ride height with 50% sag. That seems pretty high, but your car may just be heavy, because the shock angle looks good. So based on that you would need 400/400 to achive 50% droop or 4". And 500/500 to get the rear to do the same. Wow

Trust the single rate spring loading you did. The spring will not lie. Then play with the above formula to find the right rate combo for you. My $.02

 

[megadesertdiesel]

last year i went from single to dual rate just to lower the car. damn everything was expensive for all of the collars and springs.

i was running 16"x250 in the rear and 16"x200 in the front of my RZR1. i had that suspension dialed in and working perfect.

i went with 175# over 250# for the rear and 100# over 350# for the front. i had to revalve due the the different ride heigth, which started over my perfect shock valving again. its still not perfect but i am very close.

shock valving and spring rates you have to do by the seat of the pants feel and to your driving style. calculators will get you in the ballpark but keep trying different setups untill you get it the way you want.

 

[Makin' Trax]

Well said Mega. Also it can get expensive to keep changing springs to find that combo that is best for you. Many times the selection of rates to choose from can be limited. I have a bunch of springs you can use to tinker around with if you want Ben. I messed around with different combos with a couple of cars and finally went to a single spring and everything dialed right in.

 

[Wild Earp]

Thanks guys! I just bought megad's old 16" springs, just waiting for them to arrive. I haven't put 16"s on yet, but with 250f/300r 14" springs, I'm getting about 40% droop right now. My car weighed 1650 with driver at the last Lucas race I did, but I've shed some weight since then. Final race weight will probably be 1550. Once I get those springs, I'll put them on and go from there. I'd like it to be a bit lower than it is now for short course, but I would be perfectly happy with it as is for general use.

Steve, I'd love to borrow some springs from you to get started!! I'll hit you up after thanksgiving.

 

[LSRGreg]

I noticed you have your PS in front of the steering quickener.I just got a unisteer for my car and the easiest place for me to mount it would be between the quickener and the rack.Do you know if it matters were its at?

My set up has the power unit between the quickener and rack. i called uni-steer about it, and they didn't really have a suggestion, and mine has been working fine all season.. so i don't think it really matters.. but not sure.