Questions on Coilovers on Yota

[fishd00d]

Ok well I got my coilovers today. I got some 2.5 12" SAW's. I got dual rate. But I have a few questions.

1. Is it best to run Dual Rate with a 12" shock that will be getting 14" travel or did I just need single rate?

2. Anyone reccomend a spring size? Baja Concepts reccomended 500 over 500 so thats what I went with. Does this sound right for a Toyota Ext. Cab 4WD?

Its gona be a tight fit with the V6 but I think I can do it. I start making the hoops tomorrow and hopefully I can have the front end done by tomorrow because I am suppost to goto the desert Thursday afternoon!

Also I ordered some Downey springs for the back since mine are just about to break! Anyone have any thoughts on the Downey springs? I figured they cant be that bad for $135 for the pair!

Go Big Or Go Home

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[rdc]

i have an 88 toyota with a full coil-over front end. it has 12 inch king 2.5s, with duel rate coils, 600 on bottom, 500 on top.i use a 12 inch shock and have 17 inches travel, and the duel rate works great. 500 over 500 seams sort of strange, you might as well just run a single rate coil. because duel rate coils are supposed to have a main spring (bottom, longer, higher rate), and a tender spring, (top, shorter, lower rate). that is the hole purpose of using duel rate coils. anyway, as for the downy leafs, i had a pair on my truck a while back. They worked a lot better than stock, but they arent nationals thats for sure. but you cant beat the price. i heard Baja Concepts is offering some toyota 62 inch leafs for like 325 dollors, which is like half price. and they are the best leafs you can get for a yota. just something to look into. hope this helped.

BUILD IT YOURSELF, BREAK IT YOURSELF, THEN BUILD IT YOURSELF AGAIN - PTD Off-Road Motorsports

[rdc]

P.S. A buddy of mine builds front ends for yotas at his fab shop, when hes doing it on a v6, he usually uses 2.0 shocks, because of the less room in the engine compartment. but his kits are pretty involved, so maybe you wont have a problem. hope it works out for ya.

BUILD IT YOURSELF, BREAK IT YOURSELF, THEN BUILD IT YOURSELF AGAIN - PTD Off-Road Motorsports

[drtdevil93]

toyota class 7:

dual rates still have 2 different rates. if you have two 500 lb/in coils, the effective rate is 250 lb/in. once the slider hits the stop nut, then it goes to the 500 lb/in rate, giving it 2 rates.

erik

[rdc]

Well I sure like to know how that is? I mean if the primary and secondary are the same spring then why would it be any different than having one big spring? I understand that effective rate comes into play when you have two different rate springs. Maybe Dylan can spread some light on this..

Tony

[sirhk100]

It's a physics problem basically. If you take one 18" spring and compress it 8" the spring has obviously compressed 8". DUH!! If you take 2 9" springs that are the same rate as the single spring stack them so that they are 18" and compress them the same 8" each spring has only compressed a total of 4". This is a start of the explination and I'm sure that someone can explain it better. Basically though it has to do with the center part where they are stacked being able to move and that each spring is compressed only half the distance. Correct me if I'm wrong but if you're using a dual rate coilovers with say a 600lb and a 300lb spring and tested it on a machine that measured the resistance wouldn't you actually get a shock with three levels of resistance through the compression cycle. one at 300lb, another at 450lb, and then the final 600lb rate?

'99YZ400,
'92 Ford Exploder lifted work in progress,
lifted golf cart

[BradM]

That only works if the springs are different lengths or if there is a mechanical limit set on the shock body to limit the travel of one spring. If the springs are the same size (diameter, wire diameter, number of coils, and free length) then the deflection in both springs will be equal.

There are other reasons for dual springs than a variable rate. On a shock with 12" of travel, there will be 26-28" of spring (a rough guess). Springs that long will likely be custom made or very hard to find in stock if they are available. Also, shorter springs have a reduced tendency to bow and rub on the shock body.



"The only source of knowledge is experience." - Albert Einstein

[BradM]

Khris, you are wrong on that one. If you stack a 300 lb/in spring and a 600 lb/in spring in series, the equivalent spring rate of the series combination is 200 lb/in. That applies until the softer spring reaches a mechanical limit stop or until it reaches a solid state (coil bind). Most coil springs have a rated maximum deflection which is about 80-85% of the total deflection because spring rates become non-linear in the initial 15% and final 15% of deflection. That also reduces the maximum stresses in the coils.

If you take the spring rate of the softer spring by itself (300 lb/in) and multiply if by the recommended maximum deflection of that spring, that will give you the location of the mechanical limit stop (don't forget to account for preload). At that point, if the 300 lb/in spring reaches a mechanical limit stop, all remaining load will be applied to the 600 lb/in spring. Therefore your spring rate will change from 200 lb/in to 600 lb/in at that point.

Effective spring rates for springs in series can be calculated the same as resistors in parallel. For two springs: (S1 * S2) / (S1 S2) will work. For more than two springs: 1/Se = 1/S1 1/S2 1/Sn where Se is the effective spring rate for all springs and n is the total number of springs.



"The only source of knowledge is experience." - Albert Einstein<P ID="edit"><FONT SIZE=-1>Edited by BradM on 10/31/01 08:27 AM (server time).</FONT></P>

[sirhk100]

Thanks for the info, I wasn't quite sure I was right and I guess this time I wasn't. Thanks for the info!!

'99YZ400,
'92 Ford Exploder lifted work in progress,
lifted golf cart

[rdc]

BradM is right, but I think his equation was missing a sign (S1*S2)/(S1+S2), You can go to Sway-A-Way web site and they have a couple of pages that give some spring rate selection info and the dual rate spring equations.