shock positioning

slimjim

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when running leaf springs on your truck, and mounting the bottom of your shocks on the spring plate, or axle housing - is there an advantage to positioning the shocks at an angle where the top of the shock is leaned forward (toward the front of the truck)? or should the shocks just be straight up and down?

i always thought that if the bottom of the shock was mounted on a lever (ie. traction bar, or 2link), then mounting the shocks with that forward leaning angle would make the shock work more "progressively". i thought the compression gets stiffer as the angle between the shock and the lever approaches 90 degrees. so at near full bump, the shock is hardest to compress.

i have seen quite a few leaf spring setups where the bottom of the shock is mounted not on a lever, but directly to the top of the spring, or axle housing, and is positioned with the "forward leaning" angle. is there a good reason for that?

also, lets assume the shocks in question are not bypass. thanks everybody.

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heavy8

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Mounting a shock on top of the spring plate at a slight angle is ussually good. As the spring compresses the axle housing moves forward slightly ,so mounting is at a slight angle is needed to insure it dosnt go past vertical . Also a typical set up is a spring with 18" travel mated with a shock with 16" travel. Mounting at a slight angle( 10deg approx) allows you to utilize the intire travel of the spring. Yes there is more work for the shock but its speed is slowed down as well. Just make sure to take the spring pack apart and cycle it. You cant go wrong that way.
 

ntsqd

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Huh ? As a leaf spring is compressed it flattens out. As it flattens out the leaf get effectively longer, moving the housing towards the rear if the front spring eye is the fixed eye.


TS

I used swerve around my halucinations, now I drive right thru them.
 

cleartoy

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My opinion on setting up rear shocks on a leaf sprung solid axle is to have them straight up as possible. That is the way they are most efficient. Sort of like a 1:1 theory.

As the suspension compresses(again leaf spring setup only) it also moves rearward towards the shackle. If you have them leaning alot to the front, then the shocks loose some efficiency, as there is sort of a dead spot in the shock.

This is my theory, and you should talk to other people to get their ideas.



94 Toyota stdcab 2x4
99 Yamaha YZ250

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Kritter

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Have them perfectlly vertical and tilt them inwards a couple degrees. Run a traction bar or V bar to minimize axle wrap since you dont have any wrap control from an angled shock. The 1:1 is easier on the shock and the inward tilt helps with body lean.



Kris
"Buy American before it's too late"
 

hoeker

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first and most important in deciding this in your situation is making sure you can maximize your travel and not destroy your shock by bottoming it out. getting 12" travel out of a 12" travel shock requires some forward angle. you have to fully cycle the suspension to test this. if your using multiple shocks per wheel, this gets more complicated because the spring plate rotates as the suspension cycles. on my CORR truck i had to mount the rear shock at more of an angle than the front 2 to keep it from limiting my travel. also try to build in a little extra room at full bump and full droop.
when cycling the suspension, i prefer to do as much as possible with the complete spring pack. at full compression the spring pack will shape different than just the top couple leaves. this can be difficult with out having something solid to anchor the truck to, and be careful!
if your going to use some sort of anti wrap bar, this is a good time to test for the proper length. this is very critical for maximizing wheel travel without bind. i have a method i used to locate my mounts that worked very well, but i'd be interested in hearing a pro's opinion on the process.

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slimjim

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Thanks for the responses. I was just curious, because I have seen some trucks setup with that type of shock positioning

Also, i am trying to visualize the spring plate through it's whole travel, and i can't figure out which way the spring plate would rotate? and it seems that if it did rotate, that the amount of rotation would be negligible. but i guess that in the best designs, any change in the position of the springplate throughout the cycle must be accounted for. how much rotation do you get on your truck? 1 degree? 5 degrees? and what direction, top of plate toward rear on down travel?

on my current truck, i have a 2-link type setup, where the traction/anti-wrap bars also serve as a lever for mounting the shocks on. the traction bars mount to the chassis directly above the forward spring eye, and mount to the rear end on top of the spring plate. so when my truck cycles through the entire range of travel, the spring plate can't be rotating much, at least not an amount measurable to the eyes.


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hoeker

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most leaf springs are not equal length front and rear, also the shackel affects the movement of the rear half of the spring. taking both of these into consideration, the spring plate may rotate. the springs on my truck actually reversed the arch at full bump. the rotation was considerable, 10 deg. or so. with the rear portion of the plate requiring a longer shock.

the point is simple, you have to check, never assume anything.

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ntsqd

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Your spring plates have to be rotating some. The traction links are a fixed length, but the spring's length btwn the front eye and the spring plate is variable in length depending on where in the travel the spring is. You could have gotten the arm's pivot points such that the arc it travels in is very close to the arc that the spring plate travels in, but unless you were deliberately trying for that the odds of hitting it by accident are very small.

I've been told that the surest way to kill a leaf spring is to make reverse it's arch. What kind of lifespan are you getting out of those leaves ?

TS

I used swerve around my halucinations, now I drive right thru them.
 

hoeker

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i definately wasn't saying it was good to do, but when your playing with a rule book some times it works out that way.
i had 6 leaves of .218" (??) material, very soft springs, very low ride height. and they actually held up pretty well. i got 2 seasons out of the last set. they were on the truck when i sold it. the biggest problem i had was teaing the front eye out, even with a double wrap. i think the steel was just to thin. if i had kept the truck i would have gone to a triple front eye.

i totally agree on the traction point, just didn't feel like being quite that blunt.

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Kritter

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"I've been told that the surest way to kill a leaf spring is to make reverse it's arch. What kind of lifespan are you getting out of those leaves ?:

On our race truck they go about 2 or 3 inches negative to compress the air bump fully. The suspension rocks. We have our springs prepped every race and go through and swap out about 2 sets a year just to be on the safe side and then the springs go on a prerunner and last a lot longer.

Kris
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DPpatrol

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Since the rear end moves backwards on a leaf spring truck wouldn't it make sense to have the shock angled a little bit backwards instead of fowards? That way when the rear end moves backwards during compression it wants to compress the shock instead of extending it?

jason
 

ntsqd

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It moves upwards at a far faster rate than it moves rearwards. Combine a spring with a lot of arch with a damper mounted really leaned over and you might get damper extension with suspension compression.

TS

I used swerve around my halucinations, now I drive right thru them.
 
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