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Automotive Powered Off Road (AKA: Buggys, Jeeps, Trucks, Etc,Etc. ) => Chassis and Suspension => Topic started by: fabr on April 05, 2009, 08:25:59 PM
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We need a good old in depth discussion of spring selection.I'll admit I'm a bit lost in the voodoo science of it. Dual rate/spring length/rate/crossover collars/whatever.Let's hear some ideas/thoughts/tips!
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I know there is a formula out there where you plug in simple #s from the buggy design and it is usually a good starting point. I lost it and would like to know again. Anyone with any knowledgeable info please share. I am also an Eibach spring dealer.
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check FOA shocks website, they have a dual rate spring calculator. http://f-o-a.com/calculator.html
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I know there is a formula out there where you plug in simple #s from the buggy design and it is usually a good starting point. I lost it and would like to know again. Anyone with any knowledgeable info please share. I am also an Ebiach spring dealer.
So does Swayaway. Those things are just so so tho.
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I'm kind of looking personal preferences and such.
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check FOA shocks website, they have a dual rate spring calculator. http://f-o-a.com/calculator.html
Rate selector works well! Thanks.
Now if the Eibach site didn't suck I could use the info. It's one of those sites that is all fancy looking, but short of actual information. I feel like I walked into Autozone and asked for a header gasket for a big block chevy, and the clerk just keeps asking what make and model.
http://eibach.com (http://eibach.com) Good luck!
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Personal preference? Corner weight the car, figure out the unsprung weight, figure out ride height, buy single rate springs for zero pre-load drooped while getting the desired ride height.
If you need a longer spring and must run duals, stick with the same rate springs.
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hi
there is another site for spring calculators
check that one
http://www.proshocks.com/calcs/index.htm (http://www.proshocks.com/calcs/index.htm)
yossi
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Personal preference? Corner weight the car, figure out the unsprung weight, figure out ride height, buy single rate springs for zero pre-load drooped while getting the desired ride height.
If you need a longer spring and must run duals, stick with the same rate springs.
Why would you not want dual rates?
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Why would you not want dual rates?
because it takes more math to figure it out...
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Becuase they do evil things unless you have the set-up proporly.
Say you have a 300/300 combo in the rear. That gives you a 150 initial rate and 300 after you hit the secondary spring stop. No biggy on compression, but when it starts to rebound......
If you have your rebound set up for 150 spring rate, your buggy will want to kick. If you have it set up for 300 rate, it will pack up. If you have bypasses, you can get around this by having the secondary spring stop let off at the same time the rebound tube kicks in. Swayaway has a slider calculator to help set this up on their web site.
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Finally ,I get an answer after asking everywhere I could think of that clicks in my head now. I see what you're saying. BUt ,what if a person goes with a very light tender spring that's only really effective early in the stroke?
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Tender springs are used a lot to keep the main from rattling. Not an issue.
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Tender springs are used a lot to keep the main from rattling. Not an issue.
And I have always been told that you need the tender springs to absorb all the small ruts and take the hammer out of the steering wheel. Then let the mains take care of the large whoops and the jumping.
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But that puts us back to the dual rate issues with shock valving.
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And I have always been told that you need the tender springs to absorb all the small ruts and take the hammer out of the steering wheel. Then let the mains take care of the large whoops and the jumping.
Real tenders are completely collapsed at ride height. They are made from flat wire and made for this, usually with rates in the 50-75 pound range. A short round wire spring is not a tender spring, it's just a really short dual rate.
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What's your opinion as to why fox/king/foa/others all have crossover collars on nonbypass shocks?
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Ok so on my rear shocks, 18" travel, there is 40" available for springs extended. There is 12" of threads for the preload adjuster and the crossover collar. And if the crossover collar is all the way down, then the most that the slider (between the springs) could move down is 5".
Generally speaking how much static preload do you want to see to keep everything from unseating? Is it possible that you will need to install the springs with preload with the adjuster all the way at the top? Or will they generally be loose with it backed off all the way? If you run to soft of a tender spring, and run the preload adjuster down to far, you will definately be compressing the springs to less than 50% at the bottom.
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the 50% Number sounds like bullshit to me...
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I thought so too Bug. I guess I just trusted info from someone where I lacked the knowledge. I have had springs lose there "memory" by over using them before though.
That means its time to replace them, My Tender as i call it, 110 lb, can compress way more then my main spring at 275 before coil bind, the 275 has far more coils per inch than the 110...
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Ok so on my rear shocks, 18" travel, there is 40" available for springs extended. There is 12" of threads for the preload adjuster and the crossover collar. And if the crossover collar is all the way down, then the most that the slider (between the springs) could move down is 5".
Generally speaking how much static preload do you want to see to keep everything from unseating? Is it possible that you will need to install the springs with preload with the adjuster all the way at the top? Or will they generally be loose with it backed off all the way? If you run to soft of a tender spring, and run the preload adjuster down to far, you will definately be compressing the springs to less than 50% at the bottom.
If you have no pre-load, your wheels may not drop fully in a jump depending on how much unsprung weight you have. I have run triple rate shocks where the first stage collars are bottomed at ride height. The second rate was after quite a bit of compression with rebound based on the second rate. So when getting into the third rate, it will rebound fast until it gets back into the 2nd stage that returns the car to ride height. If not running bypass, I would still run at least dual rate.
Some other info to ponder: with a light buggy, you might want to run 2.25" springs instead of 2.5" to save the weight. The bigger the diameter, the thicker the wire for the same spring rate. So the spring gets heavier in two ways. You'll probably have to make your own cross over collars.
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What's your opinion as to why fox/king/foa/others all have crossover collars on nonbypass shocks?
Tuning options, everybody got different opinions on how it should be done. Also, with all the spring length combos out there, the threads must be run down a little farther to account for somebody's wild ideas.
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Ok so on my rear shocks, 18" travel, there is 40" available for springs extended. There is 12" of threads for the preload adjuster and the crossover collar. And if the crossover collar is all the way down, then the most that the slider (between the springs) could move down is 5".
Generally speaking how much static preload do you want to see to keep everything from unseating? Is it possible that you will need to install the springs with preload with the adjuster all the way at the top? Or will they generally be loose with it backed off all the way? If you run to soft of a tender spring, and run the preload adjuster down to far, you will definately be compressing the springs to less than 50% at the bottom.
18" 2.5's are a little out there as far as springing goes. due to the small diameter of the spring, the max normal spring length is 16". With the divider this will add up to about 33" of spring. You will need 7" of thread just to get the collar to the springs. I have seen triple rate set-ups on 18's due to the fact that they usually need really low spring rates and extra spring length.
Run the deep cup bottom perch, not the flat one. Also make sure that you have the long flange spring slider or you run the risk of it getting bound up on the end of the can.
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18" 2.5's are a little out there as far as springing goes. due to the small diameter of the spring, the max normal spring length is 16". With the divider this will add up to about 33" of spring. You will need 7" of thread just to get the collar to the springs. I have seen triple rate set-ups on 18's due to the fact that they usually need really low spring rates and extra spring length.
Run the deep cup bottom perch, not the flat one. Also make sure that you have the long flange spring slider or you run the risk of it getting bound up on the end of the can.
Yes, The 18's seemed like a great idea to mount direct on the 5-link bracket, but the springs may be hard to find. You are correct, a 16" spring on the bottom will let the crossover collar drop off of the shock body. Does Fox make the deep bottom cup? My slider is 3.5" long. Is that the long one? With the slider flush with the bottom of the body, it is 18" from the bottom cup to the slider flange. Any preload will start to push the slider off of the body.
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They only make 2 bottom plates, the flat one and the cup. So if yours is cupped, you have the deep cup. 3.5" is the long slider. It might be worth getting some Delrin and machining up a set of longer ones. Getting a 1' piece and making 2 6" long sliders wont break the bank and will keep your springs in line better.
You could always do a 3" spring conversion...... They come in 18's......
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2.5 comes in 18" as well...
http://bluecoilspring.com/ (http://bluecoilspring.com/)
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They only make 2 bottom plates, the flat one and the cup. So if yours is cupped, you have the deep cup. 3.5" is the long slider. It might be worth getting some Delrin and machining up a set of longer ones. Getting a 1' piece and making 2 6" long sliders wont break the bank and will keep your springs in line better.
You could always do a 3" spring conversion...... They come in 18's......
The 18" springs Bug pointed out will help, but I will still have to run the top nut down 4" to hit the springs. I am not really worried about coil bind because the springs will be so light, but I am wondering if I make some new sliders if it would hurt to make the flange about 3.5" wide instead of 1/2", so that I don't use up all the threads with the preload adjustment, and have a non-useable crossover adjustment.
Or mabey another slider and a third spring? An 18,12 and 10? Or 18,16 and 6? Dunno if either scenario would still allow the crossover to work.
The top slider would be running on threads. ;D I doubt that it will last long.
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crossover will work regardless, triple rate springs are gonna take a whole lot more math to figure it out tho, If you got the doe to buy springs and try :k I see no reason the slider couldnt be made a bit taller myself...Dunno about 3.5" make the inner sleeve longer up top so it is certain not to fall of the body... realistically you likely will have the shock shaft compressed nearly 2-3" before the main spring ever compresses "any amount" anyhow... If your up for trial and error, a tripple rate would be ideal for sure... the second spring would need to be long tho, and the top just a shorty to utulize the cross over collar well... I got 2 10" springs on my car, with 9" stroke i think, I still have 4" of threads up above the adjuster, but i think my tender is a bit soft, as i do have a few inches of preload...Something i will fxxk with this winter, it needs more rebound dampening as well, as it will bounce if i land on the back tires...
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Am I missing something here? IMO ,the shock tune determines ride characteristics,the spring is only really there to support vehicle at ride height and to drive the wheel down tp maintain ground contact during droop. The spring rate will determine the ability to use the entire suspension travel and that spring rate will determine whether a car likes whoops or jumping better. Whoops needing a lower rate spring and jumps needing a stiffer spring. Am I even in the right ballpark with this line of thought?
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well a 600 lb spring may support a light weight car at ride height, and ride like steel struts, a 275 spring may support ride height, and let it bottom out very easily, IMO you have to tune the spring just as you do the rebound and compression... A cross over collar allows a much lighter spring on the tender, to allow it to float like a butterfly in the first few inches of travel, and sting like a bee on the big hits... So you could throw to 600 lb springs on there and get it to sit just were you want it, but hit a bump with it, and its gonna stay sitting right there to...
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Oh lets not forget what shock angle does to spring rate either...
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As I understand it, springs do all the "work", shocks are there as "oscillation dampeners" ;)
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That's my point,a higher rate WILL make for a firmer ride where you do not normally want the "cushieness" of the lighter spring. and vice versa. A higher rate spring will allow for bigger jumps but at the sacrifice of plushness in the whoops. The higher rate spring may not allow full suspension travel and a lighter spring may only bottom out. No amount of shock tuning will overcome that. I agree that they both need tuned for whatever type driving you will be doing. My question really is -why do the spring calculators not address that?
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The F-O-A spring selector had angle as one of the inputs.
I think they all do.
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That's my point,a higher rate WILL make for a firmer ride where you do not normally want the "cushieness" of the lighter spring. and vice versa. A higher rate spring will allow for bigger jumps but at the sacrifice of plushness in the whoops. The higher rate spring may not allow full suspension travel and a lighter spring may only bottom out. No amount of shock tuning will overcome that. I agree that they both need tuned for whatever type driving you will be doing. My question really is -why do the spring calculators not address that?
that is the reason for dual rate spring, tripple rate springs and cross over collars...
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Hmmmm, The crossover could only work on the top spring then. Seems pointless if it is just for taking up space at full droop.
Ballpark I think. Anyone find a spring and shock tuning "how to" website?
the cross over collar needs to be on top of the slider, for the main spring, thus allowing adjustment of were the main spring takes over....
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I agree that they both need tuned for whatever type driving you will be doing. My question really is -why do the spring calculators not address that?
Springs chosen for driving, shocks tuned for springs ;)
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my cross over collars kick in at about 4" of the shock travel, dunno what that is in wheel travel, maybe 6", after that it is just like have a 275 main spring doing the work, Allbeit, it is not perfect and needs some refinement, but it works well, could work far better, I did have the opportunity to run the car a lot before the cross overs, it bottomed out very very easily... Adding the collars made the car a night and day difference in the ride quality...
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I should say, that does not include ride height preload, from full droop i have about 6" before the collar will switch to the main spring....
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I'm still concerned/intrigued with bdkw1's post. I'm really,really thinking foe what I think will make me happy is to follow his suggestion and use single rate springs. I'll need to run 2 to get the length but I think I'll like it. I plan on whoops running and small jumps. I think they will both like the same type of overall tune. I don't really care about jumping high.Just no appeal to me.I like fast and smooth.
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fxxk i dont know, they do make progresive rate springs, but it sure seems easier in my mind to work with two seperate springs than a single progresive rate spring...
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Springs chosen for driving, shocks tuned for springs ;)
I agree.
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I'm still concerned/intrigued with bdkw1's post. I'm really,really thinking foe what I think will make me happy is to follow his suggestion and use single rate springs. I'll need to run 2 to get the length but I think I'll like it. I plan on whoops running and small jumps. I think they will both like the same type of overall tune. I don't really care about jumping high.Just no appeal to me.I like fast and smooth.
It may very well be the best option...
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I thought they were primative "progressive rate" springs?
That was what I understood.
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Springs are progresive, the farther you compress them the more load it takes, now if were talking dual rate single spring, as they make them as well.... It is gonna produce far less force for a 1000 lb car to to run thru some bumps, than it will when it is 15' in the air and lands... so a light spring on top for a plush ride, and a heavy hitter at the bottom to soak up the big stuff...
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All you have in a dual spring is actually a progressive rate spring with a definite higher rateat crossover for the big bumps/jumps.I gotta admit tho that as for shock tuning bdkw1 makes sense.If I were running bypasses and tuned their times to the crossover collars I could see a big advantage to dual springs.
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Why would you run cross over collars with two same rate springs?
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Because you can't buy one long spring maybe?
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Because you can't buy one long spring maybe?
uh crossover collars thread to the body of the shock, locking the slider "piece that mates two springs" so all the weight is on the main spring, using them with 2 of the same rate springs would just take all the load off the tender and all the work it is doing and transfer it to the main, be like lowering the spring rate then...
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In easy terms, a cross over collar shuts the tender off...The tender is then useless, does no work at all....
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Cross over collars threaded to body... Rides inside of spring...
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10 years ago, spring rates were much higher, rebound in shocks was a lot stiffer. Most of the heat built up in the shock was from controlling the spring.
There has been a shift away from this. Most of the top teams out there are using similar set-ups now where the spring just holds up the vehicle and the shock does the rest. This is why there is a need for ever larger shocks as there is enough compression valving in them to lift the vehicle up in the rough sections but still allow for a low ride height for good cornering in the tight sections. This can also make the vehicle very sloppy in the slow stuff which is why a lot of the newer TT's are coming with sway bars front and rear. Most of these guys are running single rate springs with about 3" of pre-load in the rear 1-2" in the front. This gives a very linear spring rate which is very easy to control on rebound. You can run really light valving to let the tire drop out quickly without upsetting the chassis.
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I know that.You knew what I meant I think.Yes I meant slider. I always called the slider the collar and the collar as everyone else calls it was a crossover adjuster to me. Back when Fred,Barney that hottie Betty and I were talking about this shit that's what we called them. Sorry for the confusion.
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10 years ago, spring rates were much higher, rebound in shocks was a lot stiffer. Most of the heat built up in the shock was from controlling the spring.
There has been a shift away from this. Most of the top teams out there are using similar set-ups now where the spring just holds up the vehicle and the shock does the rest. This is why there is a need for ever larger shocks as there is enough compression valving in them to lift the vehicle up in the rough sections but still allow for a low ride height for good cornering in the tight sections. This can also make the vehicle very sloppy in the slow stuff which is why a lot of the newer TT's are coming with sway bars front and rear. Most of these guys are running single rate springs with about 3" of pre-load in the rear 1-2" in the front. This gives a very linear spring rate which is very easy to control on rebound. You can run really light valving to let the tire drop out quickly without upsetting the chassis.
Dude,I really really wish you'd post more often! You know more than you're telling us.Thanks for the info.I appreciate it.
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A tender does no work at all anyway, it just keeps the spring from rattling on full droop. If it's actually doing something, is a dual rate set-up.
What is the tech term for the top spring of a dual rate setup, all i ever here is tender?
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(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fwww.livermoreperformance.com%2Fimages%2FProducts%2FEibach%2FEibach%2520Logo.gif&hash=418df2827fe1d3eceee228d5aeaa0cf693fe07ef)
Tender Springs - The Tender spring relies on a Main and Tender spring concept that provides a softer initial rate when both springs are compressed together, then delivers the desired firmer ending rate once the Tender spring closes completely. "Seems this means more than 50%" The Main spring determines the final rate of the system. The Tender springs are available in a variety of linear-rate as well as progressive-rate characteristics and determine the initial rate of the system.
Spacers - A coupling Spacer is used to connect Main and Tender springs. Eibach offers both inside and outside diameter coupling Spacers depending upon the dimension and function of the specific damper utilized.
(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fwww.livermoreperformance.com%2Fimages%2FProducts%2FEibach%2FEibach%2520Logo.gif&hash=418df2827fe1d3eceee228d5aeaa0cf693fe07ef)
Helper - A Helper spring is used to prevent the main spring from becoming loose in the spring seat when the wheel is at full droop. The Helper spring, unlike the Tender spring, has very little spring rate, and therefore has no effect on the suspension characteristics of the vehicle. Up to 50 mm of spring-to-perch gap can be covered with the use of a Helper spring.
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Haha, shot down by the Eibach guys!
Looks like I have been using the wrong terminology all these years.
Ok, so for the record, I like to use a single rate spring with a helper spring.
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Haha, shot down by the Eibach guys!
Looks like I have been using the wrong terminology all these years.
Ok, so for the record, I like to use a single rate spring with a helper spring.
Was not trying to prove you wrong, Was just trying to figure out the term for the top spring and ran across that...
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Good point.I see you've been reading the spring sites. I was waiting for someone to mention that.
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If you have 2-200lb springs, 200lbs per 1" of travel... you are only going to compress 1" total... as there is only 200lbs of weight, to compress 2" you need 400... the cross over collar doesnt effect the tender spring.... scenario....
800 lbs of weight you are sinking the suspension 4"- 2" per spring...."Ideally should be even" now imagine the slider makes contact with the cross over collar, now the complete 800lbs is put to the main spring.... so bam, you just went from compressing the main 2" to 4" instantly, as you just shifted all the weight to the main...Now the tender would still be supporting some weight, as it is compressed a bit. but you just shifted most of the weight to the main spring... think of a cross over collar as removing the top adjuster, and top spring, and setting it on the main only, this is basicly what you have....
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Good point.I see you've been reading the spring sites. I was waiting for someone to mention that.
you cant compress 2 spring with the same weight equally like said... now if you had a 100 and a 200 when you put 200lbs of weight you would compress the top 2" and the bottom 1"... By compressing the top the bottom is putting a equal force out from the spring...
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I'm thinking of not using the collars.Just the slider. I don't know.I'm betting suspension will be a hot topic at the dunes Thurs and Friday. Maybe Saturday to !
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Hehehehehe. Bugs, gonna argue . Yes bug you are wrong.
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Also the shifting weight scenario isn't true. Whatever force is on the tender spring to make it hit the crossover collar stays on it as the force increases.... If just doesn't deflect anymore because the crossover collar is taking all of the additional pounds applied as the force increases.
You are correct that it is like moving the top adjuster down once the crossover is hit.
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I may be wrong here...
S1xS2/S1+S2
200x200 = 40000 / 200+200 = 400 100 lb spring rate per inch
200 lbs sinks 2" got it...
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I new the spring rate was lower with dual springs, I just didnt compute in my head how 2 identical springs could be lower... But i do see if the top spring is seeing 200 lbs, it is transferring the same 200 lbs to the main spring, thus sharing the load /2... Makes sense to me now...
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Also the shifting weight scenario isn't true. Whatever force is on the tender spring to make it hit the crossover collar stays on it as the force increases.... If just doesn't deflect anymore because the crossover collar is taking all of the additional pounds applied as the force increases.
You are correct that it is like moving the top adjuster down once the crossover is hit.
actually if that was the case the spring rate would be 200 instead of 100, so i was wrong there technically...
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There you go.It just SEEMS like it should be the other way.
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Greatr article.Glad you could find it.I'm saving a copy now.
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There are a couple assumptions in that article that depending on the car could lead someone vary far from the mark.
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Fill us in.
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1, Not everyone wants 40% sag ride height.
2, Calculating the spring rate based on the corner weigth without subtracting the unsprung weight will be really off on a light car. Cars should also be ballasted for normal occupant load.
3, Angle of shock from vertical? Should be angle of shock in relationship to the arm pivots.
4, 150/300 spring rate? Potential pogo stick unless it's got bypasses and the secondary stop collars are set correctly.
Coming from GD, it's pretty close....... ::) Most Glamis cars are set up like crap and have horrible geometry so I guess it's better than nothing. It doesn't take much to make a car look good going through the dunes.
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were is the shock angle measure, full droop, full bump?
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I would suspect it is at full bump or at ride height, My 1st guess is ride height...
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this calculator seems to factor in angle of a arms to ground, and the shock to the ground...
http://www.swayaway.com/calculators/swayawayCalc.php#step5 (http://www.swayaway.com/calculators/swayawayCalc.php#step5)
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Nowhere have I seen it addressed. I assume ride height myself but it would be nice if the mofo's that make this stuff would put out some info that was really useful instead of being full of "guessing" gaps.
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Lets throw this into the mix, with a 5 link, 3 link etc the scrub moves in and out and front/rear, now the shock would have 2 angles likely forward and sideways, how do we correct that with the calculator?
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Seems to me it will not matter were it is measured, if you use both equations, shock angle to ground, and a arm pivots to ground... The a arm is the lever, so to use the lower shock mount angle to inner arm pivot angle would not be accurate correct?
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When it comes down to it, spring selection is probably like horse shoe's and hand grenades. Close counts. A universal calculator isn't going to take into account every scenario, or slight difference. When you look at the jumps in spring selection, 150 lb, 200 lb, 250 lb, they are jumping 25% with every change, so you won't get an exact spring even if you had an exact number.
Also on the shock angle. The relationship of wheel travel to shock travel somewhat takes the angle into account. different progression rates can be in play, but generally if the wheel travels 20" and the shock travels 10", you have your ratio. If your shock is laid down so far that it goes to a radical angle at top or bottom, there is no correct spring the will fix the problem. I noticed that the F-O-A calculator didn't ask the shock travel, so they are not going this route. But others may.
I would generally agree if measuring the shock angle, do it at ride height, and measure the angle between the frame mount and spindle relative to the shock.
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We can all generally agree and be dead wrong.It would seem that we should know what was meant with the formulas.Too bad the "experts" seem to miss that we need a bit more info. Also when using dual springs as we have had seen you DO get a far more defined rate availabiity. You are not then limited to 50 # increments. I do agree tho that hand grenades and horseshoes apply here. I don't think the grenades are anything more than m-80's.LOL!!! I will guarantee you this much engineer ,IF they are leaning 10-20-30 degrees or more from vertical it WILL make a huge difference in the spring requirement.
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I think you are all hitting the nail on the head. No one calculator will work for everyone. Shock angles, riding styles, were we ride etc will change. And not everyone will get the right measurements for assumptions made in the development of the calculator. What works on one car dose not always work on another.
I know I am in the process of changing out springs in my rear suspension for lighter ones and shorter ones. I am sure I need shorter, (changed the length on radios rods.) but the spring rates were working pretty well. But anymore that 200 psi in the rear shocks and it kicks like a mule. I had 325 over 400s. I am going to try 275 over 325s and more pressure in the shock.
I agree that a lot of cars are set up way to stiff.
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Have you tried changing the valving on rebound first?
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I did not use any spring calculator. I knew my motion ratio and the amount of droop I wanted. So I just figured out how much spring load I needed to hold the machine up at ride height. I divided that by the inches the shock is compressed at that point and it gave me the spring rate I needed. 80lb spring compressed 3" gives 240lbs of spring load, 2:1 motion ratio means it will support 120lbs on that corner.
If you have dual rate springs and the cross over comes unseated during rebound enough before ride height, the car won't bounce. It is like braking hard then easing off just before you come to a complete stop, the car won't lurch back so much. If the difference between the rates is huge, in theory, the tires could lift at the point the collars unseat. You could stop that by putting a spacer on top of your spring washer then another either large solid washer or a another spring washer. A solid washer would limit the rebound rate no matter what the second spring rate was. The oil can only go through a fixed hole at a fixed rate. A second spring washer spaced out from the first would give you a higher damping rate at higher shaft speeds. So during the rebound of the second rate, your damping would be greater.
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I did not use any spring calculator. I knew my motion ratio and the amount of droop I wanted. So I just figured out how much spring load I needed to hold the machine up at ride height. I divided that by the inches the shock is compressed at that point and it gave me the spring rate I needed. 80lb spring compressed 3" gives 240lbs of spring load, 2:1 motion ratio means it will support 120lbs on that corner.
If you have dual rate springs and the cross over comes unseated during rebound enough before ride height, the car won't bounce. It is like braking hard then easing off just before you come to a complete stop, the car won't lurch back so much. If the difference between the rates is huge, in theory, the tires could lift at the point the collars unseat. You could stop that by putting a spacer on top of your spring washer then another either large solid washer or a another spring washer. A solid washer would limit the rebound rate no matter what the second spring rate was. The oil can only go through a fixed hole at a fixed rate. A second spring washer spaced out from the first would give you a higher damping rate at higher shaft speeds. So during the rebound of the second rate, your damping would be greater.
That only works if the shock is at or near plumb.
Huh?????????
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That only works if the shock is at or near plumb.
Huh?????????
Motion ratio does the calculation for angle tho... the more angle the more motion ratio... Livewire is talking motion ratio of travel to shock shaft... not arm pivots to shock mount...
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You guys are going to have to explain better than that.
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You guys are going to have to explain better than that.
All that matters is wheel travel to shock shaft ratio. if the wheel moves 2" and the shock shaft moves 1" you have a 2:1 ratio, spring will do half the work... that is all they are doing by figuring shock angle etc in the calculator...
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i don't think so.
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Ok tell me why not, a coil over shock has not a care in the world what angle it is laying. All it cares about is the lever making it work, more leverage, less spring will effect the wheel movement, Please show me otherwise.. what does more leverage do generally it changes the angle at which it lays, exactly why the calculators ask for that variable...
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What happens when you have a shock 90 degrees and a 2/1 ratio? then say lay the shock 45 degrees and what does it do, It slows up the shaft of the shock, changing the motion ratio of the wheel to shock shaft... Correct? Assuming you would have to alter the length of the shock to get it at 45 degrees.. Or lengthen it to make it 90... Shock shaft to wheel movement, Only variable that counts for correction error...
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Ok i do stand corrected, the wheel rate would also be factored in...
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;D ;D ;D ;D I may not know much but I know when I'm right. ;D ;D ;D ;D 8)
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Ok explain how the wheel rate effects the equation.. :)
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I kinda agree with ya Bug. however, the motion ratio changes throughout wheel travel as the shock approaches or retreats from 90 degrees to the arm. If you are going for an average, wheel travel to shock shaft travel is ok. You just have to know that it is an average.
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every motion that is not 1:1 in relation to the shock travel has to have a correction factor. Simple.
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Bottom line is that spring rate/shock valving is voodoo science. Best guess and then test,test,test.
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that's kinda what I meant in my last post, I just didn't spell it out.
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If you figure motion ratio from the center of the tire and not the ball joint, there would be no correction factor correct? for wheel rate..
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Bottom line is that spring rate/shock valving is voodoo science. Best guess and then test,test,test.
It is only voodoo science when you are going for a ride quality judged by the seat of your pants.
When going for traction in a straight line and around corners, it can be figured mathmaticaly if you have enough information.
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no, because that "center of tire" is still at the end of a lever that still causes the shock to approach and retreat from 90 degrees.
close enuff for the available spring rates on the market...
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I kinda agree with ya Bug. however, the motion ratio changes throughout wheel travel as the shock approaches or retreats from 90 degrees to the arm. If you are going for an average, wheel travel to shock shaft travel is ok. You just have to know that it is an average.
I think Boost sumed it up.
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I think Boost sumed it up.
Does that mean I'm right? I was just talking out my ass as usual. I guess everybody gets one right sooner or later. ;D
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It is only voodoo science when you are going for a ride quality judged by the seat of your pants.
When going for traction in a straight line and around corners, it can be figured mathmaticaly if you have enough information.
Sort of but pretty damn close.IMO.
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My motion ratio is more than 2:1 from full droop to ride height and less than 2:1 from ride height to full bump giving me a rising rate suspension. From +/- 1" of ride height it is 2:1, so that is what I am going by. I calculated spring load needed at ride height to support the machine using the motion ratio at ride height. Taking an average of the entire travel would yield a similar result, but it could be off a little. Using the overall motion ratio from the shock to the tire is going to factor in all the details that the spring calculators ignore. If a calculator takes shock angle into consideration, that is just an attempt to better estimate the motion ratio. Since they assume the arm is level, it will be off. Neither ride height nor the average angle puts my arms at level to the ground. All the calculators are flawed in that they all are trying to calculate a number that most on this board already know, but without all the needed inputs. You don't need to even do it that way if you can just measure the result. It's like having an elaborate calculation with gearing charts and tire diameter when you can just use a GPS to check your speed at a given RPM, voila, you know your final gearing factoring everything in. Calculations with crap in give crap out. If you can measure the real thing then just use it.
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That's really my point about the calculators.They are just guesstimators to give a HUGE point to start from.
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Actually, they always spit out a specific number, which most people assume to be precise. Actually understanding your suspension and motion ratio and ratio change through the travel range, like Livewire pointed out, is the best way to get a good pick to start with. I think his plan of looking at the motion ratio 1" either side of ride height to use for the calculations would be an excellent way to start. If I had my buggy together enough to weigh, I would be ordering springs off of this formula today. ;D
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A specific number yes,but,it is a huge guess at any rate.
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Yah they really don't take enough variable's into account. We have talked about the shock layed over, and possibly in two axis on a 5-link, how about rake in the front... That will change it just like angle from the shock to the arm.
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As long as the shock lays the same as the rake it can not effect it...
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Up to 90 degrees you are only using a portion of the shocks ability. The angle the shock "lays" at determines the amount of work it can do. eg at Zero degrees it does Zero work and at 90 degrees it does the most it can. Further if you allow the shock to go past 90 degrees it will effectively "give way".
In the same way, the rake angle should affect the suspension performance. In saying that I acknowledged that rake angle is usually small (less than 15 degrees) and won't play a great role like shock angle will.
It's trigonometry, not voodoo. Where it becomes voodoo is when you use "constant contact" mode formulas to calculate a "jumping" car's needs. Jumping cars have no interest in anything other than absorbing the landing and to do so most everything else is compromised (to the point of being not relevant) as a result.
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Up to 90 degrees you are only using a portion of the shocks ability. The angle the shock "lays" at determines the amount of work it can do. eg at Zero degrees it does Zero work and at 90 degrees it does the most it can. Further if you allow the shock to go past 90 degrees it will effectively "give way".
In the same way, the rake angle should affect the suspension performance. In saying that I acknowledged that rake angle is usually small (less than 15 degrees) and won't play a great role like shock angle will.
It's trigonometry, not voodoo. Where it becomes voodoo is when you use "constant contact" mode formulas to calculate a "jumping" car's needs. Jumping cars have no interest in anything other than absorbing the landing and to do so most everything else is compromised (to the point of being not relevant) as a result.
Still all comes to Motion ratio...
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I don't think so.??? Maybe but I need convinced.
if you just wacked off the whole front end of a non raked car, shocks mounts etc, and welded it back on with rake, it would not effect the spring rate, IMO... How could it?
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Because now the (raked)shock will have a different travel for a given vertical travel of the car compared to the non raked shock.
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It would not change the rate but rather change the NEEDED rate. Am I wrong in this thinking?
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coz the motion is not at 90 degrees to the force applied ;)
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Because now the (raked)shock will have a different travel for a given vertical travel of the car compared to the non raked shock.
Wont be a bit different to the wheel rate...
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That's what I think but if I understand it right bug doesn't.
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The wheel rate, motion ratio, and sprung weight will all be exactly the same... Raked or not... Now maybe the valving would change but i dont see how the spring rate would differ all...
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THe vertical travel of the car changes in relationship to the shock/spring travel therefore the NEEDED spring rate will be different.I am not saying that it will change the spring rate.
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IMO you are wrong, But hey, whatever floats your boat..
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I said why I thought I was right.Your turn to say how I'm wrong.
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Its not about the car its about the wheel, hell maybe i am wrong to..
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I SHOULD be saying wheel travel and not car travel.Sorry. The shock travel is greater in relationship to the wheel travel when raked as opposed to straight up. Therefore the NEEDED rate is different.Just laying it over tho does not change that particular spring rate. Now are we on the same page?
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if the shock layed back the same as the rake angle, then i cant see any difference in wheel travel to shock travel... As i said, if it was ideal with 0 rake, and you raked everything equal, shocks, mounts etc, the wheel travel shock travel will not change...
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Yes it will.
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How?
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With rake, the vertical wheel travel will be slightly less than if measured perpendicular to the A-arm pivot axis. Less travel for the same springs would be stiffer.
So if being anal, Bug is technically wrong. Use words like close instead of same to protect yourself from being nit picked. :police:
When I said motion ratio, I was referring to vertical wheel travel as compared to shock shaft travel. So I took rake into account as well.
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How does the wheel travel any bit different to the shock? That is what is being debated..
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The shock will travel/stroke farther with rake for the same amount of vertical wheel travel as compared to a non raked front suspension.
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Note VERTICAL wheel travel and not rake travel. Does that help?
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Note VERTICAL wheel travel and not rake travel. Does that help?
This is in line with what I was saying, just in fewer words. ;D
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Well with rake, the wheels dont move vertical...
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Actually they do, they just also move horizontal at the same time. That is why you need a correction factor.
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Actually the force can only move whatever way the pivots let it, so it is not moving vertical either... Would my spring rate and motion ratio change if i had a non rake car and hit the approach to a hill? effectively the force would be pushing back correct?
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does you plumb bob hang crooked too? According to what you are spewing, your springrate would still be correct on the moon. ::) It wouldn't, the variable is gravity. which direction does gravity apply it's force? Straight down. I'm done.
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Ok scenario 2, If a zero rake car had the ass end set lower so the pivots were at an angle to gravity, would the spring rate and motion ratio change?
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I understand the needed rate may change, but rake does not alter motion ratio, and the spring would be doing the same amount of work, now 10 degrees may call for the spring to do more work, I understand that part, but taking a 0 rake car and raking the entire front suspension equal, no ratios have changed. Am i not correct?
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But the spring rate will actually need to be higher with rake due to the increases angle UNLESS you go to the extemes that you described.