Spring preload
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Originally Posted by SundayDriver
Thanks. However, the guy who wrote this does not understand what preload is. Preload works with droop limiting and not at all as he describes. All he is talking about is threaded shock bodies where you can adjust height. With a preload setup, you adjust the perch to get the preload you want, and ride height is set elsewhere (other adjustable suspension component or changing shock lengths).
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Originally Posted by SundayDriver
What I would take away in regards to production cars is that preload could be used to cure nasty understeer at corner entry, BUT you must be able to limit droop which is neither an inherent feature or your suspension (nor mine) nor easy to add.
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Originally Posted by GhettoRacer
We use body length adjustable shocks too actually. :-)
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Originally Posted by Matt Romanowski
It's not inherent in the design, but people are making shocks that can be droop limited now. Coming off this dumb cold I can't remember anything, but the guy that works with Stimola is selling a line of shocks that has Penske internals in a standard looking Porsche front strut setup. That could easily be droop limited. Almost any rebuildable shock can be droop limited with spacers inside the body on the shaft.
BTW - There are some more great insights on the DSR thread referenced above. Pay attention to both Richard Pare and Ren.
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Originally Posted by Matt Graham
For reference, the post on the SportsRacer forum that Mark referred to above.
http://p081.ezboard.com/fdsrforumfrm...icID=241.topic
Mark is 100% right about Mr. Pare. Knows his stuff, and doesn't mind taking the time to share it.
The link that adrial posted, and the one I just posted are two excellent definitions of preload and when/how one can use it in suspension tuning.
-Matt
http://p081.ezboard.com/fdsrforumfrm...icID=241.topic
Mark is 100% right about Mr. Pare. Knows his stuff, and doesn't mind taking the time to share it.
The link that adrial posted, and the one I just posted are two excellent definitions of preload and when/how one can use it in suspension tuning.
-Matt
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GR, please. You have two very popular threads of your own. Please let the rest of us digital mortals chat about and read up on interesting stuff without unwanted interruption. We don't care if you had the book for two years. Keep in mind that it is not you personaly it is the fact that a lot of us have the book in question and the thread would drag down if we all pointed that fact out.
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Now, back to our regular programming!!!!!!
I'm not smart enough to wrap my tiny brain around this stuff. I'm not sure it makes much of a difference on anything but a finely tuned lightweight car. But I may have some pertinent insights.
I know from my work wit 944 owners trying to avoid re-indexing their torsion bars that preload is important. Sometimes you can get sufficient rear coil preload by just sagging the ride height eccentrics, and sometimes not. When you do not have sufficient preload, transient handling suffers. Not only is there audible clunking and banging as the coil springs seat/unseat, but this does seem to make the transient handling somewhat less predictable than would be desired. I realize this is not directly germain to Mark's question, but it is noteable nonetheless.
Also, as Larry briefly eluded to from the bicycle realm, preload, or more accurately sag, is important to shock function, and I have a hunch this may be at least part of the issue here.
As a for-instance, my Santa Cruz Heckler (5.5" front/rear travel) has a FIVE way adjustable Progressive Suspension 5th Element Coilover rear shock; 1) spring preload, 2) short stroke (high speed) compression, 3) long stroke (low speed) compression, 4) rebound, and 5) what is called Stable Platform Valving, which cancels low amplitude, low frequency oscillation (peddling forces).
These shocks require a pretty healthy amount of sag (upwards of 20%) to be set in a static state for proper function of the system. You need to access some portion of the positive travel of the shock in order for the damping circuits to function optimally, both in the positive (compression), and negative (rebound) portions of the stroke. Could this be what the car people are tweaking when they have a preload variable vehicle?
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I'm not smart enough to wrap my tiny brain around this stuff. I'm not sure it makes much of a difference on anything but a finely tuned lightweight car. But I may have some pertinent insights.
I know from my work wit 944 owners trying to avoid re-indexing their torsion bars that preload is important. Sometimes you can get sufficient rear coil preload by just sagging the ride height eccentrics, and sometimes not. When you do not have sufficient preload, transient handling suffers. Not only is there audible clunking and banging as the coil springs seat/unseat, but this does seem to make the transient handling somewhat less predictable than would be desired. I realize this is not directly germain to Mark's question, but it is noteable nonetheless.
Also, as Larry briefly eluded to from the bicycle realm, preload, or more accurately sag, is important to shock function, and I have a hunch this may be at least part of the issue here.
As a for-instance, my Santa Cruz Heckler (5.5" front/rear travel) has a FIVE way adjustable Progressive Suspension 5th Element Coilover rear shock; 1) spring preload, 2) short stroke (high speed) compression, 3) long stroke (low speed) compression, 4) rebound, and 5) what is called Stable Platform Valving, which cancels low amplitude, low frequency oscillation (peddling forces).
These shocks require a pretty healthy amount of sag (upwards of 20%) to be set in a static state for proper function of the system. You need to access some portion of the positive travel of the shock in order for the damping circuits to function optimally, both in the positive (compression), and negative (rebound) portions of the stroke. Could this be what the car people are tweaking when they have a preload variable vehicle?
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bah, kurt there is the ignore function. learn to use it. it's pretty good. you don't see me responding to VR anymore do you? back on topic.
FWIW, the coilovers on the del Sol are not valving adjustable. however it does have adjustable body length feature as well as spring pre-load adjustment. it is short stroke and is droop limited (not sure if it's by design or by product of short stroke?). the shock is mono tube pressurized design. if there isn't preload on the spring, the car handling feels a little "floating" like... so the manufacturer recommends like at least 1/4" preload. i'm not really sure if it is used to fine tune handling like that thread suggests... at least i've never heard of it on production cars.
FWIW, the coilovers on the del Sol are not valving adjustable. however it does have adjustable body length feature as well as spring pre-load adjustment. it is short stroke and is droop limited (not sure if it's by design or by product of short stroke?). the shock is mono tube pressurized design. if there isn't preload on the spring, the car handling feels a little "floating" like... so the manufacturer recommends like at least 1/4" preload. i'm not really sure if it is used to fine tune handling like that thread suggests... at least i've never heard of it on production cars.
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Originally Posted by GhettoRacer
if there isn't preload on the spring, the car handling feels a little "floating" like... so the manufacturer recommends like at least 1/4" preload.
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Retired Club Racer & National PCA Instructor
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1984 911 Carrera Club Racer
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CLICK HERE to see some of my ancient racing videos.
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Originally Posted by GhettoRacer
bah, kurt there is the ignore function. learn to use it. it's pretty good.
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Originally Posted by SundayDriver
That is interesting and I am not surprised that someone is doing that. But how practical can that be on a production car? Wouldn't you have to be able to easily change the limiters anytime you change the ride height (or even set the ride height)? I guess it would make sense if you were doing something like 25mm of droop - it would not be a big deal to be off a few mm. But it seems like it would be very time consuming to try to do zero droop with that.
BTW - There are some more great insights on the DSR thread referenced above. Pay attention to both Richard Pare and Ren.
BTW - There are some more great insights on the DSR thread referenced above. Pay attention to both Richard Pare and Ren.
Sorry for the mixed up response before. I'm working through a nasty cold/flu things and geting better. If your interested in the racecar shocks, call Stimola. He rebuilds everything and can probably give you some good info. AMF in NH is also really good on Ohlins (I think Konis and Bilsteins too).
Thanks for the links.
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Originally Posted by Larry Herman
It is having enough tension on the springs so the car does not compress the suspension at all when it is sitting on the ground. That would be the starting point for zero pre-load. Now compress the spring further and you are adding pre-load.
Mechanically, how does one go about adjusting the pre-load (or load) on the springs before including the shocks in the equation? (Not sure if I've stated that correctly). Is a particular type of lift or jack(s) required?
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Originally Posted by richard glickel.
Larry, John, et al.,
Mechanically, how does one go about adjusting the pre-load (or load) on the springs before including the shocks in the equation? (Not sure if I've stated that correctly). Is a particular type of lift or jack(s) required?
Mechanically, how does one go about adjusting the pre-load (or load) on the springs before including the shocks in the equation? (Not sure if I've stated that correctly). Is a particular type of lift or jack(s) required?
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Mark,
Thanks for the easy to understand explanation. I have no immediate plans to try this (and may never give it try), but I now understand what's been discussed here.
Thanks for the easy to understand explanation. I have no immediate plans to try this (and may never give it try), but I now understand what's been discussed here.
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Originally Posted by Larry Herman
I am not certain that what you are referring to is suspension pre-load. Having the spring sit tightly in the perch is not the type of pre-load that this discussion is talking about. It is having enough tension on the springs so the car does not compress the suspension at all when it is sitting on the ground. That would be the starting point for zero pre-load. Now compress the spring further and you are adding pre-load.