Adj ride height changing preload w/ Tein Basics Counterintuitive?

[Woodsy0]

Here's what I've been thinking...

I have Tein Basics coilovers, which are ride height adjustible but have no damping adjustibility. However, the notion I get is that when you lower the ride height (using sliding plates on the base of the springs) you bring the sliding plates further down on the shock, thus decreasing the preload on the springs as well as lowering the ride height. Vice versa, when you raise the sliding plates, further compressing the springs, you raise the preload on the springs as well as raising the ride height. I don't know a whole lot about suspension theories, but it seems counterintuitive that when you lower the car with these springs, you would have more suspension travel...Shouldn't it be the other way around? Any input would be great. Also, any advice on how I should set the ride height, given the odd (in my opinion) application?

This may be blatantly obvious to some, I'm just sitting here scratching my head. Thanks a bunch for any help to clear this up.

Scott

 

[stirpicult]

Here's what I've been thinking...

I have Tein Basics coilovers, which are ride height adjustible but have no damping adjustibility. However, the notion I get is that when you lower the ride height (using sliding plates on the base of the springs) you bring the sliding plates further down on the shock, thus decreasing the preload on the springs as well as lowering the ride height. Vice versa, when you raise the sliding plates, further compressing the springs, you raise the preload on the springs as well as raising the ride height. I don't know a whole lot about suspension theories, but it seems counterintuitive that when you lower the car with these springs, you would have more suspension travel...Shouldn't it be the other way around? Any input would be great. Also, any advice on how I should set the ride height, given the odd (in my opinion) application?

This may be blatantly obvious to some, I'm just sitting here scratching my head. Thanks a bunch for any help to clear this up.

Scott

i don't know what preload is, but lowering the springs on the struts and shocks doesn't really change the load on them. the strut/shock are meant to keep the springs from bouncing forever, and the springs are what the car rides on. so with lowering it or raising it, essentially the weight on the spring stays the same (minus corner balancing, which the weights on the springs would still be in the same ballpark).
raising it shouldn't change the load on the springs, either. there should be enough room between the top of the spring and the tophat to give you room enough to move the spring up and down without compressing it. that's at least how my gc's worked.
and no, when you lower the springs you will get less travel as the strut/shock goes down with it, taking away some of its movement.

 

[drivemusicnow]

Here's what I've been thinking...

I have Tein Basics coilovers, which are ride height adjustible but have no damping adjustibility. However, the notion I get is that when you lower the ride height (using sliding plates on the base of the springs) you bring the sliding plates further down on the shock, thus decreasing the preload on the springs as well as lowering the ride height. Vice versa, when you raise the sliding plates, further compressing the springs, you raise the preload on the springs as well as raising the ride height. I don't know a whole lot about suspension theories, but it seems counterintuitive that when you lower the car with these springs, you would have more suspension travel...Shouldn't it be the other way around? Any input would be great. Also, any advice on how I should set the ride height, given the odd (in my opinion) application?

This may be blatantly obvious to some, I'm just sitting here scratching my head. Thanks a bunch for any help to clear this up.

Scott

I'm not QUITE sure about the Teins specifically, however I do understand the preload.

This is why "coilovers" that only have an adjustable spring perch, without helper springs, are not really the best way to do it. however they are still better than just throwing a 2 inch shorter spring on stock shocks, because the shocks length is what limits suspension travel (other than bumpstops)

As far as suspension travel, thats not quite as big of an issue as you're making it out to be.

Lets take two situations, A is with a car that is at a lower ride height, B is with a car that is at a higher ride height. This is ASSuming that the Tein kit has a shock that is equal length and travel as a stock shock. If they are shorter housings, (ie designed to be lowered) then the benefit of being higher is negated.

Car A is travelling 40 mph down a road that has a speed bump and a pot hole. When it hits the speed bump, you'll still have enough upward travel such that you don't hit the bumpstops (or at least you should) however because of the higher preload on the springs, you're going to REALLY feel that speed bump. With the pothole, you're essentially letting the wheel extend to where it would be in an unlowerd car (slightly farther possibly) You have plenty of shock travel in this case.

Car B Does the same thing. It will absorb the speed bump better, and with fewer broken teeth for the driver, It won't absorb the pothole quite as well, however I'm sure it has plenty of downward travel to do its job (no negative effect, Mitsu engineers got paid big $$ to ensure this)


The benifit of a coilover like JIC, or Hotbits, is that you have a shock length made for the car to be lowered or raised depending, or a threaded housing that allows you to keep full travel all the way up and down.


THE BEST way to adjust ride height and preload is to corner weigh your car and adjust the perches to give you the crossweights that equal half of the car's total weight. (and some other details) If you can't corner weigh your car, adjust them all to the same height (ground to fender) as was proportional with stock. I'd add some preload on the drivers side to compensate for the higher weight on that side, and adjust as you see neccesary.

This is just my simplified take on it. if you notice anything I assumed wrong, please point it out, as I am just trying to give a really basic look at the differences.

 

[drivemusicnow]

i don't know what preload is, but lowering the springs on the struts and shocks doesn't really change the load on them. the strut/shock are meant to keep the springs from bouncing forever, and the springs are what the car rides on. so with lowering it or raising it, essentially the weight on the spring stays the same (minus corner balancing, which the weights on the springs would still be in the same ballpark).
raising it shouldn't change the load on the springs, either. there should be enough room between the top of the spring and the tophat to give you room enough to move the spring up and down without compressing it. that's at least how my gc's worked.
and no, when you lower the springs you will get less travel as the strut/shock goes down with it, taking away some of its movement.

when lowered, you get less shock travel in a BUMP situation, you have MORE shock travel in a pothole situation.

As far as the preload is concerned, it is counter intuitive (as woodsy stated) for you to have a HIGHER preload when the car is higher. You're essentially increase the initial spring pressure (... force it takes to move the spring from its "resting" position) when you have more shock travel, and decreasing it when you have less shock travel (for bump sitautions)

 

[Woodsy0]

Thanks, I think I'm starting to understand the operation of these Teins...Really regretting not shelling out the extra few hundred for the Tein Flexs with adjustable damping...So what you're saying is to keep it as close to stock height as possible? I have no qualms whatsoever doing that, I could care less how unasthetic it may look. However, on the Tein site (http://tein.com/ti/r56-d38a.html), they state in the coilover specs that the ride height (is supposed to be?) lowered -1.79 in in the front and -1.48 in in the back. Is that just a suggestion, or do you think the coilovers were designed for this amount of chassis lowering?

Thanks again for the help,
Scott

 

[jtmcinder]

As far as suspension travel, thats not quite as big of an issue as you're making it out to be.

Says the guy with a 1G. It is 90% of the issue when you have a 2G.

As to preload, you need to distinguish between two types: there is preload that exists in the coilover package before the car is lowered off the jackstands but not after, and there is preload that continues to exist after the car is put back on the ground. In the second case, the car has zero available travel in rebound. This would be nuts. Therefore, when people talk about preload, I assume they are talking about the former type, which is what people are getting when they add low-rate (as in soft, not lousy) tender springs. These have no effect on the effective rate of the springs once the car is sitting on the ground, since the tender springs fully compress when the car is taken off the jackstands.

- Jtoby

 

[wret]

Adjusting preload will affect the ratio of shock travel between compression and extension. The Tein recommendations for preload adjustment do little more than snug the adjusting nut against the spring and keep it in place. This setting allows the maximum amount of extension. The only way to increase extension beyond that is with helper or tender springs. Increasing the preload will allow a greater range of compression and less extension.

Jtoby, do you know if there is a formula for optimum compression/extension ration for any given application?

 

[jtmcinder]

Optimum ratio of available bounce to rebound depends on a heck of lot, including total amount of travel available to partition, expected amount of bodyroll (which requires that you know total roll stiffness and maximum lateral g), and smoothness of the surface on which you will be running. I'm sort of happy that my set-up does not allow me to change the ratio, since I'd just spend hours and hours reading about it and then probably still get it wrong. (For those keeping score at home: I vehemently denied the value of coaxial hats for a long time before actually trying it and being amazed by the increase in grip.) The people who need to pay attention are those with 1Gs or Scoobies who rallycross as well as drive on the street or autocross. Slamming the bumpstops in my 2G last winter while rallycrossing under awful conditions did an amazing amount of damage to my car. I don't plan on repeating this in the next few months.

- Jtoby

ps. note that I said "don't plan" ... I probably will because I loved it and would be killed if I used the daily driver

 

[Woodsy0]

Okay, I just looked up the installation instructions for Tein, they recommended ~20 pounds of torque on the upper mount locknut, which is what I think you're (wret) referring to, so I'll go ahead and torque them to that. I put them on with a impact wrench earlier, and now realize that I put way too much torque into them.

Also, I know that I'm a relative newbie compared to JToby and Wret, but can someone please explain what the hell helper/tender springs are? Besides knowing that my coilovers don't have them, I am very much in the dark.

Thanks,
Scott

 

[drivemusicnow]

Okay, I just looked up the installation instructions for Tein, they recommended ~20 pounds of torque on the upper mount locknut, which is what I think you're (wret) referring to, so I'll go ahead and torque them to that. I put them on with a impact wrench earlier, and now realize that I put way too much torque into them.

Also, I know that I'm a relative newbie compared to JToby and Wret, but can someone please explain what the hell helper/tender springs are? Besides knowing that my coilovers don't have them, I am very much in the dark.

Thanks,
Scott

Its a second spring. take a look here: http://hotbits.org/v2/main.cfm

The red spring is the "helper" spring or "tender" spring. It basically absorbs any preload that may exist.

Jtoby/Wret

Are the Teins designed such that those figures he posted (lowered approx. 1.5 inches) would give you a proper ride height (ie: enough travel in both directions?) or is that them saying "this is how much you can drop your car if you really want to without destroying things"

I will state that I didn't notice the 2g, and am really not aware of the suspension issues it has.

 

[wret]

When I istalled Tein coilovers I was concerned about the lack of extension travel. I inquired with Tein if helper springs would um, help. They said no.

To get the maximum possible extension, one would set the preload adjuster nut so that it barely touches the spring, basically just enough to keep it from rattling around or falling out of the upper cup. To allow more extention you would need something to hold the spring in place. That's basically what a tender spring does. As soon as weight is applied to the wheels, the spring collapses completely and does not contribute to the spring rate. Of course, now the car is sitting lower so you would compensate by raising the height adjustment.

By doing this you have changed how much of the shock rod is inside the body in the resting position. The ride height may be exactly the same but there is less compression travel and more extension travel available. I have not seen much in the way of advice on the optimum ratio so I have simply fallen back on macturer recommedations.

And curse on you jtoby, now you will be stuck thinking about it too.

 

[wret]

Are the Teins designed such that those figures he posted (lowered approx. 1.5 inches) would give you a proper ride height (ie: enough travel in both directions?) or is that them saying "this is how much you can drop your car if you really want to without destroying things"

I will state that I didn't notice the 2g, and am really not aware of the suspension issues it has.

Tein's stated lowering amount is based on how low the ride height can be and have the suspenion touch the bump stops under maximum compression, rather than the tires hitting the fenders or parts of the car hitting the ground.