How important is preload?
 

I am in the process of replacing my front 200mm 6kg springs with 150mm 8kg springs. Unfortunately the coilover I am using adjusts height and preload at the same time.

Doing a straight swap of the springs without any other changes makes the car sit about 10mm lower, even though the new spring is 50mm shorter. What does change dramatically is the preload - the new spring can rattle around when the car (not wheel) is raised more than about 25mm. With the old springs fitted they were always slightly loaded.

I'm guessing a raised ride height with more preload would be better than the current situation?

The car is only used on the track.

are you saying that when you jack the car up just 1 inch, the springs already unseat from the tophat?

Sounds to me like you have done a bad job adjusting the correct length of your shock body. You need, at this point, remove the term "preload" from your vocabulary and really start understand how to adjust your shock length and spring perches for optimal performance.

It's the Tein SS, you can't adjust the shock body.

I'm guessing ideally I should use a helper spring?

okay. well don't be afraid of preload. the ricer market has put a stigma on it.

Let's just say you'd have to raise your spring perch 4.5" inches before you need to worry about the negatives of preload.

Right now, if you raise your spring perch you will gain both bump and droop travel (since the spring is more likely to be seated).

Yeah I was more worried about lack of it. I assumed it was important to keep the wheels firmly on the ground through all conditions (droop travel is probably what I mean).

I'll raise the perch 10mm then get a more accurate measurement of when the spring starts getting really lose.

So, is this what you're saying? Because that's probably not good as the car will move around side-to-side more than 1 inch.

real racers have loose springs.

you can optionally ziptie the springs to the top hats if you have the right holes in the top hats. the lower part of the shock will self-center the spring.

a HELPER (not TENDER) spring (super low spring rate, can squish with your fingers) will prevent the loose springs but cost you an extra $200 for all four plus spacer blocks.

You want to screw the lower adjuster all the way in, to give you as much travel as possible. You don't need a tender (whatever you want to call it) to hold the spring tight, it won't come off the perch when you're driving if you have a sway bar.

read page four

http://www.ksportusa.com/edocs/Coilo...structions.pdf

1. those are horrible instructions. Ricer company K-sport, is case and point why I say they give preload a negative stimga.

2. he doesn't have adjustable shock bodies.

i promise k-sport doesnt have me on their payroll but im just curious on why you say they're ricer. Also, never said preload was bad. however, i do think its not something to do half hazardly and can upset a car very easily.

IMO ksport = a very cheap knock off version of stance coilovers. For the baller on a budget

lol @ anyone knocking off Stance. What makes Stance so great?

the price lol

KW would be a better example i guess... still too rich for my blood.

Good point about the swaybar. I'll jack the spring perches up a bit to try and remedy the issue a bit (and buy me more shock travel) but it will always be at the expense of increased ride height.

I think I should stop throwing good money after bad and save my $ for some XIDAs or Mono Flex. :)

Xida and twin are not remotely close to the same category.

[quote=v01canic;791254]i promise k-sport doesnt have me on their payroll but im just curious on why you say they're ricer.[quote]

Because ksport makes a very cheap knock off version of stance coilovers. They provide products to be baller on a budget.

and they do suggest preload is bad, the tell you to setup the spring so it's at zero preload, then go on to tell customers to adjust the height of your suspension by adjusting the shock body length up and down and always maintaining zero preload.

this is how a ricer company without any knowledge in the subject would tell someone how to setup a suspension.

you dont think adjusting the shock body length haphazardly will have negative effects?

Not that I know better, but I'm curious why you think adjusting shock body length would be bad?

Ideally of course the threaded sleeve/area of the shock would just be at a correct location to allow proper adjustment of the spring.

At zero-preload, you have essentially setup your shock with the minimal amount of bump travel available to it. So right then and there your suspension has servely suffered a negative strike against it.

Let's say you followed KSport's instructions, set the spring at zero pre-load and threw it on the car and the setup was too low -- which is will be. In order to raise the suspension, they tell you to adjust the shock length.

When you raise the car this way, you are raising the car in relation to the wheel, so the bump travel still remains as limited as possible.

Why in the world would you want to limit bump travel, especially in a miata?


Now also, think about what happens when teh shock body is too short...The tire can easily hit the fender well before the bumpstop is fully compressed. So let's say that you set the spring to zero preload, toss it in, and you're happy with the ride height. But let's also say in this situation, the tire rubs the fender wall. Now you've limited the bump travel even further than before.



In my instructions, I would instruct the user to set the shock body length in such a manner that you were certain that the tire never made contact with the fender. This would be the minimum length I'd instruct a user to allow the body to go. (Acutally my coilover kit wouldn't have adjustable bodies, I'd determine this length for them -- like Xidas) Then I would instruct the user to then set the spring so it's at zero preload and if the setup is too low, which it will be, then to raise the spring perch in order to raise the car. Yes, I know there are certain limitations to doing this, but it only is result of excessive preload due to too short of supplied springs from vendors that do not design the shock around the application as with 99% of the adjustablee shock body coilovers out there: ksport, stance, tein, etc.

But. When you raise the car in this manner, you are raising the car in relation to the spring perch, so you actually gain suspension travel. You are moving the resting position of the positon higher up within the shock body, exposing more shaft, adding bump travel.

MY coilover kit would also have spring rates and lengths coupled with the shock, so you know you will be able to balance the shock length and spring perches, in such a way to acutally dial in your ratio of bump:droop travel for optimal performance.

maybe you should take a second look, with these coilovers you are never adjusting the travel of the actual damper. That would be counter productive. The damper actually maintains its length and when you raise or lower the car the entire damper actually moves within the coilover body. Also the damper is actually valved according to the spring rate.


If you have to adjust preload to cross-balance/corner-balance your car, youre fixing one problem by causing another.

The Grand-AM Riley chassis I worked with set preload via a conventional threaded spring perch. The ride height was set adjusting the length of the upper shock mount in the chassis. Many Touring and GT cars still use just the threaded spring perches to adjust ride height, which does effect preload. I personally would not worry about pre load to much given what I have seen. If you can avoid it then do but I wouldn't stress.

Wheel travel is determined by spring length, shaft length and room in the wheel arch. It is also not uncommon for a race car to unload the springs completely in droop. This can be used to tune the cars roll and pitch.