KTS coilover questions

[Bosrudorfer]

I'm new to coilovers and have searched but haven't found anything that address' me specifically. I have KTS coilovers. My first question would be:

1) It appears that the top bolt that hold the shock/piston/shaft to the upper mount already comes FULLY tighten from the factory, or am I misinformed? If not how the heck do I tighten them (the shaft spins).

2) I don't have a rear sway bar nor an closed diff, when I go up and hill while turning it feels like one of my wheels gets airborne. Is this common? I don't have the car very low, maybe 2 finger. My coilover assemble is not short, I made sure to follow Kuah's guide and have equal "preload" and assemble length.

3) Anyone have any measurements? I know this sounds stupid but I used a ruler to measure and make sure both sides are equal. For example from upper mount to the end of the spring perch, the length of the whole assemble, length between lower bracket and the spring perch.

Thanks

[Bosrudorfer]

All questions answered by SPL several minutes after email. Amazing customer service.

"The top nut that holds the piston shaft is sometimes loose from the factory, to tighten it you need to hit it with an impact gun…

It is normal to lift wheels with coilovers that do not have helper springs, that does not really affect anything. Run as little or no preload, the more preload you have the more likely it will lift the wheel.

We do not have any measurements, but you should make sure the length from upper mount to spring perch is the same on both sides because that is the pre-load. For the other lengths you should adjust them accordingly based on ride height, it is not necessary to make them even on both sides on the coilovers."

[Dano]

Awesome! This is why I love SPL, thanks for sharing the answers they gave you to your questions with the rest of us!!!

-Dan

[Bronze MFP]

if you have an s14 i can give you my measurements i'm currently running.

[Bosrudorfer]

if you have an s14 i can give you my measurements i'm currently running.

Thanks but I wont need it anymore. I have everything perfect now. I used zip ties to make sure I had enough travel (the fronts had plenty because I have good amount of preload but the rears with zero preload where bottoming out so I increased the preload until I had enough travel).

Turned out the rear passenger bolt that holds the upper mount, etc. was lose and the alignment shop tightened it to fix the noise problem. I still hear stuff but that's because the upper mounts aren't rubber like the stocks.

As for damper I'm running 5 in front and 7 in rear. Its good, a little bumpy but I like it. I might switch here and there to 5 front and 6 rear.

Anyhow its all done and I'm enjoying them.

P.S. The alignment tech was handling out compliments on the coilovers and tension rods left and right. Good quality stuff he said.

[naed240sx]

There is no way you were bottoming out your rear shocks running a captive spring. People run like 10+mm droop and don't have problems.

[Bosrudorfer]

There is no way you were bottoming out your rear shocks running a captive spring. People run like 10+mm droop and don't have problems.

The zip tie ended up at the upper mount

[ddgsxr504]

I am a little confused. You said that your fronts have plenty of preload. Are you referring to the sprung weight of the car once it's sitting on the ground or are you saying that you have the front springs pre-loaded with the wheels off the ground (actaully compressing the sping with car on lift/jack stands)?

I thought preoad wasn't a good thing to have since it shortened the stroke of the dampner which can ead to premature failure.?

[EazyBreazy]

preload doesnt shorten the shock stroke it stays the same only it makes the shock work harder to compress. you're thinking about lowering the car by loosening the lower perch so that the shock compresses a little before it comes to rest on the spring

[ddgsxr504]

ok ok I got it now, thanks. I get a little confused sometimes.

So how much preload should one use for street set-up and how do you know how much you are applying?

[naed240sx]

preload doesnt shorten the shock stroke it stays the same only it makes the shock work harder to compress. you're thinking about lowering the car by loosening the lower perch so that the shock compresses a little before it comes to rest on the spring

In actuality, neither preload or drooping the spring shortens the stroke/travel. The shock travel is going to stay the same. The only thing you can change is the amount of compression travel and rebound travel. People don't often enough discuss these when discussing travel. Of course the sum of the compression and rebound travel amounts will always be equal to the same number(the total damper stroke).

Preload lengthens compression travel and reduces rebound travel.

Sagging lengthens rebound travel and reduces compression travel.

Preload doesn't really make it harder for the suspension to compress, unless you are running progressive springs. The force on the car from the coilover assembly will still be the same when the car is static, and it won't affect spring stiffness, so body roll won't really change.

I'm pretty sure this is what you were trying to say. Just thought I would expand that thought a bit.

DDGSXR: Preload is generally measured in millimeters. If you move the spring perch up 10mm from the captive point, you are running 10mm of preload. If the spring rate is 8kg/mm, you have now effectively created 80 pounds of force in the spring.

[ddgsxr504]

So what your saying is that I need to corner weight my car to figure out what preload I should be running? My ride is a little stiff and I was wondering if there was a way for me to fix that a little. I know that coilovers are not intended for street use but surely there is a little tweaking that can be done.

[Bosrudorfer]

In actuality, neither preload or drooping the spring shortens the stroke/travel. The shock travel is going to stay the same. The only thing you can change is the amount of compression travel and rebound travel. People don't often enough discuss these when discussing travel. Of course the sum of the compression and rebound travel amounts will always be equal to the same number(the total damper stroke).

Preload lengthens compression travel and reduces rebound travel.

Sagging lengthens rebound travel and reduces compression travel.

Preload doesn't really make it harder for the suspension to compress, unless you are running progressive springs. The force on the car from the coilover assembly will still be the same when the car is static, and it won't affect spring stiffness, so body roll won't really change.

I'm pretty sure this is what you were trying to say. Just thought I would expand that thought a bit.

DDGSXR: Preload is generally measured in millimeters. If you move the spring perch up 10mm from the captive point, you are running 10mm of preload. If the spring rate is 8kg/mm, you have now effectively created 80 pounds of force in the spring.

you know your stuff

[Bosrudorfer]

In actuality, neither preload or drooping the spring shortens the stroke/travel. The shock travel is going to stay the same.

What about this?

"Which method should you use? Preloading the spring allows more stroke/travel for the shock, which is very important; if the shock stroke/travel is too short you will be constantly hitting the bump stop. However, preloading the spring too much can create problems - it would become easier for the tire to lift off the ground when the weight transfers away from that corner, and it would also effectively increase the spring rate."

[naed240sx]

So what your saying is that I need to corner weight my car to figure out what preload I should be running? My ride is a little stiff and I was wondering if there was a way for me to fix that a little. I know that coilovers are not intended for street use but surely there is a little tweaking that can be done.

Preload is used to adjust corner weights.

Evening corner weights won't give you a softer ride, it will just give you more even frictional forces at each tire, which will give better handling.

IMO, it's not worth doing for a street car. For the track, it can improve times.

[naed240sx]

What about this?

"Which method should you use? Preloading the spring allows more stroke/travel for the shock, which is very important; if the shock stroke/travel is too short you will be constantly hitting the bump stop. However, preloading the spring too much can create problems - it would become easier for the tire to lift off the ground when the weight transfers away from that corner, and it would also effectively increase the spring rate."

First sentence is correct, except that "travel" should read "compression travel"

Preloading does make it easier to lift wheels.

Preloading doesn't increase the spring rate. The spring rate is constant for most typical springs. You can't change it without changing the spring.

[Bosrudorfer]

First sentence is correct, except that "travel" should read "compression travel"

Preloading does make it easier to lift wheels.

Preloading doesn't increase the spring rate. The spring rate is constant for most typical springs. You can't change it without changing the spring.

Hmm makes sense. Well you should inform Kuah from SPL to correct his install guide then.

BTW I have one last question. Since I run more preload in the front than the rear what will the effects be?
Modified by Bosrudorfer at 4:58 PM 6/8/2006