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Guru of Supercharged ISs
8,744 Posts
Discussion Starter #1
Hey brothas..

For those of you running Coilovers...& specifically Tein Flex to correlate with my specific concern & equipment....:)

What did you/do you do with the preload settings on your coils for daily driving...???

traditionally I have been running NO preload on my springs... but i am not sure if i might try a few turns here & there to see if it changes the ride much...?

I thought that tightening up the rings & putting preload on the springs generally stiffens them up.... but i have also heard & felt on my MTB coilover suspensions that a little preload can actually make the spring act a bit more supple as the spring is already "INTO" its travel when slightly compressed to you are not starting out with a fully extended spring that then has to be pressed past the fully extended threshold point & THEN begins to compress.

Not sure how much sense this makes as i assume when you have a car sitting on the ground the weight of the car is compressing the spring a bit at all 4 corners....

I thought theoretically, Preload would make a spring a touch "stiffer" I think as the spring is flexed a bit, i know preload can increase spring rate...but it think this is more true on a rising rate spring vs a straight rate spring...?

I am not sure what these Flex springs are, i believe straight rate?

I was thinking that if the springs are totally UN- or only very lightly compressed when installed this might be the cause for some of us to experience a light knocking when driving smoothly but at low speed over bumps & rougher surfaces...? I am hearing this now from the right rear & i think it sounds like the spring shifting back & forth on the perch over light bumps....

Also on the flex, when i set them up, I generally tightened the bottom spring seat collar up to the bottom of the spring just enough to where the spring will not spin easily on the perch by hand so there is just enough presure on the spring to keep it snug when fully extended between the top & bottom spring perches.. I saw NO instructions regarding Preload & or recommended settings for this adjustment in the flex paperwork

I am thinking mabey i need to go past this point to two or three turns of preload to see if this either:

A. stops the slight knocking i am gettign from the right rear....?
B. Makes the ride a touch more supple,.......or stiffer...?

so what do you do...?

8,219 Posts
Ed, with the tein flex you should have almost NO preload for the IS300. If you set a preload on this car you will adversely affect the handling and characteristics of your car.

Our cars handle well because of its extremely dynamic suspension, setting too much preload will defeat all that and in turn cause your handling to suffer.

I repeat, do NOT set preload on the FLEX. I have many many many people come to me with thier flex saying something isnt right. 95% of the time, the owner/installer set too much preload.


in case i wasnt clear enough, your preload should be to the point where it holds the spring in place and doesnt rattle or spin around easily.

Setting higher preload makes the ride stiffer.

Tein FLEX springs are straight rate and not progressive. Your rates are 10 and 8.
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