Tein Flex Z opinion

[shiumai]

Originally Posted by bfrank1972

For the Flex Z's spring rate doesn't change with preload, they're linear springs. Only progressive rate springs change their rate as they're compressed.

that makes sense if they're linear. thanks for the correction. then the only drawback is reduced shock absorber travel?

[bfrank1972]

Originally Posted by Mars2

that's also how I UNDERSTAND IT.

Like on Dirt bike the preload is just their to adjust the sag but doesn't affect spring rate.

Same thing. Preload mechanics can be confusing - I've been reading up a lot on it lately and think I have a decent grasp. People often think that increasing preload will lower bump stroke because you're shortening the spring, but it actually has the reverse effect when you add load (lower the car off the jack).

Let's assume we have a coilover with a 400 lb/in spring. This means that the spring will compress 1 inch for every 400 lbs of load on it. It's a linear spring, so if you put 400 lbs on it, it will compress 1". If you add another 400 lbs (800 total), it will compress another 1" (2" total). It will act this way until the coils bind.

Our 'test' car is a 2400 lb race car, perfect weight balance f/r and l/r so it's 600 lbs per corner while it's sitting in the garage. These numbers are just for easy math.

Scenario 1: you have a coilover, completely unloaded, with 0 preload. The damper is at full stroke and the spring is not compressed, just snugly seated. Here you have maximum bump travel and zero droop travel. Let's say total travel is 4". Let the car down from the lift, and with 600lbs per corner, the coilover will compress 1.5". That means it will lose 1.5" bump travel, and gain 1.5" of droop travel. In other words, 2.5" bump travel, 1.5" droop travel.

Scenario 2: you have a coilover, preloaded 1". 1" of preload on a 400lb/in spring is a 400 lb preload. This means that the spring has that much stored energy in it, and will not compress at all until applied weight is > 400lbs. **keep in mind with the car lifted, your damper is still at full length, 4" bump travel, 0 droop travel. Now let the car down from the lift. With 600lbs per corner, and a 400 lb preload, the spring will compress only 1/2 " due to the preload. So that means you lose .5" bump travel, and gain .5" droop travel. Total bump travel will be 3.5", droop travel will be .5". Preload increased your bump travel.

This is just to illustrate the effect, obviously preloading so you have .5" of droop is not a good thing!

edit: all of the above is assuming that your spring is long enough so you'll hit the bump stop before coil binding. If your spring is preloaded to the point where the coils bind before bump stop, then that will effectively limit your bump travel and is something you want to avoid.

edit edit: Preloading will obviously increase your ride height, in scenario 2 the car will sag only 1/2 " under full weight once off the lift vs. 1.5" for the scenario 1 car. That means to get the same ride height with #2 car, you'd have to spin the coilovers to lower the car another 1". Lastly keep in mind we're talking about coilovers with independent height and preload settings (like the Teins), some coilovers don't have this, as you adjust height you change preload at the same time.

[chaoskaze]

Originally Posted by shiumai

that makes sense if they're linear. thanks for the correction. then the only drawback is reduced shock absorber travel?

It doesn't. Tein z only changes in case length, damper stroke & spring preload stays the same.

[shiumai]

Originally Posted by chaoskaze

It doesn't. Tein z only changes in case length, damper stroke & spring preload stays the same.

Isn't it possible to adjust the preload such that the spring compresses completely and limits damper stroke?

[bfrank1972]

Originally Posted by shiumai

Isn't it possible to adjust the preload such that the spring compresses completely and limits damper stroke?

Probably, but you shouldn't need to get to that point. The whole idea is 1) spring rate doesn't change on a linear spring with pre-load, although how the spring reacts to load does, and 2) pre-load will increase bump travel, not decrease it, up to the point where the spring binds. If you find for some reason you're having to set preload that much, then you probably need another coilover.

[Shady195]

@CSG Mike Do we know if its possible to run any firmer of a spring on these with the stock valving? Any plans to test this?

Also Tein says they will re-valve the flex Z's when ordering replacement struts to specs, if so would I be able to give them a spring rate and they would re-valve accordingly?

[CSG Mike]

Originally Posted by Shady195

@CSG Mike Do we know if its possible to run any firmer of a spring on these with the stock valving? Any plans to test this?

Also Tein says they will re-valve the flex Z's when ordering replacement struts to specs, if so would I be able to give them a spring rate and they would re-valve accordingly?

You *can* but it won't work well.

Theoretically yes, but you'd be subject to a pretty long lead time unless you pay for airfreight, and possibly a spec fee.

[Mars2]

Originally Posted by bfrank1972

Same thing. Preload mechanics can be confusing - I've been reading up a lot on it lately and think I have a decent grasp. People often think that increasing preload will lower bump stroke because you're shortening the spring, but it actually has the reverse effect when you add load (lower the car off the jack).

Let's assume we have a coilover with a 400 lb/in spring. This means that the spring will compress 1 inch for every 400 lbs of load on it. It's a linear spring, so if you put 400 lbs on it, it will compress 1". If you add another 400 lbs (800 total), it will compress another 1" (2" total). It will act this way until the coils bind.

Our 'test' car is a 2400 lb race car, perfect weight balance f/r and l/r so it's 600 lbs per corner while it's sitting in the garage. These numbers are just for easy math.

Scenario 1: you have a coilover, completely unloaded, with 0 preload. The damper is at full stroke and the spring is not compressed, just snugly seated. Here you have maximum bump travel and zero droop travel. Let's say total travel is 4". Let the car down from the lift, and with 600lbs per corner, the coilover will compress 1.5". That means it will lose 1.5" bump travel, and gain 1.5" of droop travel. In other words, 2.5" bump travel, 1.5" droop travel.

Scenario 2: you have a coilover, preloaded 1". 1" of preload on a 400lb/in spring is a 400 lb preload. This means that the spring has that much stored energy in it, and will not compress at all until applied weight is > 400lbs. **keep in mind with the car lifted, your damper is still at full length, 4" bump travel, 0 droop travel. Now let the car down from the lift. With 600lbs per corner, and a 400 lb preload, the spring will compress only 1/2 " due to the preload. So that means you lose .5" bump travel, and gain .5" droop travel. Total bump travel will be 3.5", droop travel will be .5". Preload increased your bump travel.

This is just to illustrate the effect, obviously preloading so you have .5" of droop is not a good thing!

edit: all of the above is assuming that your spring is long enough so you'll hit the bump stop before coil binding. If your spring is preloaded to the point where the coils bind before bump stop, then that will effectively limit your bump travel and is something you want to avoid.

edit edit: Preloading will obviously increase your ride height, in scenario 2 the car will sag only 1/2 " under full weight once off the lift vs. 1.5" for the scenario 1 car. That means to get the same ride height with #2 car, you'd have to spin the coilovers to lower the car another 1". Lastly keep in mind we're talking about coilovers with independent height and preload settings (like the Teins), some coilovers don't have this, as you adjust height you change preload at the same time.

Yes thats exactly how I picture it in my mind.
Just don't understand why CSG mike told me:

"More preload = less compression/bump travel before hitting the bump stop."
I recommend running with minimum preload."

This is what made me confused!!!
I always knew that the separate preload and ride hieght is Bull Shit Markting. other wise all WRC car would have it. But non got that

http://www.subaruwrcspares.com/21.html

And BOS WRC Suspension leader also doesn't do separate ride height adjustment only preload like KW, Bilestein.........:
http://www.bos-engineering.com/english/cr60.html

[RBbugBITme]

Originally Posted by bfrank1972

Same thing. Preload mechanics can be confusing - I've been reading up a lot on it lately and think I have a decent grasp. People often think that increasing preload will lower bump stroke because you're shortening the spring, but it actually has the reverse effect when you add load (lower the car off the jack).

Let's assume we have a coilover with a 400 lb/in spring. This means that the spring will compress 1 inch for every 400 lbs of load on it. It's a linear spring, so if you put 400 lbs on it, it will compress 1". If you add another 400 lbs (800 total), it will compress another 1" (2" total). It will act this way until the coils bind.

Our 'test' car is a 2400 lb race car, perfect weight balance f/r and l/r so it's 600 lbs per corner while it's sitting in the garage. These numbers are just for easy math.

Scenario 1: you have a coilover, completely unloaded, with 0 preload. The damper is at full stroke and the spring is not compressed, just snugly seated. Here you have maximum bump travel and zero droop travel. Let's say total travel is 4". Let the car down from the lift, and with 600lbs per corner, the coilover will compress 1.5". That means it will lose 1.5" bump travel, and gain 1.5" of droop travel. In other words, 2.5" bump travel, 1.5" droop travel.

Scenario 2: you have a coilover, preloaded 1". 1" of preload on a 400lb/in spring is a 400 lb preload. This means that the spring has that much stored energy in it, and will not compress at all until applied weight is > 400lbs. **keep in mind with the car lifted, your damper is still at full length, 4" bump travel, 0 droop travel. Now let the car down from the lift. With 600lbs per corner, and a 400 lb preload, the spring will compress only 1/2 " due to the preload. So that means you lose .5" bump travel, and gain .5" droop travel. Total bump travel will be 3.5", droop travel will be .5". Preload increased your bump travel.

This is just to illustrate the effect, obviously preloading so you have .5" of droop is not a good thing!

edit: all of the above is assuming that your spring is long enough so you'll hit the bump stop before coil binding. If your spring is preloaded to the point where the coils bind before bump stop, then that will effectively limit your bump travel and is something you want to avoid.

edit edit: Preloading will obviously increase your ride height, in scenario 2 the car will sag only 1/2 " under full weight once off the lift vs. 1.5" for the scenario 1 car. That means to get the same ride height with #2 car, you'd have to spin the coilovers to lower the car another 1". Lastly keep in mind we're talking about coilovers with independent height and preload settings (like the Teins), some coilovers don't have this, as you adjust height you change preload at the same time.

Triple edit... all is good with this assuming front and rear suspensions have a motion ratio of 1.0.

Originally Posted by Mars2

Yes thats exactly how I picture it in my mind.
Just don't understand why CSG mike told me:

"More preload = less compression/bump travel before hitting the bump stop."
I recommend running with minimum preload."

This is what made me confused!!!
I always knew that the separate preload and ride hieght is Bull Shit Markting. other wise all WRC car would have it. But non got that

http://www.subaruwrcspares.com/21.html

And BOS WRC Suspension leader also doesn't do separate ride height adjustment only preload like KW, Bilestein.........:
http://www.bos-engineering.com/english/cr60.html

Thats cause WRC teams have 60+ damper sets per car and set ride height with custom wound springs for each one. I developed the first set of RH adjustable mounts for the Kobalt tools GRC car this year but its only for very fine tuning with limited range.

Independent RH adjustability is a great feature to have that typically adds cost and cant always be used because of clearance issues.

[BDotG]

Had one other question. I lowered these things about as far as they go. Do you think I need new front end links or should the stockers be okay for now?

[Shady195]

Originally Posted by CSG Mike

You *can* but it won't work well.

Theoretically yes, but you'd be subject to a pretty long lead time unless you pay for airfreight, and possibly a spec fee.

Is there any thought to still possibly doing a custom valved/spring CSG Spec Flex Z?

I'd imagine it would add 2-300 bucks for the springs and if any fee tein would impose for the custom valving.

If we're talking ~1200-1400 for a easily serviceable coilover i think it would be worth it. The worst part about performance coil overs for people who daily/track or otherwise just drive their cars alot is the down time to disassemble and send out for rebuild. Would be nice to have a more performance oriented damper that could be serviced in the driveway in a few hours with a replacement insert.

[CSG Mike]

Originally Posted by Shady195

Is there any thought to still possibly doing a custom valved/spring CSG Spec Flex Z?

I'd imagine it would add 2-300 bucks for the springs and if any fee tein would impose for the custom valving.

If we're talking ~1200-1400 for a easily serviceable coilover i think it would be worth it. The worst part about performance coil overs for people who daily/track or otherwise just drive their cars alot is the down time to disassemble and send out for rebuild. Would be nice to have a more performance oriented damper that could be serviced in the driveway in a few hours with a replacement insert.

The R&D cost of that versus the cost of the damper is something that has been debated. It's not cheap to develop a truly functional part. Sure, we could "CSG spec" a damper with a higher spring rate, but that's not how we do things.

It's something thats been discussed, but nothing solid, yet.

[Shady195]

Originally Posted by CSG Mike

The R&D cost of that versus the cost of the damper is something that has been debated. It's not cheap to develop a truly functional part. Sure, we could "CSG spec" a damper with a higher spring rate, but that's not how we do things.

It's something thats been discussed, but nothing solid, yet.

I like that.

[kbye]

Originally Posted by Shady195

Is there any thought to still possibly doing a custom valved/spring CSG Spec Flex Z?

I'd imagine it would add 2-300 bucks for the springs and if any fee tein would impose for the custom valving.

If we're talking ~1200-1400 for a easily serviceable coilover i think it would be worth it. The worst part about performance coil overs for people who daily/track or otherwise just drive their cars alot is the down time to disassemble and send out for rebuild. Would be nice to have a more performance oriented damper that could be serviced in the driveway in a few hours with a replacement insert.

If you want custom spring rates, you can buy them direct from Tein and swap them out yourself. Dampers are fine as is, I don't see a need for more aggressive valving unless you track often, which in that case the Flex Z is not for you. Remember, these are entry-level coilovers.