Z3 TCKR Single Adjustable Coilover Kit

[solimans]

Gents, I'm considering purchasing this kit (tckline). Have no idea what spring rate to choose...they offer 300-650 front, and 400 through 700 rear.

What works best for a 2.8 coupe on the street?

https://www.tcklineracing.com/webdoc...Details150.cfm


Currently have this set (from the prior owner): http://www.stsuspensions.com/product...-13220016.html

While cornering, on throttle, I get a chirp sometimes (wheel hop). And they bottom out pretty easily, especially the rear. :/

Guessing the rebound is off?

[khammack]

When I got my TCK setup, I call them and told them what I wanted to do with my car (track, autocross or street) and they helped me with the spring rate. In fact TC Kline was the person who answered the phone and helped me. (But since he sold the company I doubt you will get him).

[KBH22102]

I had a similar experience in 2008 when I called. TC himself answered the phone and we talked for about 15 minutes. I had my 2.8 roadster then and he recommended 350 front and 400 rear for my stated driving style (spirited street drives and beginner autocross). It was a very comfortable setup and I kept it for many years. Later on in 2014 a forum member was selling 550 fronts and 700 rears and I bought them and installed them. The ride was firmer for sure and the car stayed flatter in autocross, but I definitely felt road imperfections a lot more (enough that my wife noticed).

[Tim95M3]

I run this setup on both of my Z3's. One with 500/700 and the other with 440/700. I feel like the 500/700 is just right, but I like a firm suspension. My father's S54 M roady has 400lb all around and I feel like it's WAY too soft in the rear, constantly hitting the bump stops.

[kornfeld]

I would strongly, strongly recommend against getting the 400f/400r setup. I completely agree with Tim95M3---it is absurdly soft in the rear.

Back when I got my TC Kline DA suspension, I went 400f/400r, and immediately regretted it. The rear was so, so soft.

Only after I had wasted my money (and time) on those rear springs did I do the research I should have done initially. I found out that the spring rate itself isn't the important value to know---it's the rate out at the wheel that matters, which is different from the rate at the spring because the suspension components are levers that modify the final amount of force the spring puts out.

A 400f/400r spring becomes a 352f/180r at the wheel on our cars. In other words, the front spring is just shy of twice as stiff as the rear in that setup, which is bad for a street car. A 400f/700r spring combo becomes a 352f/315r at the wheel, which is closer to what you want. I'm still considering going to a 300f spring, but haven't decided if I want to give it a shot or not.

A chart showing wheel rates for different springs on our cars can be found here: https://www.bimmerforums.com/forum/s...5#post27622055


After studying that chart, the epiphany I had was that increasing spring rates does not increase them in absolute values, it increases them in multiples. For example, going from a 400 lb spring to an 800 lb spring is not 400lbs stiffer. It's 2x as stiff. In other words, an 800 lb spring is actually 180 lb stiffer than a 400 lb spring on our cars, Because the rate at the wheel goes from 180 lb to 360 lb.


By extension, a 1000lb spring in the rear is actually a 450lb spring on our cars.

[Vinci]

I think mine are 450f/500r. That was the recommendation from TCK when I ordered them. I think they ride better than the OE springs/struts, including comfort.

[JeffPortland]

Can someone comment on why some people get "double adjustable" vs "Single adjustable"? What's the difference? Thanks!

[JWin]

Just installed 400F/500R on TCK D/As and they are plenty stiff. It's a stiffer ride than stock but manages moderate road imperfections better.

[khammack]

Can someone comment on why some people get "double adjustable" vs "Single adjustable"? What's the difference? Thanks!

Double adjustable give you rebound and compression adjustments. If you track or autocross your car it gives you better adjustments to go faster. If you don't do either, then single adjustable should be all you need.

[solimans]

When I got my TCK setup, I call them and told them what I wanted to do with my car (track, autocross or street) and they helped me with the spring rate. In fact TC Kline was the person who answered the phone and helped me. (But since he sold the company I doubt you will get him).

Where's TC when you need him : )

- - - Updated - - -

I had a similar experience in 2008 when I called. TC himself answered the phone and we talked for about 15 minutes. I had my 2.8 roadster then and he recommended 350 front and 400 rear for my stated driving style (spirited street drives and beginner autocross). It was a very comfortable setup and I kept it for many years. Later on in 2014 a forum member was selling 550 fronts and 700 rears and I bought them and installed them. The ride was firmer for sure and the car stayed flatter in autocross, but I definitely felt road imperfections a lot more (enough that my wife noticed).

good info, thank you, Kelvin

so maybe 400f / 600r. still undecided

- - - Updated - - -

I run this setup on both of my Z3's. One with 500/700 and the other with 440/700. I feel like the 500/700 is just right, but I like a firm suspension. My father's S54 M roady has 400lb all around and I feel like it's WAY too soft in the rear, constantly hitting the bump stops.

right 500 / 700. I wish I knew what "firm" meant for you? gonna be in Houston any time soon? wishful thinking

[solimans]

I would strongly, strongly recommend against getting the 400f/400r setup. I completely agree with Tim95M3---it is absurdly soft in the rear.

Back when I got my TC Kline DA suspension, I went 400f/400r, and immediately regretted it. The rear was so, so soft.

Only after I had wasted my money (and time) on those rear springs did I do the research I should have done initially. I found out that the spring rate itself isn't the important value to know---it's the rate out at the wheel that matters, which is different from the rate at the spring because the suspension components are levers that modify the final amount of force the spring puts out.

A 400f/400r spring becomes a 352f/180r at the wheel on our cars. In other words, the front spring is just shy of twice as stiff as the rear in that setup, which is bad for a street car. A 400f/700r spring combo becomes a 352f/315r at the wheel, which is closer to what you want. I'm still considering going to a 300f spring, but haven't decided if I want to give it a shot or not.

A chart showing wheel rates for different springs on our cars can be found here: https://www.bimmerforums.com/forum/s...5#post27622055


After studying that chart, the epiphany I had was that increasing spring rates does not increase them in absolute values, it increases them in multiples. For example, going from a 400 lb spring to an 800 lb spring is not 400lbs stiffer. It's 2x as stiff. In other words, an 800 lb spring is actually 180 lb stiffer than a 400 lb spring on our cars, Because the rate at the wheel goes from 180 lb to 360 lb.


By extension, a 1000lb spring in the rear is actually a 450lb spring on our cars.

dude, so many light bulbs going off with this post...mucho gracias


This jumps out at me from Randy:


”From a ride stand point, you do not want the same frequency at both ends, as this will lead to a very uncopmfortable pitching motion over bumps. Really good suspension tuners (BMW is one of the best) will choose frequencies such that a disturbance will quickly decay to a purely vertical movement as motion is arrested. These are the cars that jujst feel planted. From a traction perspective, yes, it usually (always?) works out that a rear drive wants a softer rear to be able to put the power down smoothly on corner exit."


I’m left thinking...what spring rate ratio (front / back) does the car come with stock? Thinking I’d keep that balance but go a bit more firm (both in the front and rear) if that makes sense. Not sure all other things remain equal?

- - - Updated - - -

I think mine are 450f/500r. That was the recommendation from TCK when I ordered them. I think they ride better than the OE springs/struts, including comfort.

that's with a roadster? makes sense. would think the roadsters are a bit lighter in the back? just a guess. I have a coupe

[rf900rkw]

A lot has been typed in this forum over the years, I really don't want to repeat all the typos. the Cliff's are the math says TCK's suggested numbers are too soft, way too soft when compared to the front. But it is a safe sable setup. In other words, the car will go off the road into the trees nose first rather than tail first.


Stock spring rates. I started looking into this several years ago. Obviously each model / options will be slightly different. As I remember, the set I was testing turned out to 180lb front, and the rears were.... progressive. And not just progressive in the normal trick of nesting coils. the damn wire is TAPERED!!! I was going to map out the force curve, had the scale, the press, and even devised a way where the chances of launching the spring through the neighbors dining room window were low. But then life got rough and I never actually got it done.



A note. If you are bottoming, the springs are too soft. Or at least too soft for the chosen ride height. Propping up undersized springs with aggressive shock settings, or oversized swaybars, is not the righteous way.

[solimans]

A lot has been typed in this forum over the years, I really don't want to repeat all the typos. the Cliff's are the math says TCK's suggested numbers are too soft, way too soft when compared to the front. But it is a safe sable setup. In other words, the car will go off the road into the trees nose first rather than tail first.


Stock spring rates. I started looking into this several years ago. Obviously each model / options will be slightly different. As I remember, the set I was testing turned out to 180lb front, and the rears were.... progressive. And not just progressive in the normal trick of nesting coils. the damn wire is TAPERED!!! I was going to map out the force curve, had the scale, the press, and even devised a way where the chances of launching the spring through the neighbors dining room window were low. But then life got rough and I never actually got it done.



A note. If you are bottoming, the springs are too soft. Or at least too soft for the chosen ride height. Propping up undersized springs with aggressive shock settings, or oversized swaybars, is not the righteous way.

yes sir, I'm reading right now...there's a lot : )

currently on this tread. https://www.bimmerforums.com/forum/showthread.php?2016816-Spring-rate-theory-and-application-regarding-our-abnormal-chassis

think I might find more info there than I can comprehend

on deck: http://forums.bimmerforums.com/forum...s-for-drifting

[Tim95M3]

Gonna be in Houston any time soon? wishful thinking.

I'll probably be in Kerrville in April on a group drive. Closer than I am now! lol

[khammack]

I'll probably be in Kerrville in April on a group drive. Closer than I am now! lol

Me too!

[kornfeld]

right 500 / 700. I wish I knew what "firm" meant for you? gonna be in Houston any time soon? wishful thinking

This was another thing I learned back when I was putting these on the car--it's important to differentiate between which situation we're talking about when we talk about how firm a suspension is.

This term can be applied to how the suspension responds when you are in a long, sweeping turn, and you are curious about how much the body rolls/leans. For the purposes of this conversation, the springs are the main thing that dictate how firm the car feels in this situation (i.e., how much or how little it leans). Obviously other parts of the suspension (like sway bars) also play a role here, but we're just talking these suspension kits.

The term can also be applied to what happens when you go over a sudden, sharp bump of some sort in the road. For the purposes of this conversation, the valving of the damper is the main thing that dictates how the car feels in this situation (i.e., whether it just feels like a bump in the road or whether it makes your teeth hurt because it's so jarring). Obviously other parts of the suspension (like tire sidewall stiffness) also play a role here, but we're just talking about these suspension kits.

I think the second situation (sharp bumps in the road) is overwhelmingly what people are talking about when they want to know how firm a suspension feels. Is it going to make my back hurt? Will I grimace every time I'm about to hit the most minor imperfection in the road? Those sorts of things.

The spring rates we're discussing are definitely stiffer than stock, but high spring rates aren't the main thing that lead to a jarring experience (or not) when you hit bumps in the road. The valving in the dampers is what causes a suspension to feel firm/jarring (or prevents it) in the case of hitting short duration bumps in the road--and you can't tune the compression settings with the SA settings, so you get what you get here. The car will feel sports-car-ish with these dampers when you go over short duration bumps. It won't be as cushy as cars that are primarily set up for comfort, but I don't think you'll find it jarring. If you own a car like this and are asking about suspension upgrades, you're obviously willing to make some compromises , and again, I don't think you'll find it jarring.

Interestingly, the soft 400lb rear springs were jarring, specifically because they bottomed out way too frequently for me. If you picture those situations on the highway where there are sudden dips in the road that make the car drop and then come back up very quickly, and the car makes sort of a "whooooomp" sound, the rear end would hit the bump stops every single time. That is a jarring and unpleasant and abruptly very firm feeling in the suspension caused by soft springs. Going up to the 700lb springs actually make the car feel more comfortable because the springs could actually support the car in those situations. The highways around where I live may just have more of these depressions in the road than others have, so maybe this isn't an issue for other people.

[solimans]

This was another thing I learned back when I was putting these on the car--it's important to differentiate between which situation we're talking about when we talk about how firm a suspension is.

This term can be applied to how the suspension responds when you are in a long, sweeping turn, and you are curious about how much the body rolls/leans. For the purposes of this conversation, the springs are the main thing that dictate how firm the car feels in this situation (i.e., how much or how little it leans). Obviously other parts of the suspension (like sway bars) also play a role here, but we're just talking these suspension kits.

The term can also be applied to what happens when you go over a sudden, sharp bump of some sort in the road. For the purposes of this conversation, the valving of the damper is the main thing that dictates how the car feels in this situation (i.e., whether it just feels like a bump in the road or whether it makes your teeth hurt because it's so jarring). Obviously other parts of the suspension (like tire sidewall stiffness) also play a role here, but we're just talking about these suspension kits.

I think the second situation (sharp bumps in the road) is overwhelmingly what people are talking about when they want to know how firm a suspension feels. Is it going to make my back hurt? Will I grimace every time I'm about to hit the most minor imperfection in the road? Those sorts of things.

The spring rates we're discussing are definitely stiffer than stock, but high spring rates aren't the main thing that lead to a jarring experience (or not) when you hit bumps in the road. The valving in the dampers is what causes a suspension to feel firm/jarring (or prevents it) in the case of hitting short duration bumps in the road--and you can't tune the compression settings with the SA settings, so you get what you get here. The car will feel sports-car-ish with these dampers when you go over short duration bumps. It won't be as cushy as cars that are primarily set up for comfort, but I don't think you'll find it jarring. If you own a car like this and are asking about suspension upgrades, you're obviously willing to make some compromises , and again, I don't think you'll find it jarring.

Interestingly, the soft 400lb rear springs were jarring, specifically because they bottomed out way too frequently for me. If you picture those situations on the highway where there are sudden dips in the road that make the car drop and then come back up very quickly, and the car makes sort of a "whooooomp" sound, the rear end would hit the bump stops every single time. That is a jarring and unpleasant and abruptly very firm feeling in the suspension caused by soft springs. Going up to the 700lb springs actually make the car feel more comfortable because the springs could actually support the car in those situations. The highways around where I live may just have more of these depressions in the road than others have, so maybe this isn't an issue for other people.

Very good insights, sir. As I’m reading I’m discovering more gems of information. Very much appreciated.

I think this will help me make the right decision for me. : )


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[solimans]

Kerrville? What group drive is that?


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[khammack]

Kerrville? What group drive is that?

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Texas Spring Drive aka FRED R. Memorial BMW Z Series Spring Drive.

http://anachargreta.com/Z3/

[solimans]

Texas Spring Drive aka FRED R. Memorial BMW Z Series Spring Drive.

http://anachargreta.com/Z3/

Bit far for the z in its current condition. Let’s see if I can get it sorted. The pressure is on


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[solimans]

Got these done over the weekend...

I went with the single adjustable kit, 400 front, 600 back. Drove it this morning, seems solid. I will update as I drive it more if anything comes up.

Did run into one thing that I was not sure on. The rear spring mount / height adjuster. It did not seem to fit, left a gap on top / in between the body and the mount. I'll attach a pic.

Ended up keeping the old (ST) mounts on. I'm going to reach out to TC support.

Just wanted to update. Thank you again to everyone who took the time to respond here.

[solimans]

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[solimans]

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[solimans]

Normal?


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[khammack]

Mine didn't quite fit to my liking either. I had them adjusted all the way down and were not adding much to the height anyway, so I just took them out. This was many years ago and I have not noticed any issues with not having them installed.