[cyniclaus]

Hey guys,

I'm looking at ordering the TCK True Match SA coilover kit since I've heard so many good things about it. I've read all the pertinent posts on here that I could find, but since I'm a total suspension noob, I just want to get some opinions on my plans and options to make sure I end up where I want to be.

I don't care about the stance or height per se, I am just looking for the best DD setup that will offer the best handling without being petrified of speed bumps, driveways, or potholes. I used to drive an Evo X and I can put up with a reduction in compliance over stock but at the same time I don't want to have to hand out business cards to chiropractors when I take on passengers

While I don't plan on tracking the car while it remains a DD, at least the TCK should allow me the flexibility to do that in the future.

Right now I've got 18x8.5 OZ Alleggeritas with 245/40/18 Michelin PSS. I'm getting a Quaife LSD put in sometime this month.

I'm ready to order the TCK kit, but I want to be sure I get the right spring rates...I'm wondering if the suggested 400/600 will best serve me or if I should go with something more aggressive like Doyle with 450/700. Also, the TCK kit on their site says it comes with H&R springs, but other people seem to use different ones...what is the best way to go with springs? I'm not sure what settings to go with on the shocks, but obviously the whole point of the TCK is that you can experiment once you have it.

I plan on putting in Camber Plates and running -2.5 degrees. My PSS have less than 1000 miles and they're already showing excess wear on the outside edges. Not sure if I should mess with rear camber. I'm open to installing an M3 sway and subframe bushings but wouldn't want to go through the expense if the benefits are negligible.

Thanks in advance for any opinions, comments or suggestions!

[Doyle]

1) TCK is perfect for a DD. Very smooth and well controlled. Not harsh in the least. Especially in you are running 245/40 non-rft's.

2) I would absolutely pay the premium to grab the Swift spring upgrade. HPA is running a pretty good price on them. 450/700 has been pretty good to me. I would advise you grabbing the 448/784 Swifts. The front rate looks high, but there is a lot of roll up front to control. Also, the compression stroke is very short. So, you need a stiffer spring to keep it off the bump stops. When I switched from 450 Hyperco to 448 Swift, it felt like the spring dropped ~100#/in.

3) Settings. Rear rebound is fine off the shelf. For street work, the front is fine off the shelf, as well. I found increasing the front rebound at the track a little helped tame the corner exit understeer.

4) Rear camber should be fine. The front needs alot of negative camber. More so than the RWD guys need since we're powering and steering with the fronts (= more entry and exit understeer).

5) I would grab the H&R e90 rear bar and do the subframe bushings, as well. It will do a lot to limit the roll, balance the chassis, and tighten up the overall feel. Def worth it.

[cyniclaus]

Originally Posted by Doyle

1) TCK is perfect for a DD. Very smooth and well controlled. Not harsh in the least. Especially in you are running 245/40 non-rft's.

2) I would absolutely pay the premium to grab the Swift spring upgrade. HPA is running a pretty good price on them. 450/700 has been pretty good to me. I would advise you grabbing the 448/784 Swifts. The front rate looks high, but there is a lot of roll up front to control. Also, the compression stroke is very short. So, you need a stiffer spring to keep it off the bump stops. When I switched from 450 Hyperco to 448 Swift, it felt like the spring dropped ~100#/in.

3) Settings. Rear rebound is fine off the shelf. For street work, the front is fine off the shelf, as well. I found increasing the front rebound at the track a little helped tame the corner exit understeer.

4) Rear camber should be fine. The front needs alot of negative camber. More so than the RWD guys need since we're powering and steering with the fronts (= more entry and exit understeer).

5) I would grab the H&R e90 rear bar and do the subframe bushings, as well. It will do a lot to limit the roll, balance the chassis, and tighten up the overall feel. Def worth it.

Thanks Doyle, I was really hoping you might give your thoughts!

How big of a difference in ride quality do you think I would experience over stock using those settings? I'm mostly concerned that it maintains enough compliance to absorb speed bumps and the occasional pothole.

I see the swifts are an extra $450... tough pill to swallow when it was hard enough to justify paying the premium for the TCK to begin with, but if the difference is dramatic then I suppose it may be worthwhile.

Are all the camber plates more or less equal? I know the Vorshlag are recommended, but they are also the most expensive

Why would you recommend the H&R rear bar over the OEM M3 bar? I read that it's better to have the hollow M3 one. Also, do you think the 23.6mm bar would be too stiff even though I'll have the LSD? I'm trying to understand the risk that might come with the thicker bar.

[zipstic]

cyniclaus-
I'm in the same boat as you. I've been looking at the TC Klines, but adding the Swift Springs and camber plates that adds another ~$885. Eek!

Doyle-
Would you still recommend the TC Kline coilovers without the Swift springs and camber plates over the HPA Swift/Koni coilover kit? I'm not going to track my car, but I do want to upgrade the handling and aesthetics.

[cyniclaus]

Originally Posted by zipstic

cyniclaus-
I'm in the same boat as you. I've been looking at the TC Klines, but adding the Swift Springs and camber plates that adds another ~$885. Eek!

No kidding, brother. If you told me a year ago I'd be seriously considering dropping $6k on suspension upgrades (LSD, CoS, ASB, install costs) I wouldn't have believed it.

[Doyle]

Sorry, in my post I was referring to this kit when I mentioned HPA. Get the external adjusters.

http://www.e90post.com/forums/showthread.php?t=656150

Fwiw, this kit and the TCK are basically the same.

The ride with the TCK is much smoother than stock. Due to the soft springs, poor damping, and short travel I always felt like I was crashing over imperfections.

I can't speak with any authority or personal experience with regard to other plates. I've only used the vorshlags and have only heard the top opinions advising vorshlags. Take from that what you will.

As far as rear bar, you pick your sway bars after you pick your spring rates. If you are running stock, or stock like rates, then the m3 is a good choice. The H&R bar is good for the spring rates I recommended. I have the 23mm bar now, and it is too much bar.

Originally Posted by cyniclaus

Thanks Doyle, I was really hoping you might give your thoughts!

How big of a difference in ride quality do you think I would experience over stock using those settings? I'm mostly concerned that it maintains enough compliance to absorb speed bumps and the occasional pothole.

I see the swifts are an extra $450... tough pill to swallow when it was hard enough to justify paying the premium for the TCK to begin with, but if the difference is dramatic then I suppose it may be worthwhile.

Are all the camber plates more or less equal? I know the Vorshlag are recommended, but they are also the most expensive

Why would you recommend the H&R rear bar over the OEM M3 bar? I read that it's better to have the hollow M3 one. Also, do you think the 23.6mm bar would be too stiff even though I'll have the LSD? I'm trying to understand the risk that might come with the thicker bar.

[cyniclaus]

Originally Posted by Doyle

Sorry, in my post I was referring to this kit when I mentioned HPA. Get the external adjusters.

http://www.e90post.com/forums/showthread.php?t=656150

Fwiw, this kit and the TCK are basically the same.

The ride with the TCK is much smoother than stock. Due to the soft springs, poor damping, and short travel I always felt like I was crashing over imperfections.

I can't speak with any authority or personal experience with regard to other plates. I've only used the vorshlags and have only heard the top opinions advising vorshlags. Take from that what you will.

As far as rear bar, you pick your sway bars after you pick your spring rates. If you are running stock, or stock like rates, then the m3 is a good choice. The H&R bar is good for the spring rates I recommended. I have the 23mm bar now, and it is too much bar.

Thanks, so you are saying the HPA setup is a better value right now than the TCK? They seem very close in price. You recommend the externally adjustable rears, but you also state that the rear rebound is fine off the shelf and that you yourself only adjust the front at the track? What makes you recommend the 784 springs in the rear? You're running 700 yourself right?

When you say the 23mm is "too much bar", what do you mean? Does it cause too much oversteer? Cause traction issues due to wheel lifting?

I'm also having a hard time finding the difference between the 20mm M3 bar and the 20mm H&R bar. The few threads that compare them tend to say the M3 is better, though this is never adequately explained, but it is mentioned in several threads that it comes with better bushings than the H&R.

Sorry for the hundred questions, I'm just so glad there is someone who is not only knowlegable about suspension but who has already been down this road with the same car and can back up results and opinions with his experience on the street and track!

[Doyle]

Originally Posted by cyniclaus

Thanks, so you are saying the HPA setup is a better value right now than the TCK? They seem very close in price. You recommend the externally adjustable rears, but you also state that the rear rebound is fine off the shelf and that you yourself only adjust the front at the track? What makes you recommend the 784 springs in the rear? You're running 700 yourself right?

When you say the 23mm is "too much bar", what do you mean? Does it cause too much oversteer? Cause traction issues due to wheel lifting?

I'm also having a hard time finding the difference between the 20mm M3 bar and the 20mm H&R bar. The few threads that compare them tend to say the M3 is better, though this is never adequately explained, but it is mentioned in several threads that it comes with better bushings than the H&R.

Sorry for the hundred questions, I'm just so glad there is someone who is not only knowlegable about suspension but who has already been down this road with the same car and can back up results and opinions with his experience on the street and track!

You're asking all the right questions! No reason to apologize.

I believe the HPA kit is a better deal, simply for the fact that they include Swift springs instead of having to pay an upcharge.

I advised the higher rear spring rate for a few reasons. The first is that I get a fair amount of weight transfer to the rear during corner exits. This only increases understeer. So, since you will be running a higher spring rate, you will likely need to play with the rebound more than someone using a lower rate (in order to 1: control the spring, and 2: adjust for mid-corner oversteer). Also, since you'll be running a LSD, you'll won't need as soft of a rear end as open-diff cars.

This takes us to the bar:
1) Since you will be running higher spring rates, you will need less bar than me in order to maintain chassis balance. However, you will still need more roll resistance than the M3 bar can provide. The M3 bar is hollow, while the H&R bar is solid. A solid bar is stiffer than a hollow one. I have had no issues with the H&R bushings, so far.

2) I currently run a 23mm solid bar. I say that it is too much bar because I have to watch for excessive rotation during corner entry. I can mitigate it, but it means not being able to brake hard, load the front tires, and turn as quickly as I would like. Since our AWD system doesn't run on a fixed bias, if the car feels the rear end getting light (like the situation I described), it throws power to the front. Well, since the front at that point is now at corner entry, the front's grip is used up already trying to turn. This then causes an odd transition from oversteer to understeer and then it gets into a weird oscillation mid corner.

3) We are stuck with only 2 choices for front sway bars: stock and UUC. The UUC bar, once you choose proper spring rates, is too stiff to be balanced by any rear bar on the market. This means that we are now limited to the front bar only. I'm working on getting another option for the front. But, as of now, we are limited.

Hopefully that helped!

[cyniclaus]

Originally Posted by Doyle

Hopefully that helped!

Yes, very helpful, thanks! I think the plan is starting to come together

Did you ever install spacers to increase your front track? I remember someone suggesting that to you in another thread.

[Doyle]

Originally Posted by cyniclaus

Yes, very helpful, thanks! I think the plan is starting to come together

Did you ever install spacers to increase your front track? I remember someone suggesting that to you in another thread.

Yup. I'm running et30 up front. I might bump it up to et25 all around. Stance, yo!

As far as improving handling, I increased front negative camber and put on 265's, so it is hard to say how much improvement was due to the extra track. You need to be careful playing with scrub/ackerman, but I felt it was worth it to fit big meat up front.

[cyniclaus]

Originally Posted by Doyle

You need to be careful playing with scrub...but I felt it was worth it to fit big meat up front.

That's what She said!

Sorry, couldn't resist

Thanks, one more thing before I order these coilovers...

What's the deal with the $180 option for "Add OEM E82/E9X Front Strut Mounts " and the $50 option for "Swift Thrust Sheets"?

[Doyle]

Originally Posted by cyniclaus

That's what She said!

Sorry, couldn't resist

Thanks, one more thing before I order these coilovers...

What's the deal with the $180 option for "Add OEM E82/E9X Front Strut Mounts " and the $50 option for "Swift Thrust Sheets"?

Lol. Fair. I walked into that one.

The front strut mounts are a must if you aren't getting camber plates. The thrust sheets basically act as bearing, allowing the spring to spin as it is compressed. This helps prevent bind and gives the perception of a smoother ride. They are a "nice to have". Give Harold a call/PM and he'll hook you up with what you need.

[cyniclaus]

So, I'm about to order these but... Harold from HPA said they don't recommend spring rates higher than 336/672. Do you still think that 448/784 is appropriate for my application or should I be a bit more conservative to avoid possible regret?

Also, as much as I want to increase the neutrality of the car, I don't want to go so far that I risk snap oversteer situations on the street that might be exacerbated in limited traction situations like in the rain. I've heard that the H&R can cause this snap oversteer... do you think that is a justifiable concern or will my other mods overcome that? I'd rather sacrifice a little balance in the name of safety if need be, especially since I can always adjust the shocks and the tire pressure but not the sway bar once it's on.

I think I'll get the optional thrust sheets just to be on the safe side.

[Doyle]

I know some other drivers were having issues with ~300# being too soft. I have never thought that my spring rates were too high for DD work. And that is over crappy potholed roads. Up to you, though. It's only money, right?

You will never snapoversteer in this car. Every skidpad I've done has only resulted in a slight kick out of the rear, followed by teeth chattering understeer. We even tried using the handbrake. No luck. You'll understeer into the tree before you oversteer into it. The rumors of "snap" oversteer are all from the RWD guys.

[Chrisred]

Harold told me that the HPA coils are for beginner level/street use. IOW not for the track. And when compared to AST they don't even come close to match performance.

So does mean that TC Kline isn't as good as AST if they're virtually the same???

PS I'm not bashing TC KLINE, i might actually get those if my AST don't get built in time.....

[Doyle]

Originally Posted by Chrisred

Harold told me that the HPA coils are for beginner level/street use. IOW not for the track. And when compared to AST they don't even come close to match performance.

So does mean that TC Kline isn't as good as AST if they're virtually the same???

PS I'm not bashing TC KLINE, i might actually get those if my AST don't get built in time.....

It is my opinion that TC Kline is the better choice for street/light track work. The ASTs are better for intermediate track work/more experienced drivers.

It doesn't sound like you'll be hitting up 10+ track days a year. And if you are, you'll quickly realize that you will need a more suitable car for the track. Hence, my general advice to people to go with the TCK.

[cyniclaus]

Originally Posted by Doyle

You will never snapoversteer in this car. Every skidpad I've done has only resulted in a slight kick out of the rear, followed by teeth chattering understeer. We even tried using the handbrake. No luck. You'll understeer into the tree before you oversteer into it. The rumors of "snap" oversteer are all from the RWD guys.

Thanks, that's comforting, but what about lift-off oversteer...have you tested for this? AWD/RWD should be irrelevant. Of course I'm not in the habit of abruptly pulling off throttle in a turn, but just trying to figure out what I am signing up for. I'm curious as to how your car responds to trail braking as well.

[Doyle]

Originally Posted by cyniclaus

Thanks, that's comforting, but what about lift-off oversteer...have you tested for this? AWD/RWD should be irrelevant. Of course I'm not in the habit of abruptly pulling off throttle in a turn, but just trying to figure out what I am signing up for. I'm curious as to how your car responds to trail braking as well.

Neither have resulted in oversteer.

If you lift mid corner, the front bites a little more, but it still stays planted. Hell, I've even tried to scandinvaian flick the car into rotation and it just plain won't. In the ice, maybe. But if I'm driving in the ice, I'm not setting lap times.

Still experimenting with trail braking. I'll report back once I've nailed it down in this car. Again, the center diff does weird things. As of now, it just results in that oscillation that I mentioned earlier.

[cyniclaus]

Originally Posted by Doyle

Hell, I've even tried to scandinvaian flick the car into rotation and it just plain won't.

Wow, that is quite surprising considering your mods...assuming this is with DTC all the way off.

[Doyle]

Yup. On a wet skidpad in 40-ish degree weather. On NT05's.

[cyniclaus]

Doyle, I assume you must be familiar with this thread...

I wonder what your opinion is of the discussion therein where it is mentioned that BMW seems to have engineered the car for a rear spring rate approximately triple that of the front and that moving to a rate that is double (or even less) contributes to understeer?

[Doyle]

Originally Posted by cyniclaus

Doyle, I assume you must be familiar with this thread...

I wonder what your opinion is of the discussion therein where it is mentioned that BMW seems to have engineered the car for a rear spring rate approximately triple that of the front and that moving to a rate that is double (or even less) contributes to understeer?

I am indeed familiar with that thread. Like many things on the internet, take it with a grain of salt (you are supposed to be a cynic, right?). There is certainly good info in there, but there are alot of opinions/half-truths/mis-construed conclusions.

The stock frequency bias is great for a smooth, street car, but seriosuly compromises some driving dynamics.

If you look at all the top e90 platforms, they all run variations of the bias where the rear spring is 1.5 to 2 times higher than the rear (as opposed to 3 times). KW M3 clubsport (and therefore M3 GTS/CRT, Alpina B3 GT3), GT4/S2000, HPA, certain unnamed Grand Am teams, all use a similar frequency bias.

Step 1 is to understand the "unchangeables". This is the suspension geometry/design and to some degree the weight. With a MacStrut design up front, controlling the front roll is the key to a proper handling BMW. In the past some have decided that one wheel with tons of grip is better than 2 wheels with little grip. This is the "3 wheel motion" that both Orb and Harold mention. So, instead of a heavy bar up front, you use stiffer springs to control the roll and maintain contact patches with both wheels.

For the xi's, this is even more important. Here are the reasons why a stiffer front spring than even the RWD cars is needed:

-the front wheels must steer and turn at the same time

-due to the open front diff, if you pop one wheel in the air, all the power gets directed to the wheel with no traction (yes, I know DTC brakes that wheel and tries to divert power to the other wheel, but the point is there is a delay and a dead weight loss of power application)

-The front travel is even shorter than the RWD struts, so combined with extra weight, extra roll the xi might hit the bumpstops more frequently

When all of this is taken into account (combined with the general thought that a stiff front end is prefer so the car can take set early), you end up with the front spring rates between 400 and 500 for a street/track setup.

Now, in the rear, since there is a multi-link setup and the car has a RWD bias, drivers are going to want a softer rear end. On a more practical matter, due to the design of the rear suspension, there is a very low motion ratio. This means that you'll have to run a higher spring rate, but not too high as to cause bind/stiction. Most reccomendations that I have seen (Harold, Orb, TCK, RRT, etc) feel that 700-800 is the sweet spot. Anything north of around 800 will need different bushings (Delrin) and really good shocks, so it should be reserved for serious track rats.

It is my belief that the xi's will need stiffer rear springs than the RWD cars, for two reasons:

-we send power to both front and rear, therefore, the need for the rear wheels to put down power is diminished

-with an AWD car, there is a strong tendency to power-on understeer. Since weight gets transferred to the rear, and the car is still recovering from a turn, the front end tends to get light (front inside wheel, in particular). To control that weight transfer, stiffer rear springs might be needed.

I plan on experimenting with stiffer rear springs (around 800-850) at some point. I also wonder if a rear LSD might help (if power is getting to the ground at the rear, less power will need to be directed to the front).

From there, we can choose the sway bars to balance out the chassis. We have a veritable cornucopia if rear bar choices, but a paltry 2 for front bar choices. A vendor seriously needs to hop on that. The UUC front bar was designed around the stock frequency bias, so it is uber-stiff (going back to the 3 wheel motion). With the proper springs selected, none of the rear bars out there are stiff enough to balance it. It is a moot point, anyways, as getting a matching rear bar would likely start diminishing mechanical grip. So, that is why either the e90/92 M3 bar or H&R e90/92 bar is usually suggested. The M3 bar is better with the lower end coilovers (H&R, KW V1/3). The H&R bar is better with proper spring rates.

There you go. Super long answer to a simple question!