CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[Racecomp Engineering]

Originally Posted by sdemo

Before I post, I searched this thread for "preload" and I couldn't find an explicit answer to this question. If this has been answered, please point me to it! Anyway, here goes:

What is the proper way to set up a suspension that has separate "preload" and "ride height" adjustments? A ubiquitous example of this type of coilover would be the Tein Flex.

With these coils, "preload" is typically set by moving the spring perch up or down, and "ride height" and/or shock length is set by threading the shock body further into or out of the lower mount "cup."

I've seen two methods proposed (though there may be more):

First method - use the spring perch to set ride height
1. With the suspension off the car, remove the spring.
2. Put the spring-less assembly on the car, and mount the wheel tire.
3. Jack up the control arms / wheel + tire and adjust shock length until the tire does no longer contacts the top of the wheel well at full compression.
4. Remove the shock assembly from the car, reinstall the spring, and set final ride height via spring perch aka "preloading the spring."

Second method - use shock length to set ride height
1. With the suspension out of the car, first set preload. If preload is set by the manufacturer, don't touch it. Otherwise, adjust lower perch until the spring is "snug," then tighten another 1/4 turn (varies).
2. Install the coilover assembly into the car then adjust ride height by turning the entire shock assembly into or out of the lower cup, careful not to move the spring perch / change preload amount.

I can see pros and cons of both methods, but they undeniably produce different results. Which way is the correct way?

I wouldn't bother with method 1 for this car.

Method 2 is the easy way.

The alternative is to decide how much bump travel and how much droop travel you want, and go from there.

- Andrew

[Racecomp Engineering]

Originally Posted by DerHauptDigga

Sorry about that. I will probably run an "extreme summer tire" I've been looking at Dunlop DZII Star Specs, Hankook RS3s, Yokohama Advan's, etc. So a similar tire to that.

Right now it's sitting on TRD springs, which is hardly an inch drop if that, I'd like to go down at least another inch.

Side note, if I bought 18x9.5 +40 wheels and wrapped them in 265/35/18 tires, would I rub? I know I would rub on stock Suspension, but since I have springs, would it still rub?

Thanks for all your help though, really appreciate it.

If you can afford the KW V3s, they'd be a good fit for you as long as you get them from someone that can help you dial them in.

With a big wide heavy wheel, you're going to want a decent quality damper. It's noticeable.

- Andrew

[Kellhound]

Alright guys figured I would start here as the “search” feature did not answer my questions.

I have completely destroyed the handling on my 2015 BRZ with SKUNK2 Pro C coilovers and P-TUNING sway bars (21mm front) (18mm rear) with Whiteline end links.

Let me preface this conversation with this: while I may not be an automotive mechanic, I feel my experience as an aircraft mechanic has afforded me the right to at least tinker with simple suspension dynamics on a relatively simple design.

I guess I was wrong about the tinkering part because I am either completely inept with suspension geometry, or I just lack the tools to complete this task correctly.

This car is as loose as a 2 dollar hooker in downtown Detroit. I have lost complete confidence in high speed maneuverability. The body rolls and the arse end snaps out from underneath as if I’m skating on wet pavement. Car handling was better when she was 1.5 inches higher with bone stock struts and thinner swaybars. I see the traction control system engage on just about every turn, yes I drive aggressively… I’d own a sedan if I wanted to be passive.

What I have done based on reading these forums:
(first step) Set preload and ride height with a set of calipers. (equal on all 4 points)
Set the front dampening to 3 clicks from full and the exact opposite in the rear.
Had the car aligned with -1 degree camber all the way around (zero tow).
Finally I increased preload on front coilovers to help induce a little push and of course I backed out a little on the rear preload in an attempt to gain grip.

The body roll bothers me the most. I don’t understand how lowering the car, increasing springload, increasing the swaybar tension, and adding camber could have had such a negative and drastic effect on the car.

Sorry for the drawn out complaint. I’m at my wits end with this thing. Short of getting the vehicle corner balanced, I have no idea what to do other than reverse all my changes because the car is nowhere near as fun to drive now.

Thanks


Dan

[MaximeT]

Originally Posted by Kellhound

Alright guys figured I would start here as the “search” feature did not answer my questions.

I have completely destroyed the handling on my 2015 BRZ with SKUNK2 Pro C coilovers and P-TUNING sway bars (21mm front) (18mm rear) with Whiteline end links.

Let me preface this conversation with this: while I may not be an automotive mechanic, I feel my experience as an aircraft mechanic has afforded me the right to at least tinker with simple suspension dynamics on a relatively simple design.

I guess I was wrong about the tinkering part because I am either completely inept with suspension geometry, or I just lack the tools to complete this task correctly.

This car is as loose as a 2 dollar hooker in downtown Detroit. I have lost complete confidence in high speed maneuverability. The body rolls and the arse end snaps out from underneath as if I’m skating on wet pavement. Car handling was better when she was 1.5 inches higher with bone stock struts and thinner swaybars. I see the traction control system engage on just about every turn, yes I drive aggressively… I’d own a sedan if I wanted to be passive.

What I have done based on reading these forums:
(first step) Set preload and ride height with a set of calipers. (equal on all 4 points)
Set the front dampening to 3 clicks from full and the exact opposite in the rear.
Had the car aligned with -1 degree camber all the way around (zero tow).
Finally I increased preload on front coilovers to help induce a little push and of course I backed out a little on the rear preload in an attempt to gain grip.

The body roll bothers me the most. I don’t understand how lowering the car, increasing springload, increasing the swaybar tension, and adding camber could have had such a negative and drastic effect on the car.

Sorry for the drawn out complaint. I’m at my wits end with this thing. Short of getting the vehicle corner balanced, I have no idea what to do other than reverse all my changes because the car is nowhere near as fun to drive now.

Thanks


Dan

Maybe a stupid question, but, are you sure you don't have toe out in the rear ?

[Kellhound]

I really wanted to get this car corner balanced and re-aligned but wasn't sure I was going to stick with the after market parts I installed. Plus i'm having trouble finding someone in Virginia that can do it.

According to my last alignment the report shows as follows:

Toe
LF+.01
RF+.01

LR-.09
RR-.06

I have not touched the car since.

your question leads to another I actually had. How exactly do you change the rear toe in this car? I don't have adjustable tow arms in the back. Its just a solid link.

[jvincent]

There's an eccentric bolt that adjusts the toe in the rear.

[MaximeT]

Originally Posted by Kellhound

I really wanted to get this car corner balanced and re-aligned but wasn't sure I was going to stick with the after market parts I installed. Plus i'm having trouble finding someone in Virginia that can do it.

According to my last alignment the report shows as follows:

Toe
LF+.01
RF+.01

LR-.09
RR-.06

I have not touched the car since.

your question leads to another I actually had. How exactly do you change the rear toe in this car? I don't have adjustable tow arms in the back. Its just a solid link.

The car was aligned with this coilovers ?
Alignment looks OK.

If the corner balance is very wrong, I guess the car can drive this bad.

Are the rear springs much harder than front ?

[Kellhound]

1/4" softer in the rear actually. I cant measure the pounds though i'm half tempted to drop a grand on scales as the plan is to AutoX sometime next year with my son and his Miata. (mid life crisis i guess... its a bucket list item I want to cross off, plus VIR is right up the road so thats nailing two birds with one stone) Yes, the alignment came after the install of the coilovers but before I installed the swaybars.

Adding the swaybars did nothing to help the body roll.

I did not adjust ride height or preload after alignment. Swaybars were adjusted with full load on vehicle (not sitting on jacks)

[MaximeT]

Originally Posted by Kellhound

1/4" softer in the rear actually. I cant measure the pounds though i'm half tempted to drop a grand on scales as the plan is to AutoX sometime next year with my son and his Miata. (mid life crisis i guess... its a bucket list item I want to cross off, plus VIR is right up the road so thats nailing two birds with one stone) Yes, the alignment came after the install of the coilovers but before I installed the swaybars.

Adding the swaybars did nothing to help the body roll.

I did not adjust ride height or preload after alignment. Swaybars were adjusted with full load on vehicle (not sitting on jacks)

With what you say, I don't understand how you get this much oversteer. Especially body roll and oversteer at the same time. Are you maybe too low ? Or a lot higher in the back ?

Are the sway bars adjustable ?

[Racecomp Engineering]

Originally Posted by Kellhound

Alright guys figured I would start here as the “search” feature did not answer my questions.

I have completely destroyed the handling on my 2015 BRZ with SKUNK2 Pro C coilovers and P-TUNING sway bars (21mm front) (18mm rear) with Whiteline end links.

Let me preface this conversation with this: while I may not be an automotive mechanic, I feel my experience as an aircraft mechanic has afforded me the right to at least tinker with simple suspension dynamics on a relatively simple design.

I guess I was wrong about the tinkering part because I am either completely inept with suspension geometry, or I just lack the tools to complete this task correctly.

This car is as loose as a 2 dollar hooker in downtown Detroit. I have lost complete confidence in high speed maneuverability. The body rolls and the arse end snaps out from underneath as if I’m skating on wet pavement. Car handling was better when she was 1.5 inches higher with bone stock struts and thinner swaybars. I see the traction control system engage on just about every turn, yes I drive aggressively… I’d own a sedan if I wanted to be passive.

What I have done based on reading these forums:
(first step) Set preload and ride height with a set of calipers. (equal on all 4 points)
Set the front dampening to 3 clicks from full and the exact opposite in the rear.
Had the car aligned with -1 degree camber all the way around (zero tow).
Finally I increased preload on front coilovers to help induce a little push and of course I backed out a little on the rear preload in an attempt to gain grip.

The body roll bothers me the most. I don’t understand how lowering the car, increasing springload, increasing the swaybar tension, and adding camber could have had such a negative and drastic effect on the car.

Sorry for the drawn out complaint. I’m at my wits end with this thing. Short of getting the vehicle corner balanced, I have no idea what to do other than reverse all my changes because the car is nowhere near as fun to drive now.

Thanks


Dan

Originally Posted by Kellhound

I really wanted to get this car corner balanced and re-aligned but wasn't sure I was going to stick with the after market parts I installed. Plus i'm having trouble finding someone in Virginia that can do it.

According to my last alignment the report shows as follows:

Toe
LF+.01
RF+.01

LR-.09
RR-.06

I have not touched the car since.

your question leads to another I actually had. How exactly do you change the rear toe in this car? I don't have adjustable tow arms in the back. Its just a solid link.

Originally Posted by Kellhound

1/4" softer in the rear actually. I cant measure the pounds though i'm half tempted to drop a grand on scales as the plan is to AutoX sometime next year with my son and his Miata. (mid life crisis i guess... its a bucket list item I want to cross off, plus VIR is right up the road so thats nailing two birds with one stone) Yes, the alignment came after the install of the coilovers but before I installed the swaybars.

Adding the swaybars did nothing to help the body roll.

I did not adjust ride height or preload after alignment. Swaybars were adjusted with full load on vehicle (not sitting on jacks)

Alright lets start with the basics:

1. What kind and what size tires are you running? What tire pressures?
2. What spring rates did your coilovers come with? You will usually see it in lbs/in or kg/mm (sometimes just k). I'm not sure what you mean by 1/4" softer in the rear.
3. Your alignment could use improvement. -1 degree of camber is not very much especially in the rear. That in combination with the slight toe out you have is a big part of your oversteer issue. 0 toe is 0 toe...not a little bit in or a little bit out.
4. Is your rear swaybar adjustable? Have you tried it on the softest setting? (the farthest out holes)
5. What are your damper settings? 3 clicks from full stiff front and 3 clicks from full soft in the rear?
6. How much preload are you running exactly? Preload is often a misused tool...it doesn't increase spring rate on a linear spring.

In general, I suggest not necessarily worrying about body roll at this point. With your mods and the fact that it's skating around like it's on wet pavement, it probably isn't actually rolling all that much (which makes sense if you're lacking grip). I often see people complain about too much roll in a situation like this but in reality they're mixing up signals and the feeling of instability feels like excessive body roll to them. So they'll stiffen up the car more which results in even less grip. You may want to consider putting your stock swaybars back actually.

Excessive spring preload can cause a car to behave jittery and unpredictably. Reduce it all around to a few mm just to keep the springs captive.

I usually wouldn't recommend running such a drastic difference in damper settings front to rear, but it's hard to say since I'm not familiar with Skunk2 products so I'm not sure how they're tuned. Probably good to be in the same neighborhood though. Don't try to use dampers to adjust mid-corner balance or body roll...they're for reactions to bumps and corner entry/exit.

My advice is to raise the car to about a 1 inch drop from stock (and make sure the ass end isn't up in the air), get it aligned with -2 degrees camber front, -1.8 camber rear, 0 toe front, and a tiny bit of rear toe IN. Reduce your preload to a minimal amount. Set your dampers to just 1/4 stiff front and rear (just to start, adjust later). Set your rear bar to soft or put the stock bars on. Give that a shot.

There are a couple good shops in NOVA...if you can make it to PTuning or Mach V they'll be able to get you a good solid performance alignment.

Hope that helps.

- Andrew

[Kellhound]

The rear swaybar has two settings and I am using the the hole closest to the inside of the bar (stiff). The Whiteline end links are adjustable but as instructed in another post, they were aligned with load on the chassis and set to the shortest length possible.

I'm running zero rake as well.

I agree with you man, Its why I've been pulling my hair out for the last two weeks.

P-Tuning happens to be about an hour north of me. I am going to get them to corner balance and align the car. THANK YOU P-TUNING!!!

If they cant figure it out I'll sell the Skunk2's and bite the bullet for the Ohlins.

Gawd this car will be the death of me and the end of my marriage. I've already been told there is plenty of room in the crawl space under the house for a 6 foot deep hole and nobody would ever know.

[Racecomp Engineering]

Originally Posted by Kellhound

The rear swaybar has two settings and I am using the the hole closest to the inside of the bar (stiff). The Whiteline end links are adjustable but as instructed in another post, they were aligned with load on the chassis and set to the shortest length possible.

I'm running zero rake as well.

I agree with you man, Its why I've been pulling my hair out for the last two weeks.

P-Tuning happens to be about an hour north of me. I am going to get them to corner balance and align the car. THANK YOU P-TUNING!!!

If they cant figure it out I'll sell the Skunk2's and bite the bullet for the Ohlins.

Gawd this car will be the death of me and the end of my marriage. I've already been told there is plenty of room in the crawl space under the house for a 6 foot deep hole and nobody would ever know.

Yeah definitely set the rear bar to soft. That's not helping!

That + a good alignment should go a long way.

- Andrew

[Kellhound]

Alright lets start with the basics:

1. What kind and what size tires are you running? What tire pressures?
Im running stock rims and tires @ 34 pounds at all 4 points. Just bare in mind that the car is worse now than when I drove it off the dealers lot with the same tires and pressure
2. What spring rates did your coilovers come with? You will usually see it in lbs/in or kg/mm (sometimes just k). I'm not sure what you mean by 1/4" softer in the rear.
1/4 inch less preload on the spring (using a caliper vs. the front preload) 6kg on the springs
3. Your alignment could use improvement. -1 degree of camber is not very much especially in the rear. That in combination with the slight toe out you have is a big part of your oversteer issue. 0 toe is 0 toe...not a little bit in or a little bit out.
I'll take your recommendations to P-Tuning when they align the car. Thanks for the input
4. Is your rear swaybar adjustable? Have you tried it on the softest setting? (the farthest out holes)
I have not tried the furthest setting out. That makes sense as I am trying to increase grip in the rear and push in the front. I was trying to stop the car from feeling like it was rolling on the edges of the tires during high speed cornering. I'll make that change this weekend
5. What are your damper settings? 3 clicks from full stiff front and 3 clicks from full soft in the rear?
That is correct
6. How much preload are you running exactly? Preload is often a misused tool...it doesn't increase spring rate on a linear spring.
I will say that I started with the settings Skunk2 recommended in the configuration video. The springs can spin on their perch and still do. I did however increase the front preload by 1/4", and reduced the preload by 1/4" in the rear

So...
I will change the sway settings on the rear bar to the end hole
I will raise the car .5 inches as I only dropped her 1.5 inches.
I will run the dampening back to stock and adjust for bump instead of trying to set it as a crutch for handling.
I'll move the preload back to Skunk2's recommended setting on all 4 points
and of course the master alignment and corner balance for a 200 pound driver.

Thanks for your input guys. I'll feel a little better driving home from work today. 8)

[rx3]

I hope this is the correct spot to place this question:

Assuming you were to go with KW competition 2-way coil overs for a slalom-racing-application (sort of autocrosses which partially resemble hillclimbs and/or rally's on tarmac), where one run would never exceed 3 minutes and 30 seconds on super soft racing slicks (mostly and sometimes on racing rain tires) (on 17"x9" rims), with what suspension set up would you start with?

Spring rates, sway bars, ride height, camber, rake, toe?

(Minimum height above ground has to be 80 mm or 3.15".)