I currently have KWV3 and I find them to roll a bit too much than I like.

I also have Cusco 32mm bar with stock AP1 rear bar, along with bumper steer, and roll center adjusters.

If I want to reduce the roll, would it be better to get a different coilover setup with stiffer springs, or get a matching set of swaybar that are stiffer?

For coilovers I have these choices: HKS Hipermax III / KW Clubsport / Tein SRC

For swaybars I am thinking of the Gendron .25" wall Hollow Bar along with the Eibach rear adjustable bar. According to my calculation this setup is about 25% stiffer than my current swaybar setup.

My current setup is very neutral with 245/265 tires and I want to keep the balance. All I want is to reduce roll.

Any help from you experts are greatly appreciated!

 

a) Why do you want to reduce roll?

b) Rather than buying entirely new coilovers, why not just get stiffer springs?

 

Well, anything you do is going to change the way the car handles. I'd say to start with the sway bar to reduce roll but the Gendron 1.25" = 32mm so I'm not sure how much its going to help over the Cusco...I'm sure the solid bar would help but that is certainly going to change the way the car handles.

If you went with other coilovers the KW clubsports certainly wouldn't do it for you (I have them) the difference over the V3s isn't THAT significant. I'd say go for the SRC's with their 16kg springs they are considerably stiffer than the 9kg springs in the V3s and absolutely will reduce roll.

Now that I answered your question though, I'd like to know, why do you care about the body rolling...with your current setup it cant possibly be rolling enough to truly have major negative effects on alignment. Body roll is not a bad thing, and having a little is perfectly fine.

 

I guess reducing roll is a personal preference which does not necessary improve performance or lap time. I am also planning to switch to R compound tires for the next season and thought that with the higher grip, I will need something to control the body roll.

I could definitely get stiffer springs, which is also another option. However at this moment I am not sure which springs would best fit my needs.

 

Here is how I calculated the swaybar stiffness.

Stock AP1 Front sway bar part number: 51300-S2A-003
28.2mm (HOLLOW) with a 5mm Sidewall
Rating at 61.6N/mm

The Cusco 32mm bar claims to be 172% stiffer. So it's rate should be 106.57N/mm

Stock AP1 Rear sway bar part number: 52300-S2A-013
27.2mm (HOLLOW) with a 5.3mm Sidewall
Rating at 73N/mm

So currently with my setup, the front to rear swaybar stiffness ratio is about 1.459:1


Here is the rate of the Gendron .25" wall Hollow Bar. Max of 832# /in and a minimum of 460 #/in. Each step is 62 #.

Here is the Eibach Rear Swaybar rate:
Rear: 29mm Adjustable (HOLLOW)
Pos.1 - 90 N/mm (515lbs/in)
Pos.2 - 106 N/mm (605lbs/in)
Weight - 4.9kg (10.8lbs.)

In order to achieve the ratio of 1.459:1, if the rear bar is at the Position 1 setting (515lbs/in), then I would need a front bar that is at 751.385lbs/in which is well within the range of the Gendron Bar.

Comparing the rates of the Gendron Bar / Eibach Bar vs the Cusco / Stock Ap1 bar, the first combo is about 25% stiffer.

 

There are a lot of threads in this forum about various spring rates. Alternately, you could find out what spring rates are included with the coilovers you listed, and just buy springs matching those rates instead of the coilovers themselves.

Remember that roll stiffness is a function of both sway bars and springs. I think any attempt to match roll stiffness ratios will be a rough exercise at best, but if you want to take that approach, you'll want to find out your current spring rates, as well as the relative contributions springs and sway bars make to roll stiffness (I think someone mentioned this in one of the past few days' threads).

 

Thanks for the tips!

I will definitely do more research in this directions!

 

OE spring and swaybar analysis:
https://www.s2ki.com/forums/index.php?showtopic=818884

I wouldn't go any bigger on the rear swaybar; even the CR uses a softer bar than either '00-'01 or '02-'03. If you can find a big honkin' front bar that might help. Use springs to reduce roll in the rear, since they will not lift the inside wheel as much in corner exit.

 

Check your KW V3 spring rates. The V3 came in 2 different spring rates:
80 N/mm and 90 N/mm which is 456 and 514 lbs/in respectively.

The KW Club sports use 100 N/mm which is 570 lbs/in. you could go to 11 or 12 kg springs which would be 616 and 672 lbs/in respectively. I would not go over 672.

The Saner bar is 1.25" and adjustable with S- 556, m- 644, and h 739 lbs/in.

If you are using the car for road racing and not auto x my opinion is that the soft setting is best with a square tire setup. auto x guys use the higher rate bars.

All this of course depends on your alignment, wheels, tires, aero etc..
I think you will create an significant understeer condition using a bar rate as high as your are considering because of the staggered tire setup.