Body Roll

[Adz2332]

Hey all

looking to stop some body roll on my track only r33gtst

im getting some HSD monocoils with 8kq front 7kg rear

ive had some shocking body roll problems. it only has a half cage at this stage, but will be adding side intrusion bars soon.

What would you recommend? still have stock sway bars etc

[GH05T]

to reduce body roll u have to upgrade swaybars, thats essentially whats controlling it.

harder springs wont really fix body roll.

cage/ bar work will only really affect body flex, not roll.

Edited October 26, 2017 by GH05T

[Adz2332]

excellent thanks will look into some

 

[Duncan]

f**k it must be frustrating on the track with standard sway bars

[admS15]

I agree, its interesting though that mca suggests using stock sway bars with their shocks and to control roll with spring rate. Personally i run whiteline bars but it's hard to argue with mca when you look at the performance of their time attack car.

[Duncan]

well, there is kind of a religious war out there about whether springs on their own are sufficient, or whether sway bars and springs are better.  In production cars we have to run stock sway bars so we run heavier springs (ie the MCA and common Japanese approach) but when I'm not doing prod cars I run heavier bars and lighter springs and I think it handles better, particularly over bumps.

The MCA time attack car is a good advertisement, but not really relevant for the average full chassis race car.  Only time attack cars run on the smoothest track, 1 lap at a time on super soft tyres and with massive downforce. The rest of us live in a world with compromised track surfaces or roads with plenty of bumps, little to no downforce and tyres that are expected to last hours of racing and not degrade.

[GH05T]

its definitely detrimental to go big sway bars for no reason and definitely bad to be too heavy, but same for spring rates.

fair to say though if you have heavier spring rates and still struggeling with body roll that the stock swaybar setup is not holding its own enough.

Edited October 26, 2017 by GH05T

[admS15]

Very good explanation, thanks Duncan. Im quite happy with my bar setup although my rear unknown spring rates are probably a touch firm on the street. Quite good at the track though. I suppose you can't have it all without a bit of trial and error.

[Adz2332]

Im tossing up between spring weighs of 10f 8r or  8f 7r

[Dale FZ1]

17 hours ago, Adz2332 said:

looking to stop some body roll on my track only r33gtst

im getting some HSD monocoils with 8kq front 7kg rear

ive had some shocking body roll problems. 

What would you recommend? still have stock sway bars etc

Firstly - is the body roll causing problems? Or are you indicating a handling problem?  The real objective is to chase an acceptable balance front to rear for understeer/oversteer without spending big on components (eg why go to replacement bars if you can get a workable outcome without changing from OEM).

Tyre size and spec WILL influence what suspension spec is necessary or best.  eg. a set of 235 ADO8R vs 295 A050 will require different choices.

Secondly, a nose heavy boat WILL tend to flog its front tyres. That's unavoidable.

I'd review what ride height you have it set at, as this impacts roll centre and the tendency to resist body roll.

Then I'd contact MCA, speak with Josh about your needs and his prices and recommendations.  Then make a decision whether you want to run with their product or the HSD you have mentioned.

Quite probably it's going to require 13kg fronts at a minimum.  Ignore what GTR owners use, this is a 2wd chassis with different requirements.

[GRKGTR]

Upgraded my sway bars on the weekend to ARC ones (Auto Refine Company), fully adjustable etc.. Basically eliminated the body roll i had.. Not sure why I didn't do it sooner!

 

[Adz2332]

excellent, was looking at the whiteline stuff.

they have a 24mm front and back adjustable stuff. but im unsure just how much id use it to adjust. i wouldnt have much idea??

[GTSBoy]

Be cautious mating the 24mm bars front and rear.  I have them on a 32GTSt (so I acknowledge not the same chassis set up, but nevertheless.....) set to max stiff front and min stiff rear.  I really feel that the mid corner balance would be better if I had a 22mm rear.  It's very happy to make the rear step out, which becomes progressively more alarming the faster you go.

Otherwise.....yes, just do it.  Or at least do something.  Stiffer front bar drastically sharpens the immediacy of turn in response.

[djr81]

12 hours ago, GRKGTR said:

Upgraded my sway bars on the weekend to ARC ones (Auto Refine Company), fully adjustable etc.. Basically eliminated the body roll i had.. Not sure why I didn't do it sooner!

 

Where did you get them from - and what diameter are they?

[GRKGTR]

1 hour ago, djr81 said:

Where did you get them from - and what diameter are they?

From Japan through Jesse Streeter.

Diameter is 30mm and they are hollow.

[djr81]

Front and rear the same diameter?

[GRKGTR]

4 hours ago, djr81 said:

Front and rear the same diameter?

Yep

 

[djr81]

Wow. OK. Understeeeeeeeeeeer.

Looked up the Cusco ones as a comparison (%'s compared to stock). 

Front

Cusco 24 dia, 192% stiffer.  ARC 30 dia (From your number) 240% stiffer.

Rear

Cusco 30 dia , 162% stiffer. ARC 30 dia 180% stiffer.

Guessing ARC quote the numbers with the drop links on their hardest setting.

[GRKGTR]

3 hours ago, djr81 said:

Wow. OK. Understeeeeeeeeeeer.

Looked up the Cusco ones as a comparison (%'s compared to stock). 

Front

Cusco 24 dia, 192% stiffer.  ARC 30 dia (From your number) 240% stiffer.

Rear

Cusco 30 dia , 162% stiffer. ARC 30 dia 180% stiffer.

Guessing ARC quote the numbers with the drop links on their hardest setting.

They are quoting 2.40 times stiffer at front and 1.8 times stiffer at rear
 

[dan.1337]

I went for 12kg/10kg rates on BC Racing ER coilovers, still using stock sway bars.

Yes, it still rolls a little, but you also need to consider the relationship between sway bars and springs.  A thicker sway bar will help reduce roll, but you'll also lose some suspension independence and comfort (lol what's that anyway?) on the street.

I can still manage a 1:35 around Winton with a bit more in it, so I'd try going for a good shock and spring setup first before adding sway bars.

Pic is of my car (like yours - half caged) at pretty much full load.