Rear anti roll bar sizes

[Ricky]

Further to the subject of rear anti roll bar mounting on the RF which has been covered in an earlier thread, what size bars and lever arm lengths are people using?

I am combating a reasonable amount of understeer which is occuring on the track (typically on corners of more than 90 degrees where the car is heavily loaded) I feel that the inclusion of the rear bar will be a better option than over springing the rear. I think this should maintain some suppleness within the suspension for the street but provide better balance in high load cornering on the track.

Also, is anyone using an adjustable bar and if so how much adjustment do you have in effective lever arm length?

Cheers,
RV

[Kalun D]

A race car isn't a race car without sway bars.

The Mark V I've measured has a front bar 5/8" thick with 8-1/2" arms. Rear bar 3/4" thick with 8-1/2" arms. Both are solid with about 26" between pivot mounts.

The rear bar has about 4" to 6" arm length adjustment, front a little less.

If your only running a rear bar you probably want smaller.

[Mark Worthington]

I believe the rear sway bars on the Wyer cars were 3/4" solid bars, but not sure about the arm length.

[Ricky]

Thanks for your input gent's.
I am running a front bar only at present but it is a stiffer than stock bar. I am also still using the std RF front springs but am not sure of their rate. I really need to take them out and get them tested to establish this.

I am sure the heavier bar is contributing to the understeer but from photos taken of the car at the track there is still a fair amount of body roll so thought that adding a rear bar will help limit this roll and "as per the books" stiffening the rear will reduce understeer / increase over steer.

I have no rear bar at all and thought this rather strange, particularly if the original cars had them fitted. I am also sure they had to be there for good reason.

Thanks again for your help.
RV

[Kalun D]

"I have no rear bar at all and thought this rather strange"

Definitely, you should have a rear bar before you even have a front bar because that's were the weight is.

[Ricky]

I guess I hve been running the car "almost" as defined in the RF manual, hence no rear bar. It looks like this will change very shortly.

Thanks for your input.
RV

[flatchat(Chris)]

Although still analysing ---I run 10" slicks all round with a 1" bar front and 5/8" at rear --juggle between understeer and oversteer -- oversteer is quite managable from a slight step out to a gentle drift.

Just drive slower [img]/ubbthreads/images/graemlins/grin.gif[/img]

Is your chassis flexing a problem???

For normal road use the as from factory should be fine

Look more towards spring rates and shocker selection--good bump and rebound control

Good luck
[img]/ubbthreads/images/graemlins/cool.gif[/img]

[DenisBedford]

Guys you cant design a anti-rollbar by comparing the diameter and the arm length with other similar cars, the calculations are also controlled by the location of the connecting rods to the control arms, the angle of the connecting rods, the distance the arms are away from the bearings, etc etc also they will be a whole lot less effective if rubber bushes and rod ends are used--there are a lot of really good racing cars suspension books available that explain everything in detail which will help you design your anti- rollbar and evaluate what you need Regards Denis

[Trevor Booth]

Plus a few more,
Cg location,front and rear mass distribution,unsprung mass,effective length of ARB,coil spring rates,tyre spring rate,roll centre height front and rear, front to rear roll resistance relationship,plus a lot of time to play