what anti roll bars?

[AdamGardner]

Did a track day yesterday at cadwell park, car went well but felt it could do with a stiffer rear anti roll bar at least. wondered what other people are using and opinions?

[Black_Potato]

Depends on all the other bits on your car but rear anti roll bars arnt really an issue on these cars, if anything many run without them to improve drive out of the corners.

Your probably better off looking at dampers/spring rates if you havent already.

[GeoffBob]

Did a track day yesterday at cadwell park, car went well but felt it could do with a stiffer rear anti roll bar at least. wondered what other people are using and opinions?

Out of interest, what makes you think you need a stiffer rear ARB? If you have a specific problem with understeer then a stiffer rear ARB might be worth looking at, but if your issue is with body-roll then stiffening up the springs and dampers (as above) would be a better option. FYI, I have no rear ARB on my track car.

[DanThe]

First thing I did with mine was take the rear bar off

[timmy1701]

I am also running mine without a rear bar, compensate for the lost spring rate with stiffer rear springs, better tracktion out of corners.

[eb4]

I have a set of this:

http://cgi.ebay.de/H-R-Sport-Stabilisat ... 588d4e4e39

[anton89]

as everyone has already said look at the specific spring stiffness at the rear if you want to reduce roll. However you should be focusing more on how much camber change your settup creates when it rolls, the aim of the ARB in a track car is to keep the loaded wheel at the optimum camber to generate the highest lateral force when cornering ( usualy around -1.6 to -1.8 degrees) this allows for the highest grip. there wont be one fix to make a perfect system in suspension its about compromise. having roll allows the static camber to be around -0.1 which allows the max amount of rubber for transmitting power to the wheels when going down the straights then when you corner the roll causes the loaded wheels to go into bump causing a camber change to -1.8 which is the optimal camber for grip around corners.

If you stiffen the sstem up you will need to run a higher static camber to allow for the lack of movement in the system when you enter the corner.

you can see evidence of this if you look at F1 cars.

i probably did a bad job of explaining but i tried.

[timmy1701]

When you lower it you increase the amount of camber. I think mine was at -2.5 on the alignement machine, even more when its loaded. And my last set of r888s were worn mostly on the outside (warranting the use of even more negative camber).

[Mikey_Boy]

Hmm - I hope I am not throwing a cat amongst the pigeons here...

I use Gaz coilovers and Eibach uprated anti-roll bars. Agree entirely with the above that spring and damper rates have a big effect here - however, I put these roll bars onto a Koni kit and found it to be a super modification and it works well with the coilvers too...

So, what did that tell me? That there are in fact 2 issues to consider - the spring/damper rate AND also the control of the vehicle's roll axis through the centre of the car. The spring and dampers will help with this, but a recent roll bar will help you to be able to LOWER the spring/damper rate whilst controlling the roll axis through the centre of the vehicle... So uprating the rear roll bar a touch more than the front helped with my ongoing understeer issues and made the car more adjustable generally - I keep backing off the stiffness of the springs and keep the bars fairly stiff - why? To allow the wheels to move freely and stay in touch with the road and let the roll bars to the work around corners. This also depends on other factors such as body stiffness, geometry set up, suspension type, tyre pressures and type, sidewall stiffness etc etc.

A mistake often made is that the suspension is set so stiff that it doesn't move much and the car rolls very little as well - whilst this may work on some levels, it doesn't address some of the fundamental issues, which is of course to keep the optimum contact patch at all times during bump and rebound.. It's that word compromise again...

A topic that divides opinion for sure! Anti roll bars at front and back works for me, but not for others - best to try for yourself and see what FEELS best for your driving style...

Cheers,
Mike

[UweM3]

The stiffer your anti roll bar, the LESS the wheels can move independently. Think about it, you a LINKING left and right together.

There is a limit to everything and sure there comes a point when anti roll bars are too stiff for a spring rate.

[Mikey_Boy]

Indeed Uwe - you are absolutely right! Just trying to illustrate there is more than one way to go...

Cheers,
Mike

[anton89]

there are many factors to understand rather than taking the amature STIFFER STIFFER method. ARBs are there for one reason alone, to control the contact patch. Camber angle control in roll is the KEY information you have to know to make a descent set up.

The higher resistance to roll the higher static camber is needed. optimal camber is 1.8 negative to get the highest lateral load capabilities of the tyre. so at when cornering you want to acheive a camber of -1.8.

this is much much more important at the front. the rear transmits power so its optimal power contact patch is 0 degrees. however cornering is -1.8 so the closer to -1.8 at the rear the faster you can go round the corner without the rear tyres loosing grip , but rear tyre wear will be uneaven and the amount of power the tyres can transfer to the road will be reduced so a ballance is needed.

people who generally just wack the biggest gurder they can find on CLAIM they go faster but its nonsense. the system feels faster because its not rolling so much. A properly set up car with correct camber control will go faster round the corner, be able to ride the apex (because they can still allow each corner to opperate indipendantly) and wont rinse their wallets by paying out for tyres every 30 miles.

Instead of wacking a stiffer ARB on get some adjustable top mounts, do some calcs into how much roll your getting and then adjust the static camber so that wen you cane a 1g corner your camber angle is -1.8 and you will rinse everyone who has simply gone with manufacturers adverts

two great books on suspension are





hope it helps somewhat. sorry for ranting

[anton89]

Oh if people want some calculations to get the ARB stiffness you want i can post the calculations. I wont bother unless people want them as itl be a pain to write up for no reason.

[Motorhole]

I like calculations

[anton89]

calculations are in a seperate post called weight transfer and roll , its in the motorsport section or heres the link

http://www.e30zone.net/modules.php?name ... c&t=197634