Anti Roll Bars - Nerd Alert

[Fury1630]

Someone enlighten me.

I'm obviously not a suspension designer, but I do understand some geometry.
I fully understand why my Zafira has ARBs, it's a tall car & the suspension design is compromised by the need maximise internal volume. I can also understand why bigger anti-roll bars make tin-tops handle better - most have suspension designed to prioritise comfort over performance (huge castor angles to work with power steering for example), flattening the cornering prevents the suspension going into non-ideal areas of the geometry envelope.

What I can't understand is what ARBs would do for me on the Fury. The Fury is some idealised suspension with a chassis drawn between the ends & just enough space for a human shaped hole. It has unequal length wishbones, so as the car leans into a corner, the wheel maintains the correct angle to the road, a little pre-set camber allows for tyre deformation under side load. This much I understand.

Introduce ARBs & the car won't roll so much, the unequal wishbones still maintain the correct angle of wheel to road, but the ARB is trying to lift the inside wheel - which I know isn't doing much under hard cornering, but it's still less rubber on the road. There's also more unsprung weight, which is never a good thing. Hitting a pot hole with one wheel affects the other wheel on the same axle & that doesn't seem like a good thing either.

So it seems to me that all the ARB is doing is making a flatter ride for the occupants - which frankly I don't care about, one of the most enjoyable cars I ever drove was a 2CV.

Like I said - enlighten me because I'm confused.

[Dick]

[Nick Slater]

Dicks confused also, he's just put laughing faces on a real meaningful question.

[Matth93]

We found on the stockrods that it actually handled better without a front arb as it helped to keep the inside wheel on the ground. We used to run one on the back but we were running front wheel drive at the time and the inside back wheel would be off the ground in the corner. Most of our weight was on the front and we were set up for turning one way only so the car when parked would lean quite a lot the inside rear wheel didn't really do much.

[DJ.]

I think McLaren think much the same as you, as there more expensive models have a very complicated system designed to avoid the drawbacks you described.

2CVs can be made to corner very quickly, but the passengers do complain. My Mum gave me a good telling off when I got mine onto 3 wheels.

The original Lotus Elan does roll considerably as well, and I've never heard any complaints about that cars handling. It does have a front anti-roll bar, but it is thin.

The major advantage of an anti-roll bar that I can see is that by reducing the body movement, the car settles back more quickly which is an advantage in an S bend situation. For a road car, the reduced grip on a bumpy corner would out weigh this on most UK surfaces in my opinion.

[steve m]

Were do we buy Arb's from, as I MUST have one, and soon

[Fury1630]

2CVs can be made to corner very quickly, but the passengers do complain. My Mum gave me a good telling off when I got mine onto 3 wheels.

The original Lotus Elan does roll considerably as well, and I've never heard any complaints about that cars handling. It does have a front anti-roll bar, but it is thin.

Which is what I've always thought:-
1/ Handling & road holding are two completely separate things, the 2CV has good road holding, rubbish handing.

2/ Anti Roll Bars are there to tune out inadequacies in a suspension system.

But as I say, I've never read a suspension theory book, these opinions come only from running the Fury & messing with Radio Control racers many MANY years ago.

[Crunchie Gears]

I will start with the thought that many suspension designers are not great lovers of arbs as they argue that you can get similar effects without using them.

IMO what you have not looked at Tony is roll centres and the difference between the need for bump control and cornering. If you consider the fury currently the roll centre is quite high compared to many of the cars on Friday.

The next thing to consider is that you need more Spring pressure under cornering that you do under bump. There are a number of ways you can get this. For example Iave modified the suspension on my Morgan Brooklands by fitting rising rate springs which allow the car to have compliant suspension on bump and then allows the car to roll onto harder Spring rates under cornering.

Rising rate does not do what an arb does. If you consider what is happening with a stiff arb regarding the roll centre, it is moving the roll centre towards the contact patch of the outside tyre and the stiffer it is the nearer it moves. This increases the moment of the cars weight applied to the outside tyre. If you have sufficient grip this works well and increases corner speeds.

If you have limited grip on the outside tyre, for example if it is wet, then race cars would reduce or even remove arb as arbs reduce the work done by the inside tyre and spreading the work in poorer grip situation works better.

I hope this helps.

[Fury1630]

Yes that helps, cheers. Roll centres always been a bit of a mystery to me - never been interested enough to read up on it.

So the bottom line then is what Jeff said, not for a road car, but possibly for a regular track car.

Understanding improved.

[jeffw]

Or more accurately it will work well on a road car but is not essential but it you track it regularly and want to get the most out of it you'll fit an front ARB. Rear ARB is required if you change the stock bushes for rose joints on a live axle car as you have removed all resistance to roll, they are recommended for IRS rear if you want to get the most out of it.