Rear anti-roll bar good idea or bad?

[Martins Stag]

So I have had a Triumpetune rear antiroll bar in my garage for years and I often wonder if it would work on a Rotflexed 1500 Spitfire with a 2.5 lump.
Currently it has a Canleys classice Cv conversion with the orignal thick 1500 front antiroll bar. It all seems to work ok although apparently I should have the thinner front antiroll bar?
I've looked at the possibility of mounting the rear antiroll bar round the wrong way i.e. facing forwards. It looks like it would fit mounted on the chassis and connected to the lowere wishbones via droplinks. It would even clear the exhaust system.
Can anyone tell me if they think this is a bad idea before I progress it further? Or has anyone doen this before?

Martin

[Clive]

First thing is to understand how arb's affect handling.
My understanding is "more" front arb gives more understeer,
More rear arb more oversteer.
In your current setup you could achieve similar results by using the thinner or even no arb.
Personally, I like the idea of keeping things simple. But with a six pot up front, you already have a car that will tend to under steer. Even more so as you are using the thick arb.
Maybe experiment, thin/no front arb before adding bits to the car?

[Tim Bancroft]

Martin,

I had a rear bar on my GT6 for a couple of years back in the late 80s, mine was mounted on chassis extensions to the rear of the chassis. This coupled with a Spitfire 1500 arb made absolutely no difference to the handling of the car. All it did was reduce ground clearance!

I would not bother!

[John Bonnett]

cliftyhanger wrote:

First thing is to understand how arb's affect handling.
My understanding is "more" front arb gives more understeer,
More rear arb more oversteer.
In your current setup you could achieve similar results by using the thinner or even no arb.
Personally, I like the idea of keeping things simple. But with a six pot up front, you already have a car that will tend to under steer. Even more so as you are using the thick arb.
Maybe experiment, thin/no front arb before adding bits to the car?

My understanding too Clive so why is it that some GT6 owners have thicker anti roll bars fitted as well as very high front spring ratings? All without stiffening the rear, or have they? How do they get their cars round a corner?

Having said that, before I realised that the understeer on my GT6 was a function of an inadequate rear spring I tried the car without an arb and it rolled very badly into final oversteer; most unpleasant a bit like my old MGV8.

I hope this provokes a discussion because it is a subject that I am very interested in.

[GT6 M]

I had one fitted, but for any thing other than  a smooth road surface, forget it.

reason, it limits the amount of rear wheel droop by about 2 inches, or mine did.
which  means that the rear end is airbourne, as much as its on the road on a bumpy B road at speed. Which actually limits just hoo fast ye could go, with oot hopping owa,t dyke.
quite scary really, as yer arshe end can feel the situation,
before the  rev counter and speedo  end up going round the clock,!!!

On a smooothe surface, it was good
but it must be used with a front bar,or an add on bar.{ TR6 bars fit with made up links }

the later baris 7/8th, and is 4 times as stiff as the 5/8th bar. { i think, as it goes up by a factor of 4 }

At the moment, I run a fatter bar, and 600LB springs up front,
this gives slight understeer  on trailing throttle,or just going steady,
butt, is very neutral when ye put yer foot doon,

Tyres, and tyre pressure has also got alot,t  dee wid it too,
34-36  im on, not what yer books says, but it works quite well for my likings.

M

[GT6]

My experience of using a rear arb on a rotorflex 2.5 GT6 echo's the above. Car had heavy front springs and 7/8ths front roll bar, not enough clearance for road use, but I liked the change in handling for track use.  

[John Bonnett]

I'm not sure if this is possible but if coil overs could be fitted to the rear this would be an easy way to add stiffness and by selecting the spring rate could be made to balance increased stiffness at the front.

[Martins Stag]

Ok so it looks like Clive is correct. Looks like I need to put the rollbar up for sale!

Thanks for all the input,

Martin