Twisted anti roll bar

[Johno]

My old car which is undergoing restoring has about a 3/4" twist on the anti roll bar. I got a second hand one and lo, ... It's the same. I've heard the old ones all have it but new replacements are straight. Does this twist make a great deal of difference if the old ones do have it? I would think it almost impossible to straighten. Any oracles out there?

Johno

[Peter Truman]

Is it a Vitesse my Mk2 was the same I had it straightened with 1/4in the other way to allow for any subsequent set.

It was done by a local spring repair co. Here in Melb put in his elect furnace and treated, it’s performing well.

I think I read somewhere where the Triumph smaller dia ARB were susceptible to twist but the later larger dia as fitted to Spits were OK.

Ironically the heavier Vitesse had the thinner ARB, it’s all in the suspension set up & reqd handling!

[Clive]

5 hours ago, Peter Truman said:

 

I think I read somewhere where the Triumph smaller dia ARB were susceptible to twist but the later larger dia as fitted to Spits were OK.

Ironically the heavier Vitesse had the thinner ARB, it’s all in the suspension set up & reqd handling!

The thicker ARB was not used on any car during vitesse production. And only introduced to compensate for the lack of roll resistance from th elater spit (and GT6) swingspring. And as a thicker ARB will increse understeer, it is not at all desirable on a vitesse. It will only make things worse. 

Back to the OP, I have never seen a straight thin ARB, and I am certain back in the early 90's I saw a trader selling NOS ARBs, which all had the twist. My memory could be playing tricks, but I have never worried about the twist. I would happily use one on my cars. So fret not. 

[Pete Lewis]

to add a twist by design is a very odd way to bias the roll resistance  its normal to pack or change the spring load if the car has any camber tendance to need 

some uplifting   or bias 

one wonders why a twist was used to correct  just what ????

i used a thickun and courier spring and roundabouts were on rails  so i differ on the understeer problems I  might drive  fast but dont have any racing experience

you must check out the basic toe in front and rear if you make any changes  to ride conditions 

Pete

[Johno]

It's a spitfire 1300 mk iv. So it's the thick arb. No reason not to use it then. I will search for a local spring place though, great idea.

Cheers johno

[Casper]

Quote

Back to the OP, I have never seen a straight thin ARB, and I am certain back in the early 90's I saw a trader selling NOS ARBs, which all had the twist. My memory could be playing tricks, but I have never worried about the twist. I would happily use one on my cars. So fret not. 

I recall John Kipping on another forum saying  "They are all like that".

Good enough for me.

C. 

[Clive]

26 minutes ago, Johno said:

It's a spitfire 1300 mk iv. So it's the thick arb. No reason not to use it then. I will search for a local spring place though, great idea.

Cheers johno

Probably better to find a flat used one? I am sure they are usually OK

[Johno]

I think thats.the point the old ones all appear to be twisted or its £80 for a new one.

[Rutty]

I know in theory a twisted ARB could make a difference in the front ride height left to right but in practice does it.

My Vitesse sites about 2.5cm higher at the front  on the left.

I have just replaced the shocks as it had odd ones fitted on the front at some point in its past and one of the shocks had just started to leak. But in doing this it has made me wonder why it sits at different heights.

One of my thoughts is has it had a spring replaced on one side when the single shock was replaced.  I did check the spring free height and they are the same but am wondering if one of them is a heavy duty spring. I am going to swap the springs left to right to see if the problem moves or stays to rule this out but I did also notice the ARB had a twist.

Could a twisted ARB cause this much difference in ride height what are peoples thoughts.

Mark

[Clive]

7 minutes ago, Rutty said:

I know in theory a twisted ARB could make a difference in the front ride height left to right but in practice does it.

My Vitesse sites about 2.5cm higher at the front  on the left.

I have just replaced the shocks as it had odd ones fitted on the front at some point in its past and one of the shocks had just started to leak. But in doing this it has made me wonder why it sits at different heights.

One of my thoughts is has it had a spring replaced on one side when the single shock was replaced.  I did check the spring free height and they are the same but am wondering if one of them is a heavy duty spring. I am going to swap the springs left to right to see if the problem moves or stays to rule this out but I did also notice the ARB had a twist.

Could a twisted ARB cause this much difference in ride height what are peoples thoughts.

Mark

You should be able to disconnect one end ofthe arb and see if that changes anything?

[NonMember]

12 minutes ago, Rutty said:

Could a twisted ARB cause this much difference in ride height

My Spitfire sits quite a bit higher on the left. It has a (rather weak) swing spring on the back but still a thin ARB. I've changed the front springs and shocks, and swapped them across, and the lean has remained through all this. One of these days I'll try Clive's suggestion to positively confirm it.

[Peter Truman]

On my Vitesse Mk2 the straightened ARB gave me an extra 3/16in increase on the drivers side. I think from memory the drivers side was down 3/4in, but changing the springs and GAZ shocks pulled  9/16in increase, before restoring the ARB.

[Pete Lewis]

if you are ever investigating a lean you need to drop a arb link to see if thats the cause

then jack in the front in the centre and next do a jack at the rear  to see which end of the car has the lean 

i just dont get the theme behind adding a arb twist ,goes against all i was ever taught on suspension needs 

it obviouslt adds some bias but why ??

pete

 

[Colin Lindsay]

43 minutes ago, Pete Lewis said:

if you are ever investigating a lean you need to drop a arb link to see if thats the cause

then jack in the front in the centre and next do a jack at the rear  to see which end of the car has the lean 

i just dont get the theme behind adding a arb twist ,goes against all i was ever taught on suspension needs 

it obviouslt adds some bias but why ??

pete

 

Same puzzling question as to why some cars have a spacer above the shock absorber on one side of the suspension turret, but not the other...

[Rutty]

2 hours ago, clive said:

You should be able to disconnect one end ofthe arb and see if that changes anything?

I didn't think of that. I will give it a try. Thanks Clive

[JohnD]

The one sided spring spacer was a US dealer option on GT6s, never available in the UK.     It is sometimes said to be needed because the cars were LHD and the GT6 has a fuel tank very much on the left side of the car., so that weight  distribution made it necessary.     I'm afraid that in the past, I've attributed it instead to the dealers noting that their customer was, er, shall we say weight-challenged?   They added the spacer before delivery to avoid any complaints about uneven suspension.   That, of course, is a vicious calumny, and I would never make it now.

The twisted ARB has also been alleged to have been original, factory fitted, for similar reasons, as most GT6s and Spitfires would have been driven at the limit by a solo driver, with weight distribution problem as a result.       I have no  evidence on this, and it seems unlikely to me.

John

 

 

[Pete Lewis]

the spacer is the correct way 

putting a set in the ARB is i guess a cheaper option   saves the cost of a spacer  thats if the offset in the ARB actually works to 

bias the ride height  so why with a swinger was it flat ..........  this is a good conundrum 

Pete

[Johno]

Glad Ive got you all thinking.