anti roll bar confusion

[Spiti1976]

In a lot of posts and even in the tuning manual from G.Thomas it was stated: "don't put a bigger front anti roll bar on a Vitesse or a GT6" or it will understeer terribly then.

But I found reports about Vitesses and GT6 with a twin ARB setup (in the Courier.. Beastie)

I've installed a stiffer rear spring, stiffer front spring, adjustable dampers all around and a rear ARB on my Vitesse Mk2, but she is still rolling a bit too much for me.
Especially when driving slalom.  :o

Anyone has changed the front ARB with a similar setup? What is the secret behind the twin setup?

[Clive]

Welcome.

lets start with the basics. Which rear spring and which front springs have you fitted?
fitting harder still front springs may achieve what you wish....I know some on here are running 600lb+

[cammmy]

It's the balance between the two. If you have a stiffer front ARB without one to match in the rear, as the rear of the car leans the thicker front bar will end up lifting the inside front wheel. The same reason that a lot of hot hatches cock a rear wheel.

At least that's how it was explained to me

[heraldcoupe]

When ST fitted a 512lb rear spring to the Courier Van, they did away with the front ARB altogether. Front springs were moderately uprated at the same time.

Six cylinder cars will behave differently, but don't assume that stiffening one end automatically requires the same at the other end.
Ironically, given it's intended purpose, the Courier is the best handling of all (standard) four cylinder cars.

Cheers,
Bill.

[Spiti1976]

Well,
I try to explain my setup a bit more in detail.

I have unknown springs at the front but based on the wire diameter and the number of windings I assume somewhat 350 lb/inch (they are definitely not standard)
I fitted a 385lb/inch leaf spring from an GT6. It is a swing spring, but I bolted the leafs together, though no swing anymore.
The car has 1degree negative chamber at the front and 3 degree neg at the rear. It sits 1" lower.
I added a anti roll bar wit 1/2" diameter at the rear.

The car tends to oversteer now a bit, with less roll. It is quite controllable at the edge ( in dry condition, well its a convertible.... I drive only fast if it is dry) ;)

It feels as if the car rolls now mostly at the front.

I intended to set up the car more like a modern car (firm but not stiff springs and stiff anti roll bars) but I am not sure if this will work in spite of the weight distribution.

What's the solution? stiffer front springs, a ARB from the 1500 Spit or a leaf spring from the Courier ( hopefully I will find one at Beaulieu this weekend, they are a bit rare..... especially here in germany  :()

By the way... thanks for the replies
Alex

[Clive]

I would suggest stronger front springs. My vitesse ran 440lb fronts and a swing spring rear. I would probably go even stronger than that, maybe 600lb if the car is used in anger. Mine was an everyday car (as in used for work every day for many many years)

[JohnD]

SofS (race Vitesse) runs 600lb front springs, but has a rear spring that is not OE and is probably stiffer than a Courier spring. I don't know how stiff it is.  
It also has a 1" front ARB., and can still lift the inside rear wheel.

I ran a rear ARB on Suilverback for a while.  It gave me a problem in qualifying once, I took it off and in the race and thereafter could feel no difference!

It is important to match the front and rear springing, to keep them in balance, so 3-400+ frotns MUST be accompanied by a stiffer rear.

Always make sure that your front ARB is running as smoothly as possible.  The OE rubber drop links will by now be sloppy - install proper spherical joint links.  McGill Motorsport (no connection, just a satisfied customer) have a comprehensive list of sizes and lengths: http://www.mcgillmotorsport.com/advanced_search_result.php?keywords=drop+links&inc_subcat=1

John

[MrSpeedy]

I've fitted lower 440lb springs on the front of my Vitesse, along with adjustable Gaz shocks. It's also lowered about 3" at the front and fitted with a 7/8" Spitfire front ARB. This was also fitted with spherical joint drop links instead of the original type rubber ones.

The rear has a 1" lowering block along with a new (well, it was new 4 years ago) standard rear spring and adjustable Spax shocks.

Fitted with wide (7" & 8") wheels it corners pretty well imo with little understeer and certainly no excessive body roll

[JohnD]

Intersting, MrSpeedy.
It's a feature of swing axles, and even Rotaflex, that the camber angle changes a lot.
Thus the tyre is presented to the road surface at a much varied angle, when adhesion is best with the tyre flat on the road.
That's the rationale for a very strong rear spring, so that it only moves a little and camber will vary little also.
But you still need more negative camber than a standard car can provide, which is why the spring lifting block helps - it puts the suspension geometry into a different part, a more camber negative part, of the envelope.
But even that is of limited effect, because very wide treads assume a greater angle on the road with camber change, because those tyres have stiffer side walls.
Moreover, such a wide tread sits on a narrow wheel with the side walls pointing inwards, making the tyre less stable on the wheel (think pyramid on its point)  And wider wheels 6 or 7 'J' are just too wide for our arches without major mods.
Well done if you have improved your car with such wide tread!  What 'J' are your wheels?
John

[Hughbert]

On my GT6 I have 600lbs springs with adjustable Spaxs and a 1inch ARB fitted on the front with a 3/4 inch lowering block on the rear with gas shocks plus 15inch wheels with 205/50 on the rear and 195/50 on the front. The car is a wee bit pointy but I prefer my car not to under steer I am happy with the way it handles. I did have to put 5mm wheel spacers on the rear and front to get the right offset which prevents the wheels rubbing slightly on the various suspension bits. I have no problems with the tires rubbing on any part of the wheel arches.  

[MrSpeedy]

To be honest John (no pun intended), I'm suprised how well it feels considering all the 'horror stories' surrounding the small chassis rear ends. (Unless I'm just not trying hard enough  :-/)

I guess you would say it's had 'major mods' to accomodate the wheels and tyres ;)



And a slightly long shot example of cornering. If you know Prescott, you'll know the camber change on that corner ;)

[esxefi]

7433 wrote:

Well,
I try to explain my setup a bit more in detail.

I have unknown springs at the front but based on the wire diameter and the number of windings I assume somewhat 350 lb/inch (they are definitely not standard)
I fitted a 385lb/inch leaf spring from an GT6. It is a swing spring, but I bolted the leafs together, though no swing anymore.
The car has 1degree negative chamber at the front and 3 degree neg at the rear. It sits 1" lower.
I added a anti roll bar wit 1/2" diameter at the rear.

The car tends to oversteer now a bit, with less roll. It is quite controllable at the edge ( in dry condition, well its a convertible.... I drive only fast if it is dry) ;)

It feels as if the car rolls now mostly at the front.

I intended to set up the car more like a modern car (firm but not stiff springs and stiff anti roll bars) but I am not sure if this will work in spite of the weight distribution.

What's the solution? stiffer front springs, a ARB from the 1500 Spit or a leaf spring from the Courier ( hopefully I will find one at Beaulieu this weekend, they are a bit rare..... especially here in germany  :()

By the way... thanks for the replies
Alex

what tyre section are you using?

stiffening up the suspension will only high light the next weak link.you may need to go to a lower profile to take advantage of what you have done already.
it's generally considered that the swing spring should be left alone to do what it was designed to do and tune the handling by changing the front settings.don't forget the original settings were configured using a high side wall tyre to compromise for comfort and handling. :)

[Hughbert]

5999 wrote:

To be honest John (no pun intended), I'm suprised how well it feels considering all the 'horror stories' surrounding the small chassis rear ends. (Unless I'm just not trying hard enough  :-/)

I guess you would say it's had 'major mods' to accomodate the wheels and tyres ;)



And a slightly long shot example of cornering. If you know Prescott, you'll know the camber change on that corner ;)

Wow nice car great to see someone with another take on a modified Vitesse too ;)

[JohnD]

Indeed, a very nive Vitesse!
Well done!

I'm not surprised you need arch extensions with those dustbins for wheels, but v.tastefully done.

John

[MrSpeedy]

Thanks fellas. I like to do things a little differently ;) lol