Front anti roll bar diameter?

Hi,

Could someone just confirm for me the diameter of a front anti roll bar on a 156 GTA. I understand that it is a bit larger than standard.

Thanks.....

Edward.

I think the sizes are as follows:-

Front 156 22mm
Front GTA 23 or 24mm
Front Eibach 26mm

Rear 156 14mm
Rear GTA 16mm or 17mm
Rear Eibach 18mm

Thanks for the reply.

That's kind of interesting, as I had heard that the front GTA one was 23mm???

This is pretty critical as I am in the process or ordering parts, would hate to get it wrong.

Does anyone have one they could measure?

....infact just been out and measured mine.....and yes it is 23m.

Thanks Pascs for helping. 1mm seems like a small difference but I guess it all counts.

E.

ummm 23mm...hardly worth the effort over a standard 156 bar - makes the Eibach 26mm look really thick.

I have the Eibach kit on my V6 and it makes a big difference - very flat in the corners without excessive understeer

So...have you just got the front bar fitted?

How difficult a job is it to swap over the bars? The Eibach kit seems quite expensive whenever I look at it, can I ask where you got your one from - as I would like to have one (set) but at about £300 it seems a bit pricey?

I bought mine from Novitec (rebadged Eibach) about 5 years back for my Selespeed - got them at a very good price from local Novitec supplier who went bust very shortly after.

Front bar is a big job and I got the dealer to swap mine from Selespeed to V6 just last month while they did the wishbones. Rear is easier and takes about 1/2hr as long as the drop link aren't seized.

Also my bars didnt come with mounting brackets (only bushes) so had to remove the brackets from the Alfa bars once the bars were off and reuse those.

They are expensive (especially with fitting costs on top) but for a road car they make a worthwhile reduction in roll without making the suspension harder.

If you are fitting a GTA bar then the cost difference might not be so big but its a lot of cash that for sure.

Of course if you sold me your GTA interior then you'd have money to spend

BTW the Alfa 3.2 GT V6 has a 17mm one, slightly stiffer than the GTA.
Edward Have a look at posts from me about the Whiteline rear ARB.
I have the 20mm up from 16mm GTA one.
The eibach one is 18mm.

FWIW My personal view is that I really don't think you should increase the size of your front ARB, it will just add understeer..

On the otherhand whack up the size of your rear ARB.
So my 20mm whiteline one is 144% stiffer than oem, i.e. 2.44 times the rate of the oem bar.. ITs a noticable difference
No drawbacks.

If this is for track use, get the rosejointed droplink kit too, I have pics in the thread. Only drawback is that they squeak slighly occasionally as indicated in their blurb.

For track use, the whiteline rear ARB on stiffest setting (its 3-way adjustable) took 2 seconds off my lap time.
Understeer was huuuuugely reduced and the car was waaay more responsive in turn-in but also all the way through the corner.


Its the relative roll stiffness front to rear (including various aspects such as springs and ARB's) that determine how much understeer you have.
The stiffer the rear the less understeer..
Especially since there isn't much we can do to increase front end grip, unless we source big neg camber wishbones from N-technology or something..

The front still hardly rolls at all (my car is lowered 30mm in track season), and I defintely will not be increasing its size, possibly at some point even experimenting with disabling it since I have much stiffer springs than standard on the fornt.

I will shortly be putting way stiffer springs on the rear, probably twice OEM, and I reckon this would take another 1 or 2 seconds off my lap time, still keeping the car streetable though.

Cheers,
TB

If you have stiff front springs then there is less requirement for a stiff front bar since you have already significantly increased the stiffness of the front.

But for a road car with softer springs a stiffer front roll bar works very well especially when matched to stiffer rear bar. My car definitely understeers less than before and can be provoked into oversteer on tight turns.

The very stiff rear bar you have fitted will equalise the front stiffness by increasing oversteer / decreasing understeer.

I assume once you have the stiff rear springs fitted you will need to soften the rear bar to reduce oversteer

TB,

Sounds interesting, and I do remember the threads about the rear Whiteline bar and will go back and read it again.

The whole reason for the question is that the bushes have gone on the front ARB and have bought a set of Superflex ones to replace. But I hear it is a bit of a job doing the bushes so thought I would investigate other (track related perhaps) solutions at the same time. I will look up the Whiteline ones as from memory you can buy the parts (front & back) separately. Interesting Superflex only have the 22 dia bushes but are going to get me a set of 23 dia to go onto the GTA.

Having read one of the websites today, possibly even Whiteline related, their clear suggestion of beefing up the rear on a front wheel drive car was promoted.

I think the first step is to get rid of the annoying clonking first from the front ARB and then go and investigate a Whiteline rear. That way I can leave the front as standard and experiment with the rear for starters.

Have to wait 10 days for the Supreflex bushes now.....boring!

Pascs,

If you would like to buy the interior from my car you are more than welcome. The cash would be handy to start to buy the necessary anti-roll bars and some suspension from either KW or Intrax.

I must start getting the track car underway soon and the interior is the first part to go.

I haven't had any issues with oversteer to date and want to change the handling bias substantially towords oversteer.
Given the big lump of a v6 up front, I will actually want to increase the overall rear stiffness and get more prolonged tail movement on hairpins and longer corners (when provoked).
I am also going to soften my front springs slightly, 10kg is too stiff in retrospect, the car is hugely stable but I don't need that now.

I have been following a mates development of a track car.
He started out with similar springs to an OEM GTA but on a much lighter car so effectively stiffer.
Over the last two years he has gradually stiffened the rear and moved to about 13Kg springs at the rear, of a 1000Kg car.
(850Kg race cars use 17kg or so)

As I was in every incarnation of my mates car on track I could see the gradual changes in handling towords nice oversteer.
This mates car is a dream to drive with a genuinely moveable rear, much more so than mine.
The thing is that FWD is so easy to catch oversteer in, and understeer robs so much time why not make the car more fun?

Right now I haven't ever felt that my car oversteers to much, except maybe on my earliest wet track days
Its still very friendly handling, I'm just going to move it towords a "sharper" trackday but still daily driver as opposed to the all rounder it is at the moment..

When its not my daily driver I might go a little radical..

I would love to be able to change the front neg camber on my car, but that doesn't seem possible

Cheers,
TB

Originally Posted by Pascs

I assume once you have the stiff rear springs fitted you will need to soften the rear bar to reduce oversteer

TB,

I used to be able to do it on the 33, by drilling 3 of the 4 mounting holes where the strut meets the hubs, but it is a much, much simpler car than the 156. You could then use a camber gauge and dial in whatever camber you wanted.

The joys of 33 ownership.

Yes things are simpler with mcpherson struts.

But then again ye ole double wishbone setup works darn well with a front LSD to transmit silly amounts of power.

Camber is increased slightly when lowered 30mm, but not hugely.
BTW Its nice that my geometry stays pretty much in whack for that, so no need for retracking just for lowering.
Any time I have had it checked its still okay.

Cheers,
TB

TB,

it might be worth mentioning to Edward that you (and I) are running with additional negtive camber for the rear. I've always felt my own car had a lively enough rear with the Eibach ARB, and was certainly not looking for more movement (not on the Ring anyway) After adding some camber to the rear very recently, (now just a tad over 2 degrees negative) the rear again feels solidly planted, but havnt really tested the car if it now understeers more. If it does, then I too might be looking to upgrade the rear ATB yet again.. If so, then i guess it's time to look at the front spring rate... ummm.. where does it all end..

Anyway, next weekend I'm off to the Ring and will hopefully get a feel for what the Camber has done to the car.

I'll be looking for added understeer just after T13 /Hatzenbach, in Aremberg, Adenauer Forst and Bergwerk.

For better grip at the rear through Kallenhard, Miss Hit Miss, Hohe Acht and Galgenkopf.

Yes - good point about the mcpherson struts! Forgot for just a second that I now have to think of double wishbones.

It is good to know the camber is good when lowering, as with the 33 I used to wear tyres on the inside quite alot, but then I was running quite a lot of camber and toe in.

Remind me - where did you get your Whiteline rear ARB from, I will be in the market for one before too long.

Regards,

E.

Peter,

Can I ask how you achieved the negative camber at the rear?

E.

It's pretty basic, you just elongate the two upper holes. (forgive the simple graphics) 4-5mm should equate to about 2 degrees providing you are using a bit lower suspension then stock GTA.

Peter,

Understood, much the similar process as used on the front of a 33 with it four bolts, thanks for letting me know. Good photo by the way.

Cheers.

E.

Ed, Alfisti have the Eibach kit on special offer at Euro399 plus shipping - still pretty expensive though

Originally Posted by Peter K

After adding some camber to the rear very recently, (now just a tad over 2 degrees negative) the rear again feels solidly planted, but havnt really tested the car if it now understeers more. If it does, then I too might be looking to upgrade the rear ATB yet again..

This is really tricky: you add camber, gain rear traction by that => more understeer, you counter that by adding a stiffer rear ARB => you get less traction at the rear again => more oversteer.

Have you really accompished anything by this, or are you back at square 1 again (i.e. before the above mods)? Maybe you guys with more IRL track experience than me can explain the benfit?

Benefit is more speed..

I got mine from www.whiteline.com.au.

Apparently there is a UK distributer though, which somebody mentioned in a recent post.
Given they are only made to order by the Aussies, it probably wouldn't save time, but might save on shipping to use the UK crowd.
(don't have their name, but should be findable with a search for whiteline, importer, UK or some such)

Originally Posted by edward <