What diameter are 147 GTA ARBs?

Hi

Can anyone tell me the diameter of 147 GTA ARBs front and rear?

Cheers

Sean

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

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

So you knew the answers??

Originally Posted by OperationAlfa

So you knew the answers??

Nope, but someone on another forum did and I wanted them somewhere easily accessible

Nice one.

RE Rear ARB diameter:

I'm certain the rear 156 GTA ARBs are 16mm,
I'm pretty sure the 147 GTA ones are also 16mm.

However the 3.2v6 GT has 17mm ones.

Eibachs (same one for all 156 variants) are 18mm.

The excellent Whiteline 147 GTA extra heavy duty adjustables are 20mm and also fit the 156 GTA.
(They also do 18mm as well)

Cheers,
TB

Originally Posted by GhostyDog

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

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

The Q2 147 rear one should be 18mm as well.

On my 147 JTD 8v front one is 24mm as well.

Yup 147GTA rear is 16mm so is the 147Q2, the front is probably 24mm not sure but besides that the GTA has additional stiffening plates on the subframe over a standard 147.

V6/Q2 rear bar is 17mm on GT, 14mm on stock models.

As 156/147 and GT are all variants of each other it wouldn't suprise me if you could buy any size bits you want from any model and fit it.

Just swapping the rear bar provides a decent chnage in attitude, some might not like the arse attitude out though when the loaded tyre lets go, fortunately the ESP can deal when you make a muppet mistake I think quite a few people have fitted GTA bars to twinsparks, I seem to remember posts on the subject, pascs maybe?

Just out interest when compare aftermarket ARB to Alfa's ARB. Is there any metal tensile stress different other than just thickness comparsion?

I'm sure there could be some slight variance but I don't think it would be as hugely significant as it might first appear.
The equation which relates the effective stiffness of two ARBs of the same material shows the diameter to the power of 4 as the most dominating factor.
So even if one thinner bar was made from 10% stronger material it would have less effect than having a 2mm wider diameter of the weaker material.

I don't have the equation handy at the moment, but did post it before and a link to a matrix comparing ARB thicknesses and the effective %stiffness upgrade when moving from one radius to another.

The ARB stiffness Matrix came from the whiteline.com.au website, its in their pdf catalog..

Beside this I doubt if the aftermarket ones would be made from weaker material than the OEM ones.

I can confirm that the 20mm Whitleline rear GTA ARB gave a stonkingly good transformation in handling!

Cheers,
TB

Originally Posted by ABYSS

Just out interest when compare aftermarket ARB to Alfa's ARB. Is there any metal tensile stress different other than just thickness comparsion?

Originally Posted by sandys

Yup 147GTA rear is 16mm so is the 147Q2, the front is probably 24mm not sure but besides that the GTA has additional stiffening plates on the subframe over a standard 147.

V6/Q2 rear bar is 17mm on GT, 14mm on stock models.

I'd go along with that. If the 156 workshop manual is anything to go by;

17mm rear, same ARB as GT V6/Q2.

23mm front diameter though, same on both GTA's, Q2's & GT V6.


Guess the 147 rear ARB's are shaped to fit around the floor because of the shorter wheelbase is the reason they are different to the 156/GT's.

Is the 147 GTA/Q2's definitely 16mm?

numbers are Based on info from the manual, I don't think theres much difference in bars hit points between models, I'm pretty sure it was a 156GTA Eibach bar fitted to my 147GTA, I wouldn't quote me on that, probably are different, I don't know as I didn't do it and it was about 4 years ago so details are hazy, i'm very much the pay someone a wad of dosh to so something type than get my hands dirty , worked well, though I would be a bit apprehensive about a thicker bar with stiffer springs on the 147 as mine was pretty much stock I just wanted to change the understeer tendency but with the bar on a wet slippery roundabout perhaps aslight bump the 147 would just flick out and around even with the soft springs, perhaps the culprit was the S02s though, never as good as folklore would suggest they were IMO.

Thanks for all the extra info, I'm planning on putting 147 GTA ARB on the front of my car to replace the failing standard one.

What sort of affect can I expect leaving the rear standard? Or should I be looking to change the rear one at the same time?

Thanks.

P.S. Values I posted in second post were given by someone on another forum

Discussion on my upgrade route is here

http://www.alfaowner.com/Forum/alfa-...-worth-it.html

Cheers Sandy, doesn't say in the 147 manual I have. Good to know it made a difference, hopefully more than the tyres (Have an 18 on order to replace a 20mm)

So 16 & 23mm it is... we think. Go for both I say GD, should make a nice upgrade!

The size are based on info from eper, the torsion bar itself does not have a size but the retaining clips have 14mm and 16mm on the 147 page and tells you what model they are for. went through all the parts when retrofitting Q2 to my JTD.

GD do the rear thats where it needs it and its all about balance.

Originally Posted by sandys

GD do the rear thats where it needs it and its all about balance.

So are you saying I should stick with standard for the front and GTA for the rear?

My front one is buggered and needs replacing anyway...

Could get a set of these for the front, then the money you save toward a rear ARB

Do both as yours is a non GTA and the front needs done anyway.

The bars are used to tune the handling bias so you adjust them to get what you want out of the car, I'm sure someone more technically knowledgeable can pipe in here but a simple rule of thumb is something like

stiffer front = more understeer
stiffer rear = more oversteer

Obviously there are exceptions to that as less roll leads to less geometry change in the roll and so better contact with the road so if you car has a jelly front end then it may help to a point but ultimately the bars are about balance and you should do both really, going with a stiffer percentage increase on the rear bar in relation to stock than the front to move the 147 handling bias to give more neutral handling.

Thanks guys, think i'll get both GTA Bars, had a roundabout quote of

approx £107 for the front
approx £103 for the rear

Which is about 80 squid cheaper than the Eibach setup and from what I've read the Eibach is very much track focused and I only get on track maybe once a year at the moment

Good work

I didnt find the Eibachs to make the huge difference that "track focused" would suggest.....anyway good luck with the GTA ARBs if you go that way

Originally Posted by Pascs

I didnt find the Eibachs to make the huge difference that "track focused" would suggest.....anyway good luck with the GTA ARBs if you go that way

Cheers Pascs, can't wait now I've finally made my mind up, wont get done till the 22nd though

nearly 3 weeks to wait