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147 Q2 Sport Front ARB Bushes

3K views 25 replies 10 participants last post by  typos1 
#1 ·
Hi Guys,

I am going to replace the front ARB bushes on my Q2 sport. Do I need the "standard" bushes or the GTA ones?

I thought the Q2 had the same ARB as the GTA but when I have enquired to someone selling them I'm told different.

Many Thanks,

Bertie
 
#2 ·
Subscribing. I have the same car, same need for bushes soon, same puzzle. I got as far as measuring the ARB diameter just 60mm behind the droplinks, and it was 22.3mm. Not what I expected as the ARB seems pretty stiff and the car corners quite flat. Standard is 22mm, GTA 24mm. AFAIK Powerflex bushes are only available in 22mm. So: puzzled!
 
#3 ·
This won't help then;
https://ebspares.co.uk/alfa147/suspension.cfm

Depends on ARB condition as I thought some poly bushes were made smaller to compensate for ARB wear when older.

If using poly bushes, I think viscous silicone grease (not the Car Plan stuff) or graphite powder would be the best lubricant to stop the incessant graunch my JTS has from the front ARB poly bushes.
Don't use the copper grease supplied with poly bushes as it is rubbish and will get noisy.
 
#5 · (Edited)
Taking a look on EPER, the GTA ARB is only fitted to the GTA (part number 51754199). All other models had the standard ARB (part number 51754198). It would be best though if you asked an Alfa dealer to confirm, but the copy of EPER I'm looking at is dated 2014 so it should be correct.

You could consider the following:

1) Replace the bushes with Powerflex or another brand of poly bush. As mentioned though they do need to be fitted correctly with lots of grease. This needs topping up on a fairly regular basis to stop the squeaking. I speak from experience.

2) Upgrade to the GTA ARB. This is good idea and will improve handling, but it would be best to replace the rear ARB as well.

3) Just buy another new standard ARB.

I would personally fit the GTA ARBs front and rear and avoid fitting poly bushes.
 
#12 ·
Taking a look on EPER, the GTA ARB is only fitted to the GTA (part number 51754199). All other models had the standard ARB (part number 51754198). It would be best though if you asked an Alfa dealer to confirm, but the copy of EPER I'm looking at is dated 2014 so it should be correct..
I've done a parts lookup for the specific chassis number of my Sport Q2, and it's showing 51754198, the standard ARB. Which also measures 22.0-22.3mm diameter, depending where I use the caliper. I think that's conclusive. I am surprised, as the car has very little roll, but apparently that's entirely due to the lower, stiffer suspension on this model.
 
#9 ·
I had the front suspension of my 159 done with powerflex and they squeaked as I drove out of the garage. They were regreased and lasted a few months.

There was no way of greasing them without dismantling every time they squeaked, and they did squeak.

Got rid soon after, not one of my best decisions, but that is my experience.

Some claim it stiffens the suspension too much and affects other components.
 
#10 ·
I largely completely agree with Spider95. My poly bushes got noisy after about 35-40k miles.

I'd possibly prefer GTA Eibach bars but Eibach will mean poly bushes. I don't think it's essential to update the bars so new standard bars would probably mean the least chance of noise over their lifetime.

If you don't mind a bit of spannering yourself, then update but if you just want it fixed for as long as possible then a new bar assembly (front) which has rubber bushes and brackets makes most sense.
 
#14 ·
I don't really like bluntly correcting someone as it seems like bad manners.
A stiffer front ARB would increase the understeer tendency. A stiffer rear ARB would make it less understeery/ introduce oversteer.

I found that strange when I first learned about it but I figure a GTA front arm even in a JTD just balanced the car more similar to a TS with a standard front bar.
 
#17 ·
A stiffer front ARB would increase the understeer tendency. A stiffer rear ARB would make it less understeery/ introduce oversteer.

I found that strange when I first learned about it
Me too, seems counter-intuitive, but it's correct. It's about the front vs rear distribution of the total lateral weight transfer, and how the relative stiffnesses of the front vs rear ARBs and springs affect this.

To understand this, it's also necessary to understand that while a tyres' grip increases with increased weight (vertical load), its' grip doesn't increase in a linear manner. Because of this, two equally loaded tyres will cumulatively generate more grip than the same two tyres if they are unequally loaded. This is hugely important to understand to get a handle on how cars (are likely to) respond to changes in spring and ARB rates.

The greater the 'roll stiffness' the more 'weight' will laterally transfer from the inside to the outside wheels, and the axle line (i.e. either the front wheel pair or rear wheel pair) with more roll stiffness will transfer more 'weight' from the inside tyre to the outside tyre than the axle line with relatively less roll stiffness. Less weight transfer at an axle line means that both wheels on that axle line are sharing the vertical load more equally than if the weight transfer is greater, which means effectively more 'rubber on the road' (albeit a simplistic concept) at that axle line, so more grip at that axle line (than at the other axle line with relatively more roll stiffness).

Roll stiffness comes from the springs and from the ARBs (and also the suspension geometry, and transiently the damper stiffness, but lets ignore that, to avoid pages and pages of discussion...). Stiffer springs = greater roll stiffness, stiffer ARB = greater roll stiffness. If the ARB were very weak or made from wet spaghetti, how much load could it transfer from the inside wheel to the outside wheel? If it were very thick or made from 'unbendimum', how much load could it transfer?

So, if the front roll stiffness is higher than the rear roll stiffness (because of relatively stiffer front springs, or ARB, or both, it's the total that matters), there will be more lateral weight transfer at the front of the car, from inside front tyre to outside front tyre. This is why increasing the front ARB stiffness will will create an understeering tendency because front grip will be less relative to rear grip, because less lateral rear weight transfer occurs (because there is less roll rear roll stiffness). If the rear roll stiffness were to be relatively higher than the front roll stiffness, then there will be an oversteering tendency, being why fitting a stiffer rear ARB decreases understeer (i.e. 'adds' some degree of oversteer).

'All else being equal' applies here, such as static front to rear weight distribution, suspension geometry, tyres and pressures, etc. etc. etc.

Regards,
John.
 
#18 ·
Yes, and I knew that when I posted the entirely wrong answer :) As said, it's counter-intuitive, especially before coffee, human Easy Start.

Personally I'm reluctant to mess with the existing set up, which is neutral and with little roll. The Sport Q2 has quite old school 'sports' suspension, not supple and quite harsh until you go fast enough, and it's never going to float over bad road surfaces. But it neither understeers nor oversteers. Nor do I get shoulder tyre wear at either end, so it's a case of not fixing what isn't broke. I suspect the previous owner had it tracked parallel instead of the standard slight toe-out at the front. So for me the choice is whether to polybush the existing ARB or replace with new. TBH, the original bushes are only now making a noise at 11yrs old, so I'm probably leaning toward new stock ARB, rather than polybushing.

However although I've done upper and lower wishbones, brakes, driveshaft, droplinks etc I don't think I can face DIY dropping the subframe in the gutter of an urban street. Too much traffic, too many idiots, camber not helpful and a local epidemic of attempts to steal catalysts and DPF's.
 
#19 · (Edited)
You don't actually need to completely drop the subframe to fit the ARB. Just dropping it a bit from the rear of the frame is enough to extract the old ARB.

Certainly in the case of the JTD engine, which is a heavy unit, the GTA ARB is a welcome upgrade. The increased stability and grip is a big plus over the standard ARB. Ok, so the difference is 23mm over 22mm, but it does make a difference. The rear is easy to fit, and this upgrade from 14mm to 16mm is also a big plus.

For the reasonable cost of the GTA ARBs (certainly when compared to the Eibach kit), and the relative ease to fit the ARBs, it's a no brainer. Anyone with at least the JTD engine fitted to the 147/156/GT would be mad not to consider it. Certainly Alfa Romeo considered it worthwhile fitting the GTA ARB to the GT 1.9 JTD Q2 from 2006, together with other JTD CF4 models in certain markets.
 
#21 ·
IMO and IME (in my experience) an increase in roll stiffness, whether at the front or rear end of the car, is likely to improve the responsiveness of the steering and chassis. But after the initial response, as lateral forces rise toward the limit of adhesion, will increasingly affect understeer / oversteer characteristics, depending on which end of the car has had its' roll stiffness increased.

So when it is said that (e.g.) a stiffer front ARB will increase understeer, it really means that understeer will (probably) be increased as substantial weight transfer takes place and the car increasingly approaches it's limit of adhesion, not necessarily meaning that the car will be more 'understeery' at turn in or in the early corner phase.

I suspect that some people may confuse improved steering response - which a stiffer front ARB should create - with a decrease in understeer - which a stiffer front ARB is less likely to create (unless perhaps the front suspension geometry is poor, e.g. MacPherson Strut, in which case a reduction in roll motion may keep the front wheels more 'upright', which may well decrease understeer, despite an increase in front lateral weight transfer).

Regards,
John.
 
#23 ·
I know why I got confused about this now with my 147 Q2 sport. It looks like the GT Q2 had the GTA ARB but not the 147.

You might be right about the Ducati Corse. I had one previously and I'm sure I remember the handling being slightly better than my Q2 sport although the lower profile tyres may also explain it.
 
#25 ·
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