Alfa Romeo Forum banner

1 - 20 of 26 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #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
 

·
Registered
Joined
·
1,901 Posts
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!
 

·
Registered
Joined
·
2,393 Posts
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.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #4
But is the GTA ARB the same as on the Q2?

If I can answer this I at least know what to buy.

I thought I saw somewhere listed that they were the same but maybe I dreamed it.

TBH if it is different I'll probably upgrade,
 

·
Registered
Joined
·
7,453 Posts
But is the GTA ARB the same as on the Q2?

If I can answer this I at least know what to buy.

I thought I saw somewhere listed that they were the same but maybe I dreamed it.

TBH if it is different I'll probably upgrade,
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.
 

·
Registered
Joined
·
2,999 Posts
I would personally fit the GTA ARBs front and rear and avoid fitting poly bushes.
New question.....

Are there any negatives regarding poly bushes?

Are they creaky noisy?

Ta,

Andrew
If the grease dries out they can get creaky and noisy, but the creaking and noise isn't doing any damage. Polybushes should last for the life of the car though, they won't wear like rubber bushes.

I've had a set of GTA bars on for about 2 years now. Rear bar fitted with Strongflex bushes, front bar with Powerflex. No creaking or noise from mine yet.
 

·
Registered
Joined
·
7,453 Posts
New question.....

Are there any negatives regarding poly bushes?

Are they creaky noisy?

Ta,

Andrew
They can go creaky after a while. I have Powerflex bushes on the front GTA bar and they were 're-lubricated' six months ago due to this problem, after being fitted for 3 years.

If you buy a new GTA ARB use the new bushes as they will last for some time before needing replacing.

Either way you will notice a significant improvement in handling with GTA ARBs.
 

·
Registered
Joined
·
12,526 Posts
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.
 

·
Registered
Joined
·
2,393 Posts
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.
 

·
Registered
Joined
·
1,901 Posts
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.
 

·
Registered
Joined
·
2,393 Posts
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.
 

·
Registered
Joined
·
609 Posts
Re this, maybe not so much in a daily driver, but in a track car, would you introduce some more to angle to counteract this? I can never remember which way toe-in and toe-out is but, should it look a bit this when observing from the rear of the car.....


/ \
 

·
Registered
Joined
·
427 Posts
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.
 

·
Registered
Joined
·
1,901 Posts
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.
 

·
Registered
Joined
·
7,453 Posts
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.
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.
 

·
Registered
Joined
·
427 Posts
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.
My TS 147 has a GTA front ARB (fitted by previous owner). The stock 14mm rear ARB might as well be made from coat hanger wire for all that it actually does (I couldn't detect any difference when it was removed and there was no rear ARB at all for a few days). The 16mm rear ARB must be an improvement, but I doubt it could be a big one. The car now has a 20mm rear ARB (a modified front ARB originally from a Holden Rodeo light truck), which was a huge improvement.

The car corners much more flatly, and the chassis is far more responsive (than with the 14mm ARB), but there is still some significant body roll. I suspect much of this roll is because both front and rear ARBs are still located in relatively soft rubber bushes. With very stiff ARBs, the rubber bushes become the softest part of the 'system', at least initially until the compliance in the bushes diminishes under load.

So, what I think occurs is that as load begins to be imparted into the ARB, the stiff ARB itself hardly deflects at all (doesn't 'see' all of the weight transfer load, due to initial bushing compliance), but the bushes do deflect significantly (i.e. the rubber compresses). The bushes are effectively little rubber springs, but are very non linear, i.e. at first they compress quite easily but after a small amount of initial but significant compression suddenly their 'rate' rises very sharply. At this point the ARB effectively becomes the stiffest part of the ARB 'system'. Only after the soft bushes become 'harder' (due to the rubber reaching the limit of its' elasticity / compliance) does the ARB start to 'see' all of the load and to resist deflection to the ARBs full capacity.

So according to this theory, I think my cars' initial body roll is largely a product of softness in the rubber bushes (probably), and not the (stiff) ARBs themselves. I expect that fitting stiff ARB bushes would be likely to make a noticable difference to both the degree of initial body roll and the responsiveness of the chassis, but suspect this would be a less significant affect if the ARBs themselves were a lot less stiff.

With a soft ARB I suspect this affect is likely to be less distinct, i.e. the softness of the bushes will 'blend' more seamlessly into the softness of the ARB. A soft ARB will initially start to deflect more or less simultaneously as the bushes deflect, and any 'spike' in the ARB 'system' stiffness will be more 'blurred'. A very soft ARB (such a 14mm ARB?) may even start to deflect significantly before the rubber bushes do...

So I suspect that fitting stiff bushes to a soft ARB is unlikely to make a big difference, and speculate that it is more likely to make a significant difference with a stiff ARB. I suppose I'll only really know if I ever get around to swapping my current soft rubber bushes for stiffer poly bushes.

Regards,
John.
 
1 - 20 of 26 Posts
Top