ARB choices ??

xpoweruk

TTTS 8J Smile Machine
Just a quick question.
Would understeer be reduced more by just changing the rear ARB on MY S4 B8 (no adaptive suspension or Sports diff)
measurements listed below

OEM/Stock Without ADS:
Front (25.9mm) Rear (22.0mm)

Eibach
Front 28mm rear 23mm
 

ANDYTQ

Registered User
Probably a little but 1 mm difference is not much,ive just bought a adjustable 034 one to try,i do have ads and diff too.
 

desertstorm

Moderator
Staff member
Moderator
VCDS Map User
I fitted the H and R ARB's to my car. Front is 30mm and rear is 24mm . I found the car to be much flatter in the corner which is what you would expect and some of the understeer was dialled out but I did notice on rough roads or where you hit drain covers/ potholes/ speed bumps the front was a lot more solid and you felt it more.
So I removed the front H and R bar and put the standard front bar back on.
Wow, That made the ride better over rough surfaces but also reduced understeer a lot and allowed the back to move around a bit more.
It fundamentally altered the roll stiffness of the car as previously by altering front and rear the same handling balance was maintained.
If you look at some of the videos I have done at Curbrough you can see how the car gets into and out of fairly tight corners.
You can't buy the rear bar on it's own unfortunately I don't think.
the rear ARB stiffness is a function of the diameter raised to the 4th power.
So assuming all else is the same such as the material used to make the bar the stiffness of a 22mm bar would be
22 x 22 x 22 x 22 = 234256 and a 24mm bar 24 x 24 x 24 x 24 =331776 so a 24mm bar is 1.4 times as stiff as a 22mm bar.
Sometimes ARB'S are hollow, so you could get 2 ARB's the same diameter but one would be a lot stiffer than the other.
 

Samuel c5 Q

Registered User
VCDS Map User
Silver Supporter
Interesting post this. I am really only just learning about 4wd or Quattro handling characteristics as I haven't got mine that long. Front wheel drive cars favour a stiff rear ant roll bar to dial out understeer. Rear wheel drive cars favour a stiff front ARB to aid turn in and keep both rear wheels on the black stuff and aid traction. But I'm not sure on the way of things for Quattro. I have a c5 saloon 1.8t se and the easiest thing would be to put sport ARBs in but would still like to know the way of thing if I wanted to fine tune the system after a while.

Any thoughts on this , thanks.
 

desertstorm

Moderator
Staff member
Moderator
VCDS Map User
It seems that increasing roll bar stiffness takes away grip from what ever end they are uprated.
Do it a similar amount at both ends and you maintain the balance but the car corners flatter so won't overload the outside tyres when cornering hard. Manufacturers inherently try to make there cars safe by dialling in a certain amount of understeer or tyring to avoid oversteer situations.
Increasing the rear ARB does help the turn in and it can be fun in the wet, if you turn the ESP off and provoke it with some acceleration you can get the back end moving around a bit like a RWD car. The B8 cars went from a 50/50 split to a 60/40 split with the 60 to the rear to improve the driving characteristics of the car so this helps.
 

Samuel c5 Q

Registered User
VCDS Map User
Silver Supporter
Vwey
It seems that increasing roll bar stiffness takes away grip from what ever end they are uprated.
Do it a similar amount at both ends and you maintain the balance but the car corners flatter so won't overload the outside tyres when cornering hard. Manufacturers inherently try to make there cars safe by dialling in a certain amount of understeer or tyring to avoid oversteer situations.
Increasing the rear ARB does help the turn in and it can be fun in the wet, if you turn the ESP off and provoke it with some acceleration you can get the back end moving around a bit like a RWD car. The B8 cars went from a 50/50 split to a 60/40 split with the 60 to the rear to improve the driving characteristics of the car so this helps.[/

Very helpful, thank you.
 

xpoweruk

TTTS 8J Smile Machine
The rear ARB only is a great mod IMO.As said,really help to dial out understeer.
I also now have an ultra racing S4 B8 front strut brace.This helps with turn in feel on the front.
The 2 together are a great combo
 

Samuel c5 Q

Registered User
VCDS Map User
Silver Supporter
Folks I've been looking on the net for a rear anti roll bar for my 1.8t Quattro c5 a6 but can't seem to turn anything up. Does anybody know who makes one for my vehicle?

Thanks, Samuel
 

Samuel c5 Q

Registered User
VCDS Map User
Silver Supporter
Thanks for that. I done another wee bit of searching and found on h and r do a pair of roll bars for my car on there own website. It wasn't coming up on google search or the likes of the tuners, not sure which ones I'm allowed to mention but maybe it's just my poor wee Nokia phone that can't do the business. Like other folk have said I just want to fit the rear and not both front and rear. But at least I know they do a rear. All I have to do now is figure out how to get a rear own it's own with out purchasing the front. Thanks again.
 

Kingfisher

Registered User
Going back 11 years to my B6 1.8T S Line quattro I fitted the S4 rear bar ( and left the front alone). The difference was amazing ( but the S Line suspension is rock hard ! )The car felt much more stable and flat turning in, without any detriment.
At the time the S4 bar cost £37 plus a couple of £ for rubber bushes - guys also started using RS4 rear when they came out but by that time Audi had cottoned on to what was happening and the prices rocketed to well over £100 !!
The car is still good to drive but her S3 saloon is in a different league........
 
Top