Hi there,

 

I’ve just upgraded my Vrs Octy’s suspension with a Bilstein B12 kit (+eibach -30mm). The global improvement is great but I expected the car was going to “swing” less in close turns as roundabout etc... I was wondering if replacing the front anti roll bar’s bushings with powerflex ones would feel any better, make the car turn flatter. Or, should I go straight and upgrade both bars to thicker ones (whiteline, eibach..)??

 

thanks so much in advance!

 

pd: sorry for my english

I haven't upgraded mine. Still on standard. I have replaced rear springs though. The b12 kit is very respected. If you want it to be flatter, I reckon you need new anti roll bars. 

The bushes won't make a difference, stiffer (thicker) ARB's or stiffer springs should do the job, do you get any adjustments on the shocks?

I have lowered H+R suspension and a whiteline rear ARB. The whiteline makes a big difference to body roll. It goes round much more level. 

 

I don't have uprated front ARB  but that may help also.

 

On 23/04/2021 at 14:46, pastie said:

The bushes won't make a difference, stiffer (thicker) ARB's or stiffer springs should do the job, do you get any adjustments on the shocks?

Nope. They are standard Bilstein B12.

On 24/04/2021 at 12:03, FatblokeVRS said:

I have lowered H+R suspension and a whiteline rear ARB. The whiteline makes a big difference to body roll. It goes round much more level. 

 

I don't have uprated front ARB  but that may help also.

 

Thanks for your info, sounds the thing to do. Anyway, do you feel any oversteer/understeer having installed just the rear Arb? I've been told that using just front arb gets your car to understeer, wondering if it's the same with the rear one. Thanks again for the tip!

Not noticed any under/over steer but don't push it too hard. Its much better than standard suspension, much more controlled and stable and much less bouncy and stays level round corners. Defo more precise feeling when driving.

On 01/05/2021 at 02:43, FatblokeVRS said:

Not noticed any under/over steer but don't push it too hard. Its much better than standard suspension, much more controlled and stable and much less bouncy and stays level round corners. Defo more precise feeling when driving.

Great, thanks!

I am running MCA coilovers with Whiteline front & Rear ARB. I had the coilover professional setup for corner weight, height and damping so the car handles great now

On 01/05/2021 at 01:43, FatblokeVRS said:

Not noticed any under/over steer but don't push it too hard. Its much better than standard suspension, much more controlled and stable and much less bouncy and stays level round corners. Defo more precise feeling when driving.

For clarification, that should have said "I don't push it too hard".

 

It may well be very stable if you give it a good push.

 

On 29/04/2021 at 09:30, uniteunion said:

Thanks for your info, sounds the thing to do. Anyway, do you feel any oversteer/understeer having installed just the rear Arb? I've been told that using just front arb gets your car to understeer, wondering if it's the same with the rear one. Thanks again for the tip!

 

Assuming, when you say "I've been told that using just front arb..." you mean something like "just using a stiffer front ARB" (rather than only using a front ARB, and no rear ARB then:

 

The amount of body roll is set by the total roll stiffness, and that total roll stiffness is set by a whole load of things, the (explicit) spring rates (the tyre sidewalls are also springs, which complicates the theory a little, but usually they aren't the biggest factors) and the anti-roll bar rates.

 

If all that you care about is body roll, you could just stiffen roll bars without caring about any of the details and be happy. Usually, however, balance (under/over-steer) is as big a concern as body roll.

 

If you are concerned about balance, then the ARBs at the two ends do opposite things. If you make the rear ARB stiffer, you will make the car oversteer more (or understeer less, if you prefer to look at it that way), whereas if you make the front stiffer, it will understeer more.

 

I don't want to understate the amount of 'art' in this; there are a number of ways of getting it wrong, so you'd really like to go with stuff that people have tested, and not make wild, exaggerated,  changes that can cause unpredicted effects, but mild changes are usually safe, but for less roll, a bit more ARB (at either, or both ends) is good, and, if you want to understeer less, you want to stiffen the rear end up a bit more than the front.

 

If you went really wild and stiffened the rear end up massively, the car would probably get a bit uncomfortable and would oversteer quite a bit (and, as Milliken and Milliken point out, at some speed, an oversteering car, becomes undrivable, and while that probably is quite a high speed, you want to stay well away from that).

 

If you run one end super-stiff, you can even reduce the grip (unless you get tricksy with the dampers) because the stiff end starts to patter wide on uneven surfaces.

Edited 8 May, 20215 yr by Camlobe
strange random smiley removed!

On 08/05/2021 at 18:21, Camlobe said:

 

Assuming, when you say "I've been told that using just front arb..." you mean something like "just using a stiffer front ARB" (rather than only using a front ARB, and no rear ARB then:

 

The amount of body roll is set by the total roll stiffness, and that total roll stiffness is set by a whole load of things, the (explicit) spring rates (the tyre sidewalls are also springs, which complicates the theory a little, but usually they aren't the biggest factors) and the anti-roll bar rates.

 

If all that you care about is body roll, you could just stiffen roll bars without caring about any of the details and be happy. Usually, however, balance (under/over-steer) is as big a concern as body roll.

 

If you are concerned about balance, then the ARBs at the two ends do opposite things. If you make the rear ARB stiffer, you will make the car oversteer more (or understeer less, if you prefer to look at it that way), whereas if you make the front stiffer, it will understeer more.

 

I don't want to understate the amount of 'art' in this; there are a number of ways of getting it wrong, so you'd really like to go with stuff that people have tested, and not make wild, exaggerated,  changes that can cause unpredicted effects, but mild changes are usually safe, but for less roll, a bit more ARB (at either, or both ends) is good, and, if you want to understeer less, you want to stiffen the rear end up a bit more than the front.

 

If you went really wild and stiffened the rear end up massively, the car would probably get a bit uncomfortable and would oversteer quite a bit (and, as Milliken and Milliken point out, at some speed, an oversteering car, becomes undrivable, and while that probably is quite a high speed, you want to stay well away from that).

 

If you run one end super-stiff, you can even reduce the grip (unless you get tricksy with the dampers) because the stiff end starts to patter wide on uneven surfaces.

That’s a good amount of great info, thanks. Your assumption was right, I refered to replace only the rear Arb with a stiffer one and keeping the oem Arb at the front end. Plus I won’t be using the stiffest one, a 24mm whiteline may be good, starting with the softest adjustment (out of three). After reading your words, seems a good starting point to notice handling improvements and  side effects as over steering..