Rear anti-roll bar
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Rear anti-roll bar
I've got a Prodrive rear anti-roll bar on my blob, and I'm trying to work out its size.
Ive got receipts from the previous owner for bushes that are 21mm, so I'm guessing (no sarcasm pls) this is a 21mm bar?
Would it be worth upgrading to a bigger Whiteline anti-roll bar, as shown in the link below, or shall I stick with the Prodrive bar? I was thinking 24 or 22mm would help with a bit of roll.
http://scoobyworld.co.uk/catalog/ind...lf2un08j5fo4r6
Cheers
Jack
Ive got receipts from the previous owner for bushes that are 21mm, so I'm guessing (no sarcasm pls) this is a 21mm bar?
Would it be worth upgrading to a bigger Whiteline anti-roll bar, as shown in the link below, or shall I stick with the Prodrive bar? I was thinking 24 or 22mm would help with a bit of roll.
http://scoobyworld.co.uk/catalog/ind...lf2un08j5fo4r6
Cheers
Jack
#2
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The 21mm bar will be the one usually fitted to an RB320 which is already an upgrade. (Std OEM 20mm for STi)
%age increase in stiffness
%age increase in stiffness
#4
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Not in an Impreza but I've tried the RB320 ARB in a FSTi.
Works best on the soft hole (with a 20mm OEM front ARB), spoils the balance on the hard one.
Roll isn't necessarily bad as you can feel what the car is doing and can be more progressive on the limit.
Works best on the soft hole (with a 20mm OEM front ARB), spoils the balance on the hard one.
Roll isn't necessarily bad as you can feel what the car is doing and can be more progressive on the limit.
Last edited by fpan; 16 January 2017 at 09:46 PM.
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I've just had confirmation from the previous owner it is the 21mm bar from the RB320, so I will leave that for now and play around with the settings.
I agree, roll does help, but coming from two seaters I love the feeling of being completely flat all the time. Don't get me wrong, the scooby is planted, but where it has so much grip and you can go so fast, it naturally gets roll.
Is it relatively easy to change the settings? I've changed the bushes on the roll bar, so I'm guessing you just take it out of one hole by removing the bushes?
I agree, roll does help, but coming from two seaters I love the feeling of being completely flat all the time. Don't get me wrong, the scooby is planted, but where it has so much grip and you can go so fast, it naturally gets roll.
Is it relatively easy to change the settings? I've changed the bushes on the roll bar, so I'm guessing you just take it out of one hole by removing the bushes?
Last edited by SubieJack; 16 January 2017 at 11:40 PM.
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I've recently just upgraded to a SuperPro adjustable 24mm rear bar, and honestly the difference is fantastic, feels much more planted and predictable, currently set up on the middle setting.
I went with SuperPro as the Whiteline products tend to suffer very badly with corrosion, but if I were you I'd have a play with the bar you have, and if it doesn't make enough difference for you then look to upgrade to a bigger bar.
I went with SuperPro as the Whiteline products tend to suffer very badly with corrosion, but if I were you I'd have a play with the bar you have, and if it doesn't make enough difference for you then look to upgrade to a bigger bar.
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True, but it all depends on how the rest of your suspension is setup too. I haven't found mine to step out at the back at all since the change, I guess it also depends on your driving style and how much your trying to push it.
I may look into the front to in the future but for now I'm quite happy with how it handles, and as it's adjustable its just about playing around until you like it.
#12
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https://www.scoobynet.com/suspension...-roll-bar.html
#13
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moving to the inner bolt hole is the equivalent of fitting a 22mm bar
https://www.scoobynet.com/suspension...-roll-bar.html
https://www.scoobynet.com/suspension...-roll-bar.html
It's more of an exponential thing. Have a look at Don's chart and see how much of a % increase there is from bar to bar
#14
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dont quite grasp what you are saying? i understand the % increase table what im saying is you will get the same percentage increase on a 21mm bar on 2nd setting as you would with a 22mm on a standard setting hence no point him upgrading to a 22mm bar unless it also has more than 1 setting
#15
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I found these articles a few weeks ago and found them interesting. If fitting a fatter rear ARB is your thing you may want to think twice.
http://www.pcadynamics.com/magazine-articles/
http://www.pcadynamics.com/magazine-articles/
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Lowering the centre of gravity would ultimately reduce the roll, but I want to keep the RB320 suspension really. Might look into 24mm on the rear, as that's what I feel lift in some corners. The front is pretty planted to be honest.
#19
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Can I just ask why are guys fitting stiffer ARBs?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
#20
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If you're lifting the inside rear wheel, with your sping/damper, soften the rear bar.
#21
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Can I just ask why are guys fitting stiffer ARBs?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
Don't make the balance completely neutral, on a road car, or you'll come unstuck during emergency braking, lift-off oversteer and/or slippery conditions.
#22
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Can I just ask why are guys fitting stiffer ARBs?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
I race RC cars and set up theory is pretty much the same.
If you fit a stiffer ARB then you take grip away from the end you've fitted it to.
If you fit a stiffer ARB on the rear, you're taking grip away from the rear. The rear is going to want to slide more.
If 4WD has a tendency to understeer, if you're taking grip from the rear, does that reduce the understeer at the front or will the whole car just slide more?
Longer answer is most road going cars are set up by the manufacturer to understeer, and fitting larger anti-roll bars will achieve two man things - balance of under and oversteer at the limit and an increased roll resistance, with an overall increase in grip
Larger rear bar fitment may sound like sacrificing rear grip, as the the stiffer bar will load the rear wheels more unevenly, however, as the rear resists roll more, the front resists less, and the front wheels will be more evenly loaded, increasing their grip, and overall grip
As the roll stiffness increases, chassis roll is reduced, reducing the effects of 'roll-camber' (loss of static alignment geometry, going into positive camber etc)
You could also reduce the front bar's stiffness to achieve the same, but the roll camber would reduce grip and spoil the handling
Car set-up is a personal thing, and there's many different ways to achieve your goal. I don't like understeer for example and prefer a car's rotational balance to be right under the driver's seat
Last edited by bonesetter; 18 January 2017 at 02:56 PM.
#24
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And you talked about reducing the feeling of roll, which is not the same thing as feeling "planted". In fact, increasing the size of the rear bar relative to the front will make the rear feel LESS planted.
What exactly are you seeking to achieve?
#25
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The short answer is you will have overall more grip
Longer answer is most road going cars are set up by the manufacturer to understeer, and fitting larger anti-roll bars will achieve two man things - balance of under and oversteer at the limit and an increased roll resistance, with an overall increase in grip
Larger rear bar fitment may sound like sacrificing rear grip, as the the stiffer bar will load the rear wheels more unevenly, however, as the rear resists roll more, the front resists less, and the front wheels will be more evenly loaded, increasing their grip, and overall grip
As the roll stiffness increases, chassis roll is reduced, reducing the effects of 'roll-camber' (loss of static alignment geometry, going into positive camber etc)
You could also reduce the front bar's stiffness to achieve the same, but the roll camber would reduce grip and spoil the handling
Car set-up is a personal thing, and there's many different ways to achieve your goal. I don't like understeer for example and prefer a car's rotational balance to be right under the driver's seat
Longer answer is most road going cars are set up by the manufacturer to understeer, and fitting larger anti-roll bars will achieve two man things - balance of under and oversteer at the limit and an increased roll resistance, with an overall increase in grip
Larger rear bar fitment may sound like sacrificing rear grip, as the the stiffer bar will load the rear wheels more unevenly, however, as the rear resists roll more, the front resists less, and the front wheels will be more evenly loaded, increasing their grip, and overall grip
As the roll stiffness increases, chassis roll is reduced, reducing the effects of 'roll-camber' (loss of static alignment geometry, going into positive camber etc)
You could also reduce the front bar's stiffness to achieve the same, but the roll camber would reduce grip and spoil the handling
Car set-up is a personal thing, and there's many different ways to achieve your goal. I don't like understeer for example and prefer a car's rotational balance to be right under the driver's seat
You've intentionally redistributed some grip to the front - good.
But, the larger rear bar is destablising the contact patches, on both rear tyres - no such thing as a smooth road - dampers work constantly.
The larger rear bar is coupling the motions between both sides of the rear suspension. That will have a negative impact on braking, traction and comfort - the bigger the bar/worse the road, the greater the inherent instability.
On a road car, you don't want a neutral chassis, near the limit. A previously recoverable situation, becomes an accident waiting to happen.
#26
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Chassis tuning is a lot down to personal preference - a different driving style suits a different chassis set-up. There's many ways to skin a cat
Petter Solberg liked the RB320 with its rear bar set on stiffest - bit more rear bias balance (said it was the best road car he'd driven - we don't know what else what else he drove though )
The S203 was set-up by STi to have a touch of entry corner understeer (which could be easily throttle controlled), those are just two examples
Personally, I like a neutral balance, and I think you'll find many do YMMV
Edit: I'm not saying I want a 100% neutral balance at the limit, and I understand what you're saying - the rear could easily overtake you in certain situations, usually just when you don't want it, but a good measure to help turn the car.
The car turns with much less steering input, negating to a large extent the effect of the roll resistance on the dampers/springs
Petter Solberg liked the RB320 with its rear bar set on stiffest - bit more rear bias balance (said it was the best road car he'd driven - we don't know what else what else he drove though )
The S203 was set-up by STi to have a touch of entry corner understeer (which could be easily throttle controlled), those are just two examples
Personally, I like a neutral balance, and I think you'll find many do YMMV
Edit: I'm not saying I want a 100% neutral balance at the limit, and I understand what you're saying - the rear could easily overtake you in certain situations, usually just when you don't want it, but a good measure to help turn the car.
The car turns with much less steering input, negating to a large extent the effect of the roll resistance on the dampers/springs
Last edited by bonesetter; 20 January 2017 at 01:35 PM.
#27
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For what it's worth, the STi pink rear ARB that the S203/S204 cars use is 21mm.
Agreed with bonesetter, handling/rotational balance is something personal and everything is relative and depends on a driver's experience amongst other things.
@ 2pot, why do you consider a neutral chassis at the limit as an accident waiting to happen?
The average driver will tend to lift off when a car understeers hence understeer may be seen as a "safer" behaviour, something that isn't necessarily true.
To control lift off oversteer though, lifting off or breaking (which is what most people tend to do) will make the situation worse.
When I first went around the Nurburgring with my 07 WRX wagon (Prodrive springs, 22mm front and rear ARBs, Whiteline ALK and upgraded droplinks) the car was so understeery that was scary (Toyo T1R tyres didn't help being soft like a bubble gum). You had to trail brake hard while turning in to make it turn (on all fours) which was much easier to control than understeer.
Ditto, this is not something you do at the road and I don't fancy a car that has sudden lift off oversteer without warning or being on my toes when it's wet but my 205 GTi modified by Skip Brown Cars is the best example I can give about a car that is planted while still retaining line adjustability mid-bend via the throttle.
Although a standard car's nickname was "widow maker" as many of you may have heard, the Skip Brown Cars modifications (Bilstein inverted dampers revalved in house, different springs, thicker rear ARB, thicker torsion bar and negative rear camber kit) made the car much more planted while still being able to adjust your lines mid-bend so progressively and accurately. Without one driving the car it is impossible to describe.
The thread should be moved under Suspension.
Agreed with bonesetter, handling/rotational balance is something personal and everything is relative and depends on a driver's experience amongst other things.
@ 2pot, why do you consider a neutral chassis at the limit as an accident waiting to happen?
The average driver will tend to lift off when a car understeers hence understeer may be seen as a "safer" behaviour, something that isn't necessarily true.
To control lift off oversteer though, lifting off or breaking (which is what most people tend to do) will make the situation worse.
When I first went around the Nurburgring with my 07 WRX wagon (Prodrive springs, 22mm front and rear ARBs, Whiteline ALK and upgraded droplinks) the car was so understeery that was scary (Toyo T1R tyres didn't help being soft like a bubble gum). You had to trail brake hard while turning in to make it turn (on all fours) which was much easier to control than understeer.
Ditto, this is not something you do at the road and I don't fancy a car that has sudden lift off oversteer without warning or being on my toes when it's wet but my 205 GTi modified by Skip Brown Cars is the best example I can give about a car that is planted while still retaining line adjustability mid-bend via the throttle.
Although a standard car's nickname was "widow maker" as many of you may have heard, the Skip Brown Cars modifications (Bilstein inverted dampers revalved in house, different springs, thicker rear ARB, thicker torsion bar and negative rear camber kit) made the car much more planted while still being able to adjust your lines mid-bend so progressively and accurately. Without one driving the car it is impossible to describe.
The thread should be moved under Suspension.
Last edited by fpan; 20 January 2017 at 10:18 AM.
#29
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Road car - Give yourself a margin for error - whether it's your error or someone else's.
Classic (manual) Subaru 19/20
Prodrive P1 19/20
Classic WR99 Prodrive/Bilstein kit 19/18 (stiffer rear springs)
Rear 21 or 22 - Dry, smooth, roads - more front grip.
If the roads are undulating/uneven or conditions are poor, soften the rear bar - increasing the margin for error.
Classic (manual) Subaru 19/20
Prodrive P1 19/20
Classic WR99 Prodrive/Bilstein kit 19/18 (stiffer rear springs)
Rear 21 or 22 - Dry, smooth, roads - more front grip.
If the roads are undulating/uneven or conditions are poor, soften the rear bar - increasing the margin for error.
Last edited by 2pot; 20 January 2017 at 11:50 AM.
#30
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As is the front ARB........
Brand: STI
Product: Stabilizer - Rear Impreza GD/GG
Part Num: ST204104S200
SPECIFICATIONS:
Application: Rear
Diameter (mm): 21
Color: Cherry Red
PRODUCT NOTES:
-Impreza (GD/GG) G-Type: When installing, STI lateral link set, and STI bracket link set are required (sold separately)
Brand: STI
Product: Stabilizer - Front Impreza GD/GG
Part Num: ST204104S010
SPECIFICATIONS:
Application: Front
Diameter (mm): 21