Skid pan test results using larger swaybars
19 June 2003, 08:43 AM
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G'day
We've recently started doing development work on P-Rex III (MY03 WRX) and have come across some interesting data.
A standard part of our development process includes using our data logger to acquire speed, lateral and longitudinal G force readings for various configurations and options. We conducted a whole series of tests recently but one that I thought was particularly interesting is comparing the standard setup with a BSR36Z (adjustable 22mm) rear swaybar.
We have put together a graph comparing speed and lateral G forces in a G-Circle format. The actual image can be viewed at http://www.whiteline.com.au/images/diag/Skid%20PRexIII%20RZ22%20v%20std.jpg
A bit of background to help interpret the data first. What you are seeing is the series of sample points making up the data for the 2 different configurations. Black is for the stock setup and swaybar while red is using the BSR36Z bar set to middle setting. In all cases the same tyres pressure and alignment settings were used:
Front:
Stock Potenza 215/45/17 Pressure 34 psi
Camber -1.0 deg
Caster +3.75 deg (changed for ALK testing later)
Toe 0.0 mm total
Rear:
Stock Potenza 215/45/17 Pressure 34 psi
Camber -1.33 deg
Toe 2.0 mm out total
The summary of the result for this test are;
In standard form, P-Rex III can sustain mean lateral G's of 0.83 and maximum sustainable speed of 33 kmh. After fitting the BSR36Z 22mm rear we have increased the mean lateral G's to 0.855 while also increasing maximum sustainable speed by 6 to 39 kmh. That is a very significant increase in both cases and consistent with what we experience at the race track and through "seat-of-the-pants" testing. Apart from that, the graph shows much higher G force peaks for the larger rear bar and a much more consistent and dense grip pattern.
Additional data confirms a dramatic change in the bias away from understeer toward neutral when using the Whiteline rear bar. This is shown via a more traditional G-Circle graph plotting longitudinal vs lateral G forces. With the larger bar fitted, the sample area moves upward to closely straddle the longitudinal 0 point. We can send a copy of this graph if requested. The tests are done deliberately at quite low "street" speeds for relevance but in our experience, the changes would be consistent at much higher speeds. It is also important to note that these results are representative of what you would expect to find with other vehicles albeit the exact recipes would be different depending on vehicle and drive configuration. We hope to publish results from tests on rear wheel drive and more traditional front wheel drive vehicles as well.
The key everyday conclusion from this is that fitting a BSF36Z larger Whiteline rear bar significantly increases total grip resulting in higher cornering speeds. Larger bars DO NOT simply change the handling bias as some people think, they can actually improve handling and INCREASE grip.
We should be finished with our testing quite soon and will be able to post results showing the effect of fitting an ALK (anti lift caster kit), larger front swaybars, lowered springs and a combination of other factors. We'll post the results as they come to hand.
Best regards
Jim Gurieff
jimg@whiteline.com.au
Whiteline
We've recently started doing development work on P-Rex III (MY03 WRX) and have come across some interesting data.
A standard part of our development process includes using our data logger to acquire speed, lateral and longitudinal G force readings for various configurations and options. We conducted a whole series of tests recently but one that I thought was particularly interesting is comparing the standard setup with a BSR36Z (adjustable 22mm) rear swaybar.
We have put together a graph comparing speed and lateral G forces in a G-Circle format. The actual image can be viewed at http://www.whiteline.com.au/images/diag/Skid%20PRexIII%20RZ22%20v%20std.jpg
A bit of background to help interpret the data first. What you are seeing is the series of sample points making up the data for the 2 different configurations. Black is for the stock setup and swaybar while red is using the BSR36Z bar set to middle setting. In all cases the same tyres pressure and alignment settings were used:
Front:
Stock Potenza 215/45/17 Pressure 34 psi
Camber -1.0 deg
Caster +3.75 deg (changed for ALK testing later)
Toe 0.0 mm total
Rear:
Stock Potenza 215/45/17 Pressure 34 psi
Camber -1.33 deg
Toe 2.0 mm out total
The summary of the result for this test are;
In standard form, P-Rex III can sustain mean lateral G's of 0.83 and maximum sustainable speed of 33 kmh. After fitting the BSR36Z 22mm rear we have increased the mean lateral G's to 0.855 while also increasing maximum sustainable speed by 6 to 39 kmh. That is a very significant increase in both cases and consistent with what we experience at the race track and through "seat-of-the-pants" testing. Apart from that, the graph shows much higher G force peaks for the larger rear bar and a much more consistent and dense grip pattern.
Additional data confirms a dramatic change in the bias away from understeer toward neutral when using the Whiteline rear bar. This is shown via a more traditional G-Circle graph plotting longitudinal vs lateral G forces. With the larger bar fitted, the sample area moves upward to closely straddle the longitudinal 0 point. We can send a copy of this graph if requested. The tests are done deliberately at quite low "street" speeds for relevance but in our experience, the changes would be consistent at much higher speeds. It is also important to note that these results are representative of what you would expect to find with other vehicles albeit the exact recipes would be different depending on vehicle and drive configuration. We hope to publish results from tests on rear wheel drive and more traditional front wheel drive vehicles as well.
The key everyday conclusion from this is that fitting a BSF36Z larger Whiteline rear bar significantly increases total grip resulting in higher cornering speeds. Larger bars DO NOT simply change the handling bias as some people think, they can actually improve handling and INCREASE grip.
We should be finished with our testing quite soon and will be able to post results showing the effect of fitting an ALK (anti lift caster kit), larger front swaybars, lowered springs and a combination of other factors. We'll post the results as they come to hand.
Best regards
Jim Gurieff
jimg@whiteline.com.au
Whiteline
19 June 2003, 11:51 PM
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jim, that's top. was it understeering in standard form? you took max at the point just before it left the circle right?...was it the back end that went first with the uprated arb? was it more difficult to correct with the arb? please can you give me a job at whiteline?
jim, that's top. was it understeering in standard form? you took max at the point just before it left the circle right?...was it the back end that went first with the uprated arb? was it more difficult to correct with the arb? please can you give me a job at whiteline?
20 June 2003, 12:38 AM
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Hi everyone,
Kippax, asking for a job here is the nicest thing anyones said to us for a while!! We like it here.
Seriously though, to answer your question, we have a particular deserted cul de sac near the office that we use each time. Its cambered the wrong way, is fairly tight but its ideal for these sorts of comparisons and thats exactly what they are.
We are generally loathe to publish the numeric scales for these things to avoid people making unrealsitic comparisons to their vehicles, sort of the like the chassis dyno power "arms race" we often see. The main thing is that we repeat the tests using the same method each time and always start with a fresh baseline.
What we do is drive as hard as we can around this cirlce until we are steering with a mixture of throttle and steering lock. We do 3 complete loops at speed and log this data. The analysis then involves using histograms to calculate mean values while keeping an eye on speed. Logic says that the wider the circle, the higher the potential speed and constant G's but this is limited by a very physical barrier being the gutter. The critical thing is to not get hung up with the peak values and just look at the measurable trends and sustainable values.
The traditional G-circle plot shows the standard bar/car pattern clustered below the longitudunal zero axis (understeer). The larger rear bar plot saw the pattern (would attach if forum would allow) move up to almost straddle the zero point indicating a close to neutral bias albeit still with a hint of understeer. We're a long way off overtseer, that's not our bag.
Hope that covers it. Feel free to contact me directly and I'll forward a copy of the conventional G-circle graph.
Best regards
Jim
Whiteline
Kippax, asking for a job here is the nicest thing anyones said to us for a while!! We like it here.
Seriously though, to answer your question, we have a particular deserted cul de sac near the office that we use each time. Its cambered the wrong way, is fairly tight but its ideal for these sorts of comparisons and thats exactly what they are.
We are generally loathe to publish the numeric scales for these things to avoid people making unrealsitic comparisons to their vehicles, sort of the like the chassis dyno power "arms race" we often see. The main thing is that we repeat the tests using the same method each time and always start with a fresh baseline.
What we do is drive as hard as we can around this cirlce until we are steering with a mixture of throttle and steering lock. We do 3 complete loops at speed and log this data. The analysis then involves using histograms to calculate mean values while keeping an eye on speed. Logic says that the wider the circle, the higher the potential speed and constant G's but this is limited by a very physical barrier being the gutter. The critical thing is to not get hung up with the peak values and just look at the measurable trends and sustainable values.
The traditional G-circle plot shows the standard bar/car pattern clustered below the longitudunal zero axis (understeer). The larger rear bar plot saw the pattern (would attach if forum would allow) move up to almost straddle the zero point indicating a close to neutral bias albeit still with a hint of understeer. We're a long way off overtseer, that's not our bag.
Hope that covers it. Feel free to contact me directly and I'll forward a copy of the conventional G-circle graph.
Best regards
Jim
Whiteline
20 June 2003, 07:24 AM
#4
Jim,
Great post!! Just what I have been looking for
Do you have any results using a 24mm bar? I have been considering getting one but cannot decide between the 22mm or the 24mm
Neil.
Great post!! Just what I have been looking for
Do you have any results using a 24mm bar? I have been considering getting one but cannot decide between the 22mm or the 24mm
Neil.
20 June 2003, 11:57 AM
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Whiteline Automotive,
Excellent post. Very useful information.
I have posted a link to this thread on bbs.22b.com for future reference purposes, I hope you don't mind.
Moray
Excellent post.
Very useful information. I have posted a link to this thread on bbs.22b.com for future reference purposes, I hope you don't mind.
Moray
20 June 2003, 12:40 PM
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jim,
yeah i understand completely what youve done and youve proved an increase in sustainable speed. i reckon it would be interesting to put your accelerometer in the car and mess with all your products on a larger slab of concrete to see how much g you can get, with what, and how the car behaves with different mods. if the data acquisition rate was fast enough youd get the spin out data as well (say if the back span round). you could see how quick it left the circle and therefore, how controllable the spin was. i could go on.......
stu.
yeah i understand completely what youve done and youve proved an increase in sustainable speed. i reckon it would be interesting to put your accelerometer in the car and mess with all your products on a larger slab of concrete to see how much g you can get, with what, and how the car behaves with different mods. if the data acquisition rate was fast enough youd get the spin out data as well (say if the back span round). you could see how quick it left the circle and therefore, how controllable the spin was. i could go on.......
stu.
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20 June 2003, 12:58 PM
#8
You may be interested in my experience on anSTi ver 6 Wagon.
In standard form the car understeered from day one although we are talking about driving in a manner not normally advisable for the road.
Fitted White Line adjustable rear and up-rated front. Yes. Could tell it was different but still had more understeer than acceptable.
In a moment of madness fitted a WRX front ARB,(smaller diameter than the original STi) Surprised by the great improvement. Can still get understeer on the tightest of corners on track but otherwise pretty neutral and a great benefit.
In standard form the car understeered from day one although we are talking about driving in a manner not normally advisable for the road.
Fitted White Line adjustable rear and up-rated front. Yes. Could tell it was different but still had more understeer than acceptable.
In a moment of madness fitted a WRX front ARB,(smaller diameter than the original STi) Surprised by the great improvement. Can still get understeer on the tightest of corners on track but otherwise pretty neutral and a great benefit.
21 June 2003, 02:27 AM
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G'day everyone,
Matt, thanks so much for posting the attachment. Would it be possible to also attach the more conventional G-circle graph we have showing the relative change in bias? You can contact me at jimg@whiteline.com.au and I'll forward the GIF.
Neil, we have some results being compiled using the Handling Pack which uses the same 22mm rear adjustable bar but set to max or equaivalent to nearly 24mm. But, running this on its own is a recipe for overtseer and some interesting "lift off" dynamics. Thats why its balanced in the kit with a 22mm fixed front ARB. Frankly that's why we suggest the adjustable rear in the package, running on its own, the middle setting is ideal but we simply adjusted it harder after fitting the front ARB.
Stu, we are systematically going thru all the products individually and in combination but it takes a long time even with the workshop only 5 minutes away. Our nearest big slab of concrete is 20 minutes away (Oran Park raceway) which significantly limits our flexibility (that and we have to pay :-) ). Our normal procedure is to use Wakefiled Park raceway to test this stuff at speed but we can not get as specific as we can here.
The equipment we use can deliver the information you are describing via track mapping but you need the proprietary software to see it. We dont really bother with it much because its really not that usefull unless you have much tighter control on the process. For example, changing drivers changes the results dramatically within the run as it is easy to "fake" some high G peaks. Hence why we concentrate on comparisons of mean values. Either way, if we have a willing audience, we'll keep boring you with more results that will give you some more insight.
Harvey, Matt's question is very pertinent. Really need to know the mix you're using and frankly we have no experience with an STi wagon. Specifically, what diffs does it use as this has a significant bearing on the optimum recipe?
All the best
Jim
Whiteline Automotive
Matt, thanks so much for posting the attachment. Would it be possible to also attach the more conventional G-circle graph we have showing the relative change in bias? You can contact me at jimg@whiteline.com.au and I'll forward the GIF.
Neil, we have some results being compiled using the Handling Pack which uses the same 22mm rear adjustable bar but set to max or equaivalent to nearly 24mm. But, running this on its own is a recipe for overtseer and some interesting "lift off" dynamics. Thats why its balanced in the kit with a 22mm fixed front ARB. Frankly that's why we suggest the adjustable rear in the package, running on its own, the middle setting is ideal but we simply adjusted it harder after fitting the front ARB.
Stu, we are systematically going thru all the products individually and in combination but it takes a long time even with the workshop only 5 minutes away. Our nearest big slab of concrete is 20 minutes away (Oran Park raceway) which significantly limits our flexibility (that and we have to pay :-) ). Our normal procedure is to use Wakefiled Park raceway to test this stuff at speed but we can not get as specific as we can here.
The equipment we use can deliver the information you are describing via track mapping but you need the proprietary software to see it. We dont really bother with it much because its really not that usefull unless you have much tighter control on the process. For example, changing drivers changes the results dramatically within the run as it is easy to "fake" some high G peaks. Hence why we concentrate on comparisons of mean values. Either way, if we have a willing audience, we'll keep boring you with more results that will give you some more insight.
Harvey, Matt's question is very pertinent. Really need to know the mix you're using and frankly we have no experience with an STi wagon. Specifically, what diffs does it use as this has a significant bearing on the optimum recipe?
All the best
Jim
Whiteline Automotive
21 June 2003, 12:55 PM
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Jim,
Thanks for your postings, great stuff.
I have a MY02 UK Sti saloon with PPP. I am fitting the Prodrive spring pack, and looking at your rear ARB, links and mounts, with front Strut brace. What should I do at the front, if anything?
I want a fast road set-up, that removes the natural tendency of the car to understeer (particularly in the wet), and makes it more neutral and progressive at the limit, with perhaps a touch of throttle adjustable oversteer for fun! Which of your parts do you recommend?
Also, is there any way of removing the "bounciness" of the low speed ride, it tends to porpoise and pitch unpleasantly, without making the ride harsher?
Thanks in advance for your help.
Steve Wardle
PS can you quote part numbers so my mate can order them please.
Thanks for your postings, great stuff.
I have a MY02 UK Sti saloon with PPP. I am fitting the Prodrive spring pack, and looking at your rear ARB, links and mounts, with front Strut brace. What should I do at the front, if anything?
I want a fast road set-up, that removes the natural tendency of the car to understeer (particularly in the wet), and makes it more neutral and progressive at the limit, with perhaps a touch of throttle adjustable oversteer for fun! Which of your parts do you recommend?
Also, is there any way of removing the "bounciness" of the low speed ride, it tends to porpoise and pitch unpleasantly, without making the ride harsher?
Thanks in advance for your help.
Steve Wardle
PS can you quote part numbers so my mate can order them please.
21 June 2003, 02:05 PM
#12
Hi Matt,
I think I have tried every combination with the current WRX ARB and the previous W/L when it was on the front. I am now running in the middle setting and am happy with this but prior to removing the W/L front ARB I had the back on the tightest setting but the combination I have now is the best for my car and my style. I played with the tighter setting on track as well as on the road but concluded it was best to leave it in the middle at all times.
Jim : The standard set up on the STi 6 Wagon is 4.44 diffs with LSDin rear and open front diff and a centre viscuous diff so there is no facility to vary the torque split as there is on type R and RA. I changed to 3.9s, fitted an uprated centre viscuous and a front LSD which greatly helps the exit from tight corners on track and is good in the wet. I am now trying 4.11s with the same diff set up but obviously the ratios are not relevant to the handling performance. May go back to 3.9s after my next airfield testing session.
There is a large ******** Supermarket near hear and it is deserted at 2am. Was asked by the police what I was doing and after I explained they sat in their patrol car for 5mins watching. It is ideal for low speed tight radius testing and I have tried several sets of tyres and tyre pressures in this way. It's free apart from the rubber you leave behind.!!!
I think I have tried every combination with the current WRX ARB and the previous W/L when it was on the front. I am now running in the middle setting and am happy with this but prior to removing the W/L front ARB I had the back on the tightest setting but the combination I have now is the best for my car and my style. I played with the tighter setting on track as well as on the road but concluded it was best to leave it in the middle at all times.
Jim : The standard set up on the STi 6 Wagon is 4.44 diffs with LSDin rear and open front diff and a centre viscuous diff so there is no facility to vary the torque split as there is on type R and RA. I changed to 3.9s, fitted an uprated centre viscuous and a front LSD which greatly helps the exit from tight corners on track and is good in the wet. I am now trying 4.11s with the same diff set up but obviously the ratios are not relevant to the handling performance. May go back to 3.9s after my next airfield testing session.
There is a large ******** Supermarket near hear and it is deserted at 2am. Was asked by the police what I was doing and after I explained they sat in their patrol car for 5mins watching. It is ideal for low speed tight radius testing and I have tried several sets of tyres and tyre pressures in this way. It's free apart from the rubber you leave behind.!!!
24 June 2003, 06:58 AM
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Hi everyone,
Steve, I don't really know what "PPP" is, how does that relate to the suspension?
The pitching and "pig rooting" as we call it (diagonal pitching as oppossed to classic "pitching" across front to back)is best controlled with dampers as its symptomatic of uncontrolled spring rate. Whether it be lateral, longitudunal or a combination of both, its best dealt with by uprated dampers OR more approriate rates. Suggest you look at more low speed rebound.
In fact, high speed control is the very domain of high end dampers. We can acheive great imporvements in practical dynamics at low speed using ARB's but higher road speeds means higher suspension velocities that need better more complex damper control. Using larger ARB's make this essential.
As for part numbers, would suggest BSF33 (22mm front) BSR33Z (22mm adjustable rear).
Harvey, the use of a front LSD and uprated centre changes the dynamics quite noticeable. I would suspect that your car really needs a disproportionately larger front ARB but this seems contrary to your experience and could be changed by rear alignment settings. That aside, I would be running a larger front ARB and getting some more roll resistance from the rear. Higher loads with stickier rubber means higher roll loads etc etc.
We sell many 24mm adjustable rear ARB's and our Race 26's a pretty popular as well for that reason. Our P-Rex cars ran 24/26 adjustables. The main thing is balance and moderation (just as you're mother mighjt have said) and that means an increases to both ends albeit with disproportinate increases for bias change.
Cheers
Jim Gurieff
Whiteline
PS. Try this [img]ftp://ftp.whiteline.com.au/Skid_PRexIII_RZ22_v_std_a.gif[/img]
[Edited by Whiteline Automotive - 6/24/2003 7:14:10 AM]
[Edited by Whiteline Automotive - 6/24/2003 7:24:18 AM]
Steve, I don't really know what "PPP" is, how does that relate to the suspension?
The pitching and "pig rooting" as we call it (diagonal pitching as oppossed to classic "pitching" across front to back)is best controlled with dampers as its symptomatic of uncontrolled spring rate. Whether it be lateral, longitudunal or a combination of both, its best dealt with by uprated dampers OR more approriate rates. Suggest you look at more low speed rebound.
In fact, high speed control is the very domain of high end dampers. We can acheive great imporvements in practical dynamics at low speed using ARB's but higher road speeds means higher suspension velocities that need better more complex damper control. Using larger ARB's make this essential.
As for part numbers, would suggest BSF33 (22mm front) BSR33Z (22mm adjustable rear).
Harvey, the use of a front LSD and uprated centre changes the dynamics quite noticeable. I would suspect that your car really needs a disproportionately larger front ARB but this seems contrary to your experience and could be changed by rear alignment settings. That aside, I would be running a larger front ARB and getting some more roll resistance from the rear. Higher loads with stickier rubber means higher roll loads etc etc.
We sell many 24mm adjustable rear ARB's and our Race 26's a pretty popular as well for that reason. Our P-Rex cars ran 24/26 adjustables. The main thing is balance and moderation (just as you're mother mighjt have said) and that means an increases to both ends albeit with disproportinate increases for bias change.
Cheers
Jim Gurieff
Whiteline
PS. Try this [img]ftp://ftp.whiteline.com.au/Skid_PRexIII_RZ22_v_std_a.gif[/img]
[Edited by Whiteline Automotive - 6/24/2003 7:14:10 AM]
[Edited by Whiteline Automotive - 6/24/2003 7:24:18 AM]
24 June 2003, 08:45 AM
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Jim,
The PPP is the Prodrive Performance Pack. It is basically a power hike (and has no bearing on handling). Steve did also mention Prodrive springs which are Eibach springs, designed to work with the OE dampers and are made by Eibach to Prodrive's specifications (they seem to be similar (but different) to the old pre MY01 Eibach Pro Kit springs). They seem to improve the handling through lowering the car (slightly, about 20mm) and through being stiffer (I think).
Matt
The PPP is the Prodrive Performance Pack. It is basically a power hike (and has no bearing on handling). Steve did also mention Prodrive springs which are Eibach springs, designed to work with the OE dampers and are made by Eibach to Prodrive's specifications (they seem to be similar (but different) to the old pre MY01 Eibach Pro Kit springs). They seem to improve the handling through lowering the car (slightly, about 20mm) and through being stiffer (I think).
Matt
24 June 2003, 03:32 PM
#16
Jim : Now that I have the car set up the way I want it I would be interested in trying another heavy duty front ARB and then put in a few laps back to back on our local circuit (Croft) to see what the differences were on very tight corners, where originally it washed out really badly but is now pretty good and on high speed corners where it is now almost neutral or just a touch of opposite lock may be needed.
So I am looking to borrow a stiff front ARB.
Will the performance of a hard ARB be influenced by the quality/smoothness of the road surface?
So I am looking to borrow a stiff front ARB.
Will the performance of a hard ARB be influenced by the quality/smoothness of the road surface?
24 June 2003, 06:10 PM
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As the harder ARB will reduce the "independence" of the suspension on the axle in question, on a rough bit of road, a hard ARB may well reduce that axle's suspension's overall effectiveness.
24 June 2003, 06:19 PM
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Indeed - I've spoken to people who have tried the 24mm adjustable ARB on the rear of the STi 7 with the hardest setting and found it made the car a little unstable/jittery on our superbly smooth British B-roads 
The middle and soft settings however, for the road are fine....
Matt
The middle and soft settings however, for the road are fine....
Matt
24 June 2003, 07:55 PM
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Jim,
Thanks for the advice.
What dampers/strut inserts do you do for the Sti7? Do you do any that will work with the Prodrive springs kit?
Should I also change the front ARB links as well as the rear?
Matt,
Thanks for filling Jim in on the PPP + springs. I included the PPP info as it does alter the characteristics/dynamics of the car due to the extra power/torque, which will break away the tyres sooner than a non-PPP car, so it does have an indirect influence on the handling of the car.
Regards,
Steve
Thanks for the advice.
What dampers/strut inserts do you do for the Sti7? Do you do any that will work with the Prodrive springs kit?
Should I also change the front ARB links as well as the rear?
Matt,
Thanks for filling Jim in on the PPP + springs. I included the PPP info as it does alter the characteristics/dynamics of the car due to the extra power/torque, which will break away the tyres sooner than a non-PPP car, so it does have an indirect influence on the handling of the car.
Regards,
Steve
24 June 2003, 08:13 PM
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harvey.. you can borrow mine if you want?
Dunno what size it is will have to measure..
its blue
how do you set the adjustment..
David
Dunno what size it is will have to measure..
its blue
how do you set the adjustment..
David
25 June 2003, 12:12 AM
#21
Hi David, From memory the White Line sway bars were painted light blue and if I can borrow your front S.B. I will do some more tests at Croft 6th July and report back.
There is only adjustment on the rear and the bar is connected to the drop link in one of three holes which alters the stiffness.
There is only adjustment on the rear and the bar is connected to the drop link in one of three holes which alters the stiffness.
25 June 2003, 09:00 AM
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G'day all,
Strictly speaking, any change in spring rate must be matched with an increase in damper rate. We have demonstrated on a number of occassions how even moderately stiffer/lower springs can improve handling on a race track surface IF the OE dampers are in reasonable condition. However, even near new OE dampers are not able to control the increased spring rate on less than perfect (normal) road surfaces. Add 10,000 miles to the OE unit and the degredation in handling is very noticeable.
Increased ARB rates have the effect of putting more load on dampers as they force linked wheels to operate in sympathy due to the larger effective axle linlking the two. That means even more load on the dampers.
Regretably Steve I would suggest that your dampers need some attention and heavier ARB's may simply exacerbate the problem at speed.
Just like excessive spring rates, its also possible to over-bar a car but I mention the 24/26 sizes as a specliased solution for much more serious use where you are generating high G's at high speeds. The reality is, the stickier the rubber you have, the more grip you generate, the more roll you experience, the more load you place on the springs = heavier spring and ARB rates. The extreme is when using slicks, appropriate camber angles become huge because you need to compensate for the extra roll as a result of the extra grip and G forces. I guess the simplest way to put it is if you need more roll control you need more roll control! Springs should not be used for that job as you need to try to keep the springs as supple as possible for individual wheel deflection while still having enough to resist pitch and dive.
Matt, you're right about the B-roads issue and its also very relevant in Oz but its an inevitable consequence of the pursuit of the compromise toward sharper handling. There is always a price, however adjustable ARB's are used just for that reason. Crank them up for Saturday and back them off for Monday.
As for STi dampers, we typically use whatever is available to all of us, Koni, KYB or Bilstein, depending on intended use and budget. Our main damper efforts however are being directed toward our own range that should be available within 6 months. We are starting with height/rate adjustable mono-tube coil-overs and the GD chassis is the first on the list.
All the best
Jim
Whiteline
Strictly speaking, any change in spring rate must be matched with an increase in damper rate. We have demonstrated on a number of occassions how even moderately stiffer/lower springs can improve handling on a race track surface IF the OE dampers are in reasonable condition. However, even near new OE dampers are not able to control the increased spring rate on less than perfect (normal) road surfaces. Add 10,000 miles to the OE unit and the degredation in handling is very noticeable.
Increased ARB rates have the effect of putting more load on dampers as they force linked wheels to operate in sympathy due to the larger effective axle linlking the two. That means even more load on the dampers.
Regretably Steve I would suggest that your dampers need some attention and heavier ARB's may simply exacerbate the problem at speed.
Just like excessive spring rates, its also possible to over-bar a car but I mention the 24/26 sizes as a specliased solution for much more serious use where you are generating high G's at high speeds. The reality is, the stickier the rubber you have, the more grip you generate, the more roll you experience, the more load you place on the springs = heavier spring and ARB rates. The extreme is when using slicks, appropriate camber angles become huge because you need to compensate for the extra roll as a result of the extra grip and G forces. I guess the simplest way to put it is if you need more roll control you need more roll control! Springs should not be used for that job as you need to try to keep the springs as supple as possible for individual wheel deflection while still having enough to resist pitch and dive.
Matt, you're right about the B-roads issue and its also very relevant in Oz but its an inevitable consequence of the pursuit of the compromise toward sharper handling. There is always a price, however adjustable ARB's are used just for that reason. Crank them up for Saturday and back them off for Monday.
As for STi dampers, we typically use whatever is available to all of us, Koni, KYB or Bilstein, depending on intended use and budget. Our main damper efforts however are being directed toward our own range that should be available within 6 months. We are starting with height/rate adjustable mono-tube coil-overs and the GD chassis is the first on the list.
All the best
Jim
Whiteline
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