G'day

We've recently started doing development work on P-Rex III (our new GD 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/d...%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:
Bridgestone Potenza 215/45/17 (Stock) Pressure 34 psi
Camber -1.0 deg
Caster +3.75 deg (changed for ALK testing later)
Toe 0.0 mm total

Rear:
Bridgestone Potenza 215/45/17 (Stock) 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

Go flat out with Whiteline Automotive

See us at www.whiteline.com.au
Buy online at www.whiteline.com.au/store

 

Jim:
I installed the Whiteline adjustable rear bar a few weeks ago on my new '03 sedan, along with your heavy duty mounts and new alloy endlinks. I must agree that the handling is much more neutral. I love it! I'll be fitting 17" wheels and high performance tires (still running on the 16" RE92's) within the next week or so, and will be following the reports of your future upgrades closely.
What would be the reason to go with a stiffer front bar? Would you then adjust the rear bar to full stiff to compensate and maintain the near-neutral balance?

 

G'day everyone,

Rodon, the idea is to generally increase the overall roll resistance to suit more sporting driving and handling characteristics while also changing the handling bias.

Think of it as 2 glass beakers, one for each front and rear. We pour more roll resistance into each beaker (larger swaybar) to improve roll control but then we tip a little more into the rear beaker to reduce the natural stock undertseer. We can't leave the back beaker full and the front nearly empty.

Typically, when using just a larger rear bar as shown on the test, we'll use a mid level adjustment knowing that we will move to highest when coupled with a larger front ARB.

mysubaruimp, I'm sorry to hear that your bar was finished so poorly. I'd like to see a picture of it so we can work out what to do.

We are a relatively small manufacturer of specialised handling parts, many of which are produced by hand in small batches. This has the benefit of giving us a lot of flexibility on the one hand but also means that sometimes the finish can be a little ordinary. We are working to improve that by commissioning our own powder coat line in house which will give us better control over the finish.

That said, we must be honest and say that our number one prirority is to "function" not "form" and that includes value for money. We can never see our product matching the packaging standard found in Japanese sourced brands but on the opposite side I think we will also offer excellent value for money product that works well.

Please let me see an image of the product and we'll replace it FOC if need be.

Best regards

Jim Gurieff
Whiteline

 

G'day,

mysubaruimp, thanks for the links, some good feedback that I've forwarded to our production people.

Your correct in assuming that we would prefer to know the positives and the negatives. There's litle progress with out feedback.


All the best
Jim

Whiteline

 

Hi everyone,

Steppin Razor, we have reccomended rear toe out for WRX and Impreza setup since 1997, or pretty much since we started development work on this platform. The reasons behind that are varied but all genrally lead to the same thing, its faster that way.

A small amount of toe out becomes your ally during direction change as the "twitcheness" you speak of works to unsettle the rear end prompting it to change direction and follow the front quicker.

The degree of toe out is to some extent subject to driving style and approach as some people find 1mm (total) slightly disconcerting while others maybe happy with 3mm. Braking can appear nervous but it generally is just that, appearance. Excessive tyre wear has never been an issue in 6 years of practical setup and road/racing experience.

Can I suggest that anyone interested in reading a little more about our rationale behind this position take a look at the "Toe" section of our FAQ at http://www.whiteline.com.au/faqsusp01.htm. Basically, assuming most of the torque is still sent to the front wheels, we use toe out at the rear to promote some instability to help overall turn-in and direction change. This has proven to be the fastest way around the track while giving greatly enhanced repsonse on the road.

STi Type RA cars with selectable front rear torque split or vehicles with highly preloaded centres diffs, locked front or rear diffs will require more thought as a result of the different drive characteristics but our reccomendations are based on conventional WRX, RS and STi spec vehicles with factory drivetrains.

I guess its a little unconventional compared to other tuning companies advice but I suppose most have already guessed that we're not really conventional.

Cheers
Jim

Whiteline Automotive

PS. We have some customers that ask for and maintain around 1mm total toe out on the front as well.