Whiteline - FAQ - Everything Else

Bracing	chassis and strut braces are your Strut Braces adjustable? If so, how do I adjust them?
Kit Development	how we develop car kits
FWD vs RWD	what’s the better system?
IRS	what's the story?
Motion Ratio	what are we talking about?
NVH	another useless acronym?
POLY BUSHES	How do they differ to rubber? What's the correct tightening procedure?
BUMPSTOPS	are they important?

Chassis and strut bracing - how does it work?

There are many different types of chassis braces, the most common being strut tower braces on the front or rear. Not all cars use actual struts though the term "strut brace" is still used to describe a brace between shock towers. For example Honda Civic, S2000, Nissan Skyline and Ford Falcons are sometimes fitted with a front upper shock brace but it does not have as direct an impact as bracing actual strut towers.

The reason is that a MacPherson Strut integrates the wheels upper link point into the actual strut. Hence a significant proportion of wheel load is located by and dealt with the strut. Vertical loads from the wheel pass through the strut and spring up to the strut top and towers which leads to flex in the sheet metal around the strut tower and inner guard. In fact, we've measured up to 15mm of flex on some cars which translates to up to 1 deg of dynamic camber change. Some vehicles will benefit more than others with age being a factor. But, even the newest vehicles have some rigidity problems due to the method of construction. Many new cars have the complete firewall and dash assembly lowered through the windscreen aperture then glued in place. This may actually be more rigid in some directions as claimed by the car makers but we know that fitting a strut tower brace on these vehicles makes a very noticeable difference.

Though not as noticeable or effective, shock tower braces on the cars mentioned above will make a difference. However the actual equivalent load point is usually an upper control arm and its locating points on the inner guard. Bracing these points is the preferred option and is what we have done with EF Falcons and our KSB510 kit. It braces the upper inner control arm mounts to the x-member via the engine mount points. We know it works well because we bent some 10mm bolts on the first prototype we fitted after taking 3 corners!

Whiteline range of chassis braces includes lower control arm braces, extra heavy-duty swaybar mounts and things like rear subframe lock kits.

The following is from Michael South, current (2001) NSW WRX Club Class 3 champion.

Are your strut braces adjustable, and if so how do you adjust them?

A strut tower brace is just an additional chassis brace that can be fitted by the owner to further increase chassis rigidity, specifically between the strut towers. It is not designed to pre-load their mounting points, but rather to simply provide extra strength when needed like during fast cornering.

Yes, our strut braces are adjustable, however this is purely for better fitment and to compensate for vehicle manufacturing tolerances. Significant variation between individual vehicles exist from new with age affecting dimensions even further on some cars. Either way, always fit and tighten the strut tower brace with the vehicle parked on level ground standing at normal ride height.

How Does Whiteline Develop Its Suspension Kits?

First we need to establish and confirm the suitability of a target model and/or platform. That is, knowing the time and effort required, we have to be careful to ensure we get a return for our effort. Fortunately this includes sales outside Australia so we look at other markets like the US and Asia.

Secondly and before we do any work, we look for a suitable vehicle that meets our criteria. Specifically it must be in good mechanical condition, road legal and registered with next to standard suspension. The customer must also be willing to allow us to change whatever we feel is necessary though we may not charge for some of these items even though they remain on the car. Example is a strut brace, we need to develop one but its not strictly part of a kit, just an option. We will often develop and fit this as part of the project at no cost to the customer. The owner must also be totally and unequivocally accepting up-front of the work we need to do. Having done that, we can start doing some real work.

It is not unusual to make a number of changes to spring, swaybar and shock rates along the way. This often has the affect of altering the required specification of other related parts creating a viscous circle of changes. Ultimately the car will be road tested by at least 3 people to make sure the vehicle delivers the best possible combination of ride and handling.

Where possible, we also take the car to a nearby racetrack for testing and to confirm our alignment settings and assumptions. This usually involves 2 staff for half a day (Whiteline driver with C3 license) and includes fitting G-force meters and using pyrometers to measure tyre temperatures etc.

During this whole process we also develop a list of optional items that work yet don't necessarily make the cut for the kits, which have to deliver value according to our BFYB (bang-for-your-buck) formula. This process may take 2-3 visits and a lot more if the target is a club race platform using race tyres or slicks. In amongst all this the owners drive their car and we encourage their feedback to add further input into the process.

FWD vs RWD – what’s the better system?

We are regularly asked this question so we thought it would make a good FAQ topic. The following has been copied from the most recent question and answer posted to our discussion group.

Is there a distinct advantage of one or the other when talking about Camry, Commodore sized cars....does one tow better, does one handle better etc etc or is it fundamentally down to setup.

What a great question, a good way for us to get into some serious trouble. Anyway, here goes…..

To answer this properly, it pays to first get a bit of industry background from the last 20 years. FWD was developed as a cost saving measure for vehicle manufacturers. Its cheaper to build a car with FWD for obvious reasons but also because the complete package can be lighter, smaller for a given target load volume capacity and will use less fuel. A FWD is also inherently more "Wally" friendly for the average driver as the natural balance is toward understeer. Panic reactions by the driver will result in more benign behaviour than you'd get from a RWD and it’s easier to keep it that way.

So, the manufacturers drive the demand by telling us all its a great thing, and in a big picture sense it is because cars a cheaper now than ever, they use less fuel and they're safer in both passive and active terms. But, WE enthusiasts all know something's just not right.

Early last decade the motorsport players were faced with a 2.0 litre FWD platform for developing a racing series with. They were quick to realise that the format created some fairly major technical hurdles in terms of chassis tuning etc. The most significant being that the same wheels that steer the car, now have to deliver drive torque as well. I've mentioned this before but it’s worth mentioning again. A tyre has a finite amount of grip available to deliver albeit proportionate to its load. Grip increases with load but at a diminishing rate, but then falls away dramatically when it reaches the limit of adhesion. With the same given load, a FWD front tyre has to proportion grip between lateral (cornering) and longtitudunal modes. That is, the harder you accelerate, the less grip you have left to corner with (this should start to really ring some bells in your head if you drive a FWD or a WRX with out a front anti-lift kit).

With a RWD, drive and steer are largely separated so there is greater inherent balance though poor chassis weight distribution can easily cancel out these benefits. This load/grip relationship becomes a bigger problem when you consider that a FWD can have up to 62% of its weight over the front wheels! Just think back to the last time you came into a corner too hot, under brakes and turned the wheel. What hapenned? Very little as far as cornering goes, right?

All this would suggest that RWD wins and FWD looses, but this is not the case because the racing industry responded to the reality of FWD being the dominant passenger car platform and started on a hugely steep and expensive development curve based around these problems. The result is the British Touring Car series as we know it, and the fact that a Super Tourer will run faster across the top of Mt Panorama than a V8 even with a huge power deficit, an impressive acheivement.

It's poignant to also point out at this stage that in World class rally terms, tarmac stages are generally won by the FWD's not the 4WD's. That's because grip is no substitute for good handling, something which the FWD developers have elevated to a science. This is not to say that a RWD would not ultimately be faster than a FWD but only if you could deliver the power to the rear with a similar overall power to weight ratio as the FWD, and that's highly unlikely. The most effective example showing the pinnacle of what is acheivable can be found in F1, but these cars use a mid engine RWD layout which delivers a good compromise between total weight and its distribution.

A guy said that FWD is more expensive to repair, but given the new RWD IRS systems use nearly twice as many joints, surely this must be a suspect comment. Might have been true with the old rigid axles, however tail-shaft vibration was and still is a problem .

This is a difficult one. My personal suspicion is that FWD would be marginally dearer due to the use of CV joints in the drive-shafts. These things are a relative marvel in engineering terms as they do a huge amount of work and still manage to last a reasonable period of time. But this would also apply to 4WD and IRS RWD. The counter to this is the extra cost of maintenance resulting from the extra weight of a RWD.

Volvo & SAAB actively promote fwd as safer in mud, snow & ice, certainly Scandinavian rally and f1 drivers are amongst the best !

Yes, this is probably true, but not as safe as AWD or 4WD. But, given a choice between RWD or FWD and forced to make a generalisation I would have to agree with that due to the issues raised earlier.

As far as towing goes, FWD is definitely a looser as the extra weight over the rear axle acts to raise the front, taking load off the wheels that need it the most. Even when using towing aids and weight distribution couplings, it’s always a compromise. Being a trailer boat owner, I often see a FWD madly spinning its front wheels while trying to drag a boat out of the ramp. If you do own a FWD and choose to tow a reasonable load, it would pay to invest in a weight distribution hitch system as they work very well and allow for safe enthusiastic driving even when towing.

IRS, what's the story?

IRS stands for "independent rear suspension." The argument that IRS systems are superior to live axle is neither clear cut or straightforward. As IRS systems vary in design and configuration so too do the pros and con is in any comparison.

The system used on Commodore VP to VT is a simple relatively old design, not dissimilar to the VW swing axle as it allows dramatic camber and toe change during its travel. Have a look at the rear wheels of any Commodore VT wagon next time your driving behind one, or think back to early BMW's and Datsun's. This is why Whitelines IRS Commodore rear camber/toe adjustment kits are so popular when lowering the rear.

The system on The AU Falcon however is a more modern design with a complex link arrangement to maintain angular integrity. Though superior to the Commodore in minimising dynamic angular change, the Falcon system is more complicated and expensive to produce.

It is unlikely that you will ever see the existing Commodore IRS system used in Touring Car racing even if it was allowed under the regulations due to the angular changes during wheel travel. Race tyres measuring 260mm in width are not designed to work on the extreme inner and outer edges. Dynamic camber changes do all sorts of horrible things to tyre surface temperatures resulting in increased wear rates. The smaller contact patch considerably reduces available traction in cornering acceleration and braking. Similarly, high performance road tyres are wasted on poorly aligned IRS Commodores resulting from excessive lowering. They also wear out real quick!

Formula 1, Sport Sedans or other high end applications employ double wishbone independent suspension systems that eliminate unwanted angular change even though they may have more total available suspension travel than a Touring Car. It is therefore important to note that IRS refers to any system that does not use a solid linked connection between left and right sides. Therefore, a contemporary multi-link Mercedes rear, VW Beetle swings axle, Commodore "IRS", Falcon "IRS" and F1 cars all employ "independent rear suspension" yet you couldn’t compare the individual systems by the same criteria.

On the road, the correct question is whether the car will be primarily used on relatively smooth or bumpy surfaces. A well located live axle will perform at least equal to if not superior than older designs of IRS systems on all but bumpy roads where greater independent compliance of most IRS systems will prevail. Bumps encountered by one wheel will not effect the other as much as with a live rear axle. A good IRS system will however offer suspension tuners the ability to change the rear wheel alignment setting, which is an advantage.

Probably the biggest drawback to the Commodore IRS systems in the Australian market is the load carrying problem. Though not essential, most driven IRS systems traditionally use a Mini Block coil spring, which is very short and compact. It is designed to compress into a very small shape under load due to its location inboard of the wheels. Its not unusual to see a greater than 2:1 wheel to spring motion ratio resulting in a short stout spring with little design flexibility to accommodate higher load carrying.

The AU Falcon IRS system however is similar to a Chapman strut arrangement used on small 4 cylinder front wheel drives. This allows the designer to use a much larger springs with greater load carrying capabilities.
In short, heavy load applications like LPG installations, towing or even family vacation touring will force huge camber changes in a Commodore IRS system, as the standard spring can not resist the higher load. Therefore, be mindful of the relevant comparison issues prior to deciding which system is more suitable. If you do decide on an IRS system, Whiteline has a range of heavy duty Select coil springs to suit.

Motion ratio, what are we talking about?

Probably the most misunderstood component of the sway bar and spring design functions. The effective spring or bar rate at the wheel is the only relevant number when discussing spring or bar "rates". The actual rate of the spring or swaybar itself is irrelevant without the knowledge of the effect of the motion ratio on that rate.

That is, it is rare that the spring or sway bar moves up and do over the same distance as the actual wheel. For example, a HQ Holden front wheel may move up 50mm when hitting a bump but the spring will only move (compress) around 25mm. The sway bar will move (deflect) a little bit more. These are examples of relatively large motion ratios. On the other hand, a strut based front suspension system delivers a relatively small motion ratio.

This motion ratio changes the leverage and effective rate of the spring and sway bar at the wheel. Hence a 500lb front spring for a HQ can’t be compared with a Commodores 300lb front. Whiteline always designs its replacement springs to deliver the optimum spring rate AT THE WHEEL, not at the spring.

The same applies to sway bars but is further complicated by the presence of the swaybars lever arms which also determine the effective bar rate at the wheel. That’s why a 20mm diameter sway bar with short arms can have the same bar rate as a 30mm with long arms. Our Swaybar range often uses changes in motion ratio to design better and more appropriate sway bar shapes to modify the roll characteristics rather than just a straight increase. Our Whiteline "Blade" adjustable bars use these principles to achieve much higher roll resistance with a smaller diameter bar.

NVH, another useless acronym?

Not at all. NVH is a car industry term that stands for "noise, vibration & harshness". It is used to describe the group of symptoms that we relate to when we say a vehicle is rough, noisy or harsh.

A good example of a car with poor or lots of NVH is one that has had all the bushes replaced with polyurethane or mechanical rod ends. A perfect example would be a dedicated racecar. Specifically, the items that were designed by the manufacturer to insulate the occupants from the road have had the compliance removed allowing road and tyre movement and noise to pass through to the cabin and occupants.

Spring, damper and sway bar rates also affect NVH. In fact every suspension modification WILL have an effect on NVH. It may surprise you to know that a softer spring can sometimes increase NVH while a firmer spring may improve it. Whiteline uses a computer simulator to calculate "natural frequency’s" when designing new Select coil springs to ensure that NVH levels are minimised.

Another popular source of increased NVH is mismatched springs and dampers. In almost all cases, this will lead to unnecessary increases in NVH. Hence Whiteline’s "Sports Pack" approach that provides matched and balanced solutions.

It is very easy to design the steering & suspension components to link directly with each other making steering and handling response razor sharp, but the NVH levels would be totally unacceptable for road use. The challenge is to design modifications that compromise toward improved handling with out greatly sacrificing NVH levels. Whiteline specialises in delivering this compromise. Our "Handling Pack" range is specifically designed to maximise handling improvement WITH OUT major increases to NVH.

POLLY BUSHES - HOW DO THEY DIFFER TO RUBBER

Rubber is a natural material that can compress and change its volume with load. Polyurethane (or poly for short) on the other hand is a synthetic compound derived from crude oil that acts like a liquid. That is, its volume stays constant so it can not be compressed. A rubber ball squeezed inside the palm of your hand will shrink in size relative to how hard you squeeze. Poly on the other hand will simply try to squeeze out between your fingers. This has a bearing on the way each product works, its strengths and weaknesses along with opportunities for use in the automotive industry.

For example, rubber works very well as a noise and vibration dampener as it can actually seem to absorb energy although ultimately it does convert kinetic energy to heat. Poly on the other hand needs to move in another direction to accept the load. It too will heat up but it will work much more effectively as a bearing surface than rubber for example. Rubber perishes over time (worse if exposed to sunlight) and will break down if contaminated with chemicals like oil and petrol. A perfect example is CV boots or steering rack mounts that get covered in engine oil. Poly on the other hand is relatively impervious to these sorts of chemicals.

Rubber bushings are often made with the inner and outer shells bonded together using the rubber compound in between. The rubber is allowed to flex and distort with twist while acting as a damper for NVH. Most aftermarket poly bushings that replace these types of rubber applications are simply pressed in between the inner and outer shells, without an actual bond. Even if bonded, it will only ever be to one surface as the material will try to tear itself apart if bonded to two surfaces. Unlike rubber, the poly alternative operates with a bearing surface allowing one side two turn on the bush relative to the other. This is why grease is so important.

Poly Bushes - Whats the correct tightening procedure?

Both materials are comfortable with the concept of "crush" or pre-load" where by a certain amount of force is applied as part of the fitting procedure however rubber can tolerate more due to the nature of the material. Poly is much more sensitive to the extent of "crush" and this forms an important part of the design process.

For example, poly shock or swaybar link bushes should only be tightened till the material is firmly held but before it distorts. Too much pre-load can result in prematurely failure of the associated steel components. This is a common problem with broken Commodore front swaybar links as people over tighten the replacement poly link bushes. Generally all bushes should be tightened with the vehicle at normal ride height. This is good practice with all chassis parts but is particularly critical for rubber components. On the other hand, bushing made from poly can be tightened in any position, but it is good practice to check and re-tighten all nuts and bolts after a test drive and ideally this to be done at normal ride height.

In summary, the number one rule with poly is do NOT over tighten and use plenty of grease when fitting.

Bumpstops - are they important?

Yes they are, very! We are very concerned to hear that some people are not using bump stops, whether when replacing shocks, springs or simply no self action by perishing of original bump stops due to "wear and tear" (which is only exaggerated with lowering springs).

Long gone are the days that bump stops were like the thing behind that kitchen door that simply stopped the lock going through the wall. Although solid rubber bump stops are still used in some applications and critical positions on the car to protect against suspension metal-to-metal contact, most contemporary suspension designs now use a much more sophisticated bump stop made from micro-cellular foam. This has a number of advantages including low weight but more importantly as far as vehicle dynamics is concerned it has much better energy absorption properties. Many vehicle manufacturer’s including Audi, BMW, Honda, Porsche, VW, and many others factor in the bump stop as an integral part of the spring and shock calculations. In fact, the bump stops also act as a secondary spring and without going into too much detail, and is the reason that a simple linear spring with a micro-cellular jounce bumper becomes a progressive spring as the load is increased. This is a very important relationship, which allows for a softer main spring for a more comfortable ride while cruising, with progressively increasing ride stiffness during cornering for better handling.

For the record there are only a handful of aftermarket shocks that are supplied with new bump stops. In fact 99% of all the popular performance brand shock offerings are supplied WITHOUT new bump stops. There are some exceptions, such as inverted mono-tube struts and strut inserts, which use an internal bump, stop by design.

Unfortunately it is no longer clear nor straightforward whether or not the stock or OE bump stops need to be trimmed or modified when lowering a car. It depends on the amount of lowering and the specific vehicle and sometimes its more important to replace the whole bump stop with a new one. Furthermore, in many contemporary suspension systems, which is important to realise that it is a system of interconnected components which must work in harmony, jounce bumpers are close to or in contact at normal ride height, so consider this next time you contemplate lowering your car. More on this in other sections but suffice to say, it’s a very important area that needs the input of a qualified suspension fitter or tuner, but if in doubt do not cut.

The other item that is very important is the thin white plastic discs and these are not bump stops. Aftermarket shock manufacturers use various shapes and sizes, some with a split, some are simply corrugated. These also serve a very important role. The purpose for these "split" discs is to vent pressurised air that is compressed inside the bump stops. This happens when the bump stop is being compressed and air is sealed between the shock and top spring seat. If this is not vented, this compressed air can get past the top shock seal and into the shock itself.

Tech Talk FAQ. Everything else we can think of at the moment

Bracing

Kit Development

FWD vs RWD

IRS

Motion Ratio

NVH

POLY BUSHES

BUMPSTOPS