Suspension Secrets - Part 1We talk to one of Australia's leading suspension gurus regarding front-wheel-drive vehicles...

By Michael Knowling, Pix by Julian Edgar

Jim Gurief of Whiteline is one of Australia’sleading aftermarket suspension experts. Here wetalk to him regarding factory front-wheel-driveset-ups and modification.

Front-wheel-drive handling is often criticised -is it really inferior to a rear-wheel-drive?

No, it's not a case of inferior - it's more a case ofvery different.

Back in the early '90s - when front-wheel-drivetechnology started picking up steam and thebeginning of the British Tourers and so on -manufacturers realised they had a pedestrianplatform that they had to try to make handle.Before then, front-wheel-drive packagingtechnology had out-stripped the speed of thedevelopment of the suspension engineering froma performance point of view.

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So from that 1990s period on, over the next sortof 10 years, they showed what could be done - tothe point that you can no longer say that a factoryrear-wheel-drive has better balance overall than afront-wheel-drive. Today, it's really more a caseof weight balance.

But - still - front drive cars have that inherentdrawback where one set of wheels has to managefore-aft and lateral loads. That's the big limitingfactor.

How have car manufacturers benefited frommotorsport development?

The way they set up the geometry, the way theyslow down weight shift and the way theyproportion weight shift when they need it oncornering. All of these things.

I mean, in the aftermarket, we've been puttingbigger rear swaybars on vehicles for years. We'renot rocket scientists, but when the SubaruImpreza WRX came out in '94 they had - frommemory - a 14mm bar on the back. Now theycome standard with 20mm. Even going back tothe Pulsar and Corollas in the '90s, they had 13 -14mm bars on the back. Now they're up to19mm - because the manufacturers have learntfrom the racing development. Swaybars aregreat, because you can keep the cushy ride of softsprings while also giving taught and controlledhandling.

The other thing you have to throw in is tyrerigidity. When we talk about spring rates there'retwo conversations - the effective spring rate oncethey're installed in the car, and the one that'sspecifically met. Most people talk about thespecific rate of the spring itself, but we prefer totalk about the effective spring rate - it's the onethat's effective on the contact patch. Acombination of the [spring rates of the] carcasssidewall, the bushes, etcetera, etcetera.

Without actually changing the physical lump ofwire, the effective spring rate over the contactpatch has gone up and up over the last 20 years.That's mainly because of the improvements intyre technology.

We've also had a realisation that positive castoris a good thing. Up to a point, the more themerrier - the limiting factor being steeringsensitivity and weight. But with standard powersteering [those limiting factors] have nowbecome a non-event.

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Are there any factory front-wheel-drivevehicles that handle extraordinarily well?

The best ones are Honda Civics - they've gotlovely geometry. However, they're the easiestones to stuff up with lowering. They respondvery well to better shocks and a rear bar - theyrespond badly to lowering without someexpensive changes to geometry. The frontwishbones are a very serious system - wellengineered and with great attention to detail.Lowering just puts it way out of its optimumtravel range.

Mitsubishi Lancers and Mirages are also verygood out of the box and Magnas are excellent.We've got a range of stuff for Magnas - they're areal bargain. A 3.5 V6 Magna with some sensiblechanges is a real performance bargain.

Wouldn't the grunty Magna FWD struggleputting all of its power down exiting a corner?

Oh yeah, but I mean that's a standard sort ofthing for any front-wheel-drive with decenthorsepower. That's a fact of life. That's whenyou start talking about the benefits ofall-wheel-drive.

Are there any typical weak points in today'sfront-wheel-drive vehicles?

Anti-lift. That's the main one that we see. That'swhy we have our anti-lift kits - we sell them formore than Libertys and Imprezas, we also usethem on GSR Lancers, Pulsars and Starlets.Anything that has considerable power - or thepotential for a major power upgrade. You see,because drive happens through the front wheels,they're very sensitive to weight transfer.

With anti-lift, however, you get pro-dive - that'sthe downside. Anti-lift on acceleration meanspro-dive on deceleration. What we do with ourkits is basically reverse some of the built-inanti-dive. We don't make it pro-dive, though,because maintaining some anti-dive is veryimportant for the Wally factor. For example, ifsomebody's hammering around a corner andthere's somebody in front of them and they haveto brake, the last thing you want is the nose tobury.... because then the rear will swing rightaround.

How would you describe the handling of - say- a N14 Nissan Pulsar SSS?

Basically, it's a typical front-wheel-drive wherethe manufacturer's had to deal with theconflicting aims of turning the wheels anddriving them at the same time. That's the basicweakness of any front-wheel-drive system. Witha rear-wheel-drive, the rear tyres aren't under somuch stress - they're there primarily for driveand a bit of lateral grip. In a front-wheel-drive,however, we've got the worst of both worlds.

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We've got the front wheels with a huge amountof weight over them - so it'll tend to understeer -then we've got the same wheels that have to turnand drive at the same time - which means moreundersteer. So, basically, it'll understeer onturn-in, mid corner and when you're gettingpower down to exit.

What should be someone's first FWDsuspension mods with a budget of around$500?

A decent wheel alignment, a bigger rear bar andsomething like a castor kit on the front.

We offer wheel alignment specs on our WhitelineFact Sheets, but - as a rule - we say a bit oftoe-out on the rear, which makes essentially anunstable condition. What we try to do is enhancerear end instability so it feels livelier. Camber wedo between about ½ and 1½-degrees neg,depending on how enthusiastic the people are andthe characteristics of the rear end. For example, ifyou've got an IRS on a front-wheel-drive it tendsto toe-in or out under bump - so we've got toadjust the static camber accordingly. If you'vegot a beam axle rear you can't change anything.

Wheel alignments are a good starting point.

Bigger wheels and tyres are a common firstfitment - are they effective?

They are, but they're a relative high cost item.Just a sticky set of rubber on their own won'tsolve everything, though, because the only wayyou can use that bit of rubber is to put moreweight on it. The only way you can do that is bychanging the weight distribution or the transferdynamically. A rear swaybar will do that - in factthe only thing that limits the size of the rear baryou can fit is the quality and size of the frontcontact patch.

Putting something like a set of road-legal slickson the front of your standard Pulsar is a waste oftime - it'll be diabolical in anything than anabsolute dry condition.

Upping the budget to around $1500, whatshould come next?

I'd have to say quality rubber or shocks, plus theitems I mentioned before. As far as the shocksare concerned, when you put a bigger rear baron, you have the effect of slaving one side to theother. It has to work harder. Straight away thatputs OE shocks under stress so they'll wear outsooner. An aftermarket shock should last longerand give better control.

I'd also look at the front swaybar and the bushes,depending on what car it is.

Do different bushes really make that muchdifference?

Oh yeah. They make a big difference - especiallythe castor bushes on most modernfront-wheel-drives. If you make that more rigid,it'll change the amount of dynamic castor changeat the wheel. I mean our anti-lift kit might onlyadd half a degree castor static, but the reducedbush compliance gives you about a full degreedynamic.

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Is there no limit to the amount of front castoryou can run?

No, there is a limit - but that's due to a wholebunch of geometric factors. Basically, you can'tget to a point where the wheel is way out in frontbecause every time you turn the wheel it's goingto want to climb out of your hands and it'll wantto fold over to a point.

We're talking within reasonable limits. Forexample, you'll find about half a degree morecastor on the MY01 Subaru WRX than on theMY00.

Do specific cars have any castor bushweaknesses?

Pulsars, Corollas and Lancers the rear of the frontlower arm pick-up point - the bush there. That'sthe lowest cost, highest change mod you can doafter the rear bar - it'll be like a $100. It'll give acastor change and it'll be lower compliance.

The Hyundai Excel is also a classic example.You can chuck them up on the hoist and - with adecent sized screwdriver stuck between thelower arm and the chassis - you can bend it andwatch the front wheel will move a lot. Thosebushes are really soft to give minimal NVH[noise, vibration, harshness] .

What are the downsides of the mods you'vementioned?

NVH will be increased. Just swaybars, however,are the most benign change from a NVH point ofview.

And how would wet weather handling beaffected?

Well, you've got to do it within reason. That'swhy you've got to trust people like us to saywhat we catalog is what we recommend.

Would an inexperienced driver struggle withthese changes?

They would notice a more nervous rear end indry and wet weather. Not necessarily negativenervous to the point of being uncomfortable, butit's just not dead. That could be potentiallyunsettling. But - ultimately - it will behave moreneutrally.

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If it's driven by someone experienced andsmooth it'll be better in every respect. But it'spossible that if someone's not terribly disciplinedor skilled, they can increase the amount ofundersteer on corner entry, for example. If theycome in hot, jump on the brakes and they'veremoved the anti-dive - they'll plough ahead.You have to be aware of that. Most of what we'retalking about will allow for a slow-in, fast-outdriving style - or, really, same speed in, faster out.

But tolerance is reduced. In other words, if youcome in hotter - up to a point - there's a chancethat you'll go straight ahead because all weighttransfer is towards the back. And if the tyreshaven't kept up with the rest of the packagethey'll give up.

Are strut braces truly effective?

One of the great opportunities is chassis stiffness.We no longer refer to just strut braces, we referto chassis braces - we're introducing more andmore braces. A strut brace is only one tool in thewhole arsenal.

The lower control arm braces, for example, are ahuge area for gain - because the manufacturersoften seem to build in a system that allows theengine to evacuate the engine bay as quickly aspossible in a frontal collision. So there's veryfew cross members now that are close to thefirewall - they're more forward. That means thatthe rear pick-up mounts can flap around in thebreeze, relatively speaking. One of the greatestbenefits you'll find is bracing those four points -the front pick-ups and rear pick-ups of thecontrol arms.

If we do nothing but change that on afront-wheel-drive car, you'll find a hugedifference. It's much tighter - but it'll feel likeit's understeering more in a way because you'veincreased the effective spring rate. Instead ofthings wobbling around, and there being lots ofloss of movement in chassis bending, it has totransfer it up to the pick-up points on the springs.We often hear the car understeers more when anupper or lower brace is put on. I say that's good -that means whatever you do now is more directlyrelated. A simple wheel alignment change willusually fix that understeer.

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So instead of setting the car up with negativecamber on the front (pre-empting that it'll move),you can set things and they'll stay there. So - yes- rear strut braces on front-wheel-drives are oneof the killer applications. If you accept thatincreasing rear roll stiffness improves handlingthrough diagonal weight transfer, think about thestrut towers moving in and out as you try totransfer that load from the back to the front. Ifyou brace that area it makes a very noticeabledifference. In other words, if you put a rear baron a FWD and then put a rear strut brace on,you'll notice a big difference.

Think about a box. If you imagine the struts asyour vertical sides, we'll assume the crossmember as the bottom - what's at the top? It'sopen. If you can box it in that gives it a lot morestrength.

From a launch point of view, how do youreduce weight transfer to the rear - away fromthe drive wheels?

The first thing we try to do is remove any pro-liftgeometry. In the case of a GT-P car - wherethey're limited in what they can do - they puthuge spring rates in the back. That's the simplestand easiest way. The thing is, if you increase thespring rate you're stuck with it all the time - evenif you don't need it. If you're cornering and youhit a bump, you're stuffed because it'll throw thecar off line. You lose contact with the road andyou've lost.

You can also increase the bump rate in the rearshocks to try to slow down the transfer. With ashock we can increase the bump rate so we slowdown the weight transition - and that's generallyall we need in a lot of cases.

Summary...

It's simple to make a front-wheel-drive handlebetter - easier than rear-wheel-drive to someextent. But - ultimately - they won't be as goodas a rear drive. That's because so much of thework has to be done by just the two front tyres.In Part 2, we'll be talking to Jim about constantall-wheel-drive handling and suspensionset-ups...

Contact:

Whiteline Suspension+61 2 9603 0111

www.whiteline.com.au

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