A vehicle could have height adjustable airbags that one minute give it sufficient ground clearance for off road work, and the next a low ride height for optimised centre of gravity on road. Plus they can have a sufficiently stiff rate for optimised on road handling. Even better a progressive rate, which means they are stiffer when the car is lowered. The audi allroad is an example of this. I could do this to my falcon, but don't think i'll bother, i don't like the effort/cost/complexity/risk of failure in the boondocks.



265 wide off road tyres are typically fitted to 7.5" or 8" wide rims. Wider rims make the ride too harsh, and most of all make the sidewalls and rim too vulnerable to damage.


The important thing is that tyres are selected according to the usage. 45 series tyres would not be appropriate for my usage. I need about a 170mm or more high sidewall, about what my 225/75's or 235/75's have.

The other day i placed a 265 into the wheel well of my wreck EB and from the front it's width looked hideous. Whereas tests with the 225 and 235's looked good. I will first use the 225/75's, then when they wear out the 235/75's. Some 235/70R16's would be nice, and so would 235/70R17's, if i could make them fit.


Yes. Since i like comfort and go on dirt and 4wd roads and don't want to overstress the falcon's chassis i am keeping the suspension stock in terms of springs, bushes, and swaybars. Shocks are a little stiffer, some bilsteins would be nice. I find the falcons chassis acceptable to me in this configuration, but don't think i would accept it if the suspension was 30% or more stiffer, as would be the case if the aforementioned components were uprated. If the suspension becomes 30% stiffer, the chassis will flex about 30% more. This creates more NVH, plus the chassis is an undamped spring, so the more involved it is in absorbing road irregularities the more undamped motions will occur. This creates bad handling. Stiffer suspension without a stiffer chassis is not as much an improvement as one would hope, or not an improvement at all, over stock.

A roll cage for stiffness is a bastard on a road car in terms of space consumption, although strengthening the rails is an option i could do.

Last edited by relaxed_diplomacy on Wed Oct 15, 2008 12:46 am, edited 1 time in total.

Well, i've just put an AU motor in my falc, and it might only be a few days before it's running.

As for a supercharger or turbo, more power is always nice in terms of the driving, but not the cost of establishing it, or the extra fuel usage. I'll probably focus on other areas.

Tell that to lotus, lamborgini, mclaren, ferrari, porsche, toyota's mr2, rover's mg, formula1 cars, etc. I don't think they will agree with you.

Grip increases with load, but not quite in proportion, grip increases a little less, so it's the heavy end of the car that can be a problem.

If a car has say 65% or more rear bias, it may generate problems with sudden oversteer, but porsche has shown that appropriate suspension design can minimise that.

Cars that are front heavy with thick swaybars are the cars that understeer like a pig. As mention earlier, extra weight reduces grip. And a thick front swaybar means that when going around a corner the front contributes a greater proportion of the roll resistance, which increases the load on the outside front tyre, which reduces it's grip.

The mitsubishi express van i used to own was a classic example. They put a very thick front swaybar on to make sure under all circumstances it understeered, because with a relatively short wheelbase, stiff short travel rear springs, and front weight bias when unladen, oversteer if it happenned would be dangerously sudden in the average users hands.

The car hated going around corners, it steered like a pig, with the steering loading up, and the car going more straight ahead than around the corner. I took the swaybar off and the steering was lighter, the ride comfort was much better, the handling was much better, etc. Because the front torsion bars were stiff, the rear springs were stiff, the motor was mounted low and the bodywork was lightweight, it hardly had any body roll through corners, even with no front swaybar. Plus it didn't C**k a rear wheel in the air every time you drove on uneven ground, so there were much less strandings.

Another example are jap front drivers. In the early days the front swaybars weren't much bigger than the rears, and the cars would handle neutrally with lift-off oversteer. The lift-off oversteer was great for getting around tight corners. My 1985 mazda 626 was brilliant at four wheel drifting. But then the politically correct brigade said this was unacceptable and from around 1990 onwards they had thick front swaybars, heavier motors and accessories, and understeered horribly.

I agree with all of this. Although, technology can make a car more adaptable, at the extreme end full active suspension is dramatically capable (but uses a lot of power), plus you could have in-cab adjustable tyre pressures, and adjustable bushs would also be do-able. New types of airless tyres may also have much higher lateral stability at the same time as soft absorption of bumps.

Did you fit the thicker front swaybar, rather than both slightly thicker or a thicker rear bar, because as well as reducing roll you wanted to shift grip towards the rear to balance out oversteer caused by your power output?

No the GT's from factory are understeery, caused by a rather heavy rear end, lots of power, and more the sufficient grip provided by good tyres and the IRS rear end with a stiff LSD. Stiffer front sway bar (keeping in mind from factory B series cars use liquid filled bushes - really soft) as you say helps the outer front dig in, producing grip (not loosing it) and has helped with turn in significantly. This is evidenced by the tyre wear patterns I get after a day on track. Pre sway bar I'd get heavily feathered tread blocks across the face of the tyre (tearing due to understeer), now I only get heavily worn outer shoulders (with some marbling) indicating more grip is being realised from them. With a camber adjustment I could wear more evenly, at the expense of abnormal wear on the road (inner shoulder).

Oversteer on the other hand is easily controlled by ones right foot. And while understeer is generally considered (by manufacturers) to be the safer of the two options, out on a race track oversteer is the better of the two (walls generally being on the outside of a corner).

Wow!
http://cars2.ebay.com.au/supercharged-f ... 0310242723

Think of the weight distribution!

If i drove one and agreed with your statement that they are understeery, i would say that is because they have been designed that way, particularly through the suspension settings, including the front and rear swaybar thicknesses. I bet the std front swaybar is thick, most are these days, to create understeer.

I agree that an lsd and a well handling rear end could in the right circumstances keep pushing the front into understeer, compared to without an lsd where the inside rear wheel may loose traction. I don't see this as being an argument against 50:50 or rear weight bias however.

Good tyres should increase front grip as well as rear grip, so good tyres should not contribute to understeer.


There is an interesting effect whereby a thicker front swaybar makes the steering initially more responsive. This is because it more quickly loads the outside front tyre, rather than there being body roll -> then the front tyre loading. But once the body roll is set in place, the front will indeed grip more with a thinner swaybar. My mitsubishi van was again a classic example of this, but in my previous post i didn't want to go into this level of detail prematurely.

As i said in my earlier post, a thicker swaybar on the front means the front plays a greater role in resisting body roll, meaning the front outer tyre is loaded more, and while this means it grips more, it doesn't grip quite as much more as the extra load.



I don't think you got the best out of the std setup. I think your driving style is being compromised by your views on this topic, as well as other factors.

One of the best vehicles to learn to drive with is an early range rover, because it forces you to set it up for each and every corner, and then it corners really well, even though there is heaps of body roll.


Use that foot wisely.


I agree you generally want to oversteer to avoid the walls, but if your car understeers, sometimes if not many times you can back off the accelerator and the front will grip again. Also, due to forward pitching of the car (due to releasing the accelerator), the rear may lose grip, and you get oversteer, and definitely miss the wall, as long as you don't correct with the steering!

When you start driving as a youngster you learn how to correct oversteer, then for the track you need to learn to be able to turn this faculty off.

I don't know what you're experience/quals are. But you're ideas are contrary (why I'm 'arguing') to both what I (amateur racer) and my suspension guy (amateur racer himself, as well as suspension guy to various pro racers in all classes) hold to be true.

I've picked up significant amounts of time on track adding a bigger front sway bar to the GT-P.

My experience and qualifications are the concepts i understand and the assessments and modifications i have done to cars. Grab any decent literature on the topic and you will find it agrees with me.

Suspension is typically grossly misunderstood. It is very complex, and conceptually very challenging. For instance, in my time working in the suspension industry, talking to all sorts of people including racers and some manufacturers, i didn't come across a single person that understood how it really works.

Well done. We've got something to look at now. Here's the blurb . . .

"supercharged EA falcon,
This car is the making of a real tuff streeter, I imported 3.8l ford thunderbird engine from the states, the engine is 3.8 litre aluminium head supercharged V6, It has a wolf 3D engine management system running the engine, eaton M90 supercharger, C4 auto (brand new rebuild), out back is 28 splin axle with 4.11 diff gears in a locked spood diff, king spring all round, slotted brakes , brand new paint 14months ago , dupont chrome illusion ghost flames, 2007 RX8 bucket seats, pro ratchet shifter, and much more.
This car has tones of grunt, the engine is basicly a ford 351 clevo with 2 cylinders cut off, giving it huge amouts of torque, now with over 500lbs and 300kw rwhp"


Despite what he says it sounds like a pretty tough streeter already. I suspect he didn't put the motor in, a 3.8L V6 bore and stroke is actually equivalent to a 5.0L V8. And it's the supercharger that gives it heaps of torque. What do people think of the power and torque stats, pretty high?

According to my engine weights list:
Ford 3.8 V6-90 160kg 351lbs (4) (w/start, alt, less clutch)
Ford 3.8 V6-90 141kg 311lbs (18) ("fully dressed")
Ford 3.8 V6-90 135kg 298 (126) "complete"


I wonder if he is selling it because of the locked diff and bad styling, and he wants even more power but can't get it from this motor.

Here's a pic of the engine bay. I notice you can't see the valance panel, is that what its called, i mean the bodywork in front of the top of the radiator. I wonder if his radiator is higher and/or positioned further back than normal. (and you thought the EA three belt setup was bad):

 

 

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Last edited by relaxed_diplomacy on Thu Oct 16, 2008 12:34 pm, edited 1 time in total.

What your getting at is kinda correct, but the reasoning is sligthly off.

having a softer swaybar may mean that the force applied to the outside front tire will be more gradual than that of a stiffer swaybar (car maybe rolling more/taking longer depending upon design of the swaybar), however once it reaches the maximum roll there will be greater force upon the outside front tire than what there would have been with a stiffer sway bar (and hence less angle upon the car)...

This is because both a greater proportion of the mass of the car will be centred over the outside due to roll, plus the greater angle of the car is such that it makes the car more prone to roll (think of it as the amount the mass on the right of the car has to rise as per its movement to the left, as it gets higher off the ground it becomes easier to continue, it becomes easier if your looking at a quarter of a circle )

The swaybar should be a thickness which allows some roll (as it is important for the outside wheel to gain some more weight over it) without being TOO stiff and keeping the car too flat (ie causing understeer and in extreme cases the chassis to twist)

sorry, i didnt quite make the point with the first part....softer swaybar and front outside wheel getting the vast majority of the grip with the inside wheel not getting grip can cause understeer once it is too great for the outside tire to handle....getting the right swaybar means the outside will still have more force, but it is spread more evenly towards the inside tire also

The increase in weight on the outside tyres due to body roll in and of itself is minor and insignificant on the car we are talking about. The bulk of the weight transfer is being caused by centrifugal forces.

What is relevant is the role the front is playing against bodyroll versus the back, and the implications this has for understeer and oversteer.


Are you saying the greater angle of the body makes the car more likely to experience more body roll, or to actually tip over? There's an important difference there.

By the way, the car doesn't get higher off the ground the more it rolls.


It is good to allow some roll because it reduces snap sliding and tells the driver how close he is to sliding, which are especially important on a wet road.

Even if the body does not roll, the outside wheel will gain more loading due to centrifugal forces acting on the centre of gravity. Even so, this effect doesn't increase grip, it actually reduces it. This ties back to my statement that putting more load on a tyre doesn't increase the grip quite as much as the load increases. If somehow there was a situation where there was no weight transfer, this would actually give the highest level of grip.

My above post went in before i saw this. I'll leave this for another day.