Rear camber on Live axle

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Rockit

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can someone verify for me.

every live axle car i've driven has done WAAAY better with very little rear camber, sub .5 to be exact. Anyone else notice this? i believe that gt doesn't make its live axle cars handle like IRS, in other words that camber is ALWAYS there, if you corner, you might have more outside tire grip but way less inside tire, as the tires will always be angled from each other instead of how IRS keeps them both parallel.

let me know what you think but i noticed NO loss in lap times on my 69 camaro by dropping half a degree of camber (for a total of 0), but a big decrease in 1/4 mile times(duh). there was actually a decrease in lap times as well but it's arguable if it was camber or one of the other settings i changed.
 
It's funny i was just thinking about this these last few days, how it would be difficult to add extensive rear camber (in real life) to a car with a live axle. I haven't done any experiments yet in the game, but i'll check it out...
 
people DO add tiny amounts of toe in by heating and bending the shafts, but that's uncommon. notice they go for the toe not for camber. a live axle car ought to have the best forward motion seeing as its geometry is ideal for take off and does not change no matter what. I remember reading once that in a perfectly smooth world, IRS has no real use, the body may lean over the tires but do you think camber is really going to come into play that much?
 
Rockit
people DO add tiny amounts of toe in by heating and bending the shafts, but that's uncommon. notice they go for the toe not for camber. a live axle car ought to have the best forward motion seeing as its geometry is ideal for take off and does not change no matter what. I remember reading once that in a perfectly smooth world, IRS has no real use, the body may lean over the tires but do you think camber is really going to come into play that much?
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Quite agree on the camber and toe side of things for a live axle, and while in a perfectly smooth world they may be 'potentially' superior to IRS its not quite that straightforward. The following link is quite useful (if a bit basic) on teh subject...

http://www.autozine.org/technical_school/suspension/tech_suspension1.htm

tech_pic_sus_liveaxle.jpg


Until the late 70s, most cars still used this simple non-independent suspensions, especially at the rear axle. Basically, it is a rigid axle fixed between left and right wheels. The car body is suspended by leaf springs or coil springs on the axle / wheels unit.

As you can see, the wheels are not independent. When one wheel rides on a hump, the shock will be transferred to another wheel. Besides, both wheels will be cambered, thus non-neutral steering is inevitable.

If the axle is also the driving axle, it is called Live Axle. Live axle is very heavy. It consists of the final drive / differential, drive shafts and a strong tube enclosing all these things. Since the whole axle is rigidly fixed to the wheels instead of suspended by springs, the so-called Unsprung Weight is very high.

What is the result of high unsprung weight ? Assuming a live axle meets a hump and "jump" quickly upward, the more weight it has, the more momentum it gains (because momentum = the product of mass and velocity). That means the more momentum the springs have to deal with. Of course, springs cannot absorb all the momentum, so eventually part of the latter will be transferred to the car body in the form of shock. Therefore live axle is never good at ride quality.

If the axle is not the driving axle, it is called Dead Axle. Without the driving mechanism incorporated, dead axle has much less unsprung weight, so its ride quality is better than Live Axle. Anyway, comparing them is useless - it does not make sense for a car to use dead axle in the non-drive wheels while using a suspension advancer than live axle in the driving wheels. Independent MacPherson suspension is rather easy and cost-effectively to replace the non-drive dead axle. If a car maker cannot afford such little additional cost, it must not willing to employ advancer suspensions in the driving wheels also.

Live / Dead Axle have another disadvantage - body roll is not sufficiently suppressed. Springs are the only element which control the body roll, however, stiffen the springs will inevitably deteriorate ride quality. Moreover, if coil springs are used, lateral force due to cornering will lead to transverse movement of the car body, thus result in weight transfer and affect steering response.

The popular solution was to add some control arms between the car body and the axle, such as Panhard rod and Watt link. However, they are out of our scope.

Advantage: Cheap. Body roll does not influence the camber of wheels.
Disadvantage: Non-independent, bad ride quality, both wheels cambered on bump.
Who use it ? Some American sedans, Ford Mustang, Falcon, most SUV.
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...issues such as a high unsprung weight and transverse body movement under lateral load are always going to be issues.

However we do live in a very bumpy world and as such the limitations of live (or dead) rear axles do generally outweigh the advantages, that said a good basic chassis and a descent engineer doing the set-up can help out massively. Ultimatly however if you were doing a clean sheet design of a racing car, unless you were forced to by regulations, would you use a live (or dead) rear axle?


Regards

Scaff
 
Yes if it came in the car i was racing, plenty of live axle cars were/are succesful, no if i had a choice. nascar uses live still i believe.

now back to useable information, how does GT handle the physics of a live axle? if its true to life then camber will mess up live axle cars alot. a degree of camber would literally destroy off the line traction and probably hurt your cornering as well yes?
 
Rockit
Yes if it came in the car i was racing, plenty of live axle cars were/are succesful, no if i had a choice. nascar uses live still i believe.

now back to useable information, how does GT handle the physics of a live axle? if its true to life then camber will mess up live axle cars alot. a degree of camber would literally destroy off the line traction and probably hurt your cornering as well yes?
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You are quite correct that setting camber on a live axle in the real world would have a quite unpleasant effect on the straight line traction and cornering. Its also something that would be very difficult to do on the vast majority of live axles due to the direct mounting nature of the wheel hubs. The picture below illustrates that quite clearly (this on is from an older Caterham design).

liveaxle.jpg


As for GT4, well I must confess that its been a while since I set up a car with a live axle, but I don't remember ever running them with a large amount of rear camber at all. That said GT4 does to a degree 'dumb down' the majority of the more extreme effects of extreme tuning, hopefully a situation that will not remain for GT5.


Regards

Scaff
 
so a "live" axle is the axle in which it is powered, like FR, the rear is a live and front is dead?
 
If it is a solid axle.

FFs quite often have dead axles out back.

So no. FR almost ALWAYS has IFS, except on some trucks.
 
Has anybody driven the Triumph Spitfire? It has a swing-axle suspension in real life...which had all sort of problems. I know in GT4 when you drive a stock Triumph around (no mods to suspension or limited-slip) it's constantly fishtailing and generally a pain in the neck, so PD obviously was attempting to model the limitations of this design.
 
Parnelli Bone
Has anybody driven the Triumph Spitfire? It has a swing-axle suspension in real life...which had all sort of problems. I know in GT4 when you drive a stock Triumph around (no mods to suspension or limited-slip) it's constantly fishtailing and generally a pain in the neck, so PD obviously was attempting to model the limitations of this design.
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Yeah but that's a swing axle, not a live axle.

Back on topic, it's unclear to me how you could adjust the camber (or toe) on a live axle at all, short of some cutting and welding. How would this be done with a typical American sedan?

Also if I recall correctly the '53 Corvette had a live axle and it handles just fine in GT4 even on a bumpy track, so I'm not sure if PD modeled high unsprung weight.
 
BobK
Yeah but that's a swing axle, not a live axle.
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True, but its still quite a horrible suspension concept.

Info - http://en.wikipedia.org/wiki/Swing_axle


BobK
Back on topic, it's unclear to me how you could adjust the camber (or toe) on a live axle at all, short of some cutting and welding. How would this be done with a typical American sedan?
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That's exactly how you would do it, adding Toe to a live axle (or dead one for that matter - camber just isn't adjusted on these) requires a very skilled individual.


BobK
Also if I recall correctly the '53 Corvette had a live axle and it handles just fine in GT4 even on a bumpy track, so I'm not sure if PD modeled high unsprung weight.
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I would agree that quite a few shortcomings exist in this general area in GT4.


Regards

Scaff
 
A dead axle shouldn't be too hard to add camber to... Cut out the center section, bend it, put it back in, add a brace, call it a day. Or am I way off?
 
okay buut, how does gt handle the physics of the live axle? i need to know this for tuning my cars. does it act like a true live axle, or does it act like an IRS? if it;s live then automatic 0 camber for live axle cars, toe still works much the same but camber has a huge affect.
 
Hmm... My Cougar seems to like rear camber, as it ANNHILATES the tires no matter what going straight or cornering, camber or no, and the camber lets the outside tire grab better (The inside comes loose easy anyway, so I'm not worried about it.)
 
im building a drag car at the moment (in reality not GT4 ;) its live axel so are all the other cars i race with

the only pearson ive heard complain about live axel is jeremy clarkson............but he cant drive so that doesnt count



sorry totally off topic :P
 
Mr Sam
im building a drag car at the moment (in reality not GT4 ;) its live axel so are all the other cars i race with

the only pearson ive heard complain about live axel is jeremy clarkson............but he cant drive so that doesnt count



sorry totally off topic :P
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I could point you to countless suspension design and set-up texts and reference sources that go into great detail about the problems live axles suffer from.

Straight line drag racing is just about the only environment in which a live axle will provide any sort of advantage over an independent rear set-up.


Scaff
 
Back in the late '50's US west coast road racers experimented with negative rear camber on live axle rear suspension with some positive results. I believe they did this by machining an angle to the side of the center section so that the axle tubes rode at the desired camber. Cars like the Ole' Yaller, Scarab and Chaparral 1 started to combine engineering expertise with V-8 power to make mincemeat of most European cars. This all became a non-issue with the advent of the rear engine/transaxle/IRS.

In GT4, I have tried high (3.0) negative camber on the rear of the Dodge Ram and it seems to slightly help control oversteer with high power on tarmac.

On the other hand, too much rear camber may cause less predictable breakaway. I'm currently trying to grapple with this issue on my Suzuki GSX-R/4, but so far I'm not clear what works best on this odd little machine. Who knows how the rear suspension really works on it?
 
Rotary Junkie
If it is a solid axle.

FFs quite often have dead axles out back.
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This is true. Case in point: the PT Cruiser, which has a "trailing beam" rear suspension. This is also found in many Chrysler, Dodge, and Plymouth minivans. Not sure what (if any) advantage a dead axle comprises, other than it's probably the most durable solution for the cheapest manufacturing price.

Dotini
Back in the late '50's US west coast road racers experimented with negative rear camber on live axle rear suspension with some positive results. I believe they did this by machining an angle to the side of the center section so that the axle tubes rode at the desired camber. Cars like the Ole' Yaller, Scarab and Chaparral 1 started to combine engineering expertise with V-8 power to make mincemeat of most European cars. This all became a non-issue with the advent of the rear engine/transaxle/IRS.

In GT4, I have tried high (3.0) negative camber on the rear of the Dodge Ram and it seems to slightly help control oversteer with high power on tarmac.

On the other hand, too much rear camber may cause less predictable breakaway. I'm currently trying to grapple with this issue on my Suzuki GSX-R/4, but so far I'm not clear what works best on this odd little machine. Who knows how the rear suspension really works on it?
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Interesting.

Well since i read this thread i've been putting 0º of camber on all my live rear axle cars in GT4, with varied results. But i'm too tired to type about them at the moment....i'll say this though: GT4 has tons of live axle cars! :) More than you'd think...
 
yea and the new mustang gt is bringing them back from the dead. No one expected it to do what it does on a Live rear axle.

I always use zero rear camber on live axle cars now, it causes the car to not like high speed driving usually. It will feel like the car can take more power but in reality the more speed you have the more the problems with live axle multiply. however if you stay within those rules of a relatively low speed car they make for fun cars to drive. onn flat race tracks they don't help or hurt you camber is simply not an issue the tires are parallel at all times. when you hit bumps hold on!
 
Ehm, am I missing something here, or is everyone else? To adjust camber (or toe) you have to buy a suspension. That purchase seems to make sure that you are able to adjust the things you want, thus if it was a live axle to begin with, maybe that changes when you buy a new suspension?
Just my 2 cents...
 
sounds good except that extensive testing and experience has been carried out. I'm convinced that live axle cars remain live axle cars, they most definately have a different feel to them then IRS cars. now yes you can adjust camber and toe on live axles in the game but if you did you would find that anything more then .5 degrees of camber kills traction in the rear at ALL times, as in you have reduced the contact patch at all times. Toe is less important as the behaviour doesn't change much between live and IRS cars, it still increases rear stability and tire wear. I usually don't use toe in the rear at all.

I wondered before but now that i have a way more developed feel for my cars i can tell for sure, GT treats live axle cars as live axle cars are in the real world. a bump on one side affects both tires, and camber only hurts you, you need to use it's strength which is hard takeoff. my 300 hp IROC camaro and my 500 hp FD take off the line just as hard despite a huge disavantage in design power and weight for the camaro. Then again i know how to gear a car...

You shouldn't just agree or disagree, find a live axle car like a camaro, and try it out!
 
I run my traditional 1.8 camber on the ass end of my Cougar with no problems.

Seems to corner better, albeit sacrificing some straight line traction (Actually hooks BETTER coming out of a corner).
 
the fact is that in real life camber and live axle's don't usually mix. so, what are you getting at rj? make a full point. Is it that all live axle's are treated as IRS, or just cougars, or what? I've shared my conclusion what's yours?
 
Just that, while the Cougar is modeled as a live-axle car, it benefits from camber nonetheless.

.5-1 degree of camber is a minimum for any car; the tire will be allowed to roll over onto its full contact patch easier, as opposed to bringing the inside of the contact patch AWAY from the ground. (And causing excessive outer tire wear and all that good stuff, but GT4 doesn't model that)
 
you ought to re word that to make more sense. .5-1 is not a minimum for anyone but yourself, it's up to each tuner how to do things. As your proof for that broad statement was disproven less then an inch later by you saying that gt deosn't take tire roll into account, and since live axle cars in GT and real life keep the tires parallel baring a special setup or mechanical failure, it makes no sense to add camber as it would only reduce the contact patch at all times. now, if the physics engine is flawed (as we know it is) things may change but otherwise what you're saying makes little sense, maybe i'm missing something.
 
Whiskey Tango Foxtrot?

Think ya missed something, Dave. I'm positive GT4 takes tire roll into account, I just said that it doesn't model the uneven tirewear that would be present with lack of camber (or excessive camber for that matter).

Ah well, whatever.
 
i don't think it models tire roll, but if it did it doesn't change my opinion. if you add camber to both tires and the wheels stay parallel, then yes perhaps the outside tire gains a tiny bit of contact patch in turns (which you lost TWICE as much as off the line), but then the inside tire loses just as much. granted the outside is more important but it's real hard to swallow less tire on the road equaling more traction.
 
Yes, but then we'd never have camber of any sort on anything. Just have the suspension geometry designed to add the proper amount of camber under compression/extension. (Of course, you'd still want a bit of camber for tire roll)
 

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