Ride Height and alignemnts, Audi suspension design

[stack]

what's up people
i am a student studying automotive tech i mentioned this before somewhere..doesn't matter...anyway

today in class we discussed the suspension designs that audi uses.
my teacher said they where over engineered, pointless and very hard to do a wheel alignment( one thing i learned is our caster is always at zero, and camber stays the same on corners)

also since most of us are dropped. when doing a wheel alignment is there any reference to type in new numbers in the alignment machine?

[Aragorn]

Caster on the A4 multillink setup is about 4 degrees, not zero.

Caster is required to give "feel" and also to enable the steering to self centre.

Multilink suspension gives consistent, predictable geometry as the suspension moves, unlike say a chapman strut, where you get lots of camber change (and as a result toe change too) on bump, and when the car is lowered.

[stack]

yea i know that
caster is 4.. oh ok..

audi calls is vertical axis suspension. why couldn't they go with short arm long arm....

but my teacher said the audi sucks in cornering, i looked at him like he was dead

[Stubek]

yea i know that
caster is 4.. oh ok..
audi calls is vertical axis suspension. why couldn't they go with short arm long arm....
but my teacher said the audi sucks in cornering, i looked at him like he was dead

Has your teacher driven an Audi? As Aragorn said, the multilink is a predictable geometry. You always have the same contact patch through corners and straights unlike say a BMW that uses MacPhereson fronts and I forget what for the rear, but if you look at BMW, that is why the wheels are tipped in at the top (camber, right).


Man, its been about 15 years since I actually thought about the details of suspension

[stack]

Has your teacher driven an Audi? As Aragorn said, the multilink is a predictable geometry. You always have the same contact patch through corners and straights unlike say a BMW that uses MacPhereson fronts and I forget what for the rear, but if you look at BMW, that is why the wheels are tipped in at the top (camber, right).


Man, its been about 15 years since I actually thought about the details of suspension

i agree
i guess these teachers as just hating

[dirtyb5a4]

I know many mechanics especially the ones who like american cars who hate on audis and have never driven them. Just because they don't fully understand it doesn't mean its over engineered. Its just means the designers put more thought into it than they would have

[somebody5788]

Think of this, muscle car guys all rave about the C5 double wish bone suspension. We have that plus 1 step further with multi link. It's better then Vette suspension lmao.

[BlkBullitt]

I'm on the fence with agreeing and disagreeing with your teacher.

One of the big negative handling characteristics of almost all Audis is the fact that they understeer horribly. Almost every car made in stock form is designed to have understeer. The Audi tends to have an excessive amount of understeer mainly because of how far forward the engine sits (it's entirely in front of the front axles). Granted it has to due to the design Audi chooses for most of its Quattro cars and they continue to come up with unique ways to reduce the weight and length of the engine (look at some of the current 4.2l V8s).

Now lets talk about the multilink suspension. It does have some benefits, however, those benefits are also disadvantages as well (in my opinion). The fact that you can't independently change caster and camber in the front is a big issue. Camber can be taken care of through adjustable upper control arms, but we're discussing stock suspension. Also, because camber can't be adjusted as you lower the car camber becomes more and more negative (good for handling, bad if you want tires to wear evenly on your DD). I also would argue that some of the components weren't engineered to last as long as they should... front tie rod ends and control arm ball joints for instance.

When designing anything related to automobiles you are always making a series of compromises. The best alignment specs for handling aren't the best for driving down the highway on. The best suspension design and components for handling aren't necessarily the best for daily driven family road cars. I think Audi makes a good compromise at making a family semi luxury sedan have comfort, but also a sporty feeling, especially when you also take into account the handling issues the drivetrain layout provides by itself. I wouldn't say they completely suck at handling, but I wouldn't say they are the definition of it either.

[onemoremile]

The front suspension is called QUADRAlink. It is designed to act similarly to double wishbone but also to eliminate torque steer and have a virtual steering axis.

You can actually find information that counters a lot of the above guesses. All you have to do is search here and do some googling. As you learn about the quadralink suspension your appreciation for it will grow. That prof will get much farther by talking about things he actually understands than making assumptions about things he doesn't.

[stack]

awesome awesome info
fuck the teacher... as long as i know its better than the American POS

[spindoctor]

What car does your teacher drive?

[SR-71]

audis suck at everything.

[stack]

What car does your teacher drive?

my college is upstate New York
my lab is next to cows and sheep so they are the hilly billy type,they like American GMC stuff.
they love the caddy ctsv but i dont think they know its really german

[Stubek]

my college is upstate New York
my lab is next to cows and sheep so they are the hilly billy type,they like American GMC stuff.
they love the caddy ctsv but i dont think they know its really german

Oneonta, Cobleskill, or Potsdamn?

[BlkBullitt]

The front suspension is called QUADRAlink. It is designed to act similarly to double wishbone but also to eliminate torque steer and have a virtual steering axis.

You can actually find information that counters a lot of the above guesses. All you have to do is search here and do some googling. As you learn about the quadralink suspension your appreciation for it will grow. That prof will get much farther by talking about things he actually understands than making assumptions about things he doesn't.

His teacher very well may understand it and just not care for it. I think my first post provides some sound reasons why someone might not care for the stock QUADRAlink suspension setup. For a stock suspension it's a good compromise, however, if above all else we're talking strictly about handling then in my opinion there are better options available (ones that provide you with the ability to independently adjustment multiple settings in stock form). If we're talking about a compromise between handling, ride quality, and ease of alignment for dealer techs then I personally think the Audi QUADRAlink front suspension does its job well.

my college is upstate New York
my lab is next to cows and sheep so they are the hilly billy type,they like American GMC stuff.
they love the caddy ctsv but i dont think they know its really german

Where are you getting information on the CTS-V being German? Everything I've found shows the platform (Sigma and Sigma II) were designed by GM Holden Ltd. (subsidiary of GM) in Australia. The design of the car was done in Lansing, MI. GM engineers did use the Nurbergring to fine tune the suspension on the car, however, from what I'm finding it was GM doing the engineering not a German company. Lots of auto makers use the Nurbergring for suspension testing and fine tuning, but that doesn't make all of those cars "German."

[somebody5788]

Just an FYI, good coilovers, and a 4:1 dif means really no understeer. Even going fast into a corner it wont as long as you keep it in a gear either engine braking or accelerating. The beauty of a torsen dif

[chris164935]

Somewhat off-topic, but I recently replaced my control arms, tie rods, and sway bar end links as well as installed coilovers. Went to have an alignment done and come to find out my caster is off. On the driver's side, it's 5.4º and on the passenger side it's 4.1º. I'm aware that caster is not adjustable, but what would cause the caster to be off?
Also, I have a FWD A4, and the camber is -2.4º on the driver's side and -1.7º on the passenger side in the rear. Can I loosen the bolts holding the rear axle beam and "slide" the axle beam over "even" out the camber (same principle as when you loosen the front sub-frame bolts and slide it left or right to even out camber in the front)?

[chris164935]

Somewhat off-topic, but I recently replaced my control arms, tie rods, and sway bar end links as well as installed coilovers. Went to have an alignment done and come to find out my caster is off. On the driver's side, it's 5.4º and on the passenger side it's 4.1º. I'm aware that caster is not adjustable, but what would cause the caster to be off?
Also, I have a FWD A4, and the camber is -2.4º on the driver's side and -1.7º on the passenger side in the rear. Can I loosen the bolts holding the rear axle beam and "slide" the axle beam over "even" out the camber (same principle as when you loosen the front sub-frame bolts and slide it left or right to even out camber in the front)?

I guess I should add that the car is lowered and the camber on the front driver's side is -1.8º and -2.1º on the front passenger's side. GTF is about 24.5" in the front and 25" on the rear passenger side and 25.5" on the rear driver's side...

[csosnowski]

the rear camber is adjustable via the camber bolt in the lca for quattro, but idk how it is on frontrack cars might be worth checking.

[Seerlah]

Somewhat off-topic, but I recently replaced my control arms, tie rods, and sway bar end links as well as installed coilovers. Went to have an alignment done and come to find out my caster is off. On the driver's side, it's 5.4º and on the passenger side it's 4.1º. I'm aware that caster is not adjustable, but what would cause the caster to be off?
Also, I have a FWD A4, and the camber is -2.4º on the driver's side and -1.7º on the passenger side in the rear. Can I loosen the bolts holding the rear axle beam and "slide" the axle beam over "even" out the camber (same principle as when you loosen the front sub-frame bolts and slide it left or right to even out camber in the front)?

There you go.

The camber/caster can't be adjusted on our vehicles on the front, only the rear. Since you are lowered, there is no way to compensate in the front, except with adjustable upper or camber kit (K Mac).

[terraflata]

As walky said, everything is a compromise. Multi-link, double wishbone....they are all after the same purpose keeping the contact patch in contact with the road....if you check F1 cars and other related race vehicules they use unequal-length parrallel suspensions, great for the track, but I am sure that the durability of such a type suspension would fail after X amount of miles on an actual road.

Here is a link to one of the most comprehensive collection of articles regarding auotmotive technology and design. I absolutely love this site and recommend anyone who wishes to understand more about cars to read ALL the articles, very informative and covedrs almost all aspects.

Autozine Technical Articles

[chris164935]

There you go.

The camber/caster can't be adjusted on our vehicles on the front, only the rear. Since you are lowered, there is no way to compensate in the front, except with adjustable upper or camber kit (K Mac).

But why would the caster on one side be a whole degree more than the other? Ride height on both sides is off by a couple millimeters, would that affect the caster that much?

[NeedingAnAudi]

But why would the caster on one side be a whole degree more than the other? Ride height on both sides is off by a couple millimeters, would that affect the caster that much?

Road crown. Since most roads are tapered to the sides the alignment is designed with a slight difference so the car will drive straight.

Stack: Are you going to UTI? Because I have not heard much positives about their core programs. However, they do have much better connections to manufacturer schooling.

[stack]

Road crown. Since most roads are tapered to the sides the alignment is designed with a slight difference so the car will drive straight.

Stack: Are you going to UTI? Because I have not heard much positives about their core programs. However, they do have much better connections to manufacturer schooling.

i go to a little town called DELHI NY

and caster is adjustable.( maybe not on out cars i have no idea yet)
the more pos+ caster the better

[onemoremile]

You guys have got to either ask questions or post researched answers that you know are correct. People come here looking for advice and often don't know the difference between actual fact and what is made up on the spot. If you don't know it to be fact then please ask so that the information you eventually pass along is of quality.

The suspension is not designed around "road crown". If nothing is bent or damaged then all specs should be able to be balanced equally side to side. It is a symmetric design.

I have aligned my car using toe strings and toe plates and then had it double checked at the dealership by a tech that races and sets up friend's race cars. It was dead on and evenly balanced side to side. I then tracked the car at several heights to determine the best compromise between lap times and ride quality. I found that about an inch below stock sport height is perfect. Even though it felt tight and the steering response felt quick and almost twitchy, "race spring" height was actually slower than "sport spring" height. This was confirmed by Dick Shine's research and development of his springs and dampers. I have had that same development set with custom valved Bilstein HDs on my car for a few years. I will be happy to prove it to anyone willing to ride shotgun for lapping sessions. The PCA guys that made fun of me years ago for bringing a station wagon to a PCA track day had plenty of questions after the first session.

If you guys want answers then ask and I'll answer or find the correct answer before posting it.

@Chris - the minimal difference in ride height should not create that much of a caster difference. Something is wrong somewhere.

@Stack - Caster is not directly adjustable on our cars. The subframe can be twisted (clocked) slightly which can alter it but that just means that it is misaligned. Too much caster is not a good thing since the wheels flop like on a chopper. There is a happy place for everything and too much is not it.

[chris164935]

@Chris - the minimal difference in ride height should not create that much of a caster difference. Something is wrong somewhere.

Any ideas of where to start looking? Bent wheel hub? Bent subframe? Maybe subframe is misaligned and might need to be clocked? I have removed it before. Also, would the caster being off that much cause vibration during acceleration?

[NeedingAnAudi]

The suspension is not designed around "road crown". If nothing is bent or damaged then all specs should be able to be balanced equally side to side. It is a symmetric design.

I was taught during performing alignments that the alignment is set to adjust for road crown. Designed was not the right word to use. And I do know it to be fact.

[stack]

You guys have got to either ask questions or post researched answers that you know are correct. People come here looking for advice and often don't know the difference between actual fact and what is made up on the spot. If you don't know it to be fact then please ask so that the information you eventually pass along is of quality.

The suspension is not designed around "road crown". If nothing is bent or damaged then all specs should be able to be balanced equally side to side. It is a symmetric design.

I have aligned my car using toe strings and toe plates and then had it double checked at the dealership by a tech that races and sets up friend's race cars. It was dead on and evenly balanced side to side. I then tracked the car at several heights to determine the best compromise between lap times and ride quality. I found that about an inch below stock sport height is perfect. Even though it felt tight and the steering response felt quick and almost twitchy, "race spring" height was actually slower than "sport spring" height. This was confirmed by Dick Shine's research and development of his springs and dampers. I have had that same development set with custom valved Bilstein HDs on my car for a few years. I will be happy to prove it to anyone willing to ride shotgun for lapping sessions. The PCA guys that made fun of me years ago for bringing a station wagon to a PCA track day had plenty of questions after the first session.

If you guys want answers then ask and I'll answer or find the correct answer before posting it.

@Chris - the minimal difference in ride height should not create that much of a caster difference. Something is wrong somewhere.

@Stack - Caster is not directly adjustable on our cars. The subframe can be twisted (clocked) slightly which can alter it but that just means that it is misaligned. Too much caster is not a good thing since the wheels flop like on a chopper. There is a happy place for everything and too much is not it.

thanks for the good info


are there any diff. specs since i dropped my car 2 inches.
i am doing my align. soon.
should i leave the number oem or mess with them??

[onemoremile]

Any ideas of where to start looking? Bent wheel hub? Bent subframe? Maybe subframe is misaligned and might need to be clocked? I have removed it before. Also, would the caster being off that much cause vibration during acceleration?

I really don't know for sure. If the subframe was clocked with one side forward and the other rearward then it could change caster but I don't know by how much. There isn't much movement front to rear. Other possibilities could include bent control arm(s) but that would probably throw the other specs out of whack too. Unless you competitively track the car I doubt it makes a large difference in the real world.

My allroad has vibration under acceleration too. I haven't had a chance to tear into it but my hypothesis is bad engine and or trans mount(s) which would allow the trans to torque itself crooked under power. It could also be a bad bushing or two which could allow deflection under load causing dynamic toe changes.

[onemoremile]

thanks for the good info


are there any diff. specs since i dropped my car 2 inches.
i am doing my align. soon.
should i leave the number oem or mess with them??

Any time. Thats why we're here.

Other than camber, which should be symmetric, the numbers should fall within specs - the more symmetrical the better.

[onemoremile]

I was taught during performing alignments that the alignment is set to adjust for road crown. Designed was not the right word to use. And I do know it to be fact.

Fact that you were taught that way or that the car was intended to be aligned that way? The spec sheets have symmetric numbers. Any compensation for road crown would change that. How do you compensate for something that varies so much and is completely unpredictable? I believe the car should be dead equal so that it goes and brakes in a straight line on a flat road. The driver is responsible for dealing with the road conditions. Picture a crowned two lane freeway. If you adjust for the right lane then how does that effect driving in the left lane with the opposite crown?