AntiHeroMan

I need to get rid of the marshmallows that Audi calls sport suspension. I am looking for a ride similar to the 95-99 M3s. What setup would best fit the bill? Springs? Dampers? Coilovers? What brands? I am also looking for more neutral steering and body roll to be similar to the M3. Would the suspension changes do it or should I add a anti-roll bar?

Buy hey, I could always buy another M3...<G>

Cheers!

smallTTs

weight distribution with RWD. You have, what 60-40? and AWD. While it's possible to try to duplicate the M3's ride, it's probably a better idea to maximize the 60/40 AWD chassis ride, and roll stiffness. It takes a coordinated system of springs, dampers anti-roll bars AND wheel and tire combinations. Ride/handling engineers spend more hours than you would believe developing these combinations.

My point is just picking bits isn't going to get you where you want. Look at packages of springs/dampers/bars. Eibach does some coordinated kits which work well together when combined with uprated wheels & tires. Try the link for your car. I'd seriously consider Eibach Prokit springs/dampers/bar for about $1175.

17 x 7.5 or 8's with 225/45 or 235/40's might be close. That's probably another $1400 or so. We did this to a '00 GTI and it's a auto-x winner every time out.

My $.02.<ul><li><a href="http://www.tirerack.com/suspension/Susptabl.jsp?autoMake=Audi&autoModel=A4+1.8+Turbo+ Quattro&autoYear=1998">http://www.tirerack.com/suspension/Susptabl.jsp?autoMake=Audi&autoModel=A4+1.8+Turbo+ Quattro&autoYear=1998</a</li></ul>

AntiHeroMan

Thanks. I realize this. I am just trying to get in the right direction. I am just trying to avoid the rice components that are there just to drop the car and "look cool". (Not my taste. I want something that works, looks are secondary.) Besides your list there is also suspension geometry and HP and gearing to help shift the weight. And, as you know, by the time all of this is addressed, for what I would have in the A4 there is a lot of other cars out there that would have fit the bill for less money. Like an M3. ;-)

Happy motoring.

smallTTs

"suspension geometry and HP and gearing to help shift the weight" Shift the weight? Not really.

Unfortunately shifting weight means you physically have to remove chucks of stuff from the front and/or add it to the rear. Suspension geometry, power and gears don't do that, not even dynamically during a steady-state turn. Sorry.

"Jacking" weight with adjustable shocks, etc. is great for moving diagonally from corner to corner, but it doesn't change the front/rear percentages, nor the left/right. Basic physics says it can't.

You may hear that you can shift lots of weight from the front to the rear with coilovers.
Nope. Even RAISING the front of your A4 2 inches and DROPPING the rear 2 inches for a 4 inch reverse rake only moves the CG a bit and shifts maybe 35-50 lbs max to the rear. Now that's a new rice look.

The S4 competes with the M3 because Audi uses what it has (AWD mainly) to compensate for the 60/40 weight distribution. If they could mke the S4 a 50-50 car the way you suggest it would have been done long ago.

WClark

I wanted my OEM sport suspension'd A4 to more closely follow road elevation changes, respond more quickly to steering wheel input and understeer a lot less.

I was pleased that the 18" SSR wheels with 225/40 Pilot Sports improved responsiveness of the steering and raised the limits of cornering and braking a lot, but also made the understeer problem less manageable.

Not wanting to experiment with various tuners idea of handling, I went with the Eibach springs Audi sells. They are a nice upgrade. Firmer ride and slightly lower than sport results in quicker transitions in turns, less dive under braking and better tracking of road elevation changes. They also didnt change much from day 1 in terms of settling in. The OEM Sport shocks are minimally acceptable with these when new but quickly degraded to unacceptable levels of underdamping. I went with Neuspeed/Bilstein shocks which may be tuned for a slightly firmer spring, but when they wear-in the damping seems well matched to the Audi/Eibach spring rate and they allow for some minor height adjustment.

The better chassis response of the firmer springs actually made the understeer management worse yet as it was now more difficult to get enough dynamic weight transfer forward to lighten up the rear end and get it to rotate out a bit. I was melting my front tires in 60 second autocrosses trying to get around turns. Then I added the Neuspeed 19mm rear swabar. On the "soft" setting I found the car went to a near neutral charateristic under normal driving without resorting to inflating the rear tires excessively and the extreme scuffing on the front tires went away in competition. By using a little left foot braking to load the chassis forward I can bring the rear end out on dry pavement if that is what I want - on low traction surfaces it takes very little weight transfer to get it out - I can do it under throttle, yet the shift isnt so sudden or large that you get sideways before you can countersteer.

The slight height reduction (about 3/4" from sport) increased the front and rear camber something like .3 degrees at each corner which isnt enough for serious racing but seems to be a good balance for regular road use and occasional events. Tire wear on my car is normal.

Compared to an M3? Dont know, never driven one.

AntiHeroMan

Actually I agree with everything technically said. But, we miscommunicated. I can see where we miscommunicated regarding weight. Even though I may have sounded like it, I was not talking about ratios that appear on a scale when the vehicle is at a stop. (Well maybe if we jacked up the front several feet. Boy would that look cool. But, I would have trouble seeing the road without a periscope.&lt;G&gt When you are in a turn, accelerating or stopping, weight effectively shifts. Some may call it the moment of inertia or may call it other things. Stiffness of the suspension helps change the effects of this. So does changing the point of the CG within the 3D of the object. Basic physics. Newtons law. Centripetal force. I feel we both agree on this.

I do realize that I will not be able to get the total feel of having a 50/50 balance, but I do feel that I can at least get more neutral turn in than what I currently have. I also feel that I should be able to limit the roll without a buckboard feel, too. Similar to what I had in my M3. The M3 was fun. My C4 is fun, but a little tail happy when things are slippery. The Audi is a kinda fun, but it needs help getting the smile factor where it could be.

Let's see, how many bags of sand in the trunk would it take for me to get that 50/50 weight ratio? &lt;G&gt;

Peace.
Cheers.
Happy motoring.

smallTTs

Weight transfer due to acceleration:

The amount of weight transferred is proportional to acceleration, height of the center of gravity (CG) and wheelbase (for forward/reverse acceleration) or acceleration, CG height and track (for cornering). Notice that body pitch or roll isn't part of the equation. More later.

Assume that an A4 and an M3 weigh about the same(3600 lbs), have the same wheelbase, track and CG height (at least approximately). During acceleration, braking or cornering at a given g, they will transfer the same amount of weight. So if max acceleration transfers 360 lbs. from front to rear on an assumed 3600 lbs. gross weight A4/M3, the 60%/40% A4 becomes a 50%/50% during that acceleration, but the M3 becomes 40%/60%(within 1% or so). So the M3 still acts like an M3 and the A4 is still acting like an A4.

In the case of cornering, the M3 and A4 will also transfer the same amount of weight from the inside wheels to the outside wheels. This would happen whether or not the car has a suspension system. In other words, if you bolted the suspension solid (like a go kart or F1 car!) the SAME amount of weight would be transferred but there would be no body roll except for squashing of the tires. Body (sprung mass actually) roll happens because the axis about which the body rolls is below the CG, so the distance from the roll axis to the CG, the lateral g and body weight determine the amount of roll moment.

If roll axis isn't intuitive, imagine that the front suspension has a point about which the body (near the front axle) rolls. This is usually between ground level and 4 inches above ground, and approximately on the centerline of the vehicle. The rear suspension has it's own roll center, almost always higher than the front, say 6-12 inches above the ground. For a solid rear axle with a Panhard rod (aka track bar), it's about the height that the Panhard rod passes the vehicle centerline, and easy to visualize.

The rear portion of the body wants to roll about the rear roll center and the front about the front roll center. Because the body is quite stiff, it rolls about an axis which passes through the rear and front roll center. This axis is typically inclined about 4-6 degrees nose down.

Once again, this body roll (of 1-4 degrees) doesn't transfer weight to the outside wheels, which may NOT be intuitive. What it does is make the suspension move about 2 inches or so (1 up, 1 down for 2 degrees of roll (approximately)), which can give the tires good or bad camber changes and steering angle changes (aka "bump steer"). Depending on the suspension design, you can get oversteer or understeer effects from the geometry change.

The amount of roll for a given car at a given lateral g is determined by the suspension springs and anti-roll bars. Springs are the primary resistance; usually more than 60%.

What changing spring and bar stiffness does is change the % of the roll which is resisted by the front and rear as well as the total amount of roll. In other words, if you put stiffer springs just in the front, more of the roll is resisted by the front, so extra weight is put on the outside front tire and less on the rear outside. This makes the front tire work harder and the rear work less, which results in more understeer or "push". (The 'why' is another subject on how tires work.) Similarly, increasing front antiroll bar stiffness does the same thing; more understeer.

Stiffening the rear springs and/or bar relative to the front give more oversteer or "loose" handling. So, by selection of spring and antiroll bar rates, we can tailor, or tune the handling characteristics of the car within certain limits.

A car with 60% front static, which is either FWD or AWD is going to overwork the front tires way before the rears, and way before the 50% front RWD car. Remember that tires can only produce so much force at the road, and if you are using some of it to accelerate the car, that amount is subtracted from the amount available for cornering. RWD works the front tires less.
Again, the M3 acts like an M3 and the A4 like an A4. You can tune a lot of the understeer out of the A4 but ultimately the heavily loaded A4 front tires are going to give up before the M3's. Does this suggest that we should use larger tires on the A4 front? You betcha!

The reason powerful RWD street cars need larger rears is because the rears are doing 50% of the cornering and all of the driving, so they need more traction. Steering with the throttle is just moving the rear tire grip from lateral to forward.

You really don't move the CG around within the car, nor do you change the moment of inertia unless you move large chuncks of the car around.

If you've made it this far without being po'd at me, you CAN reduce some of the body roll of your A4 with springs and bars. Traditionally VW-Audi use soft bars and allow more roll than BMW and especially more than GM does on performance cars (Vette, Camaro, etc). The Eibach bits I mentioned in my first reply above do just that. I think you'd be quite pleased with the results. There should be someone of the A4 forum who has this package with decent tires. Remember though that there is maybe 300 lbs more "road hugging weight" over the front wheels of an A4 than of a similar weight M3. That, in the end, is the problem.

Answer to your last question: About 300 lbs. located as far aft in the trunk as possible should do it.

My highly opinionated $.02

AntiHeroMan

mostly. But, using a quote from Henry Watts' book "Secrets of Solo Racing", p.90. Not that I tend hold any one individual as a total expert, but prefer the input of many to form my opinions. "...when under hard breaking, as weight *transfers* to the front of the car." It is a matter of semantics that people use. I happen to use similar terminology that Watts uses, as well as many others. You are correct, weight, in a downward direction does not change. But, the horizontal components do. Hence, centripetal forces. In conjunction with traction, slip angles, etc. Once again, the amount effect on the car are in relationship to how the suspension reacts. I believe that you have shown that in your example above. However, to get the front/rear relationship between the M3 and A4 to be equal under similar acceleration forces, 360 lbs. in your example. The A4 would need softer suspension than the M3. But, that would probably have negative affects on similar horizontal forces associated with turns, because both cars would probably be closer to a 50/50 ratio from side to side. Therefore, the softer suspension *could*(sway bars aside) cause greater weight shift(horizontal gravitational force, moment of inertial, centripetal/centrifugal force, G-force, whatever) side to side. Once again, I feel that we will both agree...semantics aside.

Cheers.

BTW...No PO'd here. Also, would you recommend sand or just welding the 300 lbs aft. (Once again, just kidding.)

smallTTs

"...when under hard braking, as weight *transfers* to the front of the car." Watts means exactly what I said; that is there is more loading on the front tires and less on the rears.

It DOES NOT mean that the physical weight of the vehicle moves within that vehicle like sloshing water. It is not semantics.

Weight is a force (mass x acceleration) and must be resisted. Thats what the road does to the tires: it pushes back exactly as hard as the tires push down on it. Maybe because the English system uses pounds for weight as well as mass, it's easy to get confused.

Suspension spring stiffness doesn't change how much weight transfers, as I said, either in acceleration/braking or cornering. This is critical: the weight transfer occurs whether there is a moving suspension or not! One small point: in a drag racing only vehicle, where the front lifts a lot (on purpose)or even carries the front wheels, the lifting just raises the CG height which causes more weight transfer, which puts more weight on the rears, which causes more acceleration which causes more weight transfer, etc. Here stiff front springs and shocks with almost no rebound control let the front rise.

Unfortunately, I don't think I can present it to you in a way that makes it clear to you. As you explain things we do not agree. While I believe you have the basic concepts, I believe your application of them "softer suspension *could*(sway bars aside) cause greater weight shift(horizontal gravitational force, moment of inertial, centripetal/centrifugal force, G-force, whatever) side to side." isn't correct.

IMO, which is never humble, you still would be best served if you purchased a coordinated package of springs, dampers, bars, wheels, tires for your A4...or just trade for an M3(?)

BTW...I'd recommend slugs of tungsten mounted as far aft and a low as you possible can get them. Sorta like one F1 team which illegally concealed tungsten in the wooden skid board which normally rides an inch or so off the road, and often hits. (That's why it's wood.) Reportedly they had quite a few kilos there which lowered the CG of the vehicle. Remember, lowering the CG height decreases weight transfer. At 4+ lateral g that's VERY important.

Good luck.

AntiHeroMan

"...when under hard braking, as weight *transfers* to the front of the car." Watts means exactly what I said; that is there is more loading on the front tires and less on the rears.

***Like I said, we agree***

It DOES NOT mean that the physical weight of the vehicle moves within that vehicle like sloshing water.

***Never said it did***

It is not semantics.

***Yes it is, or we would not have agreed***

We're picking nits. I understand fine.

Enjoy. Off to find some tungsten.