What is Handling?

peter pyce

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Nov 6, 2001
Continue from above – Ceilidh’s posts from two years ago all the way to the end:

9. Rear Bar with Stock Springs

Reminder -- GT Goals

1) excellent roadholding (good mechanical grip) on a variety of road surfaces
2) forgiveness for unexpected events
3) handling that is consistent under changing road, weather, and load conditions
4) responsiveness to good throttle/brake/steering technique
5) reasonable ride comfort

We come now to a setup that inspires a lot of discussion on the Vortex: stock springs with an aftermarket 25mm or 28mm rear antiroll bar. Some people absolutely love it, calling it an ideal first mod after improved damping; others feel it is a misguided way to improve handling. What must be very confusing to the suspension novices is that some very experienced people come out on opposite sides of this discussion. So let's see why:


The Nice Things About a Rear AntiRoll Bar

If you add a rear antiroll bar to an otherwise stock Golf/Jetta IV, you reduce the amount of roll at low to moderate-high g-forces, and you increase the lateral weight transfer (again at low to moderately high g-forces) at the rear, while decreasing the transfer at the front. All these effects serve to decrease understeer: by reducing the roll, you keep the front tires more upright; and by decreasing the front lateral weight transfer, you increase the overall grip of the front end. Moreover, because the car rolls less (and because the "roll rate" -- the "springiness" of the car in roll -- is increased), it takes less time for the car to take a set, and the transition time is decreased.

Because of all the above, many people will like what a rear bar does to an otherwise stock Golf or Jetta: the car will corner flatter (at least at low- and mid- g-forces), it will turn-in more incisively, it will be quicker in left-right transitions, and in general everything will feel more agile. So for many people, a rear bar with stock springs can be pretty nice.


What's Not Nice About a Rear Bar with Stock Springs

The problem with the rear bar/ stock springs approach is that it doesn't move you towards a GT setup. In contrast to improved damping, which significantly improves #1-4 on the GT list at a modest cost to #5 alone, the rear bar/ stock springs setup will:

1) increase roadholding in some situations, make no difference in others, and actually degrade roadholding in some circumstances.
2) decrease forgiveness
3) degrade handling consistency under different weather/ road conditions
4) retain or slightly improve handling responsiveness
5) somewhat degrade ride comfort.

In short, the rear bar / stock springs approach tends to improve #4 while losing out on #1,2,3, and 5 -- that is, it can be nice for agility, but in other GT respects it's a bit of a step back.

The reasons why can best be seen by considering a stock Golf/Jetta at the cornering limit: at high lateral-g, the stock Golf/Jetta is understeering very heavily (because of the leaned over front tires) -- but it is also cornering on three wheels. This 3-wheel stance arises because even the stock suspension applies a lot of weight transfer across the rear wheels, so as to reduce understeer at low to medium g-forces.

Now consider a rear bar / stock spring car, cornering at the same speed & lateral-g. It too is cornering in a 3-wheel stance. Moreover, the rear outside wheel is carrying the same load as before (the weight of the back of the car), while the front lateral weight transfer is the same as before (because the total weight transfer is determined by the CG, mass, and track width, not by springing). Because the front springs are the same as before, the roll must be the same as before. And if the roll is the same as before, the front tires are leaning over the same as before.

Hence at high lateral-g, the rear bar/ stock spring car is cornering exactly the way the stock car corners, with the same heavy amount of understeer. Moreover, the ultimate roadholding limits are no higher than before, and are indeed perhaps a little less on rough roads: as discussed earlier, by putting on a stiff bar, you've increased the 1-wheel spring rate (which decreases mechanical grip), and you've made it more difficult to set the shocks to cope with both 1-wheel and 2-wheel bumps (which further reduces grip).

Perhaps even worse (as discussed in an earlier post in this thread) you've now exaggerated how the handling changes with g-force: at low to moderate g, you understeer much less than before (because the car corners flatter, and there's more weight transfer at the rear wheels), but at high-g you still understeer a lot (because once you're 3-wheeling, you can't shift any more weight onto the outside rear tire, and the amount of roll is controlled entirely by the stock front suspension). If the understeer at low g-force is reduced enough, you can in some cases (judging by Forum posts) get to a point where the car handles differently on slick roads (where it's tail-happy) than it does on dry roads (where it's forgiving and benign). That's a terrible thing to have happen on a GT car: the last thing you want is a car that corners safely on dry roads, but which turns vicious when the weather is bad.

Bottom line, a rear bar on stock springs can make the car more agile and "fun" (particularly at low cornering speeds, or in gentle curves).....but it can't raise the ultimate roadholding, it still permits stock levels of understeer at the limit, and if overdone (with a big rear bar at full-stiff setting) it can significantly degrade handling consistency when the weather changes. Oh, and given how sensitive the rear is to stiffening, your ride comfort and rear traction will also deteriorate somewhat on bumpy roads.


Why Everybody is Right

Given all the above, why do so many people advocate adding a rear bar to a stock suspension? Part of it is that a mild bar (stress the word "mild") can be pretty nice -- the wet weather handling won't get too tail-happy, and the increased agility at moderate speeds can feel very welcome. Part of it is that most of us never really drive near the limits anyway, and therefore we're always in the low-to-medium g-force range where a rear bar can reduce the understeer. And part of it is that many people simply don't want a "GT" suspension. In particular, track racers want to get power to the pavement on corner exit (see Daemon42's posts on this subject), while autocrossers crave agility.

(Hmmm. Maybe here's a good time to explain something about autocross: when you have to throw a car around a tight series of cones, you a couple of related challenges. One is to get the car to quickly "rotate" around a cone; i.e., to get the car to rapidly turn-in and begin cornering. The other is to get the car to *stop* rotating at the appropriate time, so that you don't spin once you're actually in the corner. In this situation, having a car that has very little understeer (or that even oversteers) at low g-forces (which is the turn-in phase of a corner), but which gains a lot more rear-traction at high g-forces (when you're actually in the corner, and don't want to spin off), can often be a good thing. Thus a big rear bar and a relatively soft front can work for some autocrossers, depending upon their driving style, and you'll find many autocrossers who are fans of rear bars.)

Bottom line, if you want a little more snap and flatness in your suspension, especially at low to medium g-forces, go ahead and try a rear bar with stock springs. You might find it very pleasant (at the very least, to paraphrase something Peter found with a 28mm bar, increased ride harshness will make it seem like you're cornering faster!). But if your goal is "GT" -- real, effortless roadholding with good ride comfort and predictable forgiveness in all weather conditions -- there are better ways to go.

That's all for this week. See you all! =)

- Ceilidh
 

Ceilidh

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Mar 12, 2006
A brake link

Hi Folks!

Just wanted to apologize a little for the silence on my end -- things have been a bit swamped over here, so posting time has been limited. :)

Regarding the 2-year old text (how time flies!) that Peter's reposted: I'd echo Peter's caveat that our understanding of dampers -- almost entirely thanks to Peter, by the way, as he's been doing an amazing series of experiments -- is much fuller now than it was back then. From Peter's reports, it looks possible to get more handling gain with less comfort loss than it looked 2 years ago, and in time we'll be hearing more from Peter on this.

Also, on a minor point, I was a bit limited in what I wrote about the twist-beam rear suspension and its limitations -- in the text, I only mentioned how the poor impact harshness of the twistbeam setup forces one to soften the damping a bit; in reality, probably a bigger limitation of the suspension lies in its kinematics (how it moves and distorts) under load. If we compare the twistbeam to something like the multilink found at the rear of the Quattro Audi TT, the R32, or the Golf/Jetta V, the twistbeam gives the engineers much less latitude for correcting for lift throttle oversteer, mid-corner bumps, sudden yaw, and other transients that encourage a car to spin. Lacking this latitude, engineers have to pair a twistbeam with an inherently understeering front end -- but with a good multilink, the designers can take a lot of understeer out of the suspension while still retaining stability and consistency in real world conditions, with ordinary drivers. That's one reason why you see the multilink appearing in more and more high-quality cars -- and also why you don't often find it in dedicated racecars: the rear multilink doesn't do much to make the car faster at the limit, but if you're striving for GT consistency and fast safety, it's a pretty valuable tool.

And finally, a sidenote inspired by a question from sportsguy:

sportsguy said:
.....I'm asking myself if the direction should be "more" brakes up front, and perhaps some more power through chip-tuning... ;)

Duane
In modifying our cars, it's always nice (if possible) to find those rare professionals who combine a an in-depth knowledge of technical concepts with real-world experience with specific products. With brakes, the best fellow I've encountered is a one-man aftermarket brakes shop named Dave Zeckhausen:

http://www.zeckhausen.com/products.htm
http://www.zeckhausen.com/technical.htm
http://www.stoptech.com/tech_info/tech_white_papers.shtml

If you're considering a major brake modification, getting Dave on the phone would be a helpful thing to do! :)

(Oh, and as long as we're talking about impressive technical people: for lighting, there's Daniel Stern (http://www.danielsternlighting.com/ )
http://danielsternlighting.com/%29, who's a technical lighting consultant who happens to sell Cibie/Valeo lamps on the side (very tough to get hold of, but he really, really knows his stuff), as well as the (less technical, but impressive in a different way) folks at http://www.rallylights.com, if you want to talk to a Hella stockist with a wealth of real life experience fitting out race and rally cars)

Cheers again! - Ceilidh
 
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Joined
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Location
Berkeley, CA
Step-Steer testing

Thank you for more great stuff -- succinct and relevant.

Two things:

1. I'm waiting and hoping for more from our friend Adam (dingchowping) with all the varied TT driving experience, including early FWDs and all kinds of tune....?

2. I noticed the following from a Motor Trend comparo test which may be of interest to people following this thread. I wonder if anyone has seen similar testing for our cars? Is it relevant? (For darters I guess?)

http://www.motortrend.com/roadtests/coupe/112_0403_compact_sport_coupe_comparison/performance.html

"While steering feel is subjective, responsiveness can be measured. One of the best ways to do this is via a step-steer test. The concept is simple enough: Suddenly snap a predetermined amount of steering angle into the wheel and measure the time (hence, distance) the car travels before it attains its final lateral-g cornering rate. Here, we premeasured the steering angle each car needed to achieve 0.6 g at 30 mph and monitored the lateral-g forces via an accelerometer...."

Cheers, Pete
 

Golf_GTDI

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Interesting thought on the step steer test. Seems as if it could have a lot to do with rubber as well but other issues would also add into the math as well.

I'd still be interested in doing whatever sort of homework we may need to do to answer some of these larger questions. STPR is comming up in about a month for RallyVW and I'm sure many other folks will be there as well. Should be a good time to do some things if we want too... You up for a trip Peter?
 

BoosTDIt

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Wake me up when we get to the coilovers and rack&pinion discussion...i really need to learn about them all ...
if you guys already made the costly mistakes
let's hear it

i know i know ...with time it'll come
just getting anxious to get the thread to the part where what products work for sertain set-ups and which don't

Peter ...you have a suspention shop, true?
 

Golf_GTDI

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If I recall, Peter is running a Ground control system. I myself have often been tempted by the coilover monster but at this point will not be going in that direction. We can talk about the reasons for this when we cross that bridge.

As for the shop Peter is working with, it is not his own but one that does work on motorbike suspensions. That shop and Peter have done a great deal for us at RallyVW and we are thankful for their help. We feel that they are working to help produce a system that is far better than anything we know of for the A4. Thank you Peter and Aftershocks.
 
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FirstVtwin

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On the previous page it was noted that a stiff anti-roll bar will increase the response of the car at low and mid g corners, but leave the car unchanged at the limit of traction on dry pavement. I have a quick question in regards to these ideas.

-A stiff anti roll bar should increase the spring rate of a single wheel (as previously stated). So when the car is up on three wheels (past the point where the anit roll bar is supposedly doing any good), shouldn't a stiff anti roll bar increase the height of the rear corner that is planted through the increased spring rate? What does this increase in rear height do to the overall handling at the limit? Won't this increase in ride height also effect the camber of the wheel as effected by the twist beam (less twisting)?

I guess I see a real possibility of the stiff rear roll bar effecting the handling even in the three wheel corner. Looking for some expertise to shed some additional light on this.
 

Ceilidh

Member
Joined
Mar 12, 2006
3-wheeling

FirstVtwin said:
On the previous page it was noted that a stiff anti-roll bar will increase the response of the car at low and mid g corners, but leave the car unchanged at the limit of traction on dry pavement. I have a quick question in regards to these ideas.

-A stiff anti roll bar should increase the spring rate of a single wheel (as previously stated). So when the car is up on three wheels (past the point where the anit roll bar is supposedly doing any good), shouldn't a stiff anti roll bar increase the height of the rear corner that is planted through the increased spring rate? What does this increase in rear height do to the overall handling at the limit? Won't this increase in ride height also effect the camber of the wheel as effected by the twist beam (less twisting)?

I guess I see a real possibility of the stiff rear roll bar effecting the handling even in the three wheel corner. Looking for some expertise to shed some additional light on this.
As you suggest, the 3-wheel situation will be different in the stock vs. Big Rear Bar cases, but for reasons mostly having to do with the inside wheel being lifted higher off the ground in the BRB case (as mentioned on P.2 of this thread:

"....Hence at the dry-road 3-wheel cornering limit, a big-rear-bar car will understeer about as much as will a completely stock car (note: there's actually a bit of a difference in that a big rear bar will, by lifting the inside wheel higher, cause more leaning of the outside wheel, but there's so much understeer built into the stock suspension that the overall result is still understeer)."
Again as you suggest, there's a spring rate increase on the outside wheel when you have a BRB, but in practice the % increase is smaller than one might initially think: by the time the car is 3-wheeling, it has rolled heavily onto the outside rear bump rubber (i.e., the very stiff bump rubber ends up carrying a substantial portion of the car's weight), and the ride height gain caused by a BRB is likely quite small. (But yes, there will be some increase in height...)

Just for completeness (since you've brought up this fairly interesting point):

1) The small BRB-induced increase in rear ride height will (on its own) have little effect on rear camber, as the rear twist beam suspension is not really independent: with a true independent rear suspension, you (usually) get wheel camber changes with wheel motion, irrespective of whether the wheel motion arises because of ride height vs. roll; but with the twist beam, the camber is predominantly controlled by the relative positions of the inside and outside rear wheels, not by their absolute height (for the real sticklers, there's a tiny camber variation due to trailing arm inclination, which transforms some of the static negative camber into toe-in as you lower the rear ride height, but for the ride height variations we're talking about here, it's pretty small!). Far more important here is the camber change in the outside wheel caused by the inside wheel being hiked farther skywards by the big rear bar.

2) If there's any spring rate effect, it's probably more evident in the grip degradation you get with stiff springs -- if the outside rear ride rate is higher because of a stiff rear bar, we'll have less traction simply because the rear wheel is more likely to skip over the bumps. (Again, however, this effect is likely to be small, as so much of the spring rate in this situation comes from the bumpstop, not from the coil springs...)

Bottom line, a BRB car should understeer a little less in the 3-wheel situation than will a stock car (which is why the original quote said "...a big-rear-bar car will understeer about as much as will a completely stock car..."), and it would be interesting someday to conduct a real-world experiment to see how much of an effect there really is -- but the main point of the original argument still holds: in the 3-wheeling state, a stock car rolls no more than does a car with a massive rear bar, and in both cases the front tires are cambered in a way that produces extremely strong roll understeer. That's why if you want the car to perform better at the limit, you pretty much have to change the front camber: either via geometric changes (e.g., TT spindles, camber plates, pickup points, etc.) or via front roll stiffness (e.g., the Shine Kit's stiff front springs).

Anyway, an interesting point you raise -- good thinking! :)

- C
 

Radman

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So what effects would one get by running say Koni Reds on full hard vs full soft? Would that increase the roll stiffness similar to running stiffer springs? Or does it only slow down the rebound?
 

sportsguy

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Radman said:
So what effects would one get by running say Koni Reds on full hard vs full soft? Would that increase the roll stiffness similar to running stiffer springs? Or does it only slow down the rebound?
IIRC, you shouldn't use dampers to control body motions, springs do this - dampers control springs. (Though I could have that backwards...)
 

Golf_GTDI

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Maybe Peter could chime in on that thought. I know that the rally car has some very soft long springs and some very highly tuned (and brutal) dampers.
 

JetPuf

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robinhood said:
any difference in US stock, and Euro Stock setups?

also I am getting a lot of noise from my struts, I think, when I go over bumps at slow speeds. any suggestions on how to quite them down?

I have 95k on the stock setup
Time for new shocks/struts.
 

IndigoBlueWagon

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Depends on what the noise is. If it sounds like the oil moving through the struts it's no problem: you may just be noticing it for the first time. Although at 95K they probably are past their last legs, anyway. Clunking noises can mean either worn sway bar bushings (not strut related) or worn strut mounts.
 

IndigoBlueWagon

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Clunky sounds like strut mounts. And my prescription for "slow car fast" are Koni Reds.
 

cartog

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I hope the attribution of the following is clear. I've snipped out a few bits, but essentially it's all Ceilidh's two year old post with a hint of commentary by Peter. The bold is mine.

peter pyce said:
... Note: this is a copy-paste, all written by Ceilidh and ideally I would have read it again (as it was written more than two years ago!) and perhaps see if we have "discovered" some new things that would make the writtne more accurate, but I really can not afford to sit down and read it right now, so take it as a baseline on which later perhaps we can edit and add/remove things..... so, here it is, unchanged, all his the the end:


Ok, at last we turn to GT suspensions. =)

GT Reminder

First, a quick review (for more detail, look back in the "Who We Are" post):

A GT suspension is one that allows for fast, effortless, reasonably-comfortable travel on varying and difficult roads. Unlike the Agility-is-Everything Autocross suspension, and also unlike the We're-Always-at-the-Limits road race suspension, the GT setup has to have:
1) excellent roadholding (good mechanical grip) on a variety of road surfaces
2) forgiveness for unexpected events
3) handling that is consistent under changing road, weather, and load conditions
4) responsiveness to good throttle/brake/steering technique
5) reasonable ride comfort

-----snip info about stock setup-----

Picking an appropriate tradeoff between these 5 characteristics is tricky, and you cannot optimize for all of them at once. A race suspension will lose out on #2 and #5 (and often #3); autocross suspensions often lack #1,2,3,5; and a poorly designed aftermarket kit (particularly one directed toward the Darters) is capable of losing all 5 simultaneously.

The challenge with a GT setup is therefore to improve #1 (Roadholding) without losing out everywhere else. In general, it's not hard to increase #4 (Handling Responsiveness) at the same time as #1, so the tradeoff is in improving #1,4 without losing too much of #2,3,5.

-----snip about Koni Reds and Bilsteins from 2 years ago-----

-----snip about the rear axle-----

On the damping side, the need to keep the rear end soft means that the stock rear shocks are fairly soft on high-piston-velocity damping (high piston-velocity controls bumps; low piston-velocity controls pitch, roll, and heave). Soft high-piston velocity requires similarly soft Low-piston-velocity, so the stock rear shocks are too soft for good handling. In turn, the soft rear means that unfortunately the front must be underdamped as well: as Peter Pyce & I (Ceilidh) have independently noted, when front & rear damping rates are grossly unequal, a very annoying jiggling pitch sets in, making the ride uncomfortable. Hence although the front suspension can inherently take firmer damping than can the rear, the damping there too must be softened, so as to match the rear.

The upshot is that the stock Golf/Jetta IV is severely underdamped at low-piston-velocity, and hence it rolls, pitches, heaves, and generally responds to handling inputs with much less control than one would like.
Thus an excellent first GT step is to improve the damping. Within limits, it is possible to increase the low-piston-velocity damping (which would improve handling) in a shock without unduly increasing the high-piston-velocity damping (which would degrade ride comfort): such a shock is said to be highly "digressive" (opposite of progressive). (With such a shock, the damping forces ramp up very quickly at low piston speeds, but then rise more slowly if the piston begins moving faster.) It is difficult to make a shock that is highly but smoothly digressive, however, and it is even harder to have such a shock retain its nice characteristics over tens of thousands of miles. Therefore well-designed digressive shocks like the Koni Sports and Bilstein HDs are fairly costly.

With the Golf/Jetta IV, unfortunately, it appears to be impossible to get an even highly-digressive shock to be simultaneously soft enough at high-piston-speeds for bumps, while remaining stiff enough at low-piston-speeds for good handling. Hence the Koni Sport (which Peter Pyce's experiments seem to highly recommend over the Bilsteins) has to cheat:
a) to get enough low-speed damping for body control, the Koni Yellows are fairly stiff on bumps. Careful adjustment can do a lot to improve comfort (as both Pyce & Ceilidh have found), but the end result is still "busier" and firmer than stock.
b) given the overall stiff damping required, Koni appears to have specced a twin-tube design (they manufacture monotubes as well, for other applications) so that the shock is not particularly "quick-acting": when the shock begins to move (as when you hit a bump), it does very little damping for a few millimeters, and the damping force "rolls" in rather than comes in with a bang. This characteristic is undesirable for a very stiffly sprung racing car (which is why racing cars use monotube Konis, Bilsteins, Penskes, etc.), but in this application it softens the initial impact from potholes and the like. Hence by using the slower-acting twin tube design, Koni can retain reasonable comfort while increasing overall stiffness for better handling.

The upshot of the above is that, based on Peter's experiments, the extremely quick-acting Bilstein HD (which is an excellent shock, one that Ceilidh has had good experience with elsewhere) is NOT a good fitment for a GT-tuned Golf or Jetta IV. If a driver knows he will be driving on roads that do not have sharp high-speed impacts (no sharp-edged potholes or expansion strips on the highways), then Bilstein HDs should work fine. But if ride comfort is an issue, and if local roads (particularly high-speed roads) have sharp-edged bumps, it appears that Konis are the way to go.

In any event, the stock suspension is not bad at all for a GT suspension, save that it severely de-emphasizes #1 (Roadholding), and in stock form the shocks are so underdamped that body motions obscure the handling qualities. Replacing the stock shocks with Koni Sports all around will slightly degrade #5 (Ride Comfort) while improving #1-4 (everything else), chiefly by controlling the body motions and allowing the suspension to work as originally intended. As such it is an excellent first cut at the GT setup.

-----snip about rear sway bars-----

- Ceilidh
Ceilidh said:
Regarding the 2-year old text (how time flies!) that Peter's reposted: I'd echo Peter's caveat that our understanding of dampers -- almost entirely thanks to Peter, by the way, as he's been doing an amazing series of experiments -- is much fuller now than it was back then. From Peter's reports, it looks possible to get more handling gain with less comfort loss than it looked 2 years ago, and in time we'll be hearing more from Peter on this.
When I read these quotes, I couldn't help thinking about the Koni FSDs. I know we have a thread about them in particular, but I was wondering how well they fit the requirements of a GT setup. Also, is this a direction other manufaturers are pursuing? Are the FSDs the first in what will be a broad range of GT-oriented dampers for a range of cars, or are they an evolutionary oddity?
 

peter pyce

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Nov 6, 2001
Here is a pretty simple read about Sachs’ Adaptive Damper, which is an OE damper on the A-Class Mercedes:

http://www.whnet.com/4x4/adaptive_shocks.html

Here is the drawing from that article:



The drawings may look too complex, but spend some time on looking at them and it will all come together. It is very simple principle and it is very, very similar to what Koni has in their FSD. The Sachs units are acting in both compression and rebound, meanwhile the Koni FSD mechanism works only in rebound.

The whole idea behind is nothing new. The “new” part is that now all this technology is available for few hundred bucks and to the common mortals and their relatively cheap compact family sedans.

Keep in mind that as with everything else, there are compromises. The Koni FSD might work better than another off-the-shelf cheaper system for our cars, but is still not anywhere near ideal. I personally think they have not spent enough time tuning the specific for VW set as the car is not nice at all on specific surfaces (read: crap roads we have plenty of which here). It is pretty amazing on small displacement bumps, but still too “strong” on the big, longer “waves” type of bumps and upsets the whole car, pulling it down in a very unpleasant way on the back side of the bump. Here is a drawing with few types of bumps, so to put in picture the words above:



Outstanding on “A” and “B” type of surfaces. It sets the car into very strong left-right-left roll on the type “C” staggered long bumps, but still not bad. Very unnecessary dive on the back side of type “D” bump, which sorts of sets a very short (but unpleasant) pitch as well, but at least we do not have many of those here.

The other thing that leaves a lot to be desired is the bottoming resistance of the front units – there is simply none. They could have put little bit more compression, so you do not have to slow down too much on driveways, etc. At the same time the rears do now show the “delay” in rebound force, which works so nice at the front, so there is this constant feel that the front and rears are from (for) two different cars. Basically there is bog lack of feel (at high frequency) in the front and too much feel (at all time) in the rear. I hope this is just something in the first series and hopefully someone somewhere will conduct more testing with our specific platforms and fine-tune the system to work even better. But then again, where I live the roads should not be even called “roads” because they have very little to do with the original meaning of the word, so here even OE stuff does not work well. All you need to do is go around for an hour in the new A5 platform (GLI and GTI even better!) and you will end up hating the car, wondering what have they been thinking in Wolfsburg when setting the dampers this way. But in reality, they have done great job for a sporty compact sedan – it just was not meant to be driven on crap like the one we have to drive here. I personally know a guy who did not buy a new GTI because he could not stand the ride on the test drive, believe it or not!

So, yeah, “GT Suspension” sounds nice, but it really depends on where you are going to be “GT-ing”. FSD sounds nice and it is a step ahead from what we have, but still it takes time and effort to tune it for the specific application. Dampers should be (like in the motorcycle world) a lot more customizable and everyone should be able to “trim” his valving for his own tastes, comfort level, etc. but who knows, maybe 10-20 years form now our kids will enjoy those things. Like nowadays you can go to the VW dealer and get your electric steering wheel adjusted for the level of power assistance, with a touch of a button. Hopefully one day you would be able to go there and select from nice collection of pre-tuned damping levels, just with a touch of a button. Till then, use taller tires with lower pressure and enjoy what their marketing departments let us have J
 

Golf_GTDI

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Logan Ohio, USA
TDI
2001 Golf GLS
I will also ask that folks either self edit, go back and nuke your own posts or maybe even an admin remove some of the posts that take us off topic. As I read through some of the stuff over at vortex its stunning huw much you have to dig through to get the info you need.

I will also remove this post as well as go back and take out some of my others in this thread that are not up to that standard in the near future.
 

Varkias

Veteran Member
Joined
Jan 22, 2006
Location
Turners Falls, MA
TDI
'02 Golf TDI
Bumb and stickie vote for the hard work put into this great thread. I've read everything here three or four times now, and I can't wait for more!
 

Golf_GTDI

Veteran Member
Joined
Jun 12, 2004
Location
Logan Ohio, USA
TDI
2001 Golf GLS
I will see the sticky and raise a vote for taking an edited selection of posts from the Vortex threads on the same subject and the best of this and other such posts here. Make it a bit of a FAQs file if you will.
 

4vdubs

Veteran Member
Joined
Sep 9, 2005
Location
Western, NC
TDI
Jetta TDI, 2003, Silver
My vote for a re-sticky! And I'd love to see an edited version listed on the tdifaq section. This information would be perfect for newbies who are seeking as much information as possible. I know a year ago I spent hours reading everything in the FAQ section over-and-over.
 

BoosTDIt

Veteran Member
Joined
Jan 14, 2003
Location
DC area - Fairfax,VA
TDI
The Last NA 2dr 5sp
i want to know why the Audi TT and the R32 are discussed as having the same spindles but they have different part numbers in etka..

also the new 3.2 TT the roadster uses the R32 p# and the coupe uses the regular TT p#
 

platinum_overcast

Active member
Joined
Mar 20, 2006
Amazing amount of solid info here. Thank you to everybody that contributed to this thread.

One question however...

I have a 2004.5 GLI. It has the same suspension setup as the 337 and 20th AE. Directly from the Vortex FAQ, Eibach springs that are 20% stiffer than stock with 30mm drop (same as DriverGear), 21mm RSB, 23 FSB (sways same as regular GTI), gas charged Monroe shocks, metal/rubber rear bushings (instead of hydro)

Of course, the 225/40-18s also play a large part...

Any thoughts on this setup?

What I'm really curious about is how the tradeoffs work out with the three basic "stock" MkIV setups:

Jetta/Golf
GTI
337/20th AE/GLI

Along the very well defined GT parameters:

1) excellent roadholding (good mechanical grip) on a variety of road surfaces
2) forgiveness for unexpected events
3) handling that is consistent under changing road, weather, and load conditions
4) responsiveness to good throttle/brake/steering technique
5) reasonable ride comfort

Again, thanks for this wonderful thread. Maybe someday some of this information will filter back to the huge RSB obsessed Vortex.
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
Joined
Aug 16, 2004
Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
Thursday I swapped out Reds for FSDs in my wagon. I have the OE wagon springs, Shine rear bar. I replaced my bumpstops with Sport ones front and rear to provide more travel, and also renewed front and rear mounts. While at it, we replaced the rear subframe mounts with TT mounts, added a bit of rubber to the dogbone mount, and had the alignment set at .5 degrees negative camber.

I just came back from a ride on a variety of roads, and here are my impressions. Overall, the ride is a bit firmer than with the Reds, but I have to take into consideration that the Reds had 40K on them. The FSDs are deceptive in that they absorb broken pavement and small ripples so well you think you're on a better road than you are. I drove on some roads in a local state forest that are in abysmal condition: broken pavement, seams across the road, frost heaves, potholes, lots of patches. The roads are all posted for 25 MPH; very winding, lots of ups and downs, lots of dips and humps. Last time I drove on these roads it was with a full Shine setup and it was punishing enough that I didn't go back for a couple of years. On the FSDs I could actually enjoy the roads, was able to maintain 40-50 MPH, very little harshness and very good handling. I seem to be able to get the rear of the car to step out a bit more easily: maybe the pressurization of the rear shocks increases roll stiffness a bit. I only bottomed the front once, and not hard: Maybe the shorter bumpstops help there. But remember I was probably driving at about 6/10ths.

I next drove down a smooth winding road that I love, where the corners at 6-7ths are good for 55-75 MPH. The car rolls much less than with the reds, transitions better, and like on the lower speed roads I could bring the rear around pretty easily with a tug at the wheel. I can't comment on brake dive because I have new brakes and didn't want to work them too hard.

Driving home on an older limited access highway the car just sails along. On these roads the ride is a bit firmer than with the Reds, but still with less harsness over expansion joints and drainage grates, which engineers are fond of putting in the left lanes of our roads. I didn't experience any of the "D" conditions Peter describes, so I can't comment on that.

As some of you may know I loved the Reds. And the more I drove on them the better I liked them. I decided to try the FSDs because I didn't feel I could describe them to customers (or let them drive in a car with them) if I didn't have first-hand experience. In summary, I'd say the FSDs are a bit firmer and a bit sportier than the Reds, but the Reds still provide a better overall ride. Perhaps a bit more harshness on broken pavement, but smoother on long dips and humps.

One other thing: on my wagon the fronts and rears seem very well matched. I wonder if the additional weight of the wagon helps, and I also wonder how they'll perform with a load in the car. I'll find out on my way to TDIFest later this week.
 
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