Koni Reds vs. FSD's

silverbox

Veteran Member
Joined
Jul 24, 2005
Location
Halifax Nova Scotia
TDI
jetta wagon 2003 silver
I thought I should pipe in as well I have had the FSD's in my 03 Wagon since November of 05 and I love them. They are of the first batch to hit North America like Peter Pyce's the car feels fantastic; controled and solid but not harsh.
On reading that they went to a twin tube design in the rears, I was at first a bit sad because I like the ride so much, but I suppose it will be better for all the golfs and sedans out there....who knows maybe the twin tube FSD's with air bags in the springs would be the ticket for us Wagon users....Peter Pyce, Bob what do you think?
 
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Varkias

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Jan 22, 2006
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Turners Falls, MA
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'02 Golf TDI
peter pyce said:
http://forums.vwvortex.com/zerothread?id=1648157&page=1
The sad part is that if you go and read today, you will find out the same folks talk about the same old things in the exact same old way and everybody repeats the same old song they knew before, and it turns out that huge amount of work and money was kind of wasted, but perhaps it will help you some.....
I think this is why I stopped reading and looking for for information over there, I just got sick of wading through all the opinions. I just find that I much prefer a forum where there is a little sense of community ;).

I had not found that post yet, so thank you! I will spend some time looking it over and see what I can find.

And Bob from Koni, thank you for replying about the new FSD's. You have access to info that no one else here does, and it's welcome for sure.
 

Ceilidh

Member
Joined
Mar 12, 2006
A brief return to Heavy Rear Bars

peter pyce said:



There are situations at which it will actually over steer and quite badly and quite suddenly! It depends what you do with that car. and no matter how good you are, there are panic situations which you can not predict, neither prevent, at which the car is asked to perform at its limits (or beyond) and that is where it gets really scary with heavy rear bar and novice enthusiast driver. Driving a car with heavy rear bar requires very good training and reflexes, especially if the road conditions are not optimal (read: rain, snow, not smooth surface on mountain roads, etc).


It is easy to "upgrade" the car, but how many are up to the task to drive an "upgraded" car?


This post is just so whoever reads here, thinks about the other side of the story. And in case your car surprises you one day, you can't say "Hey, nobody told me so!".....


Hello Everyone :)

Peter sent me a link to this very interesting thread, and although it's been a year since I last visited the TDIclub forums, it's very nice to see that the supportive and helpful atmosphere here is still alive and well (and IndigoBlue, it's always nice to read your comments!).

Anyway, if you'll forgive me for returning to a point made a few thread pages ago, I wanted to add something to Peter's warning about a "Heavy Rear Bar" setup being a potential handful on slick roads. Many people, when they hear such warnings, make the (entirely reasonable) assumption that if they can learn to handle this setup at high speeds on a dry road (or on an autocross course), then they'll be ok at lower speeds on more slippery surfaces. Others similarly put great stock (again, for entirely understandable reasons) on assurances from racers and fast drivers that the big-rear-bar setup is so benign and easily handled on the track that it should cause no problems at ordinary street speeds. But, unfortunately, things are not so straightforward as that.

If a car's handling balance at high speeds is fundamentally similar to its balance at lower speeds, then yes, you can assume that a setup that's benign and controllable on a dry, high-speed track will be similarly benign on a slippery-but-lower-speed road surface; indeed, the slippery-road situation might even prove easier to handle, as things will be happening that much more slowly. But if the handling balance at low speeds is fundamentally different from that at high speeds, then all bets are off. And that unfortunately is the case with a Heavy Rear Bar setup on a VW Golf or Jetta (especially on an A4 or earlier chassis).

To grossly oversimplify things: an A4 Golf/Jetta derives its high-speed dry-road stability by preferentially rolling its front wheels into adverse camber; in plain English, at high cornering loads the front wheels on an A4 are leaning away from the corner much more strongly than are the rear wheels. This leaning reduces the grip on the front end, and the resulting understeer makes it relatively difficult to spin the car (you can still spin, but you have to work at it!). Surprisingly, when you add a Heavy Rear Bar to the A4 chassis, you don't really change things at the high-speed, dry-road limit: at the fastest cornering speeds, even the stock A4 has lifted its inside rear wheel, and all a Heavy Rear Bar does in this situation is to raise it a bit higher; since both the stock car and the HRB car thus have an identical 100% rear lateral weight transfer, the handling balance is roughly the same between the two vehicles, and the HRB car still strongly understeers (at the dry-road limit).

It's for this reason that people report an HRB setup as feeling benign on a high-speed track (it ought to -- at the highest cornering loads, they're essentially driving a stock vehicle). Indeed, it can be a very flattering setup: the HRB allows for a fair bit of oversteer at initial cornering loads (when the stock-car wheels would still be 4-square on the ground), which allows one to flick the tail out into a slide; once the cornering loads really build up, stock-levels of understeer set in to stabilize everything, allowing one to bring the tail smoothly back in an impressive looking drift.

The problem with an HRB setup is when you take the car away from the dry, sticky, high-speed track, and place it instead on a slick public road (e.g., one that's wet, greasy, or icy/snowy). On such a road, the car hits its cornering limits at much lower g-loadings, and the tires begin to let go while the front tires are still relatively upright. Because the front tires are still upright, breakaway happens before there's an awful lot of understeer, and even a stock A4 can readily swap ends (at least on ice) if the driver isn't careful. Add a Heavy Rear Bar (which increases the oversteer at low cornering loads), and you can get into a snap spin situation, where the terminal oversteer is so sudden and unexpected that very few drivers can correct in time.

(Note: ask Peter about the time he came around a fast, dry corner in his HRB-fitted Jetta, and unexpectedly drove across some rain runoff -- having now driven with and behind Peter on some winding mountain roads, I can vouch for his being a very skilled and experienced driver (and a great guy!)...and the resulting oversteer gave even him some heart-in-mouth moments.)

Anyway, those who've waded through the huge Vortex handling thread will have seen that Peter and I aren't huge fans of the HRB setup. When a Heavy Rear Bar is fitted as part of balanced package to an intelligently modified car, it can make a lot of sense (please note that Shine themselves say that their bar should be added to a car only after their spring kit has been fitted). But on its own, an HRB turns the benign A4 chassis into something that's benign in the dry and decidedly less so on slippery roads, and this Jekyll and Hyde transformation is NOT what one wants on an all-weather passenger vehicle driven on public roads.

As always, thank you very much for allowing me to be a guest on your wonderful forum. Best wishes to everyone for the coming spring, and may all your VW adventures be pleasant ones.:)

Cheers,
Ceilidh
 

Varkias

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Location
Turners Falls, MA
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'02 Golf TDI
Ceilidh,

Thank you very much for adding to this conversation! We (or at least I) would love to move this over to the "what is handeling" thread and keep that wonderful post going. It might be a little out of context though.

I think for me (and I would guess a lot of other people here as well) that the main thing I am unhappy with in the A4 VW cars is the way that they seem to lean, bob and bounce all over the road. Wether or not they are handeling well while doing this, it's just not a fun feeling. I had an '88 GTI and I loved the way that it felt. Even if I wasn't going very fast, it felt like I was driving on rails. I also really enjoyed how the A3 cars continued this feeling of "sharp" handeling. But the "mush" factor of my '02 Golf drives me crazy.

So the question, how does one rid the car of this feeling? Is it possible to do without loosing the built-in safty of the factory suspention set up? I want to change my perceptions without loosing the safty factor since it's more then just my life and car on the line.

If we were able to just feel better about the ride, I think people would stop wanting to "make the car handel better".

Am I crazy? Just un-educated about such things? Talking to much in the land of perception rather then fact?
 

pdxgrease

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Location
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Varkias said:
Ceilidh,

I think for me (and I would guess a lot of other people here as well) that the main thing I am unhappy with in the A4 VW cars is the way that they seem to lean, bob and bounce all over the road.
Yeah thats exactly what i hate too. So how do we cancel that out and flatten the car more?
 

IndigoBlueWagon

TDIClub Enthusiast, Principal IDParts, Vendor , w/
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Location
South of Boston
TDI
'97 Passat, '99.5 Golf, '02 Jetta Wagon, '15 GSW
If you agree with Peter Pyce on this, buy Koni Reds and be done. Stock springs and stabilizer bars. The car will handle well, will not lean a lot, and will be safe. Spend the left over money on the lightest wheels and best quality tires you can afford. I'm willing to bet a car with Reds and all else stock with R-Compound tires would run rings around most others.
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
Winston, thanks for stopping by! As usual, your posts are work of art! simply nothing to add......

Varkias - the mild upgrade and feel you are looking after is exactly what dampers will take care of. Just avoid pretty much everything that says "Sport" or "Race" and you would do well. Koni Red had been for some time the closes to OE replacement (in terms of performance). Actually we could call it the very modern this days term "OEM Plus". It is very nice upgrade, yet it keeps it civilized and friendly. Ideally you want a customizable set of mono-tube which you could service easily, but those things do not quite exist for that platform and if they do - they cost $$$, so with the Reds you get the not-so-expansive product, yet it is serviceable by you, in your garage, which makes it the damper of choice if long term ownership is in your plans. (which usually is the case with TDI owners - they keep the cars for very long, and that in many cases means a lot of miles, which is where serviceable dampers are really paying off). Let's make a quick note and mention that the way these things are made, let's say every 40.000 miles you can take them off, change the oil, inspect the product and once you put them back - you have essentially a brand new set of dampers, performing as it did in day one. On top of that, you could tweak little bit the washers and give it some flavor if you think it is too soft or too stiff, etc. It is nice hardware that gives you options and does not cost an arm and a leg.

The other important part is tires (Actually, the MOST important part, but then I know you guys are after economy and not everyone would agree to put sticky summer tires, etc). but matter of fact is, the stock car is so capable with just nice set of tires, it is beyond recognition what those donuts do to the overall feel and performance. Tires are arguably the ONLY real upgrade when it comes to enlarging the performance and safety envelope.

Performance tires (in the smallest diameter possible) and mild dampers are pretty much everything this car needs to become a very capable compact sedan, yet providing comfort and safety.

P.S: Bilstein also makes very nice hardware, do not get me wrong! It is just that their line does not offer equivalent product to the Reds. If Brillstein comes out with easily serviceable Mono-Tube for our cars, on which you can make your own mild valving, and have the damper serviceable by you in your garage - it will become my first choice right away! but they do not have such a package yet, and perhaps will never do.
 

meganuke

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Location
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2010 Ford Fusion Hybrid
But what about the body roll? The wagon rolls a lot...
 

GoFaster

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Brampton, Ontario, Canada
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2006 Jetta TDI
One thing is roll, the absolute amount that the body will roll after everything stabilizes. The other thing is the swaying and bobbing that you get after turn-in. The swaying and bobbing feeling (varying body roll) is due to inadequate low-speed damping, and for that, you need to use dampers with more low-speed damping than stock. By "low speed" I am talking about the speed of suspension collapsing or extending, not at all the speed of the vehicle which has nothing to do with how fast the suspension is moving. The thing here is that too much low-speed damping can create unsatisfactory ride motions, and too much damping in general will reduce compliance on bumpy surfaces.

If you want to reduce the absolute amount of body roll then you need more roll stiffness, and for that, there are two different methods, with the best choice likely being a combination of the two in balance. Method 1 is to use stiffer antiroll bars. Method 2 is to use stiffer springs. The trick is to get the front to rear balance correct to avoid instability issues.

The best choice is an engineered package, of which the Shine "Real Street" kit (the WHOLE thing, not just bits and pieces selected from it) seems to be the best-sorted-out commonly-available deal. I have personal experiences with the Bilstein HD dampers that he chooses, though. Too much NVH (noise vibration harshness) transmitted to the bodyshell.

If you don't want to go that far then probably the next best package is to either change front AND rear antiroll bars, and your choice of better dampers. If *that* is even too much, I still think a rear antiroll bar can help with this, but go easy on it if you are not adding more front roll stiffness (i.e. stay with a smaller diameter one, not the biggest you can find). On vehicles before the Mk5, the rear antiroll bar on its own will be more of a "feel" thing than something that absolutely increases the cornering limits (see previous discussion about these cars lifting up the inside rear wheel during hard cornering).
 

Varkias

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'02 Golf TDI
Peter,

Thank you again! I'm starting to sounds like a broken record here. This is what I wanted to hear! I think it's what I have been hearing all along, but it's really starting to sink in now. ;)

Time to find some nice tires for my 16'' BBS wheels I think....
 

peter pyce

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Joined
Nov 6, 2001
GoFaster said:
...The swaying and bobbing feeling (varying body roll) is due to inadequate low-speed damping, and for that, you need to use dampers with more low-speed damping than stock......
Brian, I would like to extend little bit on this part, for those few interested. After that big Damper thread got out of control, we kind of stop bothering, but experiments did not stop at all! Actually, I would say the biggest discoveries we made were a lot later and the results were never posted (we just exchange daily e-mails with Winston and that was it) because it was clear that the "resistance" would have been even larger as what we discovered certainly was not something the vortex would have agreed on and digested, and so I did not bother. But Brian, you seem to be very interested in all these things and perhaps could find some of the info rather intriguing....
Above, you are right about the low speed damping, but I would like to split it in two and talk about the low speed compression and low speed rebound as two separate "tools" to create a very difficult to explain "dynamic" control of an otherwise rather lousy car (from roll design point of view) that the A4 is.
What we found is that in general, the "sport" type of dampers use way, way too much low speed rebound damping and not much compression damping (the Bilsteins are a fantastic example of that). Now, all the books talk about how rebound is used to control body roll, and every kid on the internet knows how you "stiffen the rebound" and the car becomes flat, but what we have found out is that the best results are achieved by making low speed compression little bit stronger and making the rebound rather wear, very soft! We actually ended up building a pretty efficient (for this experiment) damper that had two separate circuits (one for rebound and one for compression) and both were externally adjustable without removing anything from the car. This way we could set the relation between compression and rebound in different proportions and drive the car around and experience the differences. It was not something sophisticated, but it worked great to prove concepts of ideal ratio rebound-compression and also concepts of how much damping (fraction of critical) does what, etc. It was an eye opener and in fact the things we learned were applied to the Rally Golf, and from the results and feedback I would say that things work pretty well even in environment a lot more brutal than the street. Basically we found out that Compression is a lot better (by far) means to control dynamic roll (and by saying compression, a lot has to do with the bleed in the system - lack of bleed (on purpose!) in one direction makes wonders with roll control). In fact, I am seriously involved with couple of Miata racers, developing these concepts for their race cars, and so far the results have been more than impressive. By carefully valving their dampers, the guys can afford to go to an autocross with R tires on very soft springs, with great levels of control and most of all - grip! I do realize most of this could not make sense, but it is real life experience. Bottom line is, the way they set off the shelf dampers are not really optimized and a lot could be done. Damper manufacturers are not after making our cars faster, but rather just modify the feel for "fast", while actually keeping it slower, therefore perhaps safer..... I will see if can find some old pictures and graphs, but there is some interesting stuff that was never posted.
 

pdxgrease

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none
so dang it. how can we throw a couple bucks at our car and improve things Peter? We all want our cake and to eat it too.
 

GoFaster

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Jun 16, 1999
Location
Brampton, Ontario, Canada
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2006 Jetta TDI
You bet I'm interested! I'm totally with you on having balanced low-speed damping in both compression and rebound. If it's not like this, you can get a situation where the suspension "packs down" with repeated suspension movements. A compression bump forces the wheel up, then the excessive rebound damping lets the bodyshell move down with the wheel on the return stroke, then the next compression bump forces the wheel up further, etc., and eventually you ram the bump stop (on a car) or get into the hydraulic anti-bottoming valve on a motorcycle fork (read: very excessive compression damping causing a loss of grip followed by a low-side crash!)

Which off the shelf aftermarket shocks have you found to be the "least bad" in this regard? It's too much to ask which ones are "best" ...

My area is motorcycles, which have a different set of issues, but the common element is that you have to use low-speed damping to control bulk motions of the chassis. The compression damping in particular has to level off as the speed of compression goes up, otherwise you will transmit huge shocks to the chassis. My race bike Yamaha FZR400 suffers from this. I have an aftermarket Race Tech compression valve installed (with the stock compression orifices drilled out) to help with this, but it's far from perfect. I have to use thicker than stock oil to compensate for the inadequacy of the stock forks, and that creates other problems. Ride quality is not a priority on a race bike, but on our bumpy Canadian tracks, you NEED to maximize bump absorption and minimize shock loads to the chassis, and my setup ain't where I'd like it to be, but one can only do so much with parts designed more than 20 years ago.

I have contacts at ArvinMeritor Ride Control here in Toronto (ArvinMeritor builds many truck/bus suspension systems, they own Gabriel and Monroe but those are not built at the plant I deal with, and they also build RydeFX premium snowmobile shocks at the facility I deal with). The premium rebuildable and revalvable shocks are built *completely* different from the run-of-the-mill welded-together shocks that are $18 a pair at the local parts store ...

I'm not going to take my Mk5 to an extreme of modifications; probably just Koni FSD's and a rear antiroll bar, and I have a set of Air Lift supplementary springs for the rear on order so that I can get the car sitting level with my bike trailer in tow ... The car has ESP in case this gets it too tail-happy ...
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
pdxgrease said:
so dang it. how can we throw a couple bucks at our car and improve things.....

You can't, not for couple of bucks! If it was possible and if the cost was couple of bucks - VW would have done it for you. The stock car is great, actually, if the user accepts it for what it is. Everything you buy from the aftermarket gives you a compromise to what you had before. You feel something different, you perceive it as improvement, but there are negative sides too, just those are usually ignored as it does not feel good talking about it.


The real bottom line is - change the car! A VW A4 would not become a Miata, not until you pour 20 grand in it, as which point there is no point. The whole car was born as a different concept and just getting aftermarket stuff would not fix anything much. The car was designed to roll, so it will roll and any attempt to "fix" the roll will result in other degradations. One of the many things roll contributes to is giving you feedback, so you know you are going too fast, and so you hate the roll, it scares you and as a result you slow down, which is what this is all about. It is a lot easier to learn how to live with the roll your car has built in and then you will just drive it and could even start enjoying it. It feels scary, but actually the car is still very, very capable to a point that you are already driving way too fast for the street. Track use is entirely different matter and the two should not be mixed.


There are two very specific scenarios here - the first is that the roll feels bad and induces fear and discomfort in the driver, making him feel that he is not in control and the car is not performing, etc. The second is the desire to reduce roll for better geometry at all time....


I suspect the majority is in case #1 and for that I would like to say that the car is actually very capable even when is fully on its bump stops, and even if it feels scary, it is not! It is hard to overcome the fear, but I rather have stock car tilted at 6 degree in a fast curve on crappy road, than having a car with only 3 degree tilt with sway bars and stiff springs, on the same road and at the same speed. Because the first will feel scary, but will go through it without drama - the second might snap on you anytime and you have to make that curve almost in apnea as to be able to catch the split second and react!


Brian, your question requires a lot of writing, so later one that.
 

GoFaster

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Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Rightly or wrongly, I placed the order for front and rear Mk5 Eibach antiroll bars today ... Stock rear antiroll bar is 18mm, the Eibach one is 23mm, the Neuspeed one is 25mm but doesn't come with a matching front (but cost only slightly less than the Eibach set!). I'm keeping the stock springs so the one-wheel bump rate shouldn't be *completely* out of range. Hopefully Eibach has put at least some thought into keeping the roll stiffness balanced front to rear, which wouldn't be the case with the rear-only Neuspeed bar. We'll see.

I've yet to see a Mk5 lift the inside rear off the ground the way the twist-beam earlier models do. With such soft rear spring rates and small rear antiroll bar and no axle connecting them, it probably doesn't happen.
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
Brian, there is not really right or wrong, it really is what you are happy with. You race bikes and the car world is not so different in terms of "the concept" behind tuning - the perfect setup is the one that allows the driver to be the fastest! Talking to real race car engineer, he tells me this: "If I set the car to be the fastest, the most capable - the driver will give me the slowest times as it is not going to feel confident to push!" And it is the exact same thing with what we are doing here. Everyone perceives the car differently and feels that different issues should be addressed. At the end it boils down to what makes you feel that you accomplished what you wanted.....


It would be nice if you do some tests "before and after" with your car, like see the speeds at which the front end breaks away with the stock bar and with the new bar. The car with the bars will feel better, but if you are careful with the experimenting, you will see how it gives up earlier and the transitions between are more pronounced, the break away is not as progressive, etc.


Also, pay attention on comfort, it will change a lot (even if everyone tells you bars do nothing to comfort, but they do and a lot!) Especially pay attention to side-to-side shaking your head, as the suspension will be less independent. Your steering wheel will get a lot heavier too, hope you like it. (well, you can increase the pressure and bring it back)...... I count on your feedback because I think you will be able to see the full picture and not just report the reduced roll and therefore the "wow, this thing great and there are no drawbacks what-so-eva!"..... Keep us posted!


P.S: Actually, while you are at it (I assume you are going to do the install yourself) - try removing the stock bars first and drive the car like that for some time and see what that gives you. Remove the front first, then the rear, in a different day. And again, try to catch the speeds at which the car can go through the test curves, do not rely on the feel only. I am very curious to see what you find out.
 

Tin Man

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Coastal Empire
TDI
Daughter's: 2004 NB TDI PD GLS DSG (gone to pasture)
I have been following this thread and appreciate the complexity of suspension tuning. It has, however, not satisfied what I am looking for:

The 2002 Beetle has 136,000 miles on its original shocks and still feels tight. It does, however, have trouble with long dips on the road making it bob a lot on some of the Kentucky roads built more on river beds than mountains. This is a problem for the arthritis in my neck as the head acts like a bowling ball on a fine piece of china.

I am looking to modify only the softness of the suspension when dealing with these long road dips. Any recommendations?

Thanks.

TM
 

peter pyce

Veteran Member
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Nov 6, 2001
TM, can you take a picture of such a dip? How long they are, what is the speed you are going through them? Is that something like the LA freeway hop-pala we have here?
 

alhutch

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peter pyce said:
...In fact, I am seriously involved with couple of Miata racers, developing these concepts for their race cars, and so far the results have been more than impressive. By carefully valving their dampers, the guys can afford to go to an autocross with R tires on very soft springs, with great levels of control and most of all - grip!...
Peter,

I'd love to hear more about this (off-line, if needed). The Koni Yellows on my CSP Miata are in need of rebuilding (and probably revalving). Let me know if you are game! Thanks.

Al
 

Tin Man

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Daughter's: 2004 NB TDI PD GLS DSG (gone to pasture)
peter pyce said:
TM, can you take a picture of such a dip? How long they are, what is the speed you are going through them? Is that something like the LA freeway hop-pala we have here?
Going 65 mph, the dip is about 2-3 ft. in radius and about 10-20 yards long. The pavement is smooth. This seems to be from the soft earth that the roads are made on. It happens a lot around here where most everything is built on an old riverbed.

I have only seen one measure of suspension tuning in the recent past and that is the number of g's that are felt on these kind of dips. I think it was for Buick or some such brand.

Thanks.

TM
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
alhutch - go to www.fatcatmotorsports.com and contact the owner (Shaikh) and he will take you from there. When the whole tihngs started with the Maita, decision was made to go with the Bilstein hardware, as we could get pistons from here and there that would bolt-on on the bilstein hardware (inside) and in general a mono-tube damper was a better choice, so nothing was really done on the Konis, but I am sure he could at least change the oil and perhaps make some tweaks to please you. I just do not have time for these things anymore, and he made a choice to do this for living, so he has all the time and dedication, therefore he is your man in this case.

TM - is this the sort of dip you are describing?



Imagine the car travels in the direction of the arrow "downgrade". Is this the geometry in general?
 

danix

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Oct 5, 2000
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Raleigh, NC
TDI
None now. Former: 2011 335d, 2010 Jetta TDI, 2003 Jetta TDI Wagon. 99.5 Jetta TDI, 98 NB TDI, 3 different black 96 Passat TDI wagons.
I'm watching the thread with interest, but will just chime in to say that I believe the stock suspension setup on the A4s is crap, and that I could manually compress the rear shocks off my wagon when they had 5k miles and I removed them.

I think a suspension upgrade is a very cost effective way to improve the safety and handling of almost any car. For example, most BMW 3 series have far better suspensions than the VWs, and there is little point in upgrading, for the average driver. My wife's new Mazda5 handles remarkably well, and while I would be tempted to drop in the suspension from the Mazdaspeed3, there is no real need to.

My personal choice is Bilstein HDs, Shine springs and the Shine rear bar. I have almost 40k miles on this setup, love the handling, and I don't find it harsh, not even in the Bay Area (but I suspect roads where Peter lives are worse than in my area).

I'm glad to see Peter (Pyce) and all the other suspension gurus posting again, and if Bob from Koni is still around, you would do well to continue posting, since this level of customer attention is something that sets you apart from Bilstein and other manufacturers.
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
GoFaster said:
you can get a situation where the suspension "packs down" with repeated suspension movements. A compression bump forces the wheel up, then the excessive rebound damping lets the bodyshell move down with the wheel on the return stroke, then the next compression bump forces the wheel up further, etc., and eventually you ram the bump stop (on a car) or get into the hydraulic anti-bottoming valve on a motorcycle fork (read: very excessive compression damping causing a loss of grip followed by a low-side crash!)
You know what - this above is the single most frustrating thing that people would not visualize and because of that, would argue all day long how dampers are just to control the spring and the springs are the means to control roll, dive, squat, etc....... which would be true, but only if you have really stiff springs that could deal alone with all the weight that gets transferred around while the car moves in all sorts of directions. the problem is that the springs we have on the cars (and even the stiffer aftermarket springs!) are by no means enough to deal with the huge mass the vehicle has and these cars rely heavily on what the dampers do in conjunction to help the dynamics of cornering, braking, etc.

(just for fun, take off the dampers and go for a ride - it is an eye opener of how much dampers do to everything that folks thing is "the spring's job".)

And so, it is essential to have a damper that is very well sorted to work with a specific rate springs and that is not only the value of the force it develops at specific speeds, but also the ratio compression-vs.-rebound where things get really interesting. And this is why I get so frustrated when folks just recommend dampers without even knowing how those are set internally, what kind of force they develop and most of all, what is the compression vs. rebound ratio (and the shape/nature of the curves).

Let's look at one single scenario, the so heavily discussed in the past Bilstein TC. Here is a dyno from the two models - the Standard TC and the Sport TC:



This is at 18 ips and the picture is pretty much the same in all the rest of the speeds (from 2 to 30).

Now, assume this is for a stock car, like many would buy it for. Look at the difference especially in rebound - there is 50 lb of difference and in a dynamic situation as described by you above (in the quite) that is going to play big role on what the spring is going to do. so, you get the "sport" and you will be jacked down a lot more than with the TC Standard. You will ride "stiffer", and will make you feel that you are "Sportier", but at the same time the car will "crash" over bumps, will dive more, will squat more and in general will be less capable, but it will "feel" better. And look at that ratio - we have about 270 lb in rebound versus about 70 lb in compression - that is almost 1 to 4. That is huge! That spring will fully extend to the installed ride height only on a traffic light wait!

GoFaster said:
....Which off the shelf aftermarket shocks have you found to be the "least bad" in this regard? It's too much to ask which ones are "best" ...
In general those with less rebound are better, so the spring "breaths" and follows the road (not the car!) and that keeps the car actually flatter in a corner, increases grip and in general provides a lot better ride, but some folk like more "boxy" feel and small rebound does not provide that, so such dampers are seen as "not-sporty". Anyway, the Koni Red is really the "best compromise" as far as a street car with stock springs goes. The Yellow will have a lot better bottoming resistance (the compression vs. rebound ratio is "almost" 1 to 1), but the way the compression valving is set, it does not give you smooth transition from "zero to full speed" and it is very spiky, and also it has very high level of hysterisys, so "curves wise" it makes sense, the the way those values are achieved does not give the smoothest transitions (they use washer preload and preload and comfort does not go hand by hand very well)..... but then again, the are called also "Sport" so it is ok if they are stiffer, LOL.

Here a dyno Red vs. Yellow:




Then the KYB AGX are not bad, but they are more expansive and the adjustment is kind of mild (from 1 to 8 clicks) and I did not feel comfort was as good as with the Red, but it could be valid option with OE springs, if the user wants to turn knobs.... even if that damper has compression AND rebound adjustment all at once, so it is a lot of "just change the feel" feature.

Here the KYB at full soft, compared to OE Jetta TDI damper:




And here the full soft vs. full stiff on the KYB, so you see how little things change:



In general, the best overall results are with dampers that provide curves closer to the OE damping curve. And this is for street use we are talking about. Track and Rally are totally different issues we could discuss in a different topic. Also, unfortunatelly, dyno curves do not tell the full story as you can make a damper to give you two almost identical curves, yet it could be done to feel so different on the street, so take this for what is worth.

This whole post is in so "general info" mode. The details are in the Damper thread, but difficult to find and put in order.
 

Tin Man

Top Post Dawg
Joined
Nov 18, 2001
Location
Coastal Empire
TDI
Daughter's: 2004 NB TDI PD GLS DSG (gone to pasture)
peter pyce said:
TM - is this the sort of dip you are describing?



Imagine the car travels in the direction of the arrow "downgrade". Is this the geometry in general?
From an article on building roads that talks about ride quality:
Ride quality specifications-smoothing out pavements
For the purpose of this paper, large dips, humps and bumps have been defined as long wavelength features in the pavement. In severe cases these are capable of producing 'gut wrenching' heaves that produce accelerations similar to those experienced by a passenger on a joy ride at a theme park. Long wavelength features must also be avoided if a smooth ride is to be achieved.
My problem seems to be slightly worn shocks and bushings, as well as too stiff a suspension, that make long wavelength road irregularities a problem. It would be good to improve on the original specs also on this one.

Thanks.

TM
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Wow ... I just now finished skimming the whole damper thread on Vortex. Unbelievable ... ! ! !

I feel better about leaving my stock dampers in place until they give out. I have no objection to the way the damping feels on the Mk5 anyhow.

As for getting some sort of instrumented before-and-after tests on the antiroll bar set, bit tricky to figure out how to do that, particularly at this time of year when weather and road conditions change so much day to day, but maybe I'll think of something.
 

peter pyce

Veteran Member
Joined
Nov 6, 2001
TM, do you remember what was like to drive on the same roads (the dips) when your car was new? How would you describe the difference between new and now?


The reason you feel those so much is manly because our car are designed to bottom-out easily and it gets even easier with "worn" dampers, in which the oil is like water and the whole thing does work as well as when brand new. What really happens is that you are bottoming on the buffers and at that point you have no suspension and basically the car becomes a go-kart and it moves with the tire, and so your head moves with them together and is not nice at all...... Is there anyway you could drive through those things with a soft dirt bike (lots of suspension travel) at the same speed and report back what you feel? Or even better, drive a real dune-buggy, but that is asking too much I guess.


Also, back in the first years, the NB came with stiffer springs. Not by much, but stiffer. Bit if the info I have is correct, they changed them to softer springs around year 2000, so you should have the softer springs.
 

Varkias

Veteran Member
Joined
Jan 22, 2006
Location
Turners Falls, MA
TDI
'02 Golf TDI
Quick question for you Peter, you were talking about servicing Koni Reds at around 40K miles, I'm wondering what the life span on our OE (A4) dampers is.

Having put around 180K on my Honda without any complaints about the suspension, I really have no idea what I'm looking for in a worn damper.
 
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