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Upgrades (non TDI Engine related) The place of handling, lighting and other upgrades that do not relate to the performance or economy of the TDI engine. In other words upgrades to your TDI that don't fit into TDI Fuel Economy & TDI Engine Enhancements.Please note the Performance Disclaimer

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Old March 3rd, 2007, 05:05   #61
silverbox
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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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Old March 3rd, 2007, 06:35   #62
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Quote:
Originally Posted by peter pyce
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.
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Old March 4th, 2007, 22:22   #63
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Default A brief return to Heavy Rear Bars

Quote:
Originally Posted by peter pyce



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
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Old March 5th, 2007, 02:36   #64
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Thanks for the post and information!
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Old March 5th, 2007, 07:12   #65
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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?
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Old March 5th, 2007, 10:43   #66
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Quote:
Originally Posted by Varkias
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?
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Old March 5th, 2007, 13:43   #67
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and retain mostly safe and predictable handling?
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Old March 5th, 2007, 18:40   #68
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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.
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Old March 6th, 2007, 04:39   #69
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well i'm on the right track then, thanks.

thats been thje plan since before i even had the car
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Old March 6th, 2007, 09:17   #70
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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.
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Old March 6th, 2007, 10:54   #71
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But what about the body roll? The wagon rolls a lot...
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Old March 6th, 2007, 13:01   #72
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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).
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Old March 6th, 2007, 16:01   #73
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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....
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Old March 6th, 2007, 16:55   #74
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Quote:
Originally Posted by GoFaster
...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.
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Old March 6th, 2007, 17:12   #75
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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.
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