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Go Back   TDIClub Forums > VW TDI Discussion Areas > Upgrades (non TDI Engine related)

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 April 9th, 2006, 12:16   #61
dingchowping
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Quote:
Originally Posted by peter pyce
Adam, thanks for coming in! We have tried (and failed!) to find someone with an early TT who also knew the newer TT's and who also knew what he is talking about and who also knew how to write in details - and here you are, all in one! Please, please, on behalf of me and Winston and everybody else who's interested - do try to find some time and sit down and give us as much details as you can on that early model TT. Especially if you can do a parallel comparison with other VAG products, and even more, if you can compare it to a later, post-recall TT. I never had the chance to find one and to drive it, but reading about you and your background, I am sure your words will be enough to understand in depth what was the car's character and how did behave in the most possible to describe scenarios. Take your time, please, no rush, but we will be waiting (patiently, we try) for your in dept coments. Thanks in advance!

DPM - I know they tested the Grand Vitara, just can't recall the issue, but will keep digging, so eventually will find it.

To everybody else who posted above - I do understand some of you are expecting answers to their questions, but this weekend is really dedicated to something else, so please be patient, it will all come next week.
Hi Peter,

I'm glad I could be of help. I'll try to post more later today or tomorrow but I've driven I'd guess around 100 TTs in various states of tune, so I need to organize my thoughts into something less resembling word vomit before I post. I'll get back to 'ya soon.

TTFN,
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Old April 11th, 2006, 11:21   #62
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Originally Posted by mr.mindless
.....with the massive caster angle we have, how does that factor in on a slow, hard corner. Definitely more on a concern for autoX than GT or Slow Car Fast, but with the camber that introduces at lock, that's got to have a huge effect in hairpins. As I drive, to the point where I feel totally neutral through anything that's slow and >90°, but with the front sway hooked up I have hopeless inside front tire lift and have no hope of powering out quickly........


As you observe correctly, we have pretty good amount of caster on our cars (around and between 7 and 8 degrees, it depends how low you are). That makes for an artificial camber, which comes only when the wheel is cranked in one direction or the other, and the more it is cranked, the more the camber. Here is an animation that show pretty well what is going on an A4 VW, how the camber changes with steering input due to the caster:

(note: this is the front left tire, and you are looking at the car like if you were standing in front of the car, looking back towards the car)



It is pretty visible how great the negative camber gets if the wheel is the outer in the curve and how great the positive camber gets if the wheel is the outer in the curve. Here is a graph that shows these values, so some comparison could be made between different degrees of steering input:



(note: this is degree of steering at the wheel, not steering wheel degree!)

We gain about -0,7 degree of camber in the 5 degree steering, then we gain another -0,5 degree for the next 5 degree and so on. Due to the geometry, the gain is digressive, but it is plenty and at certain point exceeds the rear, which does not change during steering inputs (ok, it changes little bit due to body movement with steering, but it is so small, we will ignore it).

So, what happens when we drive in a fast, long curve? We get less steering input, so less camber gain and as we go fast, we get into under steer (pretty well explained by Ceilidh so far) due to the front losing camber faster than the rear, etc… (let’s do not go over again). Next thing we do is panic, and with the panic the instinct kicks in, we do two major things:

1. lift and perhaps even brake and
2. steer even more as to keep the car in our line and keep it on the road.

So, the #1 was explained very well, it transfers weight to the front, so loads the front tires more, they to grip better and that helps to pull the car “in” the curve, etc. At the same time #2 is where the big caster makes it so we gain greater negative camber the more we steer into the curve, so #2 helps even further as now we have loaded front tires from #1 and also we give more negative camber to those same now loaded more tires, which makes them grip even more, so the net result is that the front grips again, the understeer is interrupted, the front “comes back” and we “save” the situation without even being trained drivers – all we did is follow our instincts.

As also explained by Ceilidh in earlier posts, the sharper the turn, the more the understeer (even with low speeds) on our cars, so the more negative camber we need on sharper turns, which is something the caster gives us. The reason your front inner tire spins in powering out of the turns is mainly due to the whole concept behind the setting for this car. It is basically ”built-in” stuff, a compromise if you wish to call it, as other things are/were more important than the power-out of a curve. Simple things like removing the front bar/going stiffer in the rear/resetting dampers, etc will cure that, but will of course bring other issues to the table. A car modified like that will not be as good for the masses, so you have to personalize it some if you want it to do few more tricks.
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Old April 11th, 2006, 14:57   #63
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Why did I wait so long to read this thread? Charts, animations, numbers, oh my! Even mention of matlab/simulink modeling! All it lacks now are some equations... but those can get pretty complex.

Reminds me of one of the questions I had during my dynamics/vibrations qual oral exam. I was asked to derive the ground force caused by a simple one-wheel-on-a-spring suspension model travelling over a sinusoidal roadbed. I was then asked if the equation I came up with would always be valid. My response was... not if the wheel comes off the ground!

nate... did you model the vehicle in full 6-dof or did you only look at rotation? and did you have realistic models of the suspension geometry? did you calculate the EOMs by hand or did you use a package?
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Old April 12th, 2006, 09:52   #64
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Just a quickie on tires….

We have been talking for quite some time how tires are the best (and most of the time – the only!) real performance enhancer when it comes to speed in curves, road holding, grip, etc. So, I ran across an interesting article on the new FIAT Panda. The car was also put under the “Elk Test” and there is something interesting that happened. The basic model had some sort of ordinary tires (all season) and performed quite well actually (for such small car, pretty tall too). Then they tested the upper tier model, which was basically the same car (suspension wise) but had performance tires, which is a trick many car companies do – just put bigger wheel and sticky tires on their “sport package” and that is it. Anyway, due to the stickier tires, not the car has actually issues in the Elk Test as it started to lift BOTH inner wheels (!) It did not roll over, but perhaps because experienced driver were behind the wheel and knew how to take care of that, but guess what could happen if the average Giovanni drives the car? Here is a pix that supports the story (The Panda on two wheels from the test):



Then there was another interesting piece, on a Honda Minivan, where they tested both the basic model and the high tier model together. They both had all season tires, the exact same brand and model, but the basic model had them H rated and the high tier model had them V rated. The basic H model did very well in the lift-throttle and change lane test (the one we were talking earlier in this thread) and went through at speed of 102 km/h. The V rate tire model, thought, barely passed at only 100 km/h and the tester was commenting that due to the soft suspension and specific geometry on such vehicle, the car rolls a lot more (it is a minivan!) and at that point the softer tire wall H rated tires actually help a lot more (work a lot better) than the stiffer side wall V rated tires, therefore the higher tier car could not go as fast as the lower tier counterpart.

P.S: By the way, if a vehicle lifts both inner wheels during the Elk Test, it is considered a failure, even if the car does not roll over.

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Old April 12th, 2006, 12:05   #65
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This is quite interesting. I wonder if it relates at all to the earlier reminiscence for old English sports cars with slippery tires. Could slightly less grip help the rear come about a bit better?
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Old April 12th, 2006, 16:31   #66
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Yes when the tires are leaned inward towar the centre of the car it is negative camber. I guess the funciton is that when the car is in a corner more of the tire is flat with the road.

With even wider tires it gets more exagerated and easier to see, this is a shot from my car.



I hope that helped a bit, this is all pretty new to me too.
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Old April 12th, 2006, 18:01   #67
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Originally Posted by peter pyce
Then there was another interesting piece, on a Honda Minivan, where they tested both the basic model and the high tier model together. They both had all season tires, the exact same brand and model, but the basic model had them H rated and the high tier model had them V rated. The basic H model did very well in the lift-throttle and change lane test (the one we were talking earlier in this thread) and went through at speed of 102 km/h. The V rate tire model, thought, barely passed at only 100 km/h and the tester was commenting that due to the soft suspension and specific geometry on such vehicle, the car rolls a lot more (it is a minivan!) and at that point the softer tire wall H rated tires actually help a lot more (work a lot better) than the stiffer side wall V rated tires, therefore the higher tier car could not go as fast as the lower tier counterpart.
That's very interesting. We've had a good number of threads on replacement tires here, and there has been some head-butting over whether it's O.K. to use lower-speed-rated tires or not. Often someone will say, "Even though you may not see the speeds that an 'H' rated tire is capable of, that tire will perform better overall and be safer because of the stiffer sidewall." This information seems to question whether the stiffer sidewall is necessarily safer.
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Old April 12th, 2006, 18:10   #68
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Originally Posted by frugality
That's very interesting. We've had a good number of threads on replacement tires here, and there has been some head-butting over whether it's O.K. to use lower-speed-rated tires or not. Often someone will say, "Even though you may not see the speeds that an 'H' rated tire is capable of, that tire will perform better overall and be safer because of the stiffer sidewall." This information seems to question whether the stiffer sidewall is necessarily safer.
But what applies to Honda Minivan...does not apply to MKIV Golf or Jetta. Or maybe it does.
Across multiple thread I read things like, better tires is what you need, not better shocks. Others are saying exactly the oposite. I think the tires have as important of a role as the springs, or the dampners. They all work together or they don't work at all. Well...they do, but the handling sucks.
What would realy lighten everything up would be The Elk test on a Golf with stock tires vs stiffer tires, or even bigger rims (17") with performance tires. Let's hope Peter will find something about that.
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Old April 12th, 2006, 22:48   #69
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Originally Posted by Davin
Why did I wait so long to read this thread? Charts, animations, numbers, oh my! Even mention of matlab/simulink modeling! All it lacks now are some equations... but those can get pretty complex.

Reminds me of one of the questions I had during my dynamics/vibrations qual oral exam. I was asked to derive the ground force caused by a simple one-wheel-on-a-spring suspension model travelling over a sinusoidal roadbed. I was then asked if the equation I came up with would always be valid. My response was... not if the wheel comes off the ground!

nate... did you model the vehicle in full 6-dof or did you only look at rotation? and did you have realistic models of the suspension geometry? did you calculate the EOMs by hand or did you use a package?
Quick reply here: Yes, we did it the hard way.

Everything by hand (I said it took a semester!), 6-DOF, and relatively realistic suspension geometry, limited by the data we had on the car (no bump steer if I remember right - didn't know the inner tie rod location)... but I believe the tire model was the limiting factor in regards to suspension. (neglected changing camber)

Off to bed now... still an awesome thread.
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Old April 13th, 2006, 01:39   #70
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I say we set up some tests to run at a GTG or maybe TDI fest this year. Let folks with all sorts of cars with all sorts of tires do some simple tests to see what happens. The driver may be an issue but then again we could have Jon or someone wheel many of the cars to keep things even from test subject to test subject.

The other day I got my car rather tail happy and had to wonder how much if any of it had to do with tires. I was stunned that the rear broke loose and did so rather easily at the speed I was going.
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Old April 13th, 2006, 06:03   #71
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Originally Posted by Golf_GTDI
I say we set up some tests to run at a GTG or maybe TDI fest this year.
That would be extremely valuable. cars everywhere from mine (bone stock suspension) to yours (just plain sweet), and we can play around with some of them pretty easilly (swapping swaybar settings on Neuspeed bars, disconnecting fronts, etc) and do some tire swapping and see what lands where.

I'm absolutely in, I wouldn't mind anything within 4 hours of here and that would probably just about get me to you (Cleveland is about 4 hours from me), further is fine if I can crash someplace. The Jet is a damn small car to sleep in

So what would be the best test(s)? As we've established, AutoX is definitely a different beast than GT and I think those of us with the most interest are more of the GT/Slow Car Fast leanings, but it's certainly the easiest thing to quantify with a stopwatch.... We could do elk test/chicane/slalom something... Other ideas?

Would be great to get a trustworthy group together so we could see how each other's cars felt and what we like/dislike too. Not sure how others might feel about that. Hell, not sure how I'd feel about that Just another thought.

This may deserve a different thread so we don't pollute the good tech in here planning a GTG. If there are a couple more people who think this is a good idea (whether in OH/PA/NY or elsewhere) let's start a new thread and move these posts there. We do get to delete our own posts on this board, right? [yes we do]

EDIT: okay, get me halfway there... I was actually remembering another guy on the board's location, "NE Ohio", Logan is about 8 hours from me. Would definitely rather meet in the middle than go all the way there, then, but we'll see if anyone else is even interested and where they're located. maybe get the other RallyVWers and the rally car involved to, that'll get me there just about any time
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Old April 13th, 2006, 07:22   #72
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Quote:
Originally Posted by cartog
This is quite interesting. I wonder if it relates at all to the earlier reminiscence for old English sports cars with slippery tires. Could slightly less grip help the rear come about a bit better?
Hello cartog,

There are actually (at least) three somewhat independent phenomena going on here:

1) One concerns the Honda minivan:

Quote:
.....Then there was another interesting piece, on a Honda Minivan, where they tested both the basic model and the high tier model together. They both had all season tires, the exact same brand and model, but the basic model had them H rated and the high tier model had them V rated. The basic H model did very well in the lift-throttle and change lane test (the one we were talking earlier in this thread) and went through at speed of 102 km/h. The V rate tire model, thought, barely passed at only 100 km/h and the tester was commenting that due to the soft suspension and specific geometry on such vehicle, the car rolls a lot more (it is a minivan!) and at that point the softer tire wall H rated tires actually help a lot more (work a lot better) than the stiffer side wall V rated tires, therefore the higher tier car could not go as fast as the lower tier counterpart.


I'm not familiar with this minivan, nor do I know the specifics of how its particular test went, but from Peter's quote it sounds like the V-shod minivan simply had less grip and agility than did the version with H-rated tires. Surprisingly, this sort of reduction can sometimes happen: different tires respond to camber in different ways, and some (A) have more camber thrust and others, and/or (B) have more loss-of-ultimate-grip due to camber. In general (though with tires, there are exceptions to almost any rule of thumb!) a stiff-walled tire tends to generate more camber thrust, so if you lean it away from a corner (as seems to be happening with the Honda), it'll steer away from it as well; and with stiffer walls, you also have more likelihood of lifting the inside portion of the tread off the road, thereby reducing your ultimate grip.

As an aside, these effects can also apply to low-profile tires: in general (again with exceptions!), the wider and lower a tire's aspect ratio, the less the tire enjoys being cambered adversely in a corner. For some -- perhaps even many -- innocent little FWD cars that get tarted up with big-wheeled "performance" packages, the cars would actually grip better if shod with taller, narrower versions of the superwide rubber that comes with these packages. Of course if you did that, people wouldn't buy the packages! (The marketers have done a good job convincing everyone that wider is better..) And if you make sure that you spec your option list such that the choice is between a narrow all-season versus a wide high-performance tire (i.e., nobody actually ever compares a narrow versus wide performance tire), the big performance tire will in fact grip better than does the narrow all-season (simply because of the rubber tread compound), so no one is ever the wiser.

In any case, suspensions that are designed for stiff and/or low-aspect-ratio tires usually keep the tires a bit more upright in a corner, either via suspension geometry, or by reducing overall roll. If you don't do this, and you continue to let the car roll, you often don't gain much from the stiffer/lower tire, and sometimes you actually lose...

2) The second one is tricky, and we won't get much into it here....

Quote:
Then they tested the upper tier model, which was basically the same car (suspension wise) but had performance tires, which is a trick many car companies do – just put bigger wheel and sticky tires on their “sport package” and that is it. Anyway, due to the stickier tires, not the car has actually issues in the Elk Test as it started to lift BOTH inner wheels (!)
....but what MIGHT be happening to the Fiat Panda referred to above is the sort of dynamic instability alluded to by Nate several weeks ago. That is, the Panda might be rocking up onto two wheels simply because it now has better grip and is cornering faster (and thus generating more g-forces), but it wouldn't be surprising if a more subtle phenomenon is also at work here.

Quote:
One interesting thing I haven't heard here yet is talk about natural frequency in steering response... I forget the actual physical ways it's controlled/derived right now, but remember the lesson well:

As vehicle speed increases, natural frequency decreases. In other words, rocking the steering wheel back and forth at, say 1 Hz, doesn't do much but weave the car around at low speeds, like on a city street.... but... if you do the same thing at the right speed, say 70 or 80 mph, you can get a real tank-slapper (to borrow a term from motorcycling) going with one or two cycles. Our professor urged us to try it sometime... it's eerie.

Any fully-engineered setup mitigates pathological behavior, but that natural frequency is still there beneath, no matter what you do. Worn-out components can negate proper controls, though... my old IROC (sold it to buy my TDI ) with worn tie rods and wheel bearings could get very excited and start a nasty steering shimmy when going just the right speed and hitting a bump just so... usually at low speed, 25-30mph, solved by lightly accelerating. But then I once hit the next harmonic at about 60 mph once in a sweeping off-ramp... the rear end started sliding around - scary religious experience... dumb me for driving it worn.

When I get some time I'll look back through my notes and post a little more about it - not sure how much a factor it is in these discussions, but it's interesting... __________________
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I'm not sure we'll ever get time to discuss this issue very much (this thread seems to have taken on a life of its own, with multiple subthreads going every which way!), but the resonance effect Nate refers to above is quite real, to the extent that -- if you believe rumors -- almost any car can be rolled if steered in just the right way at just the right speed...

(sigh)

Ok, I'd better explain a little bit right now! :

For the young whippersnappers in the audience who have no idea how the Mercedes A-class enters into this discussion: the famous-in-Europe Elk Test was just an obscure handling test performed by a more or less obscure Scandinavian motoring journal (I'm sure the Swedes & Norwegians et al read this journal, but hardly anyone else did back then!), until the day that a revolutionary, long-awaited, much ballyhooed Mercedes shocked everyone by rolling over in the middle of it. This was the A-class, and before that fateful day, Mercedes had poured millions and millions of dollars (deutsche marks back then...) into advertising how it was a safer, better-handling, more-comfortable, roomier, higher-quality, and simply better-engineered small car than had ever existed before. The advertising runup took literally months and years, and in Europe (where smaller cars are king) there was a lot of anticipation for this radical vehicle (the A-class' architecture is very unusual and clever) from the world's exemplar of engineering prowess. So the last thing anyone expected was for the Mercedes to roll in a test that more mundane cars routinely pass, and photos of the Scandinavian test driver being carted into an ambulance, with the partially destroyed Merc lying sideways in the background, were about the worst thing marketing-wise that could have happened to the folks in Stuttgart.

There were a lot of reasons why the A-class rolled, but much of it comes back to what Nate brought up: there's a certain resonance in a vehicle's handling, and the Elk Test happened to hit it on the A-class. Until that day, Mercedes never ran its cars through that particular test (it's been argued that it's quite contrived, and real people don't actually respond to an obstruction in quite that way), and thus didn't know of the problem; and hence they got very, very unlucky.

Where is this leading? Well, back to the rumors: one of the many interesting things about the whole A-class debacle was that absolutely nobody -- not a single European, Asian, or American car manufacturer -- ever came out and said anything evenly remotely critical of Mercedes or of the A-class. Not a single cheeky advert boasted that "Our cars stay planted!"; not a single press release referred to "Our engineers perform a battery of tests, to ensure that no handling surprises will catch anyone out..."; not a single commercial talked about "our cars' wide stance and stability, which keeps our cars upright where competitors fail....". If anything, an occasional competing exec would say something like (when interviewed and essentially forced to say something): "Well, Mercedes is a fine company, and I'm sure that they'll sort everything out...". So what was going on here?

Rumor has it that the reason that nobody took advantage of Mercedes' predicament was that everyone knew it could easily have happened to them. A few engineers murmured something to the effect that "...mumble...mumble...well all cars can roll if you do the right th.....mumble...mumble" before being silenced by their respective companies and having their quotes expunged from the records. And then there was a very strange rumor that shortly after the Elk Test disaster occurred, Mercedes bought an assortment of cars, trucks, vans, and hatchbacks from all its competitors, and instructed its presumably-exceptionally-highly-paid test drivers to find a way to roll each and every one of them in front of the video cameras, with the resulting footage going into a Mercedes vault somewhere, with word sent out to the various competitors that they might not wish to capitalize on Mercedes' predicament.

Interesting, non?

In any case, going back to the Fiat Panda on 2 wheels: as Nate says, there's a particular frequency where cars begin to go unstable. And when you change the tires, you change the response rate to steering motions, and sometimes -- if you're lucky/unlucky -- that's enough to nudge a car towards instability in a particular test. So it's possible with the Panda that the 2-wheel result is not just from the tires being stickier, but also from their being more responsive.


3) And finally (though I'm going to have to pick this up in a future week, as I'm out of time)...

Quote:
Originally Posted by cartog
This is quite interesting. I wonder if it relates at all to the earlier reminiscence for old English sports cars with slippery tires. Could slightly less grip help the rear come about a bit better?
On many cars, less overall tire grip can lead to reduced understeer (especially with the old English sports cars!!) -- but we'll explain that some other day.

Cheerio lads!

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Old April 13th, 2006, 17:50   #73
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Quote: " We'll talk about the big-rear-bar/ soft front setups more in a later installment, but ...
a big rear bar will only reduce the initial amount of roll. At some point, the inside rear wheel will lift ..., and when that happens, it really doesn't matter whether there's a big anti-roll bar in the back or not: as far as the car is concerned, there is one wheel on the ground in the back, and two wheels on stock springs and stock bar in the front. 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 ... Now, this is a fairly horrible handling set up (understeer sets in rapidly the moment the rear wheel leaves the ground), but there's no oversteer at the limit....
And for this someone has paid $300?"[/quote]


Oh, such a great thread! So much to comment on!! So many sidetracks I want to follow! Thank you guys. Pyce and Ceilidh make a great team. ...I pick one sidetrack:

The discussion hasn't got here yet, but for when it does.....I must comment on this rear bar discussion above from (Sir) Ceilidh (looks like I didn't do the cut/paste quote properly).

I currently have a big rear bar with otherwise stock (GTI, yes another guest gassie, tho I love TDI's) suspension, and it is an interesting set-up for me, mainly a GT man presently...

Big big turn-in improvement, big big reduction in understeer up to around 8/10's? (where I spend 98+% of my time), and still safe at the limit. Yes, wonky body motions over big bumps and yumps. Certainly not 'horrible' tho, and some of the best $300 I've ever spent.

Yes the inner rear tire lifts sooner. No this does Not mean sudden balance change. Really the transition is nearly invisible (to me at least, very high rally gravel/snow skill but light on serious tarmac experience).

At increasing cornering loads, the inner rear tire load decreases and its lateral grip decreases steadily (while outer increases). Inner tire load and lateral grip are near zero just before tire leaves the road. There's no sudden loss of lateral grip at that point, not at all. The inner wheel was already doing next to nothing by then. Its progressive as always.

Once the inner is off the ground, the big bar's effect is increased spring rate at the remaining outer rear tire = less bump/jounce, more remaining suspension travel, better able to deal with bumps. It still understeers at the limit = Safe. And believe me, I have tried everything to provoke this thing to get the rear to truly break, and it is very very hard to do so on pavement, even in the wet. That is, it's SAFE.

Unlike, apparently, with TT spindles as Golf GTDI reports. As a rally guy, I'm very comfortable with rear end movement -- I lived for it for years, reverse-flicking and left-foot-braking to bring the rear around. So I was planning to do the TT spindle swap next, but now look forward to more input here, particularly from the fellow with all the TT experience. I want a looser car, but then my wife loves me and would like to keep me around, so I need more info about the limit effects of the spindles.

Just some thoughts. Thanks all. Keep it coming.

Last edited by wishboneracing; April 13th, 2006 at 18:22.
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Old April 13th, 2006, 22:59   #74
peter pyce
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Wishbone - it is very important to specify what kind of rear bar we are talking about! There are mild bars, which do exactly as described by you and there are very stiff rear bars, which make the car behave in a quite different way in all the set scenarios. I suspect you have sort of a "mild" bar, and if that is the case it must be specified, so the general feeling in whoever reads and have no experience such as yours may not just plain assume that rear bars is plain safe, because someone said so on the internet.....

Which brings another point it is time to make right now (great you talked in your post about yourself a bit!). The point is this: we are all at different levels when it comes to driving skills. From the words you put I gather you are experienced driver and that means a lot. That means you are well trained (you have it built-in into your instincts) how to drive a car fast, how to control a car that wants to "go", how to correct, how to "bring back", etc. A driver like your would have very hard time to fall into "unsafe" situation with a stock car, because you would simply know what to do way before the situation arises, and even if the scenario is really from the "panic" type, you would know (instinct) how to put the car where you want, how to avoid the danger, how to come out of all this without even making a note that it was one hell of a situation. So, for someone like you it is very easy to come in and say "rear bar is SAFE, I have one and it only helps me put the car where I want and so far I never had a problem". All that could be so true and perfectly correct to say, but so wrong if the reader of your post is very novice driver who has no idea what even what a rear bar does to a car. The goal is to help folks have a minimum understanding of what does what, how things work together and then make a more educated choice of what they need/want. You must be a good driver if you have no issues with your rear bar, but I have seen people spinning around on on-ramps, or in the mountains. Rear bar is safe in the hands of the experience driver, like the more powerful car is also safe in the hands of the experienced driver. Good night.
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Old April 14th, 2006, 09:05   #75
wishboneracing
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Join Date: Apr 2006
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Default rear bar alone - cautions

Hello! Yes I agree that caution is needed to keep from misleading people. I'm a mech engineer too and understand the need to take care with regard to all the possible users out there. This is why I explained that I have some driving experience. You are right to raise flags of caution here. My primary points were that there is no sudden change when the inner rear tire lifts, and that limit understeer is a good safe thing, with my current set-up.

Here is my set-up: stock 'sport' GTI suspension (including stock front bar of course), good 225/45-17 tires (fresh GY F1 GSD3, excellent in wet especially), H&R 28mm rear bar on 'maximum' hole, heavy gas-guzzling VR6 out front encouraging understeer.

So it is indeed a big rear bar. This is why after adding the bar I purposely went out to provoke and toss it to see if it would be scary in extreme situations. And as I report, I haven't found it to be so. Yes, into tight corners on the brakes, the rear end is light and will step out a bit. But this is in very aggressive driving and is easily controllable.... If you have some prior experience with this stuff!! as you say. But certainly in lower grip conditions (even just in the wet with less effective tires, but especially on dirt or snow!!), different more dramatic results could be seen. Any modded car should be approached with caution at first, preferably on a track at a lapping day. And the first mod investment should always be in the driver - in a school! Thanks for having me clarify.

BTW - Another Safety Sidebar - my H&R external rear bar came with pathetic clamps for attachment to the twist beam. I had three suffer fatigue failure - not good. I have now installed the better Neuspeed clamps with my H&R bar, as many others are doing. If you have or may buy an H&R rear bar, PLEASE see: http://forums.vwvortex.com/zerothread?id=2388065

Attn SF Bay Area people: there's a rally school coming up at Thunderhill. See http://www.sfrscca.org/RallyX/

Cheers, Pete

Last edited by wishboneracing; April 14th, 2006 at 09:46.
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