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    Thread: My Audi TT front suspension (on MK4 GTI) & Front swaybar question

    1. Moderator eggroller's Avatar
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      07-08-2005 02:29 PM #36
      My alignment was done at Omni Brake and Alignment in Kirkland. I have used them for all of my cars (5 of them. 3 are VWs). Pat (front desk) and Randy (tech) are great to deal with and will set it where you want it.




      Modified by eggroller at 11:31 AM 7-8-2005


    2. 07-08-2005 02:31 PM #37
      My car saw Omni the previous week. +1 for satisfied customer.

      Heh, I'll be critiquing Ray's new setup as far as commuting style comfort goes on the way down to Auburn tonight.


    3. Senior Member 16vracer's Avatar
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      07-08-2005 03:12 PM #38
      Good deal, Ray. What do they charge?
      '05 Evo GSR '08 A4 3.2Q S-Line '10 RX-350 /// Gone and dearly missed 06 Evo RS "Formula 409"--409awhp
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    4. 07-08-2005 10:48 PM #39
      Quote, originally posted by phatvw »
      Yeah can't wait to ride in your car again!


      BTW Matrix is having a summer sale on parts and labour. You should get your transmission rebuilt and peloquin installed while they have their 15% off deal

      Yup yup, Dan is correct!

      http://forums.vwvortex.com/zerothread?id=2064755


      Modified by jeremy@matrix at 7:50 PM 7-8-2005


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      07-09-2005 09:06 PM #40
      Quote, originally posted by 16vracer »
      Good deal, Ray. What do they charge?

      I also had my alignment done at Omni several months ago. Way better job than Les Schwab. They charge about $85, which is almost double Les Schwab, but you get what you pay for.


    6. Member elRey's Avatar
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      07-11-2005 03:20 PM #41
      Quote, originally posted by RichB »
      To make eggroller's point a bit more clear, here is a pic of the TT LCA's...

      The slots on the ball joint connection (bolt holes) allow for the Camber adjustment.

      Man, that's a pretty set of LCAs, bet they came well packed too


    7. Member elRey's Avatar
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      07-11-2005 03:23 PM #42
      Quote, originally posted by tyrolkid »
      You can use the TT "nubless" arms. Just install a 3/8" or so spacer....We've done a number of these installs in the shop.....

      you drill and tap right thru the front beam? If so, you don't think this compromises the LCA's strength?


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      07-11-2005 03:31 PM #43
      Quote, originally posted by elRey »

      you drill and tap right thru the front beam? If so, you don't think this compromises the LCA's strength?

      We havent had problems using this method...the TT LCAs are very beefy....


    9. Member elRey's Avatar
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      11-16-2005 10:23 PM #44
      Quote, originally posted by eggroller »
      I am going from the oem GTI 23mm front swaybar with a lever arm of 7.5" (distance from the bushing to the endlink mounting hole). The spring rate of the Eibach Pro System springs are quite soft.

      The future setup is the Audi TT 20mm front swaybar with a lever arm of 8". Not only is the swaybar a smaller diameter, the lever arm is longer! Making it softer than a 20mm swaybar with 7.5" lever arm.

      I know this is old and may have been discussed somewhere else, but...

      The TT sway mounts to the strut which would be like mounting all the way out at the ball joint as opposed to our stock mounting point ~ mid point on LCA.

      This would increase roll resistance keeping sway the same. Tho I'm not sure if it totally cancels out the bar difference.

      Food for thought.

      Rey


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      11-16-2005 11:08 PM #45
      There would be a verical component and a horizontal component to the lever arm correct? So you can't just do an apples-to-apples 7.5" to 8" comparison can you?

      I think we'd need a Pyce diagram to figure out the difference in roll resistance between the TT and regular VW setup. Anybody know the oem Audi TT spring rate? If the sway bar does indeed resist roll less, then the springs ought to be stiffer. Or perhaps is the TT spindles that account for less roll and allow use of less sway bar.

      edit: Sorry that probably made no sense... just thinking out loud.


    11. Member elRey's Avatar
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      11-16-2005 11:31 PM #46
      All I'm saying is
      yes
      a) 23mm -> 20mm = less resistance
      yes
      b) 7.5" sway arm -> 8" sway arm = less resistence
      but
      c) force applied to middle of LCA -> far end of LCA = more resistance
      for both torque and travel (strut travels further than middle of LCA)


      question is does
      (a + b) =,<, or > c

      keeping springs and everything else the same.


    12. 11-17-2005 12:27 AM #47
      You have to calculate the differential between the two points where the VE bar bolts and the differential between the two points where the TT bar bolts. For let's say every degree of roll of the car, how much is the differential (left to right) between those points. Then you can see which bar has more twist to do due to the larger differential and then the approx. result will come.

    13. Member elRey's Avatar
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      11-17-2005 03:31 PM #48
      Please forgive my ignorance.
      It's been a great while since I've done any math beyond add/subtract/divide

      breaking it down.... way down.

      1)
      going form 7.5" arm -> 8" arm on sway decrease torque on LCA by ~ 6.7% about the sway's horizontal axis (decrease roll resistance)
      Hows does that equate to total resistance change? Way over my head.

      2)
      but moving LCA mounting point from middle to end (double the distance from
      fulcrum) increases torque on LCA ~100% about the inner LCA bolts.
      Again, hows does that equate to total resistance change? Way over my head.

      3)
      This doesn't take into count the increase travel (degrees of rotation)
      seen by moving both above points out.

      4)
      now dia. someone mention increase dia. = increase stiffness to the power of 4. (second hand info could be wrong, or I could have read wrong)
      so, 23mm -> 20mm = ~57% stiffness reduction

      so: (assuming everything is one-one w/ total resistance)
      1) -6.7%
      2) +100%
      3) ?
      4) -57%

      my stab at approx change = + ~36% INCREASE in stiffness


      Warning : I maybe be WAY off on my logic, just trying to exercise the old brain.

      And the scope was just one half of the setup (center on car/swaybar over to one wheel)

      Rey


      Modified by elRey at 12:35 PM 11-17-2005


    14. 11-17-2005 04:52 PM #49
      Your #3 is what matters first. You have to find how much the pickup points move in relation to the wheel movement first. Make it simple:

      Blue points - A4. Red points - TT.

      You have to calculate how much these move in relation to each other (the differential from the earlier post) per let's say degree roll, or inch of vertical movement of the wheel, etc.

      Only after that you can use % to compare them in different diameter scenarios. And also, have to account on what is the total length of each scenario bar, what is the shape, etc. A4 and TT bars are different in shape, not only in diameter, so you need to go much more complex than this if you want to compare them in depth.


    15. Member elRey's Avatar
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      11-17-2005 05:28 PM #50
      Quote, originally posted by pyce »
      Your #3 is what matters first. You have to find how much the pickup points move in relation to the wheel movement first.

      Let's hypothesize:
      I think it's safe to say the TT pickup points travel more than the A4 points. Agreed?

      That said, keeping it REALLY simple, would an increase in travel on the sway ends per amount of wheel travel increase resistance
      or decrease resistance along that amount of wheel travel?

      I have no idea if "spring rate" of a sway is linear or progressive.
      In either case the more you travel/twist the more force it takes.

      So I assume this would increase stiffness also bringing the total resistance change higher than my previous stab of +~36%.

      My point is not an in-depth calculation. I don't have the knowledge
      to do so. But I think using some logic, what I thought was a softer
      sway (TT) is really a stiffer setup.

      Quote, originally posted by pyce »
      what is the shape, etc. A4 and TT bars are different in shape, not only in diameter

      I'm not sure how much different each is shaped inside the outer arms, but I wouldn't think how they were shaped beyond that matter other than distance from bolt hole to horiz axis.

      And Length, I don't know. I'm guessing they're about the same.

      Again, I could be COMPLETELY wrong.

      Rey



      Modified by elRey at 2:38 PM 11-17-2005


    16. 11-17-2005 05:39 PM #51
      I think your assumption about the TT pickup points traveling more than the A4 pickup points is correct. The model shown does not have those points modeled, but if you give me the TT (and I have an A4) dimensions, we can model it and see exactly by how much they differ. Actually I have few struts at home from the Jetta and I think the hole on the strut they have is for the TT style bar, so I can measure everything by myself.

      But, yes, so far we know enough as to say that a 19 mm TT bar does not mean "softer" than 21 mm Golf bar because of the arm's design (the shapes I was referring to), length and pickup locations.


    17. Member elRey's Avatar
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      11-18-2005 09:59 AM #52
      Quote, originally posted by pyce »
      But, yes, so far we know enough as to say that a 19 mm TT bar does not mean "softer" than 21 mm Golf bar because of the arm's design (the shapes I was referring to), length and pickup locations.

      Cool. yet I was comparing the GTI 23mm to the TT 20mm as eggroller originally posted. Do you think this still holds hypothetically true?

      Rey

      edit: I meant 20mm not 19mm


      Modified by elRey at 6:00 PM 11-18-2005


    18. 11-18-2005 02:28 PM #53
      I spent the morning doing some simulations on the virtual model and it comes out that is a lot more important where you attach the sway bar in these cars. Here is a brief example:

      Both cars were steered at 5 degree to the right. Both cars were “rolled” at 3 degree first, then 5 degree, just to see what the progression is.

      (Note – this is not final numbers as I have to yet position the pickup points in their exact locations, but it is approximate, within few millimeters. More accurate data will come later)

      Results:

      OE:
      differential between left and right pickup points for 3 degree roll = 0,08 mm
      differential between left and right pickup points for 5 degree roll = 0,19 mm

      TT:
      differential between left and right pickup points for 3 degree roll = 1.69 mm
      differential between left and right pickup points for 5 degree roll = 6.63 mm

      As you can see, from even some rough estimates, the differences in differential between the two cars are very, very high. Looks like, actually, the TT 19 mm bar, twisted this much, would do a lot more than the even beefier Golf bar that is twisted this little.

      Basically, the pickup points they took move in a very, very different way (OE A4 vs. TT), so we need to actually do a graph with every degree of roll and every degree of steering as to get full picture.


    19. Moderator eggroller's Avatar
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      11-18-2005 06:39 PM #54
      wow...interesting. Please keep us posted. Thanks Pyce!

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      11-18-2005 07:01 PM #55
      Neat! Once again it takes the Pyce-man to reverse-engineer the work of those crazy Germans

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      11-18-2005 07:03 PM #56
      Quote, originally posted by eggroller »
      wow...interesting. Please keep us posted. Thanks Pyce!

      Just an FYI but the large eccentric bushing in the front of the TT LCA's are the second generation design which was implemented to increase understeer in the car near or at the limits. These are referred to as MKII arms and were installed as part of the overall voluntary suspension recall by Audi. The original MKI arms had the same size front LCA bushing as all the other MKIV's but a harder durometer. These are highly sought after by the TT crowd. As someone who's owned a TT with MKI arms and MKII arms - I can tell you there is a definite difference between the two. I recently replaced my MKII front LCA bushings with Powerflex poly bushings and the difference is noticable - about as close to the feeling of the original MKI arms as I can remember. I cannot comment on how long they will last, but I think they should be good for quite some time and are simple to replace.


    22. 11-21-2005 02:00 PM #57
      Some more data. This is now with incorporating both bars in the model, attaching them to the body and then rolling the car (and steering it some, as per last post spex.) so the calculations are directly on the bar’s holes, therefore we know how much the bar is twisted in each scenario. At 5 degree roll we have the following:

      OE A4 system shows 98.55 mm from left to right vertical differential.

      TT system shows 132.93 mm from left to right of vertical differential.

      This means that the TT bar has to twist a lot more for that given degree of roll and steer. We just need to calculate the differential in roll resistance between a 23 mm bar and 20 mm TT bar and see the end result. The shapes are different, so that perhaps will make the calculations not so easy as the VW OE bar curves down, so it will be tricky to get the length


    23. 11-21-2005 02:43 PM #58
      Good job! If I could see good pictures or animations of both setups side by side I would have more confidence in the following, but this is how I see it now. If I make these assumptions:
      1. The angular rotation of the bar is proportional to the vertical differential numbers you posted
      2. The only part of each bar that is twisting is the region between the swaybar bushings and that region is equal for both bars (this eliminates length effect). This assumption follows from assumption that the "arms" do not flex (this is not 100% true but has little effect).
      3. Ignore the effect of any bends in the part of the bar that is twisting (more bends will slightly decrease stiffness, but not much)

      The relative stiffness of TT vs VW OE bar is
      (132.93*20^4)/(98.55*23^4) = 0.77
      So the TT bar system is 77% as stiff as the VW OE bar system.

      If these assumptions are too far from true or I'm missing another factor, speak up so we can get this approximately right. I don't think we need 1% accuracy here, so we don't need to nit-pick too much.


    24. Member elRey's Avatar
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      11-21-2005 03:03 PM #59
      I installed a 20mm TT sway this past Sat.
      The TT bar was a good 3" - 3.5" shorter in overall length.

      It replaced my stock 23mm Jetta Wagon swaybar.


    25. 11-21-2005 03:05 PM #60
      Did the simulation rolling the car from one to five degrees, measuring the difference in differential at every degree of roll. Here is a diagram that shows the results:

      Basically, from simple calculations comes out the the vertical travel (differential) between the two holes on the VW A4 bar is about 65% from the travel on the TT bar. It actually starts at 65% with 1 degree roll, then goes to 66%, then to 67% and then keeps increasing but by less, so in general we have the OE A4 setup "traveling" about 66% in average less than the TT setup.

      More later......


    26. 11-21-2005 06:15 PM #61
      Actually, the whole pickup points location story is a lot more sensitive! The first diagram above (previous post) was with the LCA holes located slightly more outwards than where they really are (did not model them very accurately for the first trial) and the results were the above (A4VW does 65% of the TT vertical travel)..... Took more accurate measurements and remodeled everything to spex (was off by 50 mm before) and the new simulation reveals that the the 65% number is down to 51% now.

      Here is the same graphs as above, but the pink line is the "wrong" (w) from above and the bright blue is the "correct" (c) graph.

      So, now we have 51%, which is almost half (easier to work this way) of the TT vertical travel. But at this point it is clear that some very accurate and complete modeling has to happen if we want to get the results close to reality.

      I wonder how much difference there is between the TT setup and the New Jetta A5 setup? They do look pretty darn close, but does anyone know for sure if they are identical and if so - which parts do they share?


    27. 11-22-2005 11:27 AM #62
      Wait... color me confuzzled.

      In the school of Pyce I have learned that front sways are bad and that I should keep them to a min if at all. Now I read that the TT front end that I'm about to put on my car will have a sway bar system that is more active than my current A4 setup?

      Ummm I thought that was bad.

      So does this mean I just grab that PSS sytem that I'm eyeballing, put some stiff springs all around and nix the front sways all together? Will I need to up my life insurance as a result? Will my wife be able to drive the car after?

      Someone please toss the dumb guy a readers digest version. =-)

      PS 4 Pyce- Not sure if Jon has the parts off the rally car yet but I'm still after him to get you the stuff to test. He and I have both been sadly busy with him working a 48 over the weekend and me doing 32 hours of overtime last week.


      Modified by DanSycks at 12:13 PM 11-22-2005


    28. 11-22-2005 01:08 PM #63
      This is not a discussion about whether front bar is good or bad. We are trying to understand what VW did, how they did it and why. The front bar debates have to be kept isolated for maximum performance, on cars that are driven by people who know very well what they are doing. The dynamics of the car change (when pushed) with no front bar, and I do not want to be responsible for someone's accident, because I told him to remove his front bar. The rule of thumb should actually be that id the individual has no understanding of how the suspension works to begin with - he should not make changes to it, not at least changes driven by the Internet crowd via advises taken from a popular website like this. Thank God the aftermarket companies (the majority at least!) would never produce set of springs that would make the car less under steering. Same goes for the exploring we are trying to do here - VW's goal, by making the TT or GTI is not really to give us the ultimate capable car! The cars have to feel "sporty", but have to perform in safety, because when you buy a car, no one tests your capabilities as a driver - all it takes is money. So, they all have to be safe. Enthusiasts do not like that, therefore they modify little bit here and there. People who did not bother to learn much just drive them as it is and enjoy them as they are. The difference between what the factory gives us and the "modified" cars is not big, but it feels big when you are behind the wheel. Most of the times modified cars are actually slower, but it feels great, so the user is happy and feels fast, and at the end, most of the time that is what really matters.

      Sorry the off-topic, just wanted to say the above. Front bars are not like rears. You remove a rear bar - you notice the whole car rolls more and under steers more. You remove the front bar and it gets very tricky because very counterintuitive. The rolls is more, but the under steer is less. 99% of the folks would remove the bar, would go for a spin, which will be something like 30 mph zig-zag on the straight street around the block. They will notice immediately the roll, will u-turn, go back and conclude that no front bar is simply not doing it. And they will miss the whole point. 1% will keep the car like this for a week, will dig it, explore it, push it higher and higher, slowly in the beginning, will re-learn the new behavior and then eventually will realize that this new configuration opens whole new set of doors in front of them, opens new ways of conducting the car in a curve - which will all result at the end as quicker car through turns. But with this, the car is not as safe as before, not at leas tin everyone's hands, and with more power comes more responsibility - so I hope people explore in safety and do not lose their heads on the street.

      For street use, none of us should drive any near the point where the front bar should be removed. If you are that fast, you are braking the law by far


    29. 11-22-2005 01:33 PM #64
      Is there anyone in new jersey that would be able to perform this install on my car?

    30. Moderator eggroller's Avatar
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      11-22-2005 01:43 PM #65
      The installation is not difficult. It is just tedious. I did the entire suspension installation myself. Took me about 3 hours (the rears took me all of 40 mins).

    31. Dropped the subframe to install the swaybar (use new stretch bolts). I didn't have my cheater bar, yet. Torquing to spec + 90* took a lot of effort.
    32. Installed the TT control arms (new stretch bolts)
    33. Installed the rest of the suspension normally
    34. I installed the H2Sport spindles later

      Oh, suggestion for where to do the work...I have heard nothing but good things about Tyrolsport or PDPerformance. The former has installed the TT suspension on his personal car. He was a part of the inspiration to install the TT suspension.


      Modified by eggroller at 10:46 AM 11-22-2005


    35. 11-23-2005 01:52 AM #66
      I thought we had to rill the LCA's to install the TT sway bar if we don't have the TT suspension

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      11-23-2005 11:57 AM #67
      Quote, originally posted by GrapplingVR6 »
      Is there anyone in new jersey that would be able to perform this install on my car?

      We've done a lot of TT control arm and spindle installs. We are located about 15minutes from the GWB. Thanks for the compliments, Eggroller


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      11-23-2005 11:57 AM #68
      Quote, originally posted by WeedWolfie420 »
      I thought we had to rill the LCA's to install the TT sway bar if we don't have the TT suspension

      That is correct. It is pretty easy if you have the "nubbed" TT lower control arms.


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      11-23-2005 12:06 PM #69
      Don't know if this helps - but Audi did the following modifcations to the TT as part of the initial suspension recall.

      The specific modifications consisted of new front lower control arms with larger, softer, offset front bushings, as well as modified front and rear shocks with stiffer compression and softer rebound dampening to reduce weight transfer from rear to front when braking. The front sway bar was increased in size from 19mm to 20 mm, while the rear was reduced 1mm in diameter from 15mm to 14mm. The result in handling was slower steering response, increased understeer, and reduced lift-off oversteer.


    39. 11-23-2005 01:46 PM #70
      Joe, have you driven both I and II? Does the II roll less? How much was really the change? The feeling is one thing, but how slower the II is (if any) in comparison to the I? Thanks...

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