At what point would the rear suspension be too stiff?? What size sway bar and what spring rates? I read test of a ZR1 a while back and they said the car was too stiff all around and had almost no body roll, thus making the cars limits very sudden and hard to predict. The reason im asking is because I will be installing my 28 mm rear sway bar soon and just wanted to make sure im not making a mistake.
Edited 1 time(s). Last edited Saturday, October 30, 2010 7:17 PM
strat81 wrote:just to make sure we're all on the same page here...
the tie bar does incorporate heim joints which would still allow articulation between the two sides of the twist beam. granted it would have more limited travel but i doubt that it limits travel anymore than an aftermarket rear sway. (and the twist beam shouldn't allow THAT much range of motion for it to be a real issue) i'd also point out that most (if not all) that run the tie bar already have an aftermarket rear sway. this would be more prevent side to side flex of the arms than it would up and down motion.
If you would reference my figure at the end of the first page, you'll see why even with the heim joints there's an issue. Either the tie bar must stretch elastically (which it will not do without stripping the threads out of the ends), or the back ends of the trailing arms will bend inward, thus creating toe out, or the suspension will not be able to articulate independently at all. That is just from simple analysis of the system, in realitity it is likely a mixture of the 3 leaning heavily on the toe out compenent.
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Leafy wrote:strat81 wrote:just to make sure we're all on the same page here...
the tie bar does incorporate heim joints which would still allow articulation between the two sides of the twist beam. granted it would have more limited travel but i doubt that it limits travel anymore than an aftermarket rear sway. (and the twist beam shouldn't allow THAT much range of motion for it to be a real issue) i'd also point out that most (if not all) that run the tie bar already have an aftermarket rear sway. this would be more prevent side to side flex of the arms than it would up and down motion.
If you would reference my figure at the end of the first page, you'll see why even with the heim joints there's an issue. Either the tie bar must stretch elastically (which it will not do without stripping the threads out of the ends), or the back ends of the trailing arms will bend inward, thus creating toe out, or the suspension will not be able to articulate independently at all. That is just from simple analysis of the system, in realitity it is likely a mixture of the 3 leaning heavily on the toe out compenent.
I know we've been through all this but I still don't see it causing toe out.
Camber change yes but not toe out.
How the trailing arms are going to 'bend inward' I don't know or see this happening.
Again, I'm no engineer while some that have posted here are my visualization of how the rear end is working isn't giving me the same ideas as what's being said here.
If the tie bar were welded to the ends I could see an actual change of toe due to binding but with heims being added in the picture, there's enough freedom to prevent the bind that would cause toe issues. With the heims all I'm seeing is camber change.
I know this sounds silly but I've made mock ups of our h pattern rear to get a better vision of what's happening and would agree that the tie bar tends to alleviate some of the independent status of what little we have already but even though this is the case, there's so little independent motion out of the box it really doesn't matter.
Unless the roll or bump we're talking about is extreme there is no issue with adding a tie bar.
*sighs*
I should give up on this discussion I guess.
I can say that even though we're discussing what could be a detriment to our cars via the tie bar, I'm quite happy with my setup as it is.
Getting crazy and demoing the car at triple digits with some evasive maneuvering on the open road (3 - 4 open lanes with no traffic), the car handles superbly although the struts could stand to be of better quality.
No instability whatsoever and on the infamous on/ off ramps the car is quite neutral with me accelerating them as opposed to losing speed.
I can assure you that with the stock factory setup this could not be done at all since the car is way unstable at triple digits and scary to drive at those speeds.
I'm happy. I'll continue to have my tie bar until something better comes along but my work on the Cavy is pretty much over at this point for reasons of getting back into paintball with a team and currently unemployed for two months doesn't help either.
Misnblu.com
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Thank you Dave and JBO! 
I thought I'd post these up from some of the research I'm doing on tie bar setups.
Enjoy.
Thanks to vwvortex.com for the images and article.
Similar arguments ensue on the vw forums as they do here about the tie bar.
Interesting reading.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
^Links are on a moving part; making it less effective then attached on a solid place. This reminds me of those strut braces that are held by a nut/bolt at the edge instead of being solid, again not as effective to stiffening up the body as a solid non-moving brace... that is less prone to flexing.
Good looking piece, but I'm a Function > Form person.
Misnblu wrote:On the three wheel scenario in racing, I see this all of the time on road racing, especially the Acura TSX's in the World Challenge series when they race.
They do seem to win quite a bit so to say it's a bad thing really isn't showing it to be so with the RealTime racing team and their TSX race cars.
What you're witnessing is no or lower suspension travel. Usually coil overs will do that. The "bad thing" is when you are not using all four contact patches to ground.
Remember the most important part of the whole suspension is what meets the road. Add the best suspension component, brakes, braces, chassis, steering, etc but all of that becomes useless if you can't put those upgrades to the ground and putting it into use.
strat81 wrote:
i'd be willing to bet that many that have this bar have run on-ramps at speed in less that optimal conditions (bumps, crappy pavement, etc) and I've yet to hear "I lost control of my car on an on ramp cuz i hit a bump, the back end unloaded, and I crashed"
i've also seen j-body's (and many other fwd's for that matter) lift the rear end in a corner. (at the local autox events we even have a bmw that will pick up the front inside tire without losing grip)
On ramps tend to be banked, smooth and some carry with different asphalts to adhere better to traction and more importantly... ramps tends to be roads that orders lower speeds. The scenarios is not just on-ramps, it is also accident avoidance, off-road road courses, and evasive maneuvers... basically where suspension will be working hard and rapid, not gradual and gingerly.
Great, that you've seen cars go 3 wheeling and they didn't loose control. That still does not mean it was in the optimal setting for driver's control. Good thing they didn't loose control in their optimal scenario, but in the real roads and some tracks, roads are less than optimal, and because of that, one has to prepared. What's more, even though you didn't see them going out of control, again it doesn't tell the whole story from the driver's seat, as to how many time he/she had to over correct them self to maintain or regain control, that within itself will cost you time.
Shrugging off that 3 wheeling and considering it acceptable, only leads me to believe that you believe that 4 wheels is not necessary, or maybe you're just looking to argue for the sake of arguing.
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Mr.Goodwrench-G.T. wrote:What you're witnessing is no or lower suspension travel. Usually coil overs will do that. The "bad thing" is when you are not using all four contact patches to ground.
Remember the most important part of the whole suspension is what meets the road. Add the best suspension component, brakes, braces, chassis, steering, etc but all of that becomes useless if you can't put those upgrades to the ground and putting it into use.
The lift is important, because you basically need independent suspension in order to avoid one wheel influencing the other. That is largely irrelevant if only the outer wheel has any grip. And that is of course by design, too much grip in the rear will make the car understeer heavily. Make sense?
With twist beam:
* Lateral forces induce toe changes.
* Bump forces induce toe changes.
* Bump forces induce wheelbase changes. *This is key in applying the tie bar*
All of those cause grip and steering changes.
To minimize the toe changes, the suspension has to become stiff and what better way than with lowering springs, better struts, and a tie bar to make it less prone to the above changes?
That's my whole point of the tie bar over a stock suspension and probably why most have experienced better handling although your 'placebo effect' has been used before as this is a way to denounce something that alot of people seem to believe.
Most people don't really drive their car enough to really have that feel for driving it. But for those that do and know their car inside and out the changes that a person makes in suspension tweaks are not 'placebo effects'.
This tie bar has been a popular mod for many years with the Jbody and now we're denouncing it because of it's inferior ability to limit toe out and instability issues that no has experienced?
Remember, I'm not arguing as this is a good discussion.
I know that there's programs out there that can model our twist beams in some kind of cad animation for some kind of reference of how it all works.
So far everything I've read shows that a stock twist beam will cause more toe out and camber changes than a stiffer sprung setup with roll bar preventing more of the independent motion that promotes the said changes in toe and camber.
Isn't that the point of the mod?
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Misnblu wrote:Mr.Goodwrench-G.T. wrote:What you're witnessing is no or lower suspension travel. Usually coil overs will do that. The "bad thing" is when you are not using all four contact patches to ground.
Remember the most important part of the whole suspension is what meets the road. Add the best suspension component, brakes, braces, chassis, steering, etc but all of that becomes useless if you can't put those upgrades to the ground and putting it into use.
The lift is important, because you basically need independent suspension in order to avoid one wheel influencing the other.
That's what I said on the other page.
Quote:
And that is of course by design, too much grip in the rear will make the car understeer heavily. Make sense?
No it doesn't, and quite frankly I don't know where do you even get that. I will give you the benefit of the doubt and assume you're talking about RWD and going WOT in a corner?
Quote:
With twist beam:
* Lateral forces induce toe changes.
* Bump forces induce toe changes.
* Bump forces induce wheelbase changes.
Actually, you have better chance of seeing a temporary Camber change then a Toe change during extreme cornering. Remember our rear twist beam ends doesn't articulate well and stay rather solid in movement. What changes is the angle degree while moving in the suspension travel.
Quote:
That's my whole point of the tie bar over a stock suspension and probably why most have experienced better handling although your 'placebo effect' has been used before as this is a way to denounce something that alot of people seem to believe.
What were their measurement instrument/standards, if it wasn't the "Placebo Effect?"
Quote:
Most people don't really drive their car enough to really have that feel for driving it. But for those that do and know their car inside and out the changes that a person makes in suspension tweaks are not 'placebo effects'.
This tie bar has been a popular mod for many years with the Jbody and now we're denouncing it because of it's inferior ability to limit toe out and instability issues that no has experienced?
Remember, I'm not arguing as this is a good discussion.
So has loud mufflers, it's been a popular choice in order to make power. Just because it is popular doesn't necessarily mean it is effective.
Quote:
I know that there's programs out there that can model our twist beams in some kind of cad animation for some kind of reference of how it all works.
So far everything I've read shows that a stock twist beam will cause more toe out and camber changes than a stiffer sprung setup with roll bar preventing more of the independent motion that promotes the said changes in toe and camber.
Isn't that the point of the mod?
Yes, you are right... to a degree. Stiffer everything and the tie-bar will reduce the camber change in extreme conditions, but that only because it is not letting the suspension architecture work. It is so stiff, that suspension articulation/travel is minimal, and now you're attaching it to the other wheel to work in tandem, at this rate, might as well remove the whole semi-independent set-up and install a live axle with a Panhard Rod like the old X-body Citations.
Personally, I would say the Twist Beam is not a treacherous design, but it is not it the best design either, but the kind of crap some people invent in order remove what it is inherent in it's design, is face-palm worthy. Reminds me of the prescription medicine commercial, you take a pill for heartburn, but the side effects is nausea, headaches, water retention, loss of hearing, impaired vision, sleepiness, etc. Know what I mean?
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i'm not arguing for the sake of arguning. merely pointing out that everything is conjecture. people have run the tie bar without issue in real world situations. you can not tell me that as many people that have the mod done, nobody has hit a bump mid corner at speed. James (misnblu) has mentioned that he has done accident avoidance maneuvers using the tie bar with no ill effects and i'm sure has pushed the car on an on ramp or two.
i was merely pointing out that i don't think the effects from the tie bar are as pronounced as some seem to think.
as for the 3 wheeling, i understand that 4 contact patches are greater than 3. i also know that there are alot of cars out there that can turn fast lap times on 3 wheels. is it the best case scenario? nope. does it produce fast lap times? in my experience, there are some cars setup well enough that even lifting a tire doesn't cause the car to lose grip. (should mention that i've ridden along in some of these cars and have not seen the drivers making any correction when they go from 4 to 3 wheels on the pavement)
let the discussion continue.
Think about 3 wheeling this way, of no weight is on the inside rear wheel, more of that weight is on the more important outside front wheel giving it more grip.
We have a Miata that will pick up the inside front wheel too Spence, it's quite amazing to watch.
Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.
Ok so someone with a tie bar measure the distance between the front of the 2 tires and the rear of the tires. Then jackup one side, probably under the hub, to simulate twist as if hitting a bump. then take the same measurements. This should show if there is any toe out. I can certainly see the reasons for thinking there is toe out. The geometry makes it seem impossible to think there isn't any. My question is, is it enough to be negative towards handling
Good point ZsZ.
I'm taking my car out this coming week since I've got some tuning that I've got to do with it and get the car ready for dyno day on the 27th.
I may just do this to see if there's toe out or not, we'll see.
I'm also a believer in about -1.5 degrees of camber in the rear to eliminate any positive camber change when cornering hard with the twist beam. So far I don't have any complaints with it.
Good discussion and like so many other discussions I've seen about our beloved twist beam, there's really no solution to getting this turd polished any better than it is because with all of our polishing it's still a turd.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
Misnblu wrote:Good point ZsZ.
I'm taking my car out this coming week since I've got some tuning that I've got to do with it and get the car ready for dyno day on the 27th.
I may just do this to see if there's toe out or not, we'll see.
I'm also a believer in about -1.5 degrees of camber in the rear to eliminate any positive camber change when cornering hard with the twist beam. So far I don't have any complaints with it.
Good discussion and like so many other discussions I've seen about our beloved twist beam, there's really no solution to getting this turd polished any better than it is because with all of our polishing it's still a turd.
That would be cool and haha yes a turd is still a turd
That watts link setup looks very interesting. It probably wouldnt be THAT hard to do if you dont mind loosing some of the tire well..... hmmm, def has me thinking.
Dan
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Also this Mumford linkage looks pretty interesting also. Its similar to the Watts, but it allows for changes in the RC lower than where the middle joint attaches on the Watts (below ground even - Not that we would want that....)
http://www.not2fast.com/chassis/mumford.shtml
Dan
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Project updates and stuff:
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email: dan at clubhousecustoms dot com
why hasnt the question of the differences between the 2nd gen and 3rd gen rear suspensions been covered yet?
2nd gen, springs sit on the inside of the axle and uses shocks.
3rd gen, springs are up in the fender well as part of a coilover type strut.
2nd gen, solid, no holes.
3rd gen, holes.
they are completely different.
also, what of the helwig rear sway bar for the 3rd gen? its a COMPLETELY different setup that the 'normal' ones for our cars. which setup is better? (hellwig is a solid mounted design)
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Pics of the Hellwig rear bar?
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Old pictures but you can see the mounting of the bar etc.
I didn't like the Hellwig bar as compared to the Eibach. Hellwig used alot of metal plates to mount the bar to the shock assemblies which added alot of unsprung weight to the rear of the car.
It was only 19mm in diameter but if you were running the stock front swaybar on you Z then it was the perfect compliment to the front bar giving you nice neutral handling. For this I liked the bar.
I still have it in storage and eventually plan on retrofitting it to my Paseo if I ever get off my lazy bum to do so.
And Brad, from all the reading I've done on the twist beam design, the second gen guys have the better setup over the third gen.
Spring mounting is in a more ideal setup/ location over our coil over setup for the third gens and I'm not sure why GM did it this way.
Most every design with the twist beams have the springs mounted forward of the shocks compared to the third gen J platform.
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Ya, I saw a install instruction somewhere for it, and it looked very goofy with all the wired plates and J bolts an stuff.
Does anyone have a decent pic of the 3rd gen beam out of the car? Maybe one that shows just how and where the tie bar would mount?
Dan
Currently on jackstands.
Project updates and stuff:
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email: dan at clubhousecustoms dot com
Another question....
Do people with tie bars notice any faster wear rate of rear beam bushings than cars without??
Dan
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This is the best I've got of my rear axle...
Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.
I personally think the Hellwig bar mounting design is better, far more solid than that flimsy angle iron mount attached to a little bolt on the Addco or Eibach. Also the Hellwig mounting design would also help to prevent trailing arm deflection(not much since the bar is so small), If only the Hellwig bar would have been bigger. I will be doing the install of my 28mm rear sway bar in a week or so, I will post pictures of how its mounted. The 28mm bar I have is mounted similar to the Hellwig but the way it attaches to the trailing arm will help it keep deflection to a minimum,thus keeping me from having to run a tie bar. When I get back home next week I will snap a few photos of the bar setup I have.
Flimsy angle iron.... that's a 1/4" thick.... it's not going anywhere.
Paying someone to install parts and bragging about it being fast, is like watching someone bang your wife and being proud to raise their kids.
blu, this changes things. I didnt realizes from looking under my car the we do have an H shaped twist beam.
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