Ive always wondered what the rates of the rear swaybar and beam are, so I thought Id measure them.
Now, this may not apply to everyone here as Im using a shortened Beretta beam and bars, but it might be close between the platforms.
Here is the setup:
- removed both rear springs
- disconnected pass side shock
- blocked drivers side beam to the tire well with a block of wood, and held it all in place with a jack under it.
- angle finder on the hub studs to measure degrees of twist (for future swaybar options :snky
- caliper to measure the twist in inches
- bottle jack and wood spacers on one pad from the race scales to measure the weights (zeroed with everything on it)
I repeated the measurements several times. They were very repeatable (< 0.05" variation for the same change in angle). Considering my pretty hack setup, I thought that was awesome.
And the results are:
Beam + internal swaybar + external swaybar = 200lbs @ 5 deg (100lbs in)
Beam + internal swaybar = 100lbs @ 5 deg (55lbs in)
Beam only = ~70lbs @ 5 deg (40lbs in)**
** the beam only measurement got tricky. The beam was so flimsy with no bar that it created 10lbs of weight on the scale at the same jack height with a bar. So the numbers above reflect a 10lb difference between what I measured and what is displayed above. This measurement may have a bit of error in it.
I think the big thing to take away from this is that the rear swaybar approx doubles the roll stiffness.
Personally, I get some awesome data to base my new swaybar setup on.
Dan
YEP, my 60' times suck
247HP/267ftlbs at 13psi with built motor
Project updates and stuff:
www.clubhousecustoms.com
email: dan@clubhousecustoms.com
So in theory with what I'm seeing in your measurements is that there could be as much as 10-15 degrees of angle in the beam with twist?
That's an interesting fact and how in the world did you remove the internal bar? On the third gens the bars are welded in.
I like what you did there.
Are you going to make your own sway bars or something that's going to be adjustable?
I'm subscribed.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO! 
Hmm... Im not sure what you mean about the 10-15 degrees of twist. 5 degrees of twist was over 1.5" of deflection in the beam.
As for the internal bar, the Beretta one bolts in, so that made it pretty easy to remove.
And yes, I am going to be making my own external, body mounted, adjustable bar using a hollow splined "nascar" type bar.
Dan
YEP, my 60' times suck
247HP/267ftlbs at 13psi with built motor
Project updates and stuff:
www.clubhousecustoms.com
email: dan@clubhousecustoms.com
I was referring to the amount of twist that the beam has.
Many have considered that it does very little twisting when on the road and it's more like a solid rear as opposed to having any kind of independent action.
That's a fair amount of play.
And why not just buy something that's already out there on the market? Why make your own?
Anyway, I'm curious as to what you're doing, and how you're going about doing it. I'm like a little kid with stuff like this.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
I dont think anyone makes a splined, body mounted, adjustable rollbar setup for a cavalier with a narrowed beretta axle beam. Lol.
And really there isnt much to make. Its buy a bar, and arms and mounts and make droplinks and a way to attach them to the beam.
Im talking about something like this:
The bar is straight, and they come in all sorts of sizes and wall thicknesses (or solid). Then you attach arms, and mounts, etc.
Current plan is for it to mount to the "frame rails" behind the rear axle beam. The bar itself will acutally go THRU the spare tire well. Then the arms will point forward, towards the beam. Endlinks will drop down towards where the shock attaches.
By doing multiple holes in the arms, and probably a couple on the axle beam, I should be able to change the rate by -10% to +50% over what I have now.
The whole setup should be approx 10lbs less overall, this is just my guess so far. There will be 5lbs of additional sprung weight (with the bar on the car instead of on the beam), but 15lbs less unsprung weight.
Dan
YEP, my 60' times suck
247HP/267ftlbs at 13psi with built motor
Project updates and stuff:
www.clubhousecustoms.com
email: dan@clubhousecustoms.com
The best part is you can swap to a new bar without changing anything else. Just slide it in and have a whole new set of rates avaialbe.
They are pretty cheap too. I think I can score the bars for around 60 ea (bar only).
Dan
YEP, my 60' times suck
247HP/267ftlbs at 13psi with built motor
Project updates and stuff:
www.clubhousecustoms.com
email: dan@clubhousecustoms.com
so you're actually making a real sway bar for these cars, I've considered it a good bit. Are you also going to triangulate the trailing arms, I believe that would also help this setup, no more weird toe change, but also no messing up the function of the twist beam with a tie bar.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
Ya, I already have the beam triangulated. Its going to change some as I am moving the bearing mounting points up 2" to get the car lower without changing the geometry. But it'll basically be the same as I have now
The right side has my mockup bearing plate installed.
Dan
YEP, my 60' times suck
247HP/267ftlbs at 13psi with built motor
Project updates and stuff:
www.clubhousecustoms.com
email: dan@clubhousecustoms.com
for the amount of work... why not just do an IRS?
Underdog Racing
1. its not that much work.
2. I dont see any real advantage of the IRS, for the work involved
3. even if I did IRS, I would stll want to do this. IRS doesnt automatically give you an awesome swaybar setup
4. If Im going to do a IRS swap, its going to have a differential attached to it.
Dan
Currently on jackstands.
Project updates and stuff:
www.clubhousecustoms.com
email: dan at clubhousecustoms dot com
fair enough! i wanted an experts opinion of IRS is all
im glad you think so highly of the twist beam.
IRS on a 3rd gen doesnt seem to be to bad with work, id honestly think itd be about the same amount as making a bunch of custom bars and what not... all you gotta do is cut some arms and weld a bit from my understanding.
Underdog Racing
Juiced, have you got anymore pictures of your triangulated setup? Particularly the heim connection point on the beam axle as that has my curiosity up.
Also, where did you mount the points on the trailing arms as this too has my curiosity up as well.
Last, why not use something like a tie bar for keeping the arms from causing toe issues? Again, just curious as I love this kind of work.
It's great to see some creativity here on the forums.
Btw, I see why you went with the triangulation setup over the tie bar, and it makes sense.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
juicedz4 wrote:The best part is you can swap to a new bar without changing anything else. Just slide it in and have a whole new set of rates avaialbe.
They are pretty cheap too. I think I can score the bars for around 60 ea (bar only).
Dan
My question is how much are the arms
Im calculating about 185 bux for the complete setup, minus hardware and any needed metal stock, and welding.
Dan
Currently on jackstands.
Project updates and stuff:
www.clubhousecustoms.com
email: dan at clubhousecustoms dot com
Misnblu wrote:Juiced, have you got anymore pictures of your triangulated setup? Particularly the heim connection point on the beam axle as that has my curiosity up.
Also, where did you mount the points on the trailing arms as this too has my curiosity up as well.
Last, why not use something like a tie bar for keeping the arms from causing toe issues? Again, just curious as I love this kind of work.
It's great to see some creativity here on the forums.
Btw, I see why you went with the triangulation setup over the tie bar, and it makes sense.
You triangulate the trailing arms rather than using a tie bar because the tie bar effects how the trailing arm, twist beam setup works. With a tie bar if one side of the suspension travels up while the other stays level either the tie bar needs to stretch or its going to cause one of or both of the wheels to toe in. When people on this forum came up with the tie bar and justified that it wasnt going to mess anything up they were likely under the assumption that the twist beam didnt twist and acted like a solid axle.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
^ thank you. Well said.
Ill try to post up some more pics of the K brace later on.
Dan
Currently on jackstands.
Project updates and stuff:
www.clubhousecustoms.com
email: dan at clubhousecustoms dot com
oops when I said toe in in my post I meant toe out
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
Leafy wrote:Misnblu wrote:Juiced, have you got anymore pictures of your triangulated setup? Particularly the heim connection point on the beam axle as that has my curiosity up.
Also, where did you mount the points on the trailing arms as this too has my curiosity up as well.
Last, why not use something like a tie bar for keeping the arms from causing toe issues? Again, just curious as I love this kind of work.
It's great to see some creativity here on the forums.
Btw, I see why you went with the triangulation setup over the tie bar, and it makes sense.
You triangulate the trailing arms rather than using a tie bar because the tie bar effects how the trailing arm, twist beam setup works. With a tie bar if one side of the suspension travels up while the other stays level either the tie bar needs to stretch or its going to cause one of or both of the wheels to toe in. When people on this forum came up with the tie bar and justified that it wasnt going to mess anything up they were likely under the assumption that the twist beam didnt twist and acted like a solid axle.
I think you're misunderstanding what most do with their tie bars.
With the heim ends on the trailing arms, there's room for the arms to do their thing with little or no effect of the tie bar causing the toe conditions.
Also, juiced proved that there's no more than 10-15 degrees of total motion of the twist beams which would probably have no effect on the toe you're speaking of.
If anything the tie bar eliminates this from happening if my theory is correct.
Now with the triangulated setup, you not only have the effect of the tie bar but we all know that triangulation is always the most rigid setup for strengthening something than a box.
I would think that the triangulation of juiced's setup would make more sense in what we're trying to do.
Any comments on this?
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
Ok, I decided this was best shown with an illustration.
On the top you see the suspension with the tie bar flat, and articulated on the bottom, the Distance between the trailing arms is shown in black and the tie bar is in line with the distance between the arms, the arms are shown as the short red lines. As you can see, when the suspension articulated the tie bar line is longer than it is in the top picture. Of course the tie bar can not change in length greatly due to the fact that it is aluminum. There for the backs of the trailing arms where the tie bar is mounted to need to come closer together, this causes the rear tires to toe out. At a 15* flex in the twist beam the rear of the trailing arms are pulled in by 3.5% of the original distance between the mounting points for the tie bar. If the tie bar is 36 inches long that means that the ends of the trailing arms are pulled almost an inch closer together than originally. Assuming that they are pulled together equally thats 0.5" toe change on each side (assuming the trailing arms extend to out to be even with the backs of the tires, if they're shorter the toe change is even larger). That is a huge toe change, and since it's toe out, this could cause snap over steer when only articulating one side of the suspension during a corner, ie hitting a bump with only one rear wheel.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
while im loving this conversation i must bring up the fact that during hard corning in autoX most j-body owners see one of the rear wheels lifting and getting airborne while the other stays grounded...
is this not due to the fact that the rear axle does not 'twist' enough to keep both tires planted and therefore would make having a tie bar useful if installed? or not?
thing is though wouldnt the tie bar make the axle even less 'twistable'? so wtf is the sway bar doing then? does it allow the beam to actually 'twist' easier or something? the way i see it is having all this stuff hooked up makes it actually harder to 'twist'.
*confused
Underdog Racing
Yes, both the tie bar and swaybars make the twist beam harder to twist, the tie bar does it by adding a constraint to the system while the swaybar changes the actual spring rate of the twistbeam. We want the car to lift the inside rear wheel and do it predictably because its a front wheel drive pos and understeers otherwise. I didnt notice mine lifting the inside rear but I was driving ~8 seconds slower than the car could have gone when I auto-x'ed her. Typically even a well setup fwd car with an irs will lift the inside wheel to make it rotate better.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
interesting... see i always thought we wanted to keep them both planted.
so really what do we want more? less body roll due to the use of the rear sway bar or lifting the inside tire without it?
same goes with a tie bar... what do we want more?
Underdog Racing
We want to triangulate the trailing arms to get rid of toe change rather than the tie bar, because the tie bar may actually create more toe change then it prevents. We want is the body to stay fairly flat but the inside rear wheel to lift, but we dont want it to lift so soon that it would lift during a slalom since that would make the car just switch between rear wheels touching and make it much too tail happy in the slalom, but we want it to come one soon enough that in most (all) hard turns it does lift. We also dont want it to lift during long sweepers. A real sway bar that mounts to the chassis with the middle of the bar rather than to the twist beam will act differently than the typical swaybar we see on these cars where the middle of the bar mounts to the twistbeam along the axis of rotation. The current bars do not effect the spring rates of the wheels when the car is going of a bump with both wheels (like a speed bump), but id does effect the spring rate f the wheels when only one tire goes over a bump. A swaybar the connects to the chassis will act similarly, BUT if it binds in its bushings it will add to the spring rate. OH WAIT! you cannot have the rotational axis of the chassis connected swaybar be different than that of the twist beam or it will 100% bind and break something (be it the mounts, the links, the swaybar or trailing arms, or the twistbeam) because the distance between the chassis swaybar mounts and the end of the trailing arms will always be different at different points during suspension articulation. I'm not sure if the OP is planing on connecting his new swaybar to the chassis or not, but it wont work.
1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by:
Kronos Performance
WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
I understand completely Leafy but one thing the tie bar does is lessen the toe in/ out from it being stock.
Now with the introduction of the triangulated setup I'm seeing here, there's room for improvement which was my point once I had seen the change in the way the effect the K-brace has on the twist beams.
I really like this but since my days are pretty much numbered with the Cavalier I'm not too worried about making changes to the car as of yet.
I'm pretty happy with the setup I've got and for now, it's as far as I'm going to go with the car unless the modding bug hits me once more and I fall head over heals into it again.
But, I do like the fact that there's something better out there and again, this is what I like seeing on the forums. Change.
Change for the better and why this wasn't posted earlier I don't know.
Keeping knowledge to oneself seems to be a bit selfish because this is how we advance our platforms from ordinary to special.
Btw, I'm not knocking anyone for keeping things secret but this is the first time I've seen this triangulated setup for the twist beam and it's got me intrigued. Why I didn't think about it I don't know.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
One more quick bit of theory here.
If what you say about toe out is true, I can't see it.
What I'm seeing with the tie bar is a camber change more than any toe out.
I'm not an engineer or anything but sometimes a little visualization and some sticks with string bring out a good point with all this.
Having done the above, I could see that the camber would change because the trailing arms are traveling in an arc which is vertical not lateral.
Lateral arc would create this toe out or in while the tie bar would be more inclined to create camber changes to both tires depending on how the car is turning and which direction.
Any speculation on this?
And pardon me with all this but I'm wanting to learn more about this so I can be better informed on what's going on with our cars.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
