serbj

iTrader: (1)

I'm considering getting a Progress 24mm rear sway bar (RSB):


As well as a set of Tein Street Basis coilovers:


However, I've heard some stories about RSB mount, after installing Progress 24mm RSB, breaking because of too much stress from a stiffer bar. For example:
Progress Rear Sway Bar = Cracked Mount
https://acurazine.com/forums/3g-tl-tires-wheels-suspension-97/progress-rear-sway-bar-%3D-cracked-mount-801907/
Rear sway bar mount broke off subframe
https://acurazine.com/forums/2g-tl-problems-fixes-117/rear-sway-bar-mount-broke-off-subframe-817410/
Rear sub frame broken !!!!!
https://acurazine.com/forums/3g-tl-problems-fixes-114/rear-sub-frame-broken-688749/
Rear subframe damage: RSB mount broken
https://acurazine.com/forums/3g-tl-problems-fixes-114/rear-subframe-damage-rsb-mount-broken-711648/


Therefore my questions are:
1) If I get a set of Tein Street Basis coilovers (I'm planning 12/7kgf·mm^-1, instead of Tein's default 12/6kgf·mm^-1) first, and then put the 24mm RSB on with it stiff setting, will I have RSB mount breaking issues?

Also I'm wondering:
2) Regarding solely performance gain in handling, are Tein Street Basis (SB) coilovers worth it? I want to drop only around 1 inch (~2.5mm), which is the same as A-SPEC suspension. Here I'm not sure if Tein SB is really better than A-SPEC by means of handling.

3) What do you guys feel about stiff suspensions like Tein SB? I personally enjoy the suspension on Evo X, G35 coupe, and M3, because it feels true and solid. Yet I'm still wondering whether Tein is the way to go, because I've heard stories about back/neck pain when you drive for a few hours on the highway.

Bearcat94

What car do you have?

Unless you have a firmer front sway bar (i.e. TL-S or after-market), I'd put my RSB on 'soft'. Other wise you may shift the under-steer/over-steer 'bias' more than necessary.


As far as the sub-frame mounting point welds, this is what IHC had to say in a couple of the linked threads:

Inaccurate

Beware of who you are asking advice from. From what I have seen, everyone on this forum wants to "drop their ride" AND have a factory soft suspension.

I am the only person on this forum (that I am aware of) that believes in a firm suspension. I don't know if those Tein coilovers have adjustable damping or not. But if you want a very firm suspension, you MUST get coilovers with adjustable damping.

I have BC Racing coilovers. On the fronts, mine are set at Full Hard on the damping. My TL weighs 800 pounds less than oem too. And, I still want more stiffness !!!!

BTW - stiffer coilovers will not put more stress on the bar mounts.

And regarding the back pain - Each person is different. I am over 50 years old and my back feels fine after 2 hour commutes with my very stiff suspension. And, I have racing seats that have no cushion. My back ached a little the first few weeks with the very stiff ride, but my body adapted after a few weeks and no more back pains.

Inaccurate

And for a more aggressive suspension and perhaps having less stress on the bar mounts, check this link -

My limited droop (click here)

serbj

iTrader: (1)

Thank you for bringing up these great points. My TL has base suspension (the softest ones, lol), yet I want to put the RSB on firm and have a set of Tein SB as well. In this way I can have a feeling of driving a G35 coupe.

You may be right. Even with high spring rate coilovers, RSB on soft may be better for the mounts as well as understeer/oversteer bias.

serbj

iTrader: (1)

Thank you for the great information. So I guess I should limit the droop (aka, "raise the spring perch") to 1/2 inch (~1.3cm)? I'm not quite sure how to do this with Tein coilovers, but I will do some homework about it to figure out.

I personally enjoy firm suspensions too. When I drive a car with soft suspension, I'm constantly wondering if there is something wrong with the tires (bubbles) and wheels (crack, bent, etc.) when the car bumps, lol. When I drive the G35 coupe, I'm always very confident that it must be just something like a small pothole/rock and the car is fine, lol.
________

Okay I've figured out how to raise the perch, lol. I'm going to do some experiments when I get the coilovers.

Chad05TL

what bearcat said was correct about doing "only the rear" without the front. (which causes breakage) So why? it's because the car is still allowed to lean a lot because you have only 1 rear bar that has added tension. And that tension is too much for the rear mount points, so it breaks.

What you want to do is reduce the amount of sway. THe sway is what is causing the pressure on the rear sway bar mount points.

You can reduce sway more by adding the front anti-sway bar, and also by adding lowr profile springs or stiffer springs.

Now, beyond that, no one really knows how much torque you can apply to the RSB mounting points before they break, and no one really knows at what point of sway does the RSB break... So, all you can do is not go to extremes by installing only 1 anti-sway bar on the rear and leaving all the rest untouched, especially if you are working on a base TL. A TL-S has more tolerance in this matter because it sways less due to heavier sway bars and probably lower springs. See? It's all about the sway that causes the rear to break. If you can reduce the sway with other components like stiffer springs or lower springs or a thicker FSB or a solid FSB, then it takes the stress off the rear because the added support reduces sway.

Its also important to understand that an anti-sway bar works by resisting torque. It does so by increasing the diameter of the anti-sway bar , or by having a solid anti-sway bar instead of a factory hollow bar or by type of metal and how it is hardened. Overall, diameter and weight and solid or not determines how much it resists "sway". And sway is not when the left and right side of the car raise and lower simultaneously. Sway is when the left goes up and the right goes down.. or vise versa. This "up on one side" and "down on the other side" cause a twist to be applied on the anti-sway bar. So the thincker and more ridged this sway bar is, then the more it resists sway and the more the car stays flat in a turn.

I hate cars

This must be bring up old posts day.

The swaybar is a torsional spring. When the body leans, one side compresses and one side decompresses. As the body leans, torque is transferred through the bar from the outside spring/tire that's compressing and the bar tries to compress the inside spring. The swaybars work two different ways. One is by trying to compress the inside spring and by resisting compression on the outside spring. Seeing how the mounts break as if a downward pressure is applied to tear it away from the frame, it's the side that's decompressing that's breaking the mount.

Stiffer springs help but not quite as much as it would seem because while you limit total compression on one side, the swaybar is unable to compress the inside spring as much since it's stiffer. It's usually a net gain in reducing the swaybar tension on the mounts but not that much.

One thing I suggested early on, that lowered cars might have less of a chance of breaking the mounts is probably still true but if it's lowered enough that the swaybar ends are no longer horizontal, there's going to be a lot more load transferred in the vertical plane resulting in more stress on the mounts. On one hand you limit travel but you can actually have close to the same amount of travel and transfer more of the stess to the mounts. This is all assuming that the swaybar is not horizontal. Cars with coilovers that allow full suspension travel when lowered will most definitely have more stress on the swaybar mounts. This can be cured with adjustable end links.

In the future I plan to take a look at mine in it's normal state and see what position the swaybar is in and adjust from there. I think it needs to be said again, once the swaybar ends are no longer horizontal, the farther you get from horizontal, the more force is transferred into the frame instead of twisting the bar, resulting in a loss of ride quality and less torque trying to compress the inside spring. It acts more like a stiffer coil spring rather than a swaybar.

One theory I have is that as long as the car is not very tail happy at the limit, you're probably not going to be breaking any mounts. This would take into consideration the stiffness ratio front to back. It would mean the 5at guys that throw a Progress 24mm bar onto an otherwise stock TL would be the most likely to break a mount. Mine never broke but I didn't try it on the stiff setting until I had stiffer springs and a larger FSB. Maybe a poll is in order.

No time to proof read, I hope I didn't screw anything up.

paperboy42190

iTrader: (7)

very nice post from i hate cars, always good to learn from the posts

I hate cars

Thanks. I'm still learning as well. One thing I've started paying more attention to lately is the positioning of the swaybar ends since it's a free lunch, you get more comfort and better handling if they're horizontal. Not paying attention to that left a huge gap in the suspension tuning.

Just recently I learned that most adjustable swaybars are rated for what the imaginary "middle" hole would give you. So if you have the H&R 28mm FSB like I have, if you put it in the soft hole, it acts like a 27mm bar. If you put it in the firm hole it acts like a 29mm bar and to get the advertised 28mm you would have to do one in the soft, one in the hard position. I started to change my sig to 29mm H&R FSB and 25mm Progress RSB but I figured it would cause too many questions.

catesbros

If I remember correctly I hate cars, didn't you recommend for the 5at base 3g, to go with the type-s sway bar up front and the 24mm in the rear? I am about to make a purchase and am looking through the older threads just to make sure I remember correctly. Will this cause my mounts to break?

I hate cars

I recommend that combo for performance but upgrading the front will also help stop the rear mounts from breaking as well.

The H&R front bar is very nice as well but it's pricey. The Type S is so cheap it's a no brainer but if you're looking for a little more performance and you're for sure getting the Progress rear, the H&R is a great option.

Chad05TL

Torsional and twist is the same thing. It comes from an applied Torque when the body leans. I said all that about a decade ago.
http://en.wikipedia.org/wiki/Torsion_(mechanics)

I hate cars

Well thanks for digging up a dead thread to give everyone the wiki definition of the word torsion you smart guy you.

Chad05TL

you are welcome. I thought you may need it.

I hate cars

If you're going to be successful in pretending to be an engineer you need to have a better understanding of the most basic things. It looks like you're able to learn at least. 6 months after I taught you that a swaybar is a torsional spring you're figuring out that "twist" and "torsion" are related lol baby steps. In another year or two you might realize the swaybar is a spring as well. I even explained why having the ends not parallel can destroy ride quality without the resultant decrease in roll resistance but you're many years away from comprehending that. At least use wiki if you're going to pretend to be an engineer.

Chad05TL

Oh puhleeaase. Haha what a loon. Get off the crack ihc.

Maybe when I measure the rpms of my starter like u do, i'll be smart enough. Haha

sauceja

iTrader: (2)

So, is it important to leave sway bar mount and end links "loose" until car is on the ground supporting its own weight to tighten everything up to spec?? To get the horizontal mounting you speak off?

That is how they say to tighten the end links and I have to install rear toe and camber links so I was going to move the end links to the stiffer hole while I was down there.

I also just installed ISC N1's so I would like to get the coils, alignment and sway bar all done right now so I don't have to do it again. Can't waste time, gotta drop my mufflers and polish them.

I hate cars

It's never a bad idea to leave them loose until the car is sitting level but it's not absolutely necessary.

Getting the ends horizontal is a matter of the car's ride height (how much it's lowered affects this) and the length of the end links. When they're horizontal you're putting more twist into the bar which is what you want and less force into the frame of the car which you don't want. More force into the frame will make it ride stiffer just like a stiffer coil spring but with less twist acting on the other end of the bar so you're not getting the full benefit of the bar. Getting the ends horizontal is like having your cake and eating it too. It can be adjusted with adjustable length end links. There are a couple schools of thought. Some think perfectly horizontal is right, some think a couple degrees from horizontal is right.

paperboy42190

iTrader: (7)

So would you say with factory height, the rsb is at a perfectly horizontal position? Also, I understand what you mean about having it transfer more force into the frame instead of twisting the bar once it's lowered too much, is that difference negligible? If not, would there be a noticeable difference if a company made a sway bar that curved in such a way that the ends will be horizontal? Hope you know what I'm trying to say.

I hate cars

I think the easiest way to picture what happens when they're not horizontal is to picture the ends are completely vertical. In that position the bar would not flex, it would just transfer all of the load straight into the frame mounts. There would be no reaction on the opposite side of the car.

Having the bar not horizontal will give less leverage on the bar as well, acting as a stiffer bar. Even if you make the end where the endlinks attach horizontal, it won't make a difference. I wish I could draw worth a damn so I can illustrate what I'm trying to say but I suck at drawing.

Another way to think of this, and it only explains part of the problem but an adjustable swaybar has two or three holes that effectively make the bar longer or shorter which adjusts the stiffness by giving the endlinks more or less leverage on the bar. If the bar is hanging down not vertical, the distance from where the end link attaches and the frame pivot point is shorter, making it stiffer just like you put it in a stiffer hole.

sauceja

iTrader: (2)

IHC how about you just come over and twerk my RSB so its perfect and then I can go back to not caring about knowing how or why. Just knowing its the way its suppose to be haha.

Thanks for the info. I will attempt to get it kosher. I never really did get into the physics of suspension. I kind of did when I was going to try HPDE but did not.

My car is low, rides really well and handles awesome for what I do to it. And that makes me happy.