Write-Up: Installing a Front Strut Tower Brace (STB)

Let me suggest an experiment to convince you of the structural un-integrity of the STB with dent. Take a perfect coke can, and see how much force it takes to smash it. Now take one, put a small dent in it, and see what happens. This is your bar!

Now think about when this is most likely to happen - when you are cornering hard! All of a sudden your car will not have the cornering power it had a half second before. Maybe you save it, maybe it comes at the worst possible time and you don't.

AA wrote:

It's perceived improvement is at least as good or better than both Addco stabilizer bars with hard bushings.

Thanks, that is good info to have. It suggests, tires not being a factor, I would have the best handling Riv here with the two STBs and rancho shocks (which are better than the STBs). Of course tires are a factor, and this is a totally unscientific evaluation

While the concept may be the same, I don't think it's an "equal" comparison to the dented thin aluminum coke can. I just don't think we can corner hard enough that the dented bar will have any failure. Of course we're all just expressing our own opinions.

I forgot ewolfe's springs, he may handle better than me, taking out the tire factor (with it of course ewolfe and several others do).

1998 - It'd be like Chinese water torture, a little more stress on the weakened section, building over time, then one day - snap! (Or fold).

I remember someone once posted pictures of bent washers, with the unbraced bar, and my bar has got to be under serious stress - it's dramatically slowing the roll of a 4000 lb vehicle at speed! I wouldn't underestimate the force these bars are taking.

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Let me suggest an experiment to convince you of the structural un-integrity of the STB with dent. Take a perfect coke can, and see how much force it takes to smash it. Now take one, put a small dent in it, and see what happens. This is your bar!

Your point might apply if the force exerted during a hard corner were compression. But it's not. It's all tension, and lots of it. Perhaps 800 to 1000 lbs of it if we could hit 1G lateral. This is why a thin hollow tube is all that's needed to cope with these forces (here's an experiment: pull really hard on the ends of a soda straw, see if you can break it). Our STB was obviously designed for tensile strength. And while your pop can analogy might merit consideration under compression, a dent isn't going to matter at all under tension.

But it's true that the brace experiences some compression in operation. When the front wheel(s) hit a bump, the bar experiences compression for a brief moment. Also, in normal driving, the brace is receiving slight compression forces constantly, probably under 50 lbs, imo. The really concerning forces are the tensile ones. I researched this before doing the mod. It's one of the reasons I waited so long to do it. I did not want to take the risk of bending/breaking the bar during a high-speed turn and skidding off the road. Nor did I want that to happen to anyone else.

About the only case where my dented STB would fail is during an extreme blow to one or (worse) both of the front wheels, such as a speed bump at 70 mph, where the bar would be compressed several thousand pounds for a split second. If this were to cross the threshold for failure, the evidence would be obvious - the bar would be bent. Per your soda can, it would happen abruptly and violently, and it would show permanent damage. I doubt it would fracture, but would expect to see a bend or crease. Again, this would take an immense amount of force to push it over the edge. It would hang on during all but the most destructive events. Likely a strut or control arm would be destroyed before the STB, as the vertical forces exerted on them would be several times that of the brace. The good news is, in this situation, the STB would act as an energy absorber for the front suspension. And if it failed, it would not present much of a safety issue. The brace (and likely other parts of the car) would suffer damage, but you would not lose control.

And as for the assertion that denting the bar weakens the steel like a fuel line, that only happens when you bend it over and over again. As can be seen with any steel forming operation, the first instance of bending actually strengthens the part due to work hardening. In other words, dents can actually make a piece of material more resistant to flex and bending. Many metal and plastic parts are formed with irregular dents for this reason. Speaker cones, requiring ultimate stiffness, are a good example. Not all have plain, flat ones any more. Lots now with depressions and grooves in the design.

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It suggests, tires not being a factor, I would have the best handling Riv here with the two STBs and rancho shocks (which are better than the STBs).

I don't know if I'd go that far. I made that comparison with the consideration that the STB affects the overall ride as well as handling (hard cornering) - the STB is more noticeable because I feel it all the time while cruising. But in a really hard turn, where it's hard to make a subjective comparison, I believe the stabilizer bars may contribute just as well. In theory they should help even more in the corners. I guess that one (me) can't always tell what's really happening on feel alone.

Plus, the KYBs were a big improvement. Did you change the front struts?

I still have the Monroe's in front. I haven't heard anyone say the KYB's made a big performance difference. That would be an improvement I haven't made though, and didn't think of. But if tires were equal, I believe the only other member handling similiar to mine would be ewolfe, because he has springs and also the Rancho shocks (but no STB's, or at least no rear STB?)

I know you don't believe in the Rancho's, but I turned mine down from 5 to 3 yesterday and it took half the fun out of driving the car. I don't think a car with air shocks that aren't equal to the Rancho setting of 1 would be competitive (again, tires not being in the equation). At least not without changing springs.

I had a fuel line break with only 3 bends. You've got two, and the third will come from all the little bumps your suspension soaks up as the miles accumulate. Maybe also from the roll forces it's taking.

What did you read that says an STB is under tension? Have you got a link?

I'll definitely put a qualifier on my judgement, I don't know that your bar will fail or when. I can only give you my opinion, FWIW - denting the bar is iffy, and the best way to do this mod is with the bracing, possibly replacing the hood lining with a thinner material to eliminate hood bulge.

I don't think the Monroe struts are bad. The KYBs were very good though; they have lasted many miles and still perform. My rear Monroe Max AIrs are also performing admirably. I don't have anything against the Ranchos, I just don't prefer them personally. The Max Airs do a plenty decent job, and I like having the ability to adjust rear height. I'm pulling a 1000 lb trailer now...

I've put one bend in the tube. 1 1/2 if you count straightening it back out. The brace is still very stiff. Even if it weren't, it wouldn't matter, because the main concern is tension, and tension could care less about me bending the STB. Here's the best way for me to explain it:



It should be obvious that in a hard turn, the wheels cause the suspension to lean out, causing the top of the strut to pull out on the STB.

If the bar fails, then I'm wrong, and I might die because of it. But people live and die by their decisions, and I think I'm right about this. If anything, putting washers on and lengthening the strut bolts is a bad idea, because you're creating a lever out of them, exerting extra force on the strut mounts. I would suspect a strut bolt would brake before a dented bar. This is what turned me off from this mod from the beginning.

"What did you read that says an STB is under tension?"

I knew that once something like this was said, it would warrant a fancy-pants Aaron drawing with complex explanation.

And there it is, right on time with the 12 o'clock train!

In all seriousness, I think that my washer-stacked STB yields at LEAST 10 WHP if not more.

But HEY, that's just my opinion.

HEY GUYS! dont forget about my "kink in the bar thing"?....dont wanna be left out u know!

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The process took a careful 30 mins on the vice, then I had to straighten the bar back just a little bit (5 mins). Needed to use some mega leverage to do this, as the bar was still very stiff after making the dent. I am convinced there is no way this bar will bend significantly in operation.

Installed in about 5 mins, and it was done. Perfect fit. No washers:

How did you straighten the bar back after bending?

I read the whole thread but still have a couple of questions.

What year and type Cadillac do I order the brace for?

Anybody installed one on a 99 yet?

I will probably do this mod but it may be a while before I can work it in my schedule, I got too many vehicles...

Thanks
Bert

Ben, I did the sketch to save time. Seemed to be the easiest way to explain a complex idea. Hope it helps you to understand.

My first clue that bending/denting the STB came from observing that many aftermarket braces are in fact bent or dented. See pics:





I also saw some that were flat in design. If under compression, this would not work:



Finally, I noticed that some of the curved bars were very light. Strange Development has engineered a 1.6 lb aluminum brace. This would fold like paper if subject to high compressive forces: Link

Bert, very good question about straightening the STB. What I did is put the end (flange) of the brace under my rear tire, then slid a 2x4 under it and pushed hard. It took a lot of force, actually rolled the car backward pretty hard. I used an 18" straight edge to check the bar until it was straight.

The part number is on page #1 of this thread. It should fit a '99 Riv.

VERY NICE DRAWING........ wait aren't you an artist or something?

AA wrote:

Bert, very good question about straightening the STB. What I did is put the end (flange) of the brace under my rear tire, then slid a 2x4 under it and pushed hard. It took a lot of force, actually rolled the car backward pretty hard. I used an 18" straight edge to check the bar until it was straight.

The part number is on page #1 of this thread. It should fit a '99 Riv.

Thanks, I see it now. In the oversized bold printed numbers, DUH HUH.

I was looking and noticed my NA 95PA even has a STB. It connects to the same bolts on the strut as the one that you folks are installing on the Riv.
My 2000 Regal LS has a STB that attaches to the strut towers using two bolts that are close together inboard of the strut mounting bolts.
I will get some pics later.

Bert

Its right at $36.00 shipped to me from GM Parts Direct.

My guess is if I got a local dealer to order it the price would be about the same.

Anyone buy one from the dealer?
Its not much money either way but the Larry David in me needs to know...

Bert

Aaron, I was just messin' around. I thought you did a great job of explaining it, and your drawings are really well done. The other one I remember was when you did that writeup on the FWI.

Yeah, well I just never know. There are a lot of people who cannot read a sketch to save their life (or even to sell millions of dollars of product!). Really, it just looks like marks on paper or "art" to them. Be glad you are not part of that group!

AA wrote:

Yeah, well I just never know. There are a lot of people who cannot read a sketch to save their life (or even to sell millions of dollars of product!). Really, it just looks like marks on paper or "art" to them. Be glad you are not part of that group!

By the way the drawing is Very impressive, the style appears the same as the drawing the engineers use when rendering images of concept vehicles. I assumed you have proffesional training. Nice work.

One of my duties at work requires me to draw engineering sketches for telecommunications systems that we install and maintain. If I had your talent it would be a lot easier.

Here are some pics:
These three pics are of the STB on the 2000 Regal LS





These three are of the 95PA




Even though these are not pics of a RIV STB perhaps they will show how Buick has braced the other vehicles.



Bert

Aaron, do you have a link to any technical information saying the STB is under tension and not compression?

While your drawing is indeed a very professional illustration it appears to represent your opinion of what is happening, an opinion which you haven't yet backed up with any technical knowledge.

What you've illustrated is at best only a tiny picture of the complexity of a suspension system. You've left out the roll forces which transfer the weight of the car and inertial force onto the outside suspension - in my, admittedly untrained, opinion this would be the greatest force acting on the strut towers. The car would want to bend down the center line as the outer struts and springs counter the roll, and when that happens, compression.

It seems to me like the turning force generated by the tires would, by far to the greatest extent, be transferred laterally through the A-arms. I think you're right to assume there could be some tension at the top of the strut towers created by the steering, but I think it would be overwhelmed by the roll forces, which IMO would be putting compression on the STB.

Regarding the STB pictures you showed, I believe I can say with a very high degree of confidence that all of those braces will work under compression.

The arched Mustang braces I would say are not an example of an ideal brace architecture - it's what they could do with that big engine blocking the straight path between the strut towers. Not ideal, it probably does flex a little under a load, but it's better than nothing.

Similiarly, the aftermarket rear STB for the Aurora/Riv is a square "arch." Not ideal, I strongly suspect mine is much better, but it's the best you can do if you want to keep all your trunk space.

The flat STB, far from being the worst is likely the best of the bunch. Compression forces are fed directly, horizontally into the ends of the bar. Picture that bar stood on end, how much weight could it hold up? Who knows, an awful damn lot. It'll eat compression up and spit it out. It could eat up even more tension, but it's a general property of almost all materials to be stronger in tension than compression.

Check this out -



This is a moderately high performance German electric R/C sailplane. It is very fast, and very heavy. It has long skinny wings with a very thin airfoil. They're made of balsa, spruce, and some plywood, and never broke.



In the air they are held together by compression. The wings slide over a metal rod (which I can't find, that's not good) but are not fastened to it. Then they are bolted to the fuselage with two nylon bolts that are designed to break under shear forces (which is why I don't have them, all I had broke on landing. They broke every single time). So here is an example of a very thin structure, held together mainly by compression, but also getting twisting and bending forces fed into it - and surviving, though it is only made of lightweight woods.

It's not exactly the same thing as the flat STB, but I hope it will help convince you that a flat structure can take compression/bending/twisting forces.

One last thing - yes, you have shown tubes that were bent (once, on a special bending machine), but you have shown none with a dented wall.

Now here's a bunch of smileys so you don't think I'm a total A-hole

Just ordered the STB for the wifes 99 Riv.
Could this signal the beginning of Mods?

Bert

Bert, you should at least do a few mods.

You've already got the STB coming.

I'd say go with a gutted box, drop-in K&N, Autolite 104's, 180 t-stat, and a 3.5 or 3.6 press-on. Unfortunately this route often leads to being bit by the "mod bug," but it would really wake up your car and wouldn't affect gas mileage.

I mean, for under $500 you could add about 20 or more HP - that's cheap. Plus, you wouldn't screw up the "daily driver" aspect of the Riv.

He wouldn't screw up the "daily driver" aspect unless he blew a piston by not scanning for KR.

I can tell Aaron hasn't been here - those huge images are still up!

Got the STB today.
I will try and round up the longer bolts and install soon.

Man that stuff they wrapped around each end of the STB is killer.
I wonder if that is BearBond. The stuff they are using to repair NASCAR vehicles in the pits. It was super tough and the stickiness is almost unbelievable.

Bert

1998 Riv wrote:

I had the same experience with my 98, the STB practically installed itself. No mods to the brackets, just a couple washers at each bolt, plus I bought slightly longer bolts. You should easily notice the handling improvement in cornering.

Hey Dave, do you happen to have the bolt size/length you used?

Bert

ibmoses wrote:

Got the STB today.
I will try and round up the longer bolts and install soon.

Man that stuff they wrapped around each end of the STB is killer.
I wonder if that is BearBond. The stuff they are using to repair NASCAR vehicles in the pits. It was super tough and the stickiness is almost unbelievable.

Bert

OMFG! You got packaging!

Jack the R wrote:

ibmoses wrote:

Got the STB today.
I will try and round up the longer bolts and install soon.

Man that stuff they wrapped around each end of the STB is killer.
I wonder if that is BearBond. The stuff they are using to repair NASCAR vehicles in the pits. It was super tough and the stickiness is almost unbelievable.

Bert

OMFG! You got packaging!

Yea, somebody must have complained about the non packaging and got some reaction. The brace has some very small scratches on the tube but I dont think they will show after installation. If they do I will either touch up or paint ti again...

It looks like the bolts may line up without enlarging the holes???
I removed one of the bolts and will stop at the dealer and get some longer "body" bolts(if they have them), and some washers for the installation.

If I can remember I will take some pics and do a pre installation/post installation test drive/evaluation/comparison using the butt dyno.

Bert

Bert - I went to a specialty nuts and bolts place, and got equivalent strength bolts, as well as some nice washers. Just bring your bolt in there, you'll save a bundle of money and it will be the same (if not better quality).

And you have a '99 Riv, according to your sig - 98's and 99's are the lucky ones for this mod, it should bolt right up without any problems but you need the longer bolts and washers (of course).