So IF the 3 point does cause the windshield to crack, and IF you are concerned with the possibility of shock tower deflection, then I don't see the need to buy a 3 point for our car. Unless you want to try to prevent deflection of the whole nose (if it exists..) and then why would you want to put all of that force on that part of the car anyway?

Just trying to be logical. I still don't want an STB on my car

 

I offer a very nice two point in either dom steel or chrome moly. either bar will stiffen the front of your car. Call me if you have any questions.

http://www.bmrfabrication.com/F-bodyChassis.htm

 

Can you or someone in your company support that statement through engineering proofs alone?

I'm curious and I wonder if the original poster who's a MechEng would be curious as well.

 

The one I dug up after a quick search said he instrumented an actual brace. I took that to mean strain gauges were used.

 

I am wondering in my mind now. If the STB are just mainly for looks, and there was a post about the windshield breaking, also there was a statement said it only takes 1/8-1/4 to break the glass. Now if the bars are there for looks how is the windshield breaking. The towers would have to be flexing to a certian degree to have enough strain on cowling/Glass to break. So to me the the braces are not pointless. If you are really intreseted is seeing how much flex is really in your towers under cornering use a old trick. Tape a piece of string from both towers either monut a video camera (perferred to really measure it) or take the hood off and go take some corners and see how much the string deflects from the bowing of the towers. That would be a real is inexpenisve way of knowing.

Also since there is flexing going on proven above. Brace is keeping the towers from bowing under pressure cornering. When the towers start to bow the contact patch of the tire is now off. If you are taking a on ramp (exceeding the speed limit) turning left the weight of the car is not centered over all four wheels now, so the the right tower is bowing inward and the left tower either still straight or may be bowing out from lack of weight on it. So now the tire is not fully contacting the ground the right tire is leaning more on the outside edge and the left tire in probally wear more on the inside edge. The brace is there to beef up the towers giving the car more strength were it is need under cornering. Some what like subframe connectors in a sence.

The tower braces do serve a purpose. Mainly more in corners and not so much in a straight line.

 

I guess I'm just lazy. I tend to stray toward the advice of the 3 guys in this thread who have road race and autox experience, as opposed to the average joes who say it helps because "they thought they felt a difference". I figure it's easier to trust them than to go out and test this stuff on my own

 

They do have a few notable benefits:
- they add weight to the front end of the car (which is already too heavy)
- they add weight at the top of the engine bay, which will hurt handling
- they make it tough to do routine maintenance

Adding lets say 5lbs at the most, is the five pounds really that much weight. 100lbs will pick you up about ONE tenth of a second in a quarter of a mile, so do the math and see what five will take away. Now if you are stuck on the weight hurts performance yes it does when there is a lot of it. The brace is there to keep the contact patch of the tire on the ground while cornering. when taking a corner fast than the other drivers the end result will be worth it.

 

well technically you could do it other ways, but an FEM and strain gauge would be the most simple, the way I would do it is get measurements on everything then do a Pro Engineer model. then export it to something like NeiNastran, and that should give you all the deformations and internal stresses

If you slapped a strain gauge on the strut tower brace maybe on both sides or even in three positions you could more accurately tell, but I doubt it would elongate enough for an precise measurement

technically its not grain structures, but the dislocations that cause failure in metals

thats cool that you got a Mat Sci emphasis, most ChemE's I know just get their degrees and work for a refinery or oil company

 

Well, if the 3 point STBs exhibit a propensity to break windshields, the roads here in western New York would have broken mine a long time ago. I've had an LG Motorsports 3 point STB in place for the last 11-12 years.

 

Please go into detail in why you think the STB has an effect on the camber of the tire........ or where you heard that

 

Even if the shock tower did deflect a great deal while cornering, it would actually add negative camber to the outside wheel.

Of course now we'd be working the structure and going through fatigue cycles....



For the record, once upon a time I installed an STB and later took it off. There was no noticeable difference either way. As hard as my car gets used and as long as I've had it (ordered/bought it new back in '96), I think I could tell if there was a change.

 

It's good to know that as time marches on and the world around us changes, there are some things that remain constant ...

 

I blame it on scientology..... DAMN YOU ZENU

 

The forces being are:

1) below the lower A-Arm where the tire contacts the road
2) transmitted through the lower A-Arm and into the K-member
3) in the same direction on both sides of the car.

Creating a "box" (K-member at the bottom, STB at the top and frame/fenders on the sides) won't stop this lateral force. Now, if someone can create an "X", THAT might induce some rigidity.

What is "cowel shake"? I see folks post this all the time and I don't know what it is. Do you see it in my car?

http://www.lawmotorsports.net/mw/vid...t08HiLites.wmv

 

Well lets just say this the upper A-arm is attached to the upper part of the strut tower. IF now the angle of the tower is being deflected due to strain on it. The upper A-arm is not at the correct angle any more with the lower A-arm. So with the STB the geomertry of the suspension is kept more constant than with out one. It is really hard to explain with out a model to demostate with. One way I think I could prove this is with a flat corner somewhere safe, after you have found a corner. Drive the corner hard without the brace until you feel or hear the front tires slipping. . Then in stall the 2 or 3 piont bar and take the corner again at the same speed where you found the tire to start slipping at with out the bar. With my thoery the car should be able to be push further and hard into the corner with the bar than with out, due to the tower bar keeping the the angles of the suspension true and keep the tires flatter on the ground.

 

Theres no controversy to it, it has been proven in several past threads that there nothing more than added weight. They are a great bolt on for other cars "Mustang for example" but the fourth-gen F bodys unitized construction needs no extra bracing on the front end.

 

call it old and fatigued metal, call it worn shocks. but upon driving the same roads i drive everyday. i immediatly noticed that instead of riding over bumps in the road it tried to pull the steering wheel around them. like it wasn't flexing over them anymore it was reacting to them instead. it did eliminate cowl shake which i describe as a shutter of the front of the car due to harsh unequal bumps. it seems to vibrate the car in the percieved area under or around the bottom of the windshield hence the name. i have heard stories from both sides. i know how my car rode before and after.

 

Thanks for catching me on that one. It's down to the crystallographic defect within the grain rather than the arrangement of grains and their boundaries (grain structures). I needed to go further down to the atomic level there (whoops!).

EDIT: actually, just molecular. Jeez, I'm working and studying too much.(whoops again!)

My first line of work as a ChemE was for a pharmaceutical manufacturer, particularly dealing with plastics and elastomers. Even though it's a diverse field, it does lead itself back to some of it's biggest origins in petrochemical engineering. Materials is one significant area of it as well. As we both know, both of our fields overlap in several areas.

Now, AFA this whole rehashed STB argument goes, my vote goes with what 00TransAm, Ironhead, Jeremiah, and mitchntx have mentioned. FWIW, I do think that these cars could be stiffer, however I had this setup on two of five F-bodies I had. While both cars are similar, one of them was my daily driver:

G2 custom coil-over consisting of:
-Bilstein ASN shocks with double spherical bearing ends
-1000 lbs./in. front springs
-250 lbs./in rear springs
-optimal shock valvings to match (won't disclose them).
Stock Front lower control arms with Global West lower control arm spherical bearing kit.
Stock upper control arms with custom offset Delrin bushings (self made).
Stock K-member with Polyurethane engine mounts.
double adjustible rear LCA's and PHB with rod-ends.
G2 torque arm with spherical bearing mount.
275/40 BFG KDW tyres on 17x9 Z06 rims running 32 psi.
Corbeau racing seat on driver side.
410 rwhp/380 rwtq.

My daily driver, had full interior and nearly the factory curb weight, yet I only had the STB and SFC's for less than a month before removal, and NO roll cage.

The spring rates are almost twice of what most people in this forum would ever run in addition to the roads where I had to drive to and from work had more potholes and bumps than I care to admit. I had this car setup like this for 4 years, yet it performed very consistently with no "cowl shake" whatsoever.

EDIT: Basically, the STB and SFC's did NOTHING to improve my performance times or their consistencies over the few weeks I had them, so they were jettisoned. The alignment for the front end also has remained at nearly the same settings I've had them at during that time as well.

 

Most people dont pay much attention to the way there car handles until they make a change. By comparison fourth gen F-bodys handle pretty good in stock form.

Its when they make a change to the susp. or chassis that they start to pay attention. This is when they notice "hey, this car handles pretty damn good" the STB I just bolted on must really work.... when in reality it was like that the whole time.

You guys with your daily drivers and all season radial tires arent going to be able to push your cars in a corner to the point that there will be any deflection in the unitized chassis.. not on a fourth gen F-body.

 

That's an interesting viewpoint...One unit body car, the Mustang, NEEDS a shock tower brace while another, the F-bod, doesn't.

Actually, Mustangs have had various combinations of them since 1965. The first design, was two braces that ran from the center of the firewall to each shock tower. The second design, on the Shelby cars, called a "Monte Carlo Brace", ran from side to side, between the shock towers, and supplemented the firewall braces. Since GM never officially "raced" the F-bods, I assume that's why you didn't see them offer such additional parts.