pHEnomIC

I have seen some cars with these and I was wondering what exactly they do and if its worth anything? Should I get one? Its basically a daily driver but i do have fun with it sometimes.

slayer6x6

I didnt really notice any difference after I installed mine. I usually dont get into the turns and corners much though.

OldSStroker

Strut tower braces are helpful on MacPherson strut suspensions where cornering loads are taken by the lower control arm and the top of the strut.

Camaros have SLA (Short and Long Arm) or double wishbone front suspension, not MacPherson strut. The Camaro "strut" is just the shock and spring combination which basically takes loads along its axis. It doesn't take cornering loads, so you shouldn't feel much difference with or without the brace. Oh, the car might "push" a little more because of the added front weight.

Loony

Great...I was all excited about a titanium shock tower bar, and now its useless

O well

SFC AL

ahhh but NOW you have the "cool factor" going.. might not do alot of good.. but it LOOKS COOL!

Injuneer

One could argue that the "cornering load" taken by the upper A-arm in the 4th Gen's unequal length A-arm suspension isn't a whole lot different than the cornering load taken by the 3rd Gen upper strut mount. The 4th Gen concentrates the upper A-arm load, and the upper spring seat load concentrically at the top of the shock tower. Its likely that the brace could prove beneficial, when a drag car, without a front sway bar, tries to pull the front wheels - drivers side wheel first because of the reaction to the torque at the passenger side drive wheel.

The brace isn't going to do much of anything under "normal" driving conditions, but at the extremes of cornering, or pulling the front wheels in the 1/4-mile, it will come into play. Interestingly, some of the Auto-X and road race people don't like the upper shock tower brace, because they claim the added rigidity of the front end makes the transition to break-away more extreme, and less predictable.

jrtf83

would its affect on the rigidity of the front end have an effect on the balance (understeer/oversteer) like sway bars do?
interesting to hear they're pretty worthless esp cuz so many people have 'em.

WestCoast96Z28

I wouldn't say they're useless. I have a daily driver as well, and can definitely feel the difference on high speed turns....say offramps. Before the STB installed, I used to take my favorite offramp (speed limit 35) to work at around 50. Now with the brace, I usually hit it around 55-60 and it feels solid.

True, a bigger front sway and some SFCs would make a bigger difference, but STBs are rather cheap and easy to install. Just pick up a used one and try it out.

RS Dragster

The only thing I noticed when putting mine on was the fact that the car didn't want to follow grooves in the road as much. As soon as I took it off though, I noticed a HUGE difference in handling. The car felt mushy, and leaned a lot more. So now I put it back on and she feels really connected

Megalis

I have pics of mine in sig. I did feel a difference also. And I swear that quite a bit of the dash rattle is gone as well. It does feel tighter and firmer. I say get it.

Grave

For those of you with the STB, how on earth did you torque down the inner bolts? I can't get my wrench in there to tighten it down to the recommended 32 ft-lb... so all I could do was torque down the outer bolts, and use a close-in wrench and tighten it down to what I *think* 32 ft-lb feels like.

mitchntx

The forces applied start at the tire's contact patch.

Assuming 100% side loading traction the force is transferred to the hub assembly. Becasue the contact patch is almost a foot below the hub, the wheel tries to pry away from the hub, like when you use a church key on a bottle of beer.

Becasue the forces are below the mounting point, the majority, if not all, the lateral force moves to the lower ball joint, because the wheel is still trying to pry away from the suspension.

This is then transferred along the lower A-arm and into the K-member.

The upper A-arm is nothing more than a stabilization point to keep everything in align. The stamped, sandwiched inner fender is well suited for this job.

But let's look at real life, instead of the hypothetical 100% side loading.

When negotiating a turn, the wheel turns about 15* or so at full lock. Again assuming 1G and no braking, the cornering weight of the car is spread between the front and rear wheels ... in actuality, the front carries more because the front tire is scrubbing against the pavement in order to change directions, but this is all hypothetical, right?

The loading forces are transferred the same way, however ... we now have the wheel turned. So the forces are transferred more rearward than laterally. Could this be why the A-Arm has the rear mounting point BEHIND the the tire's contact patch? I'll go out on a limb here and say ... YES!

Now, all that to illustrate that if the upper mount is so flimsy it flexes, tieing the 2 points laterally does no good because the forces generated are longintudinal, not lateral. But because the forces are so minimal, anything is overkill ...

One I hadn't considered ... a wheelstand. As the car comes down, the suspension compresses with minimal loading to the contact patch.

If the susension bottoms out, it will either nail the bump stops (on the front frame rail, I believe) or bottom out the shock.

If the bump stops are removed and the shock bottoms out, the lower shock mount is the weak link, it would appear to a casual observer. Those 2 8mm standard grade bolts couldn't take too much shear forces.

If you have not removed the bump stops, the forces are transmitted to the bottom of the frame rail and come nowhere near stressing the upper shock mount.

whew ... that was way too much thinking for a Monday morning.

Bottom line ... an STB is $100 and your speed shop of choice will love you for buying one ...

Z28barnett

You are missing a important detail on the forces on the front end. The ball joint does recieve a lateral force but since the force is not centered at the ball joint, (As you say its about a foot below), you get a force and a Moment generated at the lower ball joint. The force is mostly taken by the ball joint but none of the moment is expended there. The moment is taken by the upper a-arm. The upper a-arm have to provide a reaction force to cancel the moment around the lower ball joint.

For the sake of the discussion lets assume a 3600 lb car with a 1g cornering load equaly split on all four wheels. 900lb * 1ft = 900 ft*lbs of moment around the lower ball joint. Lets say about 2 ft from the lower ball joint to the upper a-arm. That means a 450lb lateral reaction must be generated by the upper a-arm to keep the steering knuckle from moving. On the other side of the car an equal and oposite reaction is generated by the other wheel. That means over 900 lbs for force almost a half a ton is moving through those stamped towers.

A shock tower brace will share those loads between the two shock towers. This is not even considering the spring and shock loads that are also moving into the towers.

I think a 3-point is not as important as a 2-pt, but a 2pt should help some and there are good reasons for bracing this area.

Strut suspensions have all of the same problems to a greater degree, but the 4th gen front suspension is basicly a strut system with added upper arms that improve on the motion of the front suspension in ways a strut can't do.

In short 2-pt bars are not junk, but it is hard to tell how much they help.

mitchntx

Good points ...

I realize the opposite loading affect between the upper and lower ball joints created because the hub acts as a fulcrum. But because the fulcrum is 12-14 inches below the upper mount and only 2 or 3 inches from the lower, the lower sees the bulk of the loading. Remember the original forces generated is well below the lower ball joint at the road contact patch ... canti-levered, if you will.

Put equal amounts of weight on a see-saw, one end being 6 times further away than the other, the end furthest away from the fulcrum will have the most leverage and need SIGNIFICANTLY less weight to keep in balance. But more weight from the closest one will be seen at the fulcrum.

My analogy might not be 100% spot on, but you can see the point.

Further, that moment generated, both on the inside and the outside, sees all the force going in the same direction. If the opposite side shock tower were not being loaded, I could see some minor benefit in tieing the opposite side to it. But all the loading is in the same direction. It's like nailing a 2x4 across 2 upright pieces of wood and expecting it to carry some lateral loading.

And again, in real world application, the forces generated are more longitudinal than lateral, due to the forward motion of the car.

And again in in the real world, you really think one of those shock towers moves under 450lbs of force? I've seen guys hook chains up to those points in the shock tower of the car and raise it in order to drop the K-member. Much more than 900lbs. And I realize the loading is in a different direction, but still ... this ara is a lot stronger than one might think.

Z28barnett

[QUOTE=mitchntx]Good points ...

I realize the opposite loading affect between the upper and lower ball joints created because the hub acts as a fulcrum. QUOTE]

The hub is not the fulcrum, the lower ball joint is. The distance from the bottom of the tire contact patch to the lower ball joint is the moment arm of the force couple. The hub is the load path from the tire to the steering knuckle but that is not part of the calculation of forces.

This is a couple, a force and a moment acting together.

The lateral force times the distance from the bottom of the tire to the lower ball joint is your moment arm around the lower ball joint. The side force is not related to the distance to the lower ball joint.

You are correct that the forces are reduced by the distance from the lower ball joint to the upper ball joint. That is why chevy made the steering knuckle so tall. That is also why I made the force half of what it was to cancel the moment, otherwise the force would have been double to 1800 lbs.

So the force are not as great as they could have been but they are not zero either.

My guess is the real effect of the the STB is dynamic not static. I don't know numbers but in a tight turn the inside wheel is not loader very much, and some cars even lift the inside wheel.

In this dynamic case with the inside wheel lifted, the outside wheel is taking 100% of the load. In a left turn that means the the top of the left shock tower is being pulled to the left by nearly 100% of the side loading force acting through the moment arm. That is the bottom of the tire is resisting sliding out and the road is pushing in on the tire. The assembly tries to pivot on the lower ball joint and the top of the knuckle tries to move toward the outside of the turn until it hits the end of the play in the upper ball joint. This force then acts to bend the shock tower toward the outside of the turn with almost the full force generated by the front grip. I am glossing over some details here, and the k-member is taking most of the side load, but none of the moment force.

This is when the STB comes into play, it acts as a tension anchor to share the load with the tower on the other side through tension.

So in summary, in a hard turn the inside tower is doing little and the outside tower is being pulled toward the the outside of the turn. The STB bar can then increase the stiffness of the ouside shock tower by sharing the load through tension with the mostly unloaded inside tower.

The static anaylsis tells you where the forces will go, but a dynamic analysis tell you what they will do. If both wheels had the exact same traction the STB would not do anything it would just be displaced left or right. In a hard turn this doesn't happen due to the weight shift towards the outside tire.

As long as the STB bar is stiffer in tension than the shock tower is in bending, it will have an effect. This is pretty likely since everything is stiffer in tension than in bending. Thats why we have suspension bridges.

The STB should only help when you make hard corners, the harder you turn the more the effect. It might be a little help if you where lifting both front wheels, but mostly it is along for the ride until you turn.

I can see why you think the STB is doing little but I am pretty sure it is doing more than you give it credit for. The Miata factory "R" version from a few years ago had an STB and it is true double a-arm suspension no struts. They didn't put it on for no reason.

The only way to know for sure is to put a strain guage on the bar and see what happens.

I have an SLP 2-pt and I think it was worth the $99.00. But without testing it is only a theory.

IMHO

Z28