I'm on the hunt for a strut brace to prevent the towers from potentially cracking. I tried to find one that mounts to all three bolts on the tower and has a full circle/ring around the top of the hat. I can not find out that fits the 3.0 except cosmo but that is not hollow in the center to allow for adjusting rebound on tc/kline SA's.
Question is, do strut braces that are not full circles and only mount to 2 (or even 3) bolts but do not go all the way around the top provide the same cracking prevention as one that would be a full circle?
I have the Cosmo one on my car for about 10 years. I still had both of my strut towers crack last year. I got them repaired and still have the strut bar mounted. Maybe reinforcement plates would help. I don't think the bar itself would prevent cracking. I also have TCKs on my car, but I do have 250k miles on my car. I've only adjuste them once and it took about 15 minutes total to just unbolt the bar, adjust and re-install.
Strong Strut produced the original bars I believe. Strong Strut is still the best make IMO. Be sure to keep the black disk that goes between the hats and the towers on the bottom side of the tower. Are the cracks you are referring to at the mounting hols or the base of the tower? The disk will do more to protect the mounting holes than anything. As for the base seems, well I think they are as much luck of the draw, similar to the rear pan area, as anything.
Dan "PbFut" Rose
The best strut tower crack prevention is to run proper bump stops.
/.randy
I was under the impression that Tc/Kline either come with the bump stops they need, or should I be looking at swapping their bump stops?
Last edited by edx1; 11-28-2016 at 06:11 PM.
I just installed the TC Kline system on my 3.0, and I did not have any reinforcement plates in place with the stock setup that was still installed. And I've never read anything about them being included on the non-Ms from the factory.
The front struts did include a bump stop under the dust boot from TC Kline, but I don't know if there is a better one that should be swapped instead.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
Other than a strong strut, what else would people recommend and would braces with 2 bolts or 3 bolts and do not have a full ring offer the same upper mount reinforcement to avoid cracking around the bolts?
The only thing I could see helping prevent the mushrooming/cracking of the strut towers is the M reinforcement plates on the bottom. They work to redslistribute the force of the strut. A strut bar just connects both shock towers, and since the forces come from below I just dont see how something on top would help.
Something on top will help if it prevents the tower from ballooning out and allowing the strut bolts to fan out, like this:
righttower2_zpsb5cb436d.jpg
If the strut brace keeps those bolts in their correct location and orientation, it would definitely help prevent the metal from flexing, fatiguing, and failing. It would add rigidity, which would reduce the flexing (and subsequent problems). If a stack of things is bolted together, it will act more like a single thick object, so it can definitely help to add thickness even if the extra parts are on the opposite side of the load.
Having said that, strut braces cover a relatively small area, so they could just move the flex/fatigue/fail location further out. If you make one area more rigid, then it may just move the load elsewhere to a less rigid spot. That would be where the larger surface area of the reinforcement plate on the bottom side would come into play.
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Out of curiosity, do you have any pictures of where yours cracked?
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
It may help a marginal amount, and may keep the bolts from splaying out too much, but at the end of the day it takes a lot of force to make the strut towers mushroom out like that and the strut bar isn't doing anything to deflect or divert those forces. Stacking things and bolting them together does not force them to act together - if you had two pieces of flat metal stock bolted together in the metal, you can still bend them independently and that same logic applies here. As the strut tower is fatigued and "pushed" up, the strut tower will simply move up with the tower. And all the strut towers I've seen have holes for the strut threads much wider than the actual threads, and holes for the bolts much larger than the actual bolts - for good reason too, as there are minor differences car to car - but this will give the bolts and threads freedom to move around in the event that the mushrooming starts to happen. The bolts on the actual strut can also come loose (they are a seperate part and not welded onto the strut hat), so if there is enough force to mushroom the tower, I wouldn't rely on the bolts themselves to hold everything together.
The best way will be to reinforce the bottom to actually spread the load over a wider area. None of these solutions will do anything to prevent another failure point I've seen which is where the actual sheet metal for the shock tower itself is welded to the fender piece. If anything a strut tower may exacerbate that sort of problem by minimizing the flexing of the chassis, thus forcing additional load through the shock towers in the horizontal plane.
Last edited by BimmerBreaker; 11-29-2016 at 09:04 PM.
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Get a reinforcement plate used in the M and anticipate having to have it repaired by re-welding it if you run camber plates. It's not that difficult.
Now in E92 M3 ZCP -- Absolute beast
I'll start by saying I agree with you that the bottom plate is probably the most important piece. I completely agree with you there; but I won't get into why in this post.
As for the top, think about it this way--you mention that the strut tower bar is able to reduce chassis flex, and I completely agree. If the strut tower bar had freedom to move around, it wouldn't be able to reduce chassis flex; plus, it would be a squeaky clunky mess if it was moving around. It has to be securely squeezed onto the top of the strut tower. The friction between the plate on the strut tower bar and the strut tower itself is what holds it in place. This is why it's fine for the bolt holes to be oversized.
The tension on the bolts provides friction that keeps the bar in place, as opposed to a sideways/shear force on the bolts themselves. (This is the same idea as what happens on wheel bolts. They don't experience a sideways/shear force; stated another way, they actually don't keep the wheel in place. They are placed under tension, which creates friction between the wheel and the hub, and that friction is what actually keeps the wheel in place.)
Now think of the metal between the bolts on the strut tower. For the bolts to splay outward, the distance between them must necessarily increase. If there is a metal plate securely bolted across those areas, the force that would tend to make them splay outward can be transmitted to the plate on top via that same friction that helps support the rest of the chassis. It isn't because the bolts would directly bend over and push against the plate on the strut bar sideways (at least, not unless things were in a really bad state); it's because the friction between the strut tower and the plate on the strut bar transmits the force to the top plate. In other words, they begin to act like a single unit. This is the mechanism via which a plate on top of the tower can help strengthen it against a force coming from the bottom.
I can give you two other examples where this is seen---one on our cars, and one on boats. If a top plate is irrelevant when dealing with a force from underneath, why is the upper plate on the rear shock mount reinforcements so thick?
Rogue on the left, TC Kline on the right. On the TC Kline plate, the metal that goes on top is even thicker than what's on the bottom. Why? The answer is that the upward force coming from a hit to the suspension is transferred to that top plate via friction. For the sheet metal of the car to stretch or bend, either the plate on top must stretch or bend, or the friction force between them must be overcome. If neither of these things happen, then the top plate is reinforcing the sheet metal from a force underneath. They are acting like a single unit.
Another example of the same idea comes in boat building (and this may be way off topic, but I add it because I remember it completely confused me because it seemed so counterintuitive to me when I first learned it). To add puncture resistance to a boat, you can put a layer of kevlar *inside* the boat. If a boat hits a rock, the hull flexes upward, and an inner layer of kevlar can help reinforce the hull and prevent it from failing. Same idea as the strut towers--an inner layer protects the outside of the boat from a force coming from the outside.
I hesitate to include this because it's both an appeal to authority and it comes from an advertisement, so if you dismiss it just out of hand, I won't blame you ...but I'll include it anyway....from Rogue Engineering:
And lastly, if you don't believe me, you can test it yourself...get two pieces of metal and put them on top of each other. If you bend them back and forth, they will be twice as stiff as a single piece. If you then securely bolt them together at both ends so they are unable to slide past each other when bent, they will be more like four times as stiff, which is very similar to what you would have with a single piece of metal of equal thickness. The friction between the pieces forces them to act as a unit.For those that may believe a strut bar is only for "track cars" or "racecars", it is also street driven vehicles that benefit from a properly engineered strut tower bar. Whereas anyone can appreciate the ability for a front suspension to remain constant at all times, other benefits include support of the factory strut towers from "mushrooming". These generally occurs if the vehicle hits large potholes, causing the suspension to compress completely, and then damaging the rim. However, its not only the rim that takes the hit, but the shock tower as well. Over time, if left unprotected, it can cause expensive sheet metal damage.
Last edited by kornfeld; 11-30-2016 at 09:57 AM.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
Friction for sure. The Strong strut bar has slotted holes to allow for variations in the distance between the strut towers. The strut bar connects the towers by the friction of the tightness of the bolts and washers in the slotted holes. The black mounting plates on top of the towers are just for attaching the bar. It would not matter if they were circles, or semi-circles.
BMW MOA 696, BMW CCA 1405
I would still be interested if you have any images of your strut towers when they were cracked, and where the strut bar sits on it...it would be interesting to see how yours failed because the mounting plates are somewhat different than most of the other designs I've seen.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
No worries. Does your bar look like this?
http://www.cosmoracing.com/productin...d=241&pid=1163
When you say it cracked between the bolt holes, were the cracks like lines that connected the bolt holes, or where they lines that ran out from the center of the strut tower like the spokes of a wheel?
And were the cracks visible when the strut bar was in place, or were they completely hidden under the strut bar, or were they right along the edge of where the strut bar meets the tower?
Last edited by kornfeld; 12-03-2016 at 09:23 AM.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
I stumbled on a video that perfectly illustrates what we were talking about in this thread. In the video, they're dropping a bowling ball on a lamination of multiple sheets of glass. Before you watch it, make a guess: will the top pane of glass (that gets hit directly with the bowling ball) shatter, or will the bottom pane of glass shatter? Then you can skip forward to 5:25 if you don't want to see all of the intro:
It may make intuitive sense that the top pane of glass would break because it is taking the direct brunt of the impact, but intuition is frequently wrong. Glass is way, way stronger in compression than in tension, and when this lamination is hit with the bowling ball, the top pane is squished together, while the bottom pane is being stretched apart.
I would put a bet down that adding a thin layer of sheet metal to the *bottom* of the lamination would do more to strengthen the whole assembly than adding a layer to the top would. The sheet metal on the bottom would add tensile strength right where it's needed, even though it's being placed on the side opposite from where the force is coming from--just like adding reinforcement to the *top* of a shock tower can make it more resistant to deformation caused by forces coming from the *bottom* of the shock tower.
Last edited by kornfeld; 10-22-2018 at 11:56 AM.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
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