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Just looked at my car and the plates in their present configuration won't work. because there is extra bracing running from the firewall to the tower that the plates bolt to. I do think someone could design a simular plate that would work on a stock car. Carl
I don't know anything about welding aluminum but on steel the BMW OEM solution was to weld the reinforcement to the underside of the strut tower. The plate is designed to match the curvature of the strut tower and better spread the impact force of the shock mounts across the hat area. Since the suspension is already adjustable, it would be easy enough to just drop the front ride height to match the additional stack height of the reinforcement. Pic for reference:

If the Porsche OEM replacement parts are inexpensive it could be worth cutting the tops off to fit and double up.
Just looked at my car and the plates in their present configuration won't work. because there is extra bracing running from the firewall to the tower that the plates bolt to. I do think someone could design a simular plate that would work on a stock car. Carl
That extra bracing might be important though. In Spyder's CS pictures I see connections from the black plate to the 3 strut bolts as well as 2 other bolts, one more toward the outside of the car with a white tube (the reinforcement you mention) under it and one toward the inside of the car with black support. Are our stock cars missing both? (I can't check my car right now) If we are only missing the white tube, I think something could be fabricated pretty easily there so that we could use the CS strengthening plate.
Having these extra mounting points for the plate could be critical if the failure location is where the two strut nuts toward the back of the car are. That is, it breaks there and then pulls the whole strut top up, breaking the front strut bolt off just in the process, but not starting there. The extra bracing would reduce shock loads at those two back strut bolts by providing support further back. If you look at the damage in the picture on the first page of this thread it looks like the strut is offset toward the back of the car, which would load the rear strut bolts more, also where it broke looks to be right next to those bolts.
No this won't help at all. You need to hold the top of the strut tower down . Look at the club sport body Porsche has plates on the top of towers that are attached to the body to prevent from the top getting blown off. Carl
Do you have a link to, or can you post here, a photo of those Clubsport plates on the towers?
EDIT: Duh, guess I should read all the posts before I make a post.... hadn't finished my coffee yet.
I don't know anything about welding aluminum but on steel the BMW OEM solution was to weld the reinforcement to the underside of the strut tower. The plate is designed to match the curvature of the strut tower and better spread the impact force of the shock mounts across the hat area. Since the suspension is already adjustable, it would be easy enough to just drop the front ride height to match the additional stack height of the reinforcement. Pic for reference:

If the Porsche OEM replacement parts are inexpensive it could be worth cutting the tops off to fit and double up.
The shock tower castings are $259.95 full retail price. If they would fit inside the original casting, and the top say 2" were trimmed off the new casting part, the structural adhesive used on many other parts of the car for body repair could be smeared on all mating surfaces of both parts and the new 2" top piece jammed up in there with full weight of the front end holding it in place until it cured.
That extra bracing might be important though. In Spyder's CS pictures I see connections from the black plate to the 3 strut bolts as well as 2 other bolts, one more toward the outside of the car with a white tube (the reinforcement you mention) under it and one toward the inside of the car with black support. Are our stock cars missing both? (I can't check my car right now) If we are only missing the white tube, I think something could be fabricated pretty easily there so that we could use the CS strengthening plate.
Having these extra mounting points for the plate could be critical if the failure location is where the two strut nuts toward the back of the car are. That is, it breaks there and then pulls the whole strut top up, breaking the front strut bolt off just in the process, but not starting there. The extra bracing would reduce shock loads at those two back strut bolts by providing support further back. If you look at the damage in the picture on the first page of this thread it looks like the strut is offset toward the back of the car, which would load the rear strut bolts more, also where it broke looks to be right next to those bolts.
You are correct the CS extra bracing gives the reinforcement plates a wider platform to attach to. Some type of a cup for the inside of the tower maybe be the best solution.
If you look how they reinforced the rear towers all they did was rivet and glue an insert on the inside of the rear towers. Why they didn't also do the front? Cost??
The real question is how big of an impact does it take for failure? The 991s & 981s have been tracked for 3 years plus all the press testing of the GT4 when it came out and i never heard of any track failures with hitting all the curbs on track..
I took pictures of my cars stock towers for comparison carl
The real question is how big of an impact does it take for failure? The 991s & 981s have been tracked for 3 years plus all the press testing of the GT4 when it came out and i never heard of any track failures with hitting all the curbs on track..carl
I'm speculating without full information available, but aluminum castings are notorious for having porosity and embedded inconsistencies due to the casting process. It could be these castings are not all that consistent from part to part.
Just ask 2006-2008 Honda Civic owners who had cast aluminum engine blocks that would seep engine coolant right through the sides of the block just like it was sweating. In fact, it's common practice with aluminum castings that are subjected to high pressure fluids to be dunked in a vat of a special type of Loctite under a high vacuum to pull the gasses out and allow the Loctite into the casting porosities. The Loctite cures then the part is machined or installed as-is. One application I personally worked on as an engineer was a 5,000 psi hydraulic pump made out of one of these types of aluminum castings. The process is called vacuum impregnation.
This is another reason why machined billet and forged parts are much preferred over cast parts for strength and durability.
Last edited by okie981; 11-20-2016 at 11:02 AM.
Reason: clarification
If you look how they reinforced the rear towers all they did was rivet and glue an insert on the inside of the rear towers. Why they didn't also do the front? Cost??
Unfortunately, I can't imagine any other reason why this wasn't done on the front other than to save $$.
This is what a clubsport looks like.
I'm aware of a similar failure on a 991gt3 in the rear.
The gt3 and gt4 are similar front ends. Spring rates different but unsure of other differences.
It's possible the Clubsport uses a bespoke shock tower. Can't do an online PET search to check part number. Somehow they are attaching that white steel tube to the aft outboard portion of the shock tower. You can't just stick a steel tube to an aluminum casting and in one of those photos it looks like the tube is inserted into a small gusset. This makes me think the Clubsport part might be bespoke. If bespoke, it could be thicker and/or made of a different material.
Assuming the problem here is the suspension bottoming out and huge peak forces being applied to the strut tower and it failing due to being overly weak, then I suspect swapping in stiffer springs should help the problem as long as you keep a similar ride height.
The stiffer springs should dissipate more energy by the time they fully compress / bottom out, meaning in theory it should take a harder impact to bottom out the suspension.
That being said, I suspect Porsche would be quick to blame your aftermarket stiffer springs if you were unlucky enough to have your strut tower fail with them in place...
Assuming the problem here is the suspension bottoming out and huge peak forces being applied to the strut tower and it failing due to being overly weak, then I suspect swapping in stiffer springs should help the problem as long as you keep a similar ride height.
Well, not just a similar ride height, also a similar bump travel. Most people who are getting new springs are getting 5 inch front springs with larger than necessary helpers. To have the same bump travel as stock they'd need 6 inch front springs with shorter compressed height helpers. (Like MVEED3 did here: https://rennlist.com/forums/gt4/9522...l#post13721612)
I spent an hour or so inspecting my BS and GT4 and comparing the differences, taking photos. I think the photos will shed some light on what's happening to the GT3/GT4 cars. Also see it wouldn't be that difficult to machine and mount a bracket like the Clubsport has, or to machine an insert that plugs in from below. There may be an easier mod that plugs in from below. Back in about 3 hours with photos. There's a clue if you examine part #3 on both cars in post #62 of this thread, and take care to orient the part in your mind's eye fitting up in this shock tower with the two bolts at the aft area of the shock tower. The figure in post #62 has the parts reverse oriented from each other.
EDIT: From what I saw, I'm less likely to think the Clubsport has a bespoke shock tower.
Well, not just a similar ride height, also a similar bump travel. Most people who are getting new springs are getting 5 inch front springs with larger than necessary helpers. To have the same bump travel as stock they'd need 6 inch front springs with shorter compressed height helpers. (Like MVEED3 did here: https://rennlist.com/forums/gt4/9522...l#post13721612)
Good point. This suggests that the 5" front springs that use helpers (which stay fully compressed and act like a spacer) from Tarett are probably a bad idea, and it would be better to find the same setup with a longer main spring instead.
Good point. This suggests that the 5" front springs that use helpers (which stay fully compressed and act like a spacer) from Tarett are probably a bad idea, and it would be better to find the same setup with a longer main spring instead.
Yeah, it's all in the thread I linked to but long story short a 6 inch main with a higher spring rate will be the same length compressed as the softer 7 inch stock main. If it's the same length compressed (just with the cars weight) it has the same bump travel as stock, maybe more depending if the spring has a shorter fully compressed height, but now with a higher rate which could protect more and bottom out less. I'm writing this all because you don't want a higher rate 7 inch main either because you couldn't get the stock ride height I think, it would be too high once you consider the weight of the car would compress it less.
Does the GT4 has a different tower design than the rest of the 981 family. I owned a 981 2013 Boxster S. And 3 years ago my wife drove the car over a curb on the driver side of the car, hitting this very large curb at 40 mph. Both front & rear wheels & tires on the driver side were severely damaged and had to be replaced, but nothing else on that car was damaged. Even the alignment was only affected slightly. I was impressed. After the new wheels were installed, the car was realigned and it drove like new. I tracked and autocrossed the car after the incident and there were no issues or any ill effects from my wife lovely adventure.
Unless of course, the Boxster has a reinforced tower oppose to the Cayman to compensate for the missing roof.
Really strange failure and especially these wheels are easily bent going over the smallest pothole at speed. So if no wheel was damaged I suspect the impact could not have been that hard, and that a defect in the tower pre-existed the incident in the free way. The owner is not even sure he hit anything, and what he possibly felt was just the tower coming apart giving the impression he went over a dip on the road. I think there was a defect in the casting to start with and a crack started to propagate until it finally broke off.
I own a manufacturing company and we deal with casting on regular basis. unless you perform ultrasonic inspection or X-ray the cast parts you won't know For sure that the part does not have porosities or perhaps underwent a core shift during the casting process which results in much thinner wall thickness in some areas. In addition aluminum castings must go a heat treatment process to Preserve or enhance mechanical properties. So it is possible to have a perfect cast part, but very compromised, if it did not receive the proper heat treatment. Most castings are brought in batches and usually if there are any issues with porosities, or core shift or heat treatment, the entire batch has issues which also means there will be other failures from towers that came from the same batch. Mark
11-20-2016, 12:06 AM
