I think I finally found the source of my bizarre handling issue. Now, how to fix it?
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Thread: I think I finally found the source of my bizarre handling issue. Now, how to fix it?

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    I think I finally found the source of my bizarre handling issue. Now, how to fix it?

    Hello all. Long story (semi) short here, I have been dealing with a mysterious handling issue for the past couple years, and despite a whole lot of tinkering, multiple trips to reputable shops on both sides of the Atlantic, and a lot of money spent on replacing bushings etc, it would never go away. The basic problem was that the car started feeling unstable at anything more than about 50 mph. It behaves as if it is being randomly pushed around by strong winds, knuckleballing down the road, and basically refusing to track straight and true. The problem surfaced in the middle of a long drive initially. One minute the car feels fine, next I'm thinking "man it got windy all of a sudden". Then I stopped for gas and realized there was no wind, at all.

    A few months back I thought I had finally found the culprit, as when I removed my tow hook license plate holder to switch to a European format plate, the problem immediately improved noticeably. For a couple days, I thought it was gone, but soon realized it was still there, just not noticeable until higher speeds. The start point had moved from about 50 mph to around 90 mph. The fact that I now live in Germany makes that more of an issue than it might have been back home in the states, as I regularly cruise at around 100 mph, and would drive faster if the car wasn't all over the place.

    So the license plate issue clued me in that it was aerodynamic. I had originally thought it was suspension or alignment related after finding nothing wrong with any of the bodywork, and the other day it finally revealed itself. In the front of the car, there is a black plastic indent directly under the front license plate area. This is an area I have inspected many times over the past couple years as I washed the car, and never saw anything out of the ordinary. I guess a particularly fast run on the Autobahn the other day finally pushed things far enough that the issue was visible. This black plastic section is now visibly separated from the surrounding painted bodywork on one side, and inspection reveals that at least one of the clips that hold it together has snapped, and another one has been popped open, but appears intact. So, basically this section has been opening up on one side only and randomly allowing air through the bodywork, throwing off the balance of the aerodynamics for moments at a time, and causing the erratic behavior. I suspect that the off-center tow hook plate holder might have been shunting air forcefully into that corner, and might have been responsible for the initial failure of the clips connecting the two pieces, as well as magnifying the affect while it was still on the car.

    Now the question becomes, how do I repair this? The clips that hold this piece on are molded into the front bumper, and they have failed completely. The factory's answer to how to fix this would be to replace the bumper, but with paintwork, clear bra replacement, etc, that is a rather cost ineffective method. I need to figure out how to lock these two pieces back together in a way that will not fail down the road due to the air pressure applied on an autobahn run. Things that have crossed my mind so far range from duct tape, to glue, to even taking the whole bumper off and fiber-glassing the parts together.

    So, anyone have any thoughts on how to best repair this?

    Pic below.

    I think I finally found the source of my bizarre handling issue.  Now, how to fix it?-img_20190706_113244-jpg
    Last edited by feeshta; 07-06-2019 at 04:26 AM.
    Vehicle: 2007 Cayman S 6MT with sport chrono and 19" sport wheel package.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    I don't have any great ideas, but if it were me I'd take the front bumper off and try to fabricate something to hold it. I took the bumper off my 07 Cayman a couple years ago to clean the radiator area. It was not that difficult. Here is a picture of the center insert from the back, if that helps.
    I think I finally found the source of my bizarre handling issue.  Now, how to fix it?-back-front-bumper-jpg

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    Quote Originally Posted by danschy View Post
    I don't have any great ideas, but if it were me I'd take the front bumper off and try to fabricate something to hold it. I took the bumper off my 07 Cayman a couple years ago to clean the radiator area. It was not that difficult. Here is a picture of the center insert from the back, if that helps.
    I think I finally found the source of my bizarre handling issue.  Now, how to fix it?-back-front-bumper-jpg
    Thanks for the picture, Sir. That's roughly how I thought it would look.

    One idea that occurred since I originally posted is to replace the plastic blank with a grill. The grill wouldn't need as solid of a mounting due to the fact that it does have to hold back all of that air pressure, so one broken clip out of the bunch probably wouldn't affect it much. Other grill assemblies also seem to mount differently.

    Does anyone have any recommendations on grills?
    Vehicle: 2007 Cayman S 6MT with sport chrono and 19" sport wheel package.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    Quote Originally Posted by feeshta View Post
    Thanks for the picture, Sir. That's roughly how I thought it would look.

    One idea that occurred since I originally posted is to replace the plastic blank with a grill. The grill wouldn't need as solid of a mounting due to the fact that it does have to hold back all of that air pressure, so one broken clip out of the bunch probably wouldn't affect it much. Other grill assemblies also seem to mount differently.

    Does anyone have any recommendations on grills?
    I *think* the higher performance Porsches have a third water radiator in the center, with a grille rather than a blank insert. obviously, you don't have the radiator, so you don't have the grille. but maybe you can get the appropriate part assuming that the bumpers are the same. i dont know what is done to duct the spent air from the radiators if you go that route - maybe get a look under a car being serviced at a nearby shop???

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    When the radiator is present the site is vented through the lower panel (unless it's a GT3).

    If I were you I'd start by removing the bumper cover and see what has failed. It will be far easier to repair from the inside. If you decide to open it up is definitely open the lower panel to allow the air out. You can also go with the GT3 Smile that vents upwards. Rennline has parts for the smile as well as nice quality mesh kits.


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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    There are clips and slots that the black plastic cover fit into. The question is there damage? If so, the open round trim piece used with the third radiator may not hold. Then again, with the bumper cover off, the trim may just pop back into place.

    If there is damage, you have several options. The most expensive is a new bumper cover. The next best fix is to glue the cover in place, 3M 5200 Marine RTV will work or Wurth Bond and Seal. The final way is to get the smallest zip ties and drill very small holes and use the zip tie to hold the opening cover to the bumper or a combination of glue and ties. If done right, it will not be very visible.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    I thought I made it clear in my first post, but apparently not from the looks of things. Yes, there is damage to at least one of the loops protruding from the front bumper that the blank clips into. The one on the passenger side edge of the blank is broken completely off. At least two others are currently separated, but I don't know if that is due to damage to the piece on the blank that protrudes and locks the clip in place, or if they simply got forced open and would close properly again if I could get pressure on the blank from the back. Won't know for sure until I can take it all apart. Would have done that this weekend, but unfortunately I came down with a pretty nasty cold, which feels totally wrong this time of year.

    In any case, at least one of the clips will never work properly again without replacing the entire bumper assembly, which is cost prohibitive for such a minor problem, so I need to find a way to reinforce that section or simply replace the blank with a grill. Not sure you really need to cut vents as mentioned above, as there isn't actually a real need to evacuate hot air from the area. If vents are needed, I would choose to cut them into the bottom, as the GT3 "Smile" seems like a bit of overkill.
    Vehicle: 2007 Cayman S 6MT with sport chrono and 19" sport wheel package.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    Why not just get a 3rd radiator kit. Not too expensive (~$300) and includes the aero bits to redirect the air under the car.

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    That could be a possibility. Where do you find the kit for that price? Also, do you still need to order a grill or does it come with one?

    Quote Originally Posted by lesmurray View Post
    Why not just get a 3rd radiator kit. Not too expensive (~$300) and includes the aero bits to redirect the air under the car.
    Vehicle: 2007 Cayman S 6MT with sport chrono and 19" sport wheel package.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    Suncoasticon has them for $389. Any screens or grills are aftermarket. Here is the caption from the Suncoast website.

    Cool down your Porsche with 100% Factory Porsche Parts. Adds an additional radiator to your Boxster or Cayman for increased cooling. This is perfect for the street or track, and comes with all of the necessary hardware. Professional installation recommended, ports must be cut into the bottom of the bumper to allow air flow.Fitment (Manual Transmission Only):
    Cayman or Cayman S, 2006-08
    Boxster S, 2005-08
    Boxster 2005-08 - Center duct must be cut into bumper, painting of small trim opening required.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    I recently installed the 3rd radiator kit (form Suncoasticon) and the engine stays nice and cool on the track. BTW - my independent mechanic says that they can't get it any cheaper than the price Suncoast offers.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    There are actually outlines of 2 center radiator vent holes embossed into the plastic pan under the front of the car. Or maybe the nose itself. Anyway, foolproof. If you open up the center area I'd definitely cut out those holes as that is how it was designed.
    Bill/Memphis
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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    The third radiator kit does nothing to solve the OP's broken slots; these are moulded into the bumper cover itself.
    I have a hard time believing that this is the cause of his handling woes, however. I'd suspect something in the steering rack or tie rod ends, or even -- in a rare case -- worn or loose bolts or holes in the subframe that the steering rack bolts into. This seems much more likely to be a mechanical issue than an aerodynamic issue, IMO.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    The suggestion isn't that the radiator will help, it's that if he can't repair the part to avoid air ingress that he needs to vent that air. And if he's going to open it up and vent it, he might want to go ahead and add the radiator.


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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    So the thought is that this small plastic piece not being seated right is causing a 3,000 pound car to sway all over the road?

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    Quote Originally Posted by Rickyb View Post
    So the thought is that this small plastic piece not being seated right is causing a 3,000 pound car to sway all over the road?
    Yeah, that doesn't seem right to me either. I would think something is loose/broken in the suspension or steering.

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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    I have zero exposure to this person's car and I'm not claiming this is his problem. Just keep in mind that 1/2" piece of plastic attached to a wing (aka gurney flap) can dramatically change the stability of a car at high speeds. So is this possible, yes, I thinks it's possible. Is it definite? Certainly not.

    It's seems like it's pretty easy to test though. Pull the bumper cover, either fix the damage or remove it all together and vent the airflow.

    Quite some time ago I had a 996 that just never felt all that stable then I turned at anything above 60 mph or so. Suspension was fine, tires fine, alignment fine. I added the factory aerokit and the car was rock solid ever after. Aero can have quite an impact when it comes to higher speeds.




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    Re: I think I finally found the source of my bizarre handling issue. Now, how to fix

    I was listening to Smoking Tire video live stream - he mentioned a car that got all squirrelly on him. Turns out it was the steering wheel hub flange. Never would have thought.

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