Failures using adapters would most likely be caused by the coilover setup. Most that I've seen extend the mounting point of the shock further than the stock shocks. This increases the bending moment on the adapter. For a vehicle with high weight and/or capable of very high cornering loads would be most prone to failures as the bending moment will be higher. If the adapter doesn't compress against the trailing arm there is a high likelihood that the adapter will prematurely fatigue like it did in this case. With coilovers there will be much higher load thru that bolt and there is a large stress riser right at its base. It is apparently possible to run without issue, but without it setup correctly the risks are much higher.

The other pausibility I see at the moment is in pure shear, in which case the bolt would fail leaving a flush face with the trailing arm. This is less likely for a coilover setup because most can't mount the shock eye directly against the trailing arm, but for those that would the shear plane is going to be seriously undersized for a TB delete. There is no ability to increase the shear plane without redesigning the trailing arm. In this case my bet would be that it will take a high number of cycles (lots of track time with very high loading) would cause the bolt to eventually fatigue. It should be possible to replace them every season or so with less concern for failure.

 

All good comments 2BWise, keep them coming.

Mike, are you using helper springs on the rear coilovers?
Helper springs should keep the hat and snap ring engaged when lifting the car.
You will want to make sure that those are aligned as you drop the car and that the hat and snap ring engage.
Could this cause a problem while driving? I'm not sure, you wouldn't think so. However, if you were to get air born while driving the car and the rear suspension goes into full droop I suppose it's possible for the two pieces to become misaligned. Would they correct themselves as you come down without any ill consequences, another good question.

 

I think this is the key point. This is a failure of the bolt, not the control arm after all. The GC (and other similar) arrangement has quite a distance from the face of the control arm to the centerline of the strut. Look at the 964 pic and it is essentially flush. There still is bending load in the bolt (due to the single-shear arrangement), but much less.

The GC unit is obviously very beefy at the control arm interface with a nice, smooth taper, all good. However, it is all predicated on a very immobile junction between the control arm and bolt. Any issues there (small gap, less-than-perfect flush fit etc.) will be significant.

 

This point is key. You MUST make the surface on the trailing arm perfectly flush to the bolt. That surface is important to the stability and tension of the bolt.

Racer's edge oven makes point (refer to my earlier post) to tell the installer to file any edges or casting flashing that prevents a flush surface.

C.

 

Excellent discussion, but does anyone have any thoughts on the spring not sitting on the hat properly? The other side looks 100% (as pics show) but that spring isn't sitting in there right + I just feel like something is off a little bit compared to the other. You know when it just doesn't look right...? I am wondering what I should do about that (need to act quickly as this is my only car and its tough being without it)

 

sorry to go off topic, but it is KIND OF a good thing this has happened >_>. i dont mean it to sound that way but this has opened up other things you should look to when doing suspension etc. i hope that everything is going ok with you and your car and clearly nothing has happened physically to you except maybe a headache from the bills =/

*correct me if im wrong

 

Chances are when you jacked the car up to swap the tire the spring unloaded and came off the hat (my front's do this). Once you drive it, or screw with it a bit is should reseat itself. See if you can get it to seat.

 

Mike...with all respect intended, our thoughts on the spring are speculation. I would recommend if you have a question with Jay's stuff, contact Jay. He built them and would certainly know best. The man is a genius when it comes to all things suspension.

C.

 

I did send a Jay an email, but was just curious what the list thinks.

fwiw, the only reason I'm asking about the spring is the other side is jacked up too and the spring is still in place, but I will try and get it back in place tommorow morning once I get home from work

 

You should just be able to move the spring into place man. Like, with your pinky. Lol.

Don't worry about that unless your snap ring is actually coming out of the hat or something..

 

Its damn near impossible to get any surface flat with a file. Its better than nothing, but the best way would be to machine it flush. Not very feasible though. The best process for doing it on the car would be with a sanding block or hand held belt sander (you know the wood working tool, can't think of what its called at the moment). Just be very careful that you're working it perpendicular to the bolt hole otherwise you can make the surface flat, but not normal to the bolt which would cause failure as well.

As to the spring issue. If the spring comes unseated when you jack it up then it should be very easy to reseat it by hand, but if this is the case I'd suggest helper springs. They're relatively cheap plus reseasting the spring everytime you lift it gets old fast.

 

Agree 100%. Not sure what the man has available for smoothing up the surface.

C.

 

FYI Paragon carries the 2.5in helper springs: http://www.paragon-products.com/product_p/cs100-2.5.htm $22 each

Do these fit at the top or bottom or doesn't it matter. Also I presume you just cable-tie this to the main spring as there is no spacer supplied?

 

Doesn't matter if they go top or bottom, but you do what the proper spacers. Zip tying them to the main spring won't work. First the ties will break due to the spring force and second its going to make things worse as the main spring will wander on the surface of the helper.

 

...which leads to my next question, who makes the spacers for these coilovers? I have sent an email to Jay at GC on this subject also.