Re: [DML] Re: Anatomy of A Failed TAB

["Steel Wings" <steelwings@xxxxxxxxxxx>]

 To answer some of the questions I've been asked regarding the TAB analysis:

1. My D had approximately 25,0000 miles on her when the TABs failed.
2. I have replaced the TABS with John Hervey's 12.5 coated replacement bolts.
3. The damage was minimal to the vehicle and was mostly restricted to the rear wheel-well and some damage to the rear body-kit skirts. No other damage beyond that. (Due to the slow speed)
4. Upon further questioning of my metalurgist friends, it appears that the point of "origin" (Failure) started at some surface rust pits on the exterior of the bolt that were not evident during the last time they were inspected a year ago. The fatigue started there and this process or "reversing fatigue" progressed until complete failure. (See the photos in the photo section along with the report under "Failure Analysis of TABS".)
5. The stock bolts were more than strong enough for their designed and intended utility. Unfortunately, they simply outlived their useful life expectancy. The primare cause of failure is surface corrosion compounded by stress.
6. Apparently "loose" bolts may indeed be the result of "stretching" due to fatigue. If you observe this symptom, don't tighten the bolt..That's probably not the solution. It's time to replace it before it breaks. Tightening it will only serve to hasten the failure.
7. Bolts having a greater hardness over the originals are probably not necessary. However, they should have some cadmium or other corrosion resistant coating on them if you decide to use them. Regardless of what they are coated with, they will one day succumb to corrosion and will have to be replaced again. Be vigilant with this.8.

8. Although I do not have "Toby Tabs" , I have been told that if they are indeed made of the 718 Inconel, they have approximately the same tensile strength as the stock OEM bolts that came with the car when new. The primary advantage to having this bolt is not the strength but the corrosion resisitance and they should last the life of the car.Toby Tabs will allow you to replace the originals and virtually forget about this issue.

9. The worst part of replacing the Tabs AFTER they snap is the re-alignment of the rear suspension. Especially if you lose the shims in the process. This is indeed a nightmare and failure to re-align properly will result in premature wear of your rear tires in short order. 

10. If anyone has any questions you want me to ask the Metalurists about the bolts or if  you have some questions or comments about the photos or the report, feel free to ask away. I will do my best to get them answered by the pros.

"Live the Dream..Don't Die in a Nightmare"  (Replace those Bolts Now!)

Steelwings
#1559

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