Re: TOBY-TAB update

["Jim Reeve" <ultra@xxxx>]

As the owner of the failed bolt, I should probably chime in as Toby 
suggested doing so.

My first trailing arm bolt incident occured in fall of 2001. It was 
likely caused by those "ripple" bumps found on gravel roads. I hit a 
patch of them doing about 45 mph, and the entire car shook hard. A 
few days later I noticed the rear of the car seems to be swaying as I 
would accelerate. Checking the trailing arms revieled a complete 
loss of the alignment shims on the passenger side. That particular 
bolt had a slight bend in it, but the drivers side bolt was fine. 

The following spring (2002) I decided that I no longer wanted to 
worry about my trailing arm bolts at all. So I ordered the newly 
availible first batch of Toby-TABs. With my "as long as I'm doing 
this, I might as well do that, that, and that" philosophy, I decided 
to replace everything on the trailing arm bolt area. So I also 
ordered 2 new bushings, 4 new "medium" sized hardened washers, and 10 
new alignment shims (but not all were used). Unfortunately, the 2 
larger sized washers are unavailable, so I cleaned up and re-used my 
original ones. I removed everything, cleaned up the area, and 
reinstalled/lubed/torqued everything according to spec. I also took 
advantage of the dissasembly to clean the the battery ground for the 
entire car, which goes into one of the bushing bolts.

Fast forward an entire year. I took 2 cross-country trips (MN-
Memphis and MN-New Jersey) coupled with nearly every day driving from 
April-October. (Which performed flawlessly I might add). As Toby 
mentioned, it ended up being near 20,000 miles.

Now in May 2003, I'm in Chicago for the spring tech session getting 
my clutch changed by all the helpful folks there. While my car was 
on the lift with the transmission removed, someone pointed out to me 
that my alignment shims were askew on the driver's side bolt. So I 
loosen the bolt to reposition the shims, but I notice a definate 
twist in the bolt head and nut when doing so. I take everything off 
to find a very bent Toby-TAB. After cleaning everything up, I found 
that the two new "medium" sized hardened washers that are placed on 
either side of the bushing, were crushed in where they made contact 
with the bushing. I'm assuming this loosened the joint enough to 
displace the alignment shims, and somehow bend the trailing arm 
bolt. There were ABSOLUTELY NO signs of this when driving. No 
clunks, sways, nothing.

What does this all mean? I means that I would easily pay a premium 
to get some newly manufactured hardened washers. (Urethane bushings 
wouldn't be too bad either -hint-hint-).

My drivers side Toby-TAB was bent more than my original passenger 
side bolt. The Toby-TAB was still secured tightly, but probably not 
up to spec with the crushed washers. My original passenger side bolt 
was completely loose with the loss of all alignment shims. I would 
hate to see what would of happened if I had my original bolts in 
there still.

Wow, what a long post.

Jim Reeve
MNDMC - Minnesota DeLorean Club
DMC-6960

--- In dmcnews@xxxxxxxxxxxxxxx, "Toby Peterson" <tobyp@xxxx> wrote:
> Hello List - I have some important information that I want to pass 
> along for all interested parties regarding a bent bolt that was 
found 
> at a tech session in the midwest last spring. The bolt was one of 
my 
> bolts, and had been installed by the owner. If the owner wishes to 
> add anything to this post, he is welcome to (he is a highly 
regarded 
> member of this list). The information that I was given was that 
the 
> installation was done with new "large" flat washers obtained from 
one 
> of the DeLorean vendors, and that he had put something close to 
> 20,000 miles on the bolts, including hitting some rather 
significant 
> potholes. The car's owner noted that the new flat washers were 
worn 
> nearly half way through the thickness where the sleeves through the 
> trailing arm and bushings contact them. The bent bolt was 
eventually 
> sent back to me for evaluation. I sent it to the original 
> manufacturer in order to verify that there was nothing defective 
> about the bolt, or the materials used to make it. I received the 
> manufacturer's formal written report yesterday. The bolt was sent 
to 
> an independent testing laboratory, where it was tested to ultimate 
> tensile failure to verify material tensile properties, tested in 
> double shear to verify ultimate shear strength properties, and 
tested 
> for Rockwell hardness to see if there were any variations in 
hardness 
> in the bent area of the bolt. The bolt failed at a tensile load of 
> 31,603 lbs, which translates to a tensile strength of 245,360 PSI. 
> The shear strength (using standard double shear tests) of the bolt 
> was 265,580 PSI, with a peak load at the breaking point of 45,489 
> lbf. To get the single shear stress values, you divide the double 
> shear stress values by two, giving you a shear strength value of 
> 132,790 PSI in single shear. The minimum values for this grade of 
> inconel are 220,000 PSI (tensile) and 125,000 PSI (shear), so the 
> material was well above the minimums. The Rockwell hardness values 
> were all in the range of 47.15 - 47.97 Rc in the deformed area of 
the 
> bolt.
> 
> What the heck does all of this mean? The TOBY-TAB bolt is 
incredibly 
> strong, but even it can't survive in a loose joint where the 
washers 
> have worn significantly. The impact loads and general pounding 
that 
> the parts of the trailing arm connection take on rough roads and 
> during performance driving will eventually bend any bolt that is 
> installed there, even mine. The stock, or even "improved" bolts 
> don't stand a chance in this environment. Bottomline - The TOBY-
TAB 
> is the best that can be had, but you must still ensure that all of 
> the parts in the joint, including washers and sleeves, must be hard 
> enough to resist wear, and the tightness of the joint must be 
> maintained through normal maintenance. I am looking into a new 
flat 
> washer material that I think will solve this wear problem, but the 
> cost may be nasty. I will keep the List apprised of any further 
> developments. As always, I welcome all of your input into this 
> issue. Thank you for your support of the launch of this new 
company. 
> 
> Toby Peterson VIN 2248
> DeLorean Parts Northwest, LLC
> Winged1